Patent Application
20240413310
The present application is based upon and claims the benefit of priority to Chinese Patent Application No. 2023106812469, filed on Jun. 9, 2023, the entire contents of which are incorporated herein by reference for all purposes.
The present application relates to the technical field of battery preparation, and in particular, to a multilayer composite electrode sheet, an energy storage apparatus and a preparation method.
With the development of energy storage apparatuses, the requirement for the energy density of the energy storage apparatus is getting higher and higher. Lithium manganese iron phosphate has the same material safety property as lithium iron phosphate, and the capacity per gram of lithium manganese iron phosphate and that of lithium iron phosphate are equal, both are 170 mAh/g. However, compared with lithium iron phosphate, lithium manganese iron phosphate has a higher voltage platform. Therefore, the energy density of lithium manganese iron phosphate is higher than that of lithium iron phosphate.
In a first aspect, the present disclosure provides a multilayer composite electrode sheet. The multilayer composite electrode sheet includes: a positive current collector, a first lithium manganese iron phosphate layer, a second lithium manganese iron phosphate layer, a third lithium manganese iron phosphate layer, first conductive fibers, and second conductive fibers. The first lithium manganese iron phosphate layer is disposed on the positive current collector. The second lithium manganese iron phosphate layer is disposed on a surface of the first lithium manganese iron phosphate layer facing away from the positive current collector. The third lithium manganese iron phosphate layer is disposed on a surface of the second lithium manganese iron phosphate layer facing away from the first lithium manganese iron phosphate layer. One end of the first conductive fiber is inserted obliquely into the surface of the first lithium manganese iron phosphate layer facing away from the positive current collector, and the other end of the first conductive fiber is inserted obliquely into a surface of the second lithium manganese iron phosphate layer facing toward the positive current collector. One end of the second conductive fiber is inserted obliquely into the surface of the second lithium manganese iron phosphate layer facing away from the positive current collector, and the other end of the second conductive fiber is inserted obliquely into a surface of the third lithium manganese iron phosphate layer facing toward the positive current collector. The first conductive fibers extend along a direction that forms a first acute angle R1 with a first direction, the second conductive fibers extend along a direction that forms a second acute angle R2 with the first direction, and the first direction is a direction in which the positive current collector points to the first lithium manganese iron phosphate layer.
In a second aspect, the present disclosure further provides an energy storage apparatus. The energy storage apparatus includes the multilayer composite electrode sheet of the first aspect.
In a third aspect, the present disclosure further provides a preparation method of a multilayer composite electrode sheet. The preparation method is used to prepare the multilayer composite electrode sheet described in the first aspect. The preparation method includes:
In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the accompanying drawings to be used in the embodiments of the present disclosure will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without paying creative efforts.
100—Multilayer composite electrode sheet; 110—Positive current collector; 120—First lithium manganese iron phosphate layer; 130—Second lithium manganese iron phosphate layer; 140—Third lithium manganese iron phosphate layer; 150—First conductive fiber; 160—Second conductive fiber; 170—Needle injection apparatus.
The technical solutions in the embodiments of the present disclosure will be clearly and thoroughly described below with reference to the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, instead of all the embodiments. All other embodiments obtained based on the embodiments of the present disclosure by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present disclosure.
In the present disclosure, the orientations or positional relationships indicated by the terms “on”, “below”, “left”, “right”, “front”, “back”, “top”, “bottom”, “inside”, “outside”, “vertical”, “horizontal”, “lateral”, “longitudinal”, etc., are orientations or positional relationships shown based on the accompanying drawings. These terms are used primarily to better describe the present disclosure and the embodiments thereof and are not intended to limit that the indicated apparatuses, elements or components have to be located at specific orientations, or to be constructed and operated in the specific orientations.
Moreover, some of the above terms may be used to express other meanings in addition to indicating orientations or positional relationships. For example, the term “on” may also be used to express a certain dependence relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the present disclosure may be understood according to specific circumstances.
In addition, the terms “installed”, “set”, “provided”, “connected”, and “linked” can be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral construction; it may be a mechanical connection or an electrical connection; it may be a direct connection, or an indirect connection through an intermediate medium, or an internal communication between two apparatuses, elements or components. For those of ordinary skill in the art, the specific meanings of these terms in the present disclosure may be understood according to specific circumstances.
Furthermore, the terms “first”, “second”, etc. are used primarily to distinguish between different apparatuses, elements or components (specific types and structures may be the same or different) and are not intended to indicate or imply the relative importance or quantity of the indicated apparatuses, elements or components. Unless otherwise stated, “plurality” means two or more.
As described in the background of the present application, the requirement for the energy density of the energy storage apparatus is getting higher and higher with the development of energy storage apparatuses. Lithium manganese iron phosphate has the same material safety property as lithium iron phosphate, and the capacity per gram of lithium manganese iron phosphate and that of lithium iron phosphate are equal, both are 170 mAh/g. However, compared with lithium iron phosphate, lithium manganese iron phosphate has a higher voltage platform. Therefore, the energy density of lithium manganese iron phosphate is higher than that of lithium iron phosphate.
In order to prepare an energy storage apparatus with a relatively high energy density, in the related art, a positive electrode sheet is prepared as a multilayer composite electrode sheet. For example, a positive electrode slurry is sequentially coated on the positive current collector to form a plurality of lithium manganese iron phosphate layers, which results in a relatively large internal resistance of the formed multilayer composite electrode sheet due to the existence of a connecting interface between every two adjacent lithium manganese iron phosphate layers.
The present disclosure provides a multilayer composite electrode sheet, an energy storage apparatus and a preparation method. By providing first conductive fibers between a first lithium manganese iron phosphate layer and a second lithium manganese iron phosphate layer and inserting the first conductive fibers into the first lithium manganese iron phosphate layer and the second lithium manganese iron phosphate layer respectively in a direction that forms a first acute angle RI with the first direction, not only the connection stability between the first lithium manganese iron phosphate layer and the second lithium manganese iron phosphate layer can be improved due to the first acute angle RI formed between the first conductive fiber and the first direction, but also the interface resistance between the first lithium manganese iron phosphate layer and the second lithium manganese iron phosphate layer can be reduced due to the conductive ability of the first conductive fibers. Similarly, by providing second conductive fibers between the second lithium manganese iron phosphate layer and a third lithium manganese iron phosphate layer and inserting the second conductive fibers into the second lithium manganese iron phosphate layer and the third lithium manganese iron phosphate layer respectively in a direction that forms a second acute angle R2 with the first direction, not only the connection stability between the second lithium manganese iron phosphate layer and the third lithium manganese iron phosphate layer can be improved due to the second acute angle R2 formed between the second conductive fiber and the first direction, but also the interface resistance between the second lithium manganese iron phosphate layer and the third lithium manganese iron phosphate layer can be reduced due to the conductive ability of the second conductive fibers. In this way, the structural strength of the multilayer composite electrode sheet can be improved, and the interface resistance between the plurality of lithium manganese iron phosphate layers can be reduced, thereby reducing the internal resistance of the multilayer composite electrode sheet.
The present application will be described in detail below through specific embodiments.
Referring to
In this embodiment, the first conductive fibers 150 are provided between the first lithium manganese iron phosphate layer 120 and the second lithium manganese iron phosphate layer 130, where one end of the first conductive fiber 150 is inserted into the surface of the first lithium manganese iron phosphate layer 120 facing away from the positive current collector 110, and the other end of the first conductive fiber 150 is inserted into the surface of the second lithium manganese iron phosphate layer 130 facing toward the positive current collector 110. The second conductive fibers 160 are provided between the second lithium manganese iron phosphate layer 130 and the third lithium manganese iron phosphate layer 140, where one end of the second conductive fiber 160 is inserted into the surface of the second lithium manganese iron phosphate layer 130 facing away from the positive current collector 110, and the other end of the second conductive fiber 160 is inserted into the surface of the third lithium manganese iron phosphate layer 140 facing toward the positive current collector 110. Therefore, on the one hand, compared with the second lithium manganese iron phosphate layer 130 being directly attached to the first lithium manganese iron phosphate layer 120, it enables the first lithium manganese iron phosphate layer 120 and the second lithium manganese iron phosphate layer 130 to be connected to each other through the first conductive fibers 150, thereby improving the connection stability between the first lithium manganese iron phosphate layer 120 and the second lithium manganese iron phosphate layer 130. Similarly, it enables the second lithium manganese iron phosphate layer 130 and the third lithium manganese iron phosphate layer 140 to be connected to each other through the second conductive fibers 160, thereby improving the connection stability between the second lithium manganese iron phosphate layer 130 and the third lithium manganese iron phosphate layer 140. Therefore, the structural strength of the multilayer composite electrode sheet 100 is improved.
On another hand, conductive fibers are made of chemical fibers, metal wires or carbon fibers with conductive media, etc. Therefore, by inserting one end of the first conductive fiber 150 into the surface of the first lithium manganese iron phosphate layer 120 facing away from the positive current collector 110 and inserting the other end into the surface of the second lithium manganese iron phosphate layer 130 facing toward the positive current collector 110, and by inserting one end of the second conductive fiber 160 into the surface of the second lithium manganese iron phosphate layer 130 facing away from the positive current collector 110 and inserting the other end into the surface of the third lithium manganese iron phosphate layer 140 facing toward the positive current collector 110, the interface resistance between the first lithium manganese iron phosphate layer 120 and the second lithium manganese iron phosphate layer 130 can be reduced, and the interface resistance between the second lithium manganese iron phosphate layer 130 and the third lithium manganese iron phosphate layer 140 can also be reduced. Thus, the internal resistance of the multilayer composite electrode sheet 100 is reduced, thereby improving the electrochemical performance of the energy storage apparatus formed by the multilayer composite electrode sheet 100.
On still another hand, since the first conductive fibers 150 extend in the direction that forms the first acute angle RI with the first direction, and the second conductive fibers 160 extend in the direction that forms the second acute angle R2 with the first direction, the pulling force exerted on the first lithium manganese iron phosphate layer 120 by the portion of the first conductive fibers 150 inserted into the first lithium manganese iron phosphate layer 120 has a component force in a direction along the layer surface of the first lithium manganese iron phosphate layer 120 and a component force in the first direction. It can be seen that the connection strength between the first conductive fibers 150 and the first lithium manganese iron phosphate layer 120 is improved, and similarly, the connection strength between the first conductive fibers 150 and the second lithium manganese iron phosphate layer 130 is improved, thereby further improving the connection stability between the first lithium manganese iron phosphate layer 120 and the second lithium manganese iron phosphate layer 130. Similarly, the strength of the connection between the second conductive fibers 160 and the second lithium manganese iron phosphate layer 130 as well as the third lithium manganese iron phosphate layer 140 are enhanced. Therefore, the structural strength of the multilayer composite electrode sheet 100 is further improved.
It can be noted that the above-mentioned multilayer composite electrode sheet 100 refers to an electrode sheet with multiple lithium manganese iron phosphate layers provided on the positive current collector 110, that is, three or more lithium manganese iron phosphate layers are formed sequentially on the positive current collector 110, and conductive fibers are provided between every two adjacent lithium manganese iron phosphate layers. In addition, the above-mentioned first lithium manganese iron phosphate layer 120, second lithium manganese iron phosphate layer 130 and third lithium manganese iron phosphate layer 140 can not be understood as a limitation on the number of lithium manganese iron phosphate layers in the multilayer composite electrode sheet 100. Similarly, the first conductive fibers 150 and the second conductive fibers 160 can not be understood as a limitation on the number of layers of conductive fibers in the multilayer composite electrode sheet 100. The number of layers of conductive fibers is related to the number of lithium manganese iron phosphate layers, i.e., the greater the number of lithium manganese iron phosphate layers, for example, a fourth lithium manganese iron phosphate layer, a fifth lithium manganese iron phosphate layer, etc., then the corresponding conductive fibers also include a third conductive fiber, fourth conductive fibers, etc.
In addition, the above-mentioned first direction refers to the direction perpendicular to the layer surface of the first lithium manganese iron phosphate layer 120, i.e., the direction indicated by the arrow X in
In addition, the above-mentioned first acute angle R1 and the second acute angle R2 may be equal or different, which is not limited herein.
Further, there are a plurality of first conductive fibers and a plurality of second conductive fibers. The plurality of first conductive fibers 150 are distributed at intervals on the surface of the first lithium manganese iron phosphate layer 120 facing away from the positive current collector 110. And the greater the number of the first conductive fibers 150, the smaller the spacing between every two adjacent first conductive fibers 150, and the more significant effect on improving the interface resistance between the first lithium manganese iron phosphate layer 120 and the second lithium manganese iron phosphate layer 130 by the first conductive fibers 150. Similarly, the plurality of second conductive fibers 160 are distributed at intervals on the surface of the second lithium manganese iron phosphate layer 130 facing away from the positive current collector 110. And the greater the number of the second conductive fibers 160, the more significant effect on improving the interface resistance between the second lithium manganese iron phosphate layer 130 and the third lithium manganese iron phosphate layer 140 by the second conductive fibers 160. The number of first conductive fibers 150 and the spacing between every two adjacent first conductive fibers 150 are not limited herein, and the number of second conductive fibers 160 and the spacing between every two adjacent second conductive fibers 160 are not limited herein, both of which may be designed by those skilled in the art according to the extent to which the structural strength and interface resistance of the multilayer composite electrode sheet 100 are improved by the first conductive fibers and the second conductive fibers 160, respectively.
In some possible embodiments, the first acute angle R1 and the second acute angle R2 are both in a range between 25° and 55°.
When the first acute angle R1 and the second acute angle R2 are less than 25°, the component force of the first conductive fibers 150 or the second conductive fibers 160 in the direction along the layer surface of the first lithium manganese iron phosphate layer 120 is relatively small, thereby affecting the pulling force exerted on the first lithium manganese iron phosphate layer 120 or the second lithium manganese iron phosphate layer 130 by the first conductive fibers 120 in the direction along the layer surface of the first lithium manganese iron phosphate layer 120, or, affecting the pulling force exerted on the second lithium manganese iron phosphate layer 130 or the third lithium manganese iron phosphate layer 140 by the second conductive fibers 160 in the direction along the layer surface of the first lithium manganese iron phosphate layer 120, thus the structural strength of the multilayer composite electrode sheet 100 is affected. When the first acute angle R1 and the second acute angle R2 are greater than 55°, the component force of the first conductive fibers 150 or the second conductive fibers 160 in the first direction is relatively small, thereby affecting the pulling force exerted on the first lithium manganese iron phosphate layer 120 or the second lithium manganese iron phosphate layer 130 by the first conductive fibers 150 in the first direction, or, affecting the pulling force exerted on the second lithium manganese iron phosphate layer 130 or the third lithium manganese iron phosphate layer 140 by the second conductive fibers 160 in the first direction, thus the connection stability between the plurality of lithium manganese iron phosphate layers in the multilayer composite electrode sheet 100 are affected. Based on this, the first acute angle R1 and the second acute angle R2 are set between 25° and 55°, which can not only ensure the structural strength of the multilayer composite electrode sheet 100, but also improve the connection stability between the plurality of lithium manganese iron phosphate layers.
For example, the first acute angle R1 is 25°, 28°, 30°, 35°, 38°, 40°, 45°, 48°, 50°, 55°, etc. For instance, when the first acute angle R1 and the second acute angle R2 are 45°, the component force in the first direction and the component force in the direction along the layer surface of the first lithium manganese iron phosphate layer 120 provided by the first conductive fibers 150 and the second conductive fibers 160 are the same. In this way, the first conductive fibers 150 and the second conductive fibers 160 provide a better effect on improving the structural strength of the multilayer composite electrode sheet 100 and the connection stability between the plurality of lithium manganese iron phosphate layers.
In some possible embodiments, a cross sectional plane of the stacked first lithium manganese iron phosphate layer 120 and second lithium manganese iron phosphate layer 130 in the first direction is a first section (the area shown by A1 in
Based on the above, the projections of at least two of the first conductive fibers 150 on the first section and the projections of at least two of the second conductive fibers 160 on the second cross section are both in the crossed state, which can improve the structural strength of the first conductive fibers 150 and the second conductive fibers 160, thereby improving the bonding strength between the first lithium manganese iron phosphate layer 120 and the second lithium manganese iron phosphate layer 130, and the bonding strength between the second lithium manganese iron phosphate layer 130 and the third lithium manganese iron phosphate layer 140.
The projections of at least two of the first conductive fibers 150 on the first section are in the crossed state. It can be understood that along the width direction of the multilayer composite electrode sheet 100, every two adjacent first conductive fibers 150 in the plurality of first conductive fibers 150 are arranged to be mirrored with the first direction as a reference line, and every two adjacent first conductive fibers 150 intersect at a position near the middle in the extending directions thereof, that is, the plurality of first conductive fibers 150 form a cross-woven conductive fiber layer in the width direction of the multilayer composite electrode sheet 100. The cross arrangement of the second conductive fibers 160 is the same as the cross arrangement of the first conductive fibers 150, and will not be repeated herein.
In some possible embodiments, referring to
It can be noted that the above-mentioned insertion depth refers to the distance by which the first conductive fibers 150 extends into the first lithium manganese iron phosphate layer 120 and the second lithium manganese iron phosphate layer 130 in the first direction, and/or the distance by which the second conductive fibers 160 extends into the second lithium manganese iron phosphate layer 130 and the third lithium manganese iron phosphate layer 140 in the first direction (i.e., the above-mentioned insertion depth refers to the distance by which the first conductive fibers 150 extends into the first lithium manganese iron phosphate layer 120 and the second lithium manganese iron phosphate layer 130 in the first direction, the above-mentioned insertion depth refers to the distance by which the second conductive fibers 160 extends into the second lithium manganese iron phosphate layer 130 and the third lithium manganese iron phosphate layer 140 in the first direction, or the above-mentioned insertion depth refers to the distance by which the first conductive fibers 150 extends into the first lithium manganese iron phosphate layer 120 and the second lithium manganese iron phosphate layer 130 in the first direction and the distance by which the second conductive fibers 160 extends into the second lithium manganese iron phosphate layer 130 and the third lithium manganese iron phosphate layer 140 in the first direction).
When the first conductive fibers 150 are inserted into the first lithium manganese iron phosphate layer 120 at the same depth as they are inserted into the second lithium manganese iron phosphate layer 130, it can enable the pulling force exerted on the first lithium manganese iron phosphate layer 120 by the first conductive fibers 150 to be equal to the pulling force exerted on the second lithium manganese iron phosphate layer 130 by the first conductive fibers 150. Similarly, when the second conductive fibers are inserted into the second lithium manganese iron phosphate layer 130 at the same depth as they are inserted into the third lithium manganese iron phosphate layer 140, it can enable the pulling force exerted on the second lithium manganese iron phosphate layer 130 by the second conductive fibers 160 to be equal to the pulling force exerted on the third lithium manganese iron phosphate layer 140 by the second conductive fibers 160. The structural strength of the multilayer composite electrode sheet 100 is further improved, and the internal resistance of the multilayer composite electrode sheet 100 is improved.
In some possible embodiments, referring to
The insertion depth of the first conductive fibers 150 into the first lithium manganese iron phosphate layer 120 refers to the distance shown by a in
When the insertion depth of the first conductive fibers 150 into the first lithium manganese iron phosphate layer 120 is less than 2 μm, on the one hand, the effect on improving the structural strength of the multilayer composite electrode sheet 100 is weaker due to the shallower depth of the first conductive fibers 150 inserted into the first lithium manganese iron phosphate layer 120, and thus the effect on improving the interface resistance between the first lithium manganese iron phosphate layer 120 and the second lithium manganese iron phosphate layer 130 is also weaker on the other hand. When the insertion depth of the first conductive fibers 150 into the first lithium manganese iron phosphate layer 120 is greater than 6 μm, although the first conductive fibers 150 are able to enhance the structural strength of the multilayer composite electrode sheet 100, the effect on improving the interface resistance between the first lithium manganese iron phosphate layer 120 and the second lithium manganese iron phosphate layer 130 is weakened and the process difficulty of setting the first conductive fibers 150 is also increased at the same time. Based on this, the first conductive fibers 150 are made to be inserted into the first lithium manganese iron phosphate layer 120 to the depth of 2 μm-6 μm. In this way, the structural strength of the multilayer composite electrode sheet 100 can be improved, the interface resistance can be improved, and the process difficulty of setting the first conductive fibers 150 can be simplified.
Similarly, when the second conductive fiber 160 is set to a range of 2 μm-6 μm, it can not only improve the structural strength of the multilayer composite electrode sheet 100, but also improve the interface resistance, and also simplify the process difficulty of setting the second conductive fibers 160.
Exemplarily, the insertion depth of the first conductive fibers 150 or the second conductive fibers 160 may be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, etc.
In addition, as shown in
An energy storage apparatus prepared by using the multilayer composite electrode sheet 100 in the above embodiments and an energy storage apparatus prepared by using a multilayer composite electrode sheet 100 formed by simple coating (i.e., no conductive fiber is provided between every two adjacent lithium manganese iron phosphate layers of the plurality of the lithium manganese iron phosphate layers) are tested separately. For example, the tests are conducted under the condition that the insertion depths of the first conductive fibers 150 and the second conductive fibers 160 are 2 μm, 3 μm, 4 μm, 5 μm, and 6 μm respectively, and the data shown in
As can be seen from
Moreover, compared with the multilayer composite electrode sheet 100 formed by simple coating in the comparative example, the multilayer composite electrode sheet 100 in the present embodiment has higher structural strength, smaller internal resistance, and better electrochemical performance.
It may be noted that the preparation method of the multilayer composite electrode sheet 100 in the comparative example includes: preparing a first lithium manganese iron phosphate layer 120 (with the same element content of manganese metal as in the first lithium manganese iron phosphate layer 120 in the present embodiment) with a thickness of 30 μm firstly, then coating a positive electrode slurry on the first lithium manganese iron phosphate layer 120 to form a second lithium manganese iron phosphate layer 130 (with the same element content of manganese metal as in the second lithium manganese iron phosphate layer 130 in the present embodiment) with a thickness of 20 μm, and finally coating a positive electrode slurry on the second lithium manganese iron phosphate layer 130 to form a third lithium manganese iron phosphate layer 140 (with the same element content of manganese metal as in the third lithium manganese iron phosphate layer 140 in the present embodiment) with a thickness of 20 μm.
In some possible embodiments, the element content of manganese metal in the third lithium manganese iron phosphate layer 140 is respectively less than the element content of manganese metal in the second lithium manganese iron phosphate layer 130 and the element content of manganese metal in the first lithium manganese iron phosphate layer 120.
The third lithium manganese iron phosphate layer 140 is located on the outermost side of the multilayer composite electrode sheet 100, and during the cycle of the energy storage apparatus, the third lithium manganese iron phosphate layer 140 may be in direct contact with the electrolyte. Therefore, the amount of manganese metal dissolved and precipitated during the charging and discharging cycle of the energy storage apparatus can be reduced by making the element content of manganese metal in the third lithium manganese iron phosphate layer 140 less than the element content of manganese metal in the second lithium manganese iron phosphate layer 130 and the element content of manganese metal in the first lithium manganese iron phosphate layer 120, respectively, thereby improving the cycling performance of the energy storage apparatus.
Exemplarily, the chemical formula of the lithium manganese iron phosphate is LiMnxFe1-xPO4, where the manganese metal in the third lithium manganese iron phosphate layer 140 conforms to 0.2<x<0.4, and the manganese metal in the second lithium manganese iron phosphate layer 130 and the first lithium manganese iron phosphate layer 120 conforms to x>0.4.
In some possible embodiments, the element content of manganese metal in the second lithium manganese iron phosphate layer 130 is less than the element content of manganese metal in the first lithium manganese iron phosphate layer 120.
With the increase in the number of cycles of the energy storage apparatus, the manganese metal in the second lithium manganese iron phosphate layer 130 and the first lithium manganese iron phosphate layer 120 will slowly come into contact with the electrolyte. Therefore, the dissolution and precipitation of manganese metal can be reduced on the premise of ensuring the energy density of the energy storage apparatus by making the element content of manganese metal in the second lithium manganese iron phosphate layer 130 less than the element content of manganese metal in the first lithium manganese iron phosphate layer 120, thereby further improving the cycling performance of the energy storage apparatus.
Following the above example, the manganese metal in the second lithium manganese iron phosphate layer 130 conforms to 0.4<x<0.6, and the manganese metal in the first lithium manganese iron phosphate layer 120 conforms to 0.6<x<0.8.
In some possible embodiments, a thickness of the first lithium manganese iron phosphate layer 120 is in a range of 30 μm-50 μm; and/or, a thickness of the second lithium manganese iron phosphate layer 130 is in a range of 20 μm-30 μm; and/or, a thickness of the third lithium manganese iron phosphate layer 140 is in a range of 30 μm-40 μm (i.e., the thickness of the first lithium manganese iron phosphate layer 120 is in a range of 30 μm-50 μm, the thickness of the second lithium manganese iron phosphate layer 130 is in a range of 20 μm-30 μm, the thickness of the third lithium manganese iron phosphate layer 140 is in a range of 30 μm-40 μm, the thickness of the first lithium manganese iron phosphate layer 120 is in a range of 30 μm-50 μm and the thickness of the second lithium manganese iron phosphate layer 130 is in a range of 20 μm-30 μm, the thickness of the second lithium manganese iron phosphate layer 130 is in a range of 20 μm-30 μm and the thickness of the third lithium manganese iron phosphate layer 140 is in a range of 30 μm-40 μm, the thickness of the first lithium manganese iron phosphate layer 120 is in a range of 30 μm-50 μm and the thickness of the third lithium manganese iron phosphate layer 140 is in a range of 30 μm-40 μm, or the thickness of the first lithium manganese iron phosphate layer 120 is in a range of 30 μm-50 μm and the thickness of the second lithium manganese iron phosphate layer 130 is in a range of 20 μm-30 μm and the thickness of the third lithium manganese iron phosphate layer 140 is in a range of 30 μm-40 μm).
The thickness of the first lithium manganese iron phosphate layer 120 refers to the distance indicated by c in
When the thickness of the first lithium manganese iron phosphate layer 120 is less than 30 μm, the cycling performance of the energy storage apparatus is poor. When the first lithium manganese iron phosphate layer 120 is greater than 50 μm, the thickness of the first lithium manganese iron phosphate layer 120 is relatively thick, which increases the process difficulty of processing the first lithium manganese iron phosphate layer 120. Based on this, the thickness of the first lithium manganese iron phosphate layer 120 is set to a range of 30 μm-50 μm, which can not only improve the cycling performance of the energy storage apparatus, but also simplify the processing difficulty of the first lithium manganese iron phosphate layer 120.
In addition, when the thickness of the second lithium manganese iron phosphate layer 130 is less than 20 μm, it will also affect the cycling performance of the energy storage apparatus. When the thickness of the second lithium manganese iron phosphate layer 130 is greater than 30 μm, it will make the overall thickness of the multilayer composite electrode sheet 100 thicker, thereby affecting the energy density of the energy storage apparatus. Based on this, the thickness of the second lithium manganese iron phosphate layer 130 is set to a range of 20 μm-30 μm, which can not only improve the cycling performance of the energy storage apparatus, but also improve the energy density of the energy storage apparatus.
In addition, when the thickness of the third lithium manganese iron phosphate layer 140 is less than 30 μm, the electrolyte will easily pass through the third lithium manganese iron phosphate layer 140 during the cyclic charging and discharging process of the energy storage apparatus, thus increasing the dissolution and precipitation of manganese metal, which is not conducive to improving the cycling performance of the energy storage apparatus. When the thickness of the third lithium manganese iron phosphate layer 140 is greater than 40 μm, the overall thickness of the multilayer composite electrode sheet will be greater, which is not conducive to improving the energy density of the energy storage apparatus. Based on this, the thickness of the third lithium manganese iron phosphate layer is set to a range of 30 μm-40 μm, which can not only improve the energy density of the energy storage apparatus, but also improve the cycling performance of the energy storage apparatus.
In combination with
In addition, as the thickness of the third lithium manganese iron phosphate layer 140 increases, the peeling force also changes. As can be seen in
Moreover, compared with the multilayer composite electrode sheet 100 formed by simple coating in the comparative example, the multilayer composite electrode sheet 100 in the present embodiment has a higher structural strength, smaller internal resistance, and better electrochemical performance.
Referring to
In step S100, a positive electrode slurry is coated on a positive current collector to form a first lithium manganese iron phosphate layer.
For example, lithium manganese iron phosphate (LiMnxFe1-xPO4 and 0.6<x<0.8), conductive carbon black, and polyvinylidene fluoride are firstly weighed with a mass ratio of 95%:2%:3% and put into a stirred tank, and an appropriate amount of N-methylpyrrolidone is added to the stirred tank. The stirred tank is then started to stir for a certain period of time, for example, 6 hours to obtain a first slurry with an appropriate viscosity. Finally, the first slurry is uniformly coated on the positive current collector 110 through an extrusion manner to form the first lithium manganese iron phosphate layer 120 as shown in
In step 200, first conductive fibers are inserted into a surface of the first lithium manganese iron phosphate layer facing away from the positive current collector in a direction that forms a first acute angle R1 with a first direction, and a portion of the first conductive fiber is made protrude from the surface of the first lithium manganese iron phosphate layer facing away from the positive current collector.
For example, the first conductive fibers 150 are first dissolved in N-methylpyrrolidone, and then a uniformly mixed slurry of the first conductive fibers 150 is obtained by stirring for a certain period of time. Then, an auxiliary apparatus is used to insert the slurry of the first conductive fibers 150 into the surface of the first lithium manganese iron phosphate layer 120 facing away from the positive current collector 110 in the direction that forms a first acute angle R1 with the first direction, and a portion of the first conductive fiber 150 is made protrude from the surface of the first lithium manganese iron phosphate layer 120 facing away from the positive current collector 110 as shown in
In step S300, a positive electrode slurry is coated on a side of the first lithium manganese iron phosphate layer into which the first conductive fibers are inserted, to form a second lithium manganese iron phosphate layer, so that the first conductive fibers protruding from the first lithium manganese iron phosphate layer are inserted into the second lithium manganese iron phosphate layer in the direction that forms the first acute angle RI with the first direction.
For example, lithium manganese iron phosphate (LiMnxFe1-xPO4 and 0.4<x<0.6), conductive carbon black, and polyvinylidene fluoride are firstly weighed with a mass ratio of 95%:2%:3% and put into a stirred tank, and an appropriate amount of N-methylpyrrolidone is added to the stirred tank. The stirred tank is then started to stir for a certain period of time, for example, 6 hours to obtain a second slurry with an appropriate viscosity. Finally, the second slurry is uniformly coated on the first lithium manganese iron phosphate layer 120 through an extrusion manner to form the second lithium manganese iron phosphate layer 130 as shown in
In addition, the surface of the first lithium manganese iron phosphate layer 120 facing away from the positive current collector 110 is provided with the first conductive fiber 150 that forms the first acute angle RI with the first direction, and a portion of the first conductive fiber 150 protrudes from the first lithium manganese iron phosphate layer 120. Therefore, the first conductive fibers 150 protruding from the first lithium manganese iron phosphate layer 120 will be inserted into the second lithium manganese iron phosphate layer 130 in the direction that forms the first acute angle RI with the first direction.
In step S400, the second conductive fibers are inserted into the surface of the second lithium manganese iron phosphate layer facing away from the positive current collector in the direction that forms the second acute angle R2 with the first direction, and a portion of the second conductive fiber is made protrude from the surface of the second lithium manganese iron phosphate layer facing away from the positive current collector.
For example, the second conductive fibers 160 are first dissolved in N-methylpyrrolidone, and then a uniformly mixed slurry of the second conductive fibers 160 is obtained by stirring for a certain period of time. Then, an auxiliary apparatus is used to insert the slurry of the second conductive fibers 160 into the surface of the second lithium manganese iron phosphate layer 130 facing away from the positive current collector 110 in the direction that forms a second acute angle R2 with the first direction, and a portion of the second conductive fiber 160 is made protrude from the surface of the second lithium manganese iron phosphate layer 130 facing away from the positive current collector 110 as shown in
In step 500, a positive electrode slurry is coated on a side of the second lithium manganese iron phosphate layer into which the second conductive fibers are inserted, to form the third lithium manganese iron phosphate layer, so that the second conductive fibers protruding from the second lithium manganese iron phosphate layer are inserted into the third lithium manganese iron phosphate layer in the direction that forms the second acute angle R2 with the first direction.
For example, lithium manganese iron phosphate (LiMnxFe1-xPO4 and 0.2<x<0.4), conductive carbon black, and polyvinylidene fluoride are firstly weighed with a mass ratio of 95%:2%:3% and put into a stirred tank, and an appropriate amount of N-methylpyrrolidone is added to the stirred tank. The stirred tank is then started to stir for a certain period of time, for example, 6 hours to obtain a third slurry with an appropriate viscosity. Finally, the third slurry is uniformly coated on the second lithium manganese iron phosphate layer 130 through an extrusion manner to form the third lithium manganese iron phosphate layer 140 as shown in
In addition, the surface of the second lithium manganese iron phosphate layer 130 facing away from the positive current collector 110 is provided with the second conductive fiber 160 that forms the second acute angle R2 with the first direction, and a portion of the second conductive fiber 160 protrudes from the second lithium manganese iron phosphate layer 130. Therefore, the second conductive fibers 160 protruding from the second lithium manganese iron phosphate layer 130 will be inserted into the third lithium manganese iron phosphate layer 140 in the direction that forms the second acute angle R2 with the first direction.
In this embodiment, before forming the first lithium manganese iron phosphate layer 120 with the second lithium manganese iron phosphate layer 130, first conductive fibers 150 forming a first acute angle R1 with the first direction are disposed on the first lithium manganese iron phosphate layer 120. Before forming the second lithium manganese iron phosphate layer 130 with the third lithium manganese iron phosphate layer 140, second conductive fibers 160 forming a second acute angle R2 with the first direction are disposed on the second lithium manganese iron phosphate layer 130. Therefore, on the one hand, compared with the second lithium manganese iron phosphate layer 130 being directly attached to the first lithium manganese iron phosphate layer 120, it enables the first lithium manganese iron phosphate layer 120 and the second lithium manganese iron phosphate layer 130 to be connected to each other through the first conductive fibers 150, thereby improving the connection stability between the first lithium manganese iron phosphate layer 120 and the second lithium manganese iron phosphate layer 130. Similarly, it enables the second lithium manganese iron phosphate layer 130 and the third lithium manganese iron phosphate layer 140 to be connected to each other through the second conductive fibers 160, thereby improving the connection stability between the second lithium manganese iron phosphate layer 130 and the third lithium manganese iron phosphate layer 140. Therefore, the structural strength of the multilayer composite electrode sheet 100 is improved.
On another hand, conductive fibers are made of chemical fibers, metal wires or carbon fibers with conductive media, etc. Therefore, the interface resistance between the first lithium manganese iron phosphate layer 120 and the second lithium manganese iron phosphate layer 130 can be reduced through the first conductive fibers 150 and the interface resistance between the second lithium manganese iron phosphate layer 130 and the third lithium manganese iron phosphate layer 140 can be reduced through the second conductive fibers 160. Thus, the internal resistance of the multilayer composite electrode sheet 100 is reduced, thereby improving the electrochemical performance of the energy storage apparatus formed by the multilayer composite electrode sheet 100.
On still another hand, since the first conductive fiber 150 forms a first acute angle R1 with the first direction, and the second conductive fiber 160 forms a second acute angle R2 with the first direction, the pulling force exerted on the first lithium manganese iron phosphate layer 120 by the portion of the first conductive fibers 150 inserted into the first lithium manganese iron phosphate layer 120 has a component force in a direction along the layer surface of the first lithium manganese iron phosphate layer 120 and a component force in the first direction. It can be seen that the connection strength between the first conductive fibers 150 and the first lithium manganese iron phosphate layer 120 is improved, and similarly, the connection strength between the first conductive fibers 150 and the second lithium manganese iron phosphate layer 130 is improved, thereby improving the connection stability between the first lithium manganese iron phosphate layer 120 and the second lithium manganese iron phosphate layer 130. Similarly, the connection strength between the second conductive fibers 160 and the second lithium manganese iron phosphate layer 130 as well as the third lithium manganese iron phosphate layer 140 are enhanced. Therefore, the structural strength of the multilayer composite electrode sheet 100 is further improved.
In some possible embodiments, regarding the preparation method of inserting the first conductive fibers 150 into the surface of the first lithium manganese iron phosphate layer 120 facing away from the positive current collector 110 in the direction forming a first acute angle R1 with the first direction in the above embodiment, the preparation method includes: injecting one end of the first conductive fiber 150 into the surface of the first lithium manganese iron phosphate layer 120 facing away from the positive current collector 110 in the direction that forms the first acute angle R1 with the first direction by using a needle injection apparatus 170.
For example, during the process of injecting the first conductive fibers 150 into the first lithium manganese iron phosphate layer 120 by using the needle injection apparatus 170, the injection volume, the movement speed, and the injection frequency of the needle injection apparatus 170 are controlled to extend the slurry of the first conductive fibers 150 into the interior of the first lithium manganese iron phosphate layer 120 so as to insert the first conductive fibers 150 into the interior of the first lithium manganese iron phosphate layer 120.
It can be seen that the operation process of injecting the first conductive fibers 150 into the first lithium manganese iron phosphate layer 120 by using the needle injection apparatus 170 is simple and the operation efficiency is high.
In some possible embodiments, the preparation method includes: injecting, by the needle injection apparatus 170, the first conductive fibers 150 in a state where the first lithium manganese iron phosphate layer 120 is not completely dry.
As a result, the first lithium manganese iron phosphate layer 120 in an incompletely dried state is relatively soft, which enables the first conductive fibers 150 to be inserted into the first lithium manganese iron phosphate layer 120 with less resistance, thereby facilitating the formation of the first conductive fibers 150 in the crossed state.
In addition, the humidity of the first lithium manganese iron phosphate layer 120 in the incompletely dried state is around 30%, for example, the humidity of the first lithium manganese iron phosphate layer 120 in the incompletely dried state is 30%, 31%, etc.
The injection of the second conductive fibers 160 is carried out when the second lithium manganese iron phosphate layer 130 is in an incompletely dried state.
In some possible embodiments, referring to
For example, the principle of inserting the second conductive fibers 160 into the second lithium manganese iron phosphate layer 130 is the same as the principle of inserting the first conductive fibers 150 into the first lithium manganese iron phosphate layer 120, and details may refer to the above description, which will not be repeated herein.
In some possible embodiments, with reference to
In step S210, two groups of the needle injection apparatuses are provided.
For example, each group of needle injection apparatuses 170 may inject multiple first conductive fibers 150 simultaneously, which improves the efficiency of arranging the first conductive fibers 150.
In step S220, the injection directions of the two groups of the needle injection apparatuses are adjusted to be mirrored with respect to the first direction, so that the injection directions of both groups of needle injection apparatuses form the first acute angle RI with the first direction.
For example, before starting the injection, the injection directions of the needle injection apparatuses 170 are first adjusted, either manually or automatically, until the injection directions of the needle injection apparatus 170 form a first acute angle R1 with the first direction, where the first acute angle R1 may be understood as an acute angle or an obtuse angle.
In step S230, the first conductive fibers that form the first acute angle R1 with the first direction are injected into the surface of the first lithium manganese iron phosphate layer facing away from the positive current collector by using the two groups of the needle injection apparatuses, respectively.
For example, the two groups of needle injection apparatuses 170 with the injection directions adjusted are moved to directly above the area where the first lithium manganese iron phosphate layer 120 is to be provided with the first conductive fibers 150. In addition, the needle injection apparatus 170 includes a storage bin that is communicated with the injection head and is used to store the slurry of the first conductive fibers 150. When the needle injection apparatus 170 is pressurized and squeezed, the slurry of the first conductive fibers 150 in the storage bin will be injected into the first lithium manganese iron phosphate layer 120 through the injection head. The first lithium manganese iron phosphate layer 120 provided with the first conductive fibers 150 is then sufficiently dried by an oven (the drying temperature of the oven is about 120° C., and the drying time is about 5 hours) to form the first lithium manganese iron phosphate layer 120 with a special distribution of the first conductive fibers 150.
By providing the first conductive fibers 150 forming the acute angle RI with the first direction, the pulling force exerted on the first lithium manganese iron phosphate layer 120 by the portion of the first conductive fibers 150 inserted into the first lithium manganese iron phosphate layer 120 has a component force in a direction along the layer surface of the first lithium manganese iron phosphate layer 120 and a component force in the first direction. It can be seen that the connection strength between the first conductive fibers 150 and the first lithium manganese iron phosphate layer 120 is improved, and similarly, the connection strength between the first conductive fibers 150 and the second lithium manganese iron phosphate layer 130 is improved, thereby improving the connection stability between the first lithium manganese iron phosphate layer 120 and the second lithium manganese iron phosphate layer 130.
In addition, the arrangement process of the second conductive fibers 160 is the same as the arrangement process of the first conductive fibers 150. The preparation process of the second conductive fibers 160 may refer to the above-mentioned preparation process of the first conductive fibers 150, and the specific preparation process of the second conductive fibers 160 will not be repeated herein.
In some possible embodiments, the adjusting the injection directions of the two groups of the needle injection apparatuses to be mirrored with respect to the first direction, so that the injection directions of both groups of needle injection apparatuses form the first acute angle R1 with the first direction includes:
For example, the injection directions of the two groups of needle injection apparatuses 170 are adjusted respectively, so that the injection directions of the two groups of the needle injection apparatuses 170 are symmetrical with respect to the first direction, and the symmetry herein refers to approximately symmetry.
When the angles between the injection direction of both groups of needle injection apparatuses 170 and the first direction are less than 25°, the component force of the first conductive fibers 150 or the second conductive fibers 160 in the direction along the layer surface of the first lithium manganese iron phosphate layer 120 is smaller, thereby affecting the pulling force exerted on the first lithium manganese iron phosphate layer 120 or the second lithium manganese iron phosphate layer 130 by the first conductive fibers 150 in the direction along the layer surface of the first lithium manganese iron phosphate layer 120, or, affecting the pulling force exerted on the second lithium manganese iron phosphate layer 130 or the third lithium manganese iron phosphate layer 140 by the second conductive fibers 160 in the direction along the layer surface of the first lithium manganese iron phosphate layer 120, thus the structural strength of the multilayer composite electrode sheet 100 is affected. When the angles between the injection direction of both groups of needle injection apparatuses 170 and the first direction are greater than 55°, the component force of the first conductive fibers 150 or the second conductive fibers 160 in the first direction is smaller, thereby affecting the pulling force exerted on the first lithium manganese iron phosphate layer 120 or the second lithium manganese iron phosphate layer 130 by the first conductive fibers 150 in the first direction, or, affecting the pulling force exerted on the second lithium manganese iron phosphate layer 130 or the third lithium manganese iron phosphate layer 140 by the second conductive fibers 160 in the first direction, thus the connection stability between the plurality of lithium manganese iron phosphate layers in the multilayer composite electrode sheet 100 are affected. Based on this, the angles between the injection direction of both groups of needle injection apparatuses 170 and the first direction are set between 25° and 55°, which can not only ensure the structural strength of the multilayer composite electrode sheet 100, but also improve the connection stability between the plurality of lithium manganese iron phosphate layers.
Referring to
In step S10, a positive electrode sheet is prepared.
The positive electrode sheet is prepared by using the preparation method of the multilayer composite electrode sheet 100 in the above embodiment, and details may refer to the description in the above embodiment, which will not be repeated herein.
In step S20, a negative electrode sheet and a separator are provided.
In step S30, the positive electrode sheet, the separator and the negative electrode sheet are assembled and wound to form a wound electrode assembly.
In step S40, a end cap assembly is provided and connected to the wound electrode assembly.
In step S50, a housing is provided, the wound electrode assembly is installed into the housing, and the end cap assembly is welded and fixed to the housing.
In step S60, an electrolyte is provided, the electrolyte is injected into the interior of the housing and encapsulated after battery formation.
In step S70, an outer film is provided to wrap an outer peripheral wall of the housing to form an energy storage apparatus cell.
Since the positive electrode sheet in the energy storage apparatus preparation method is prepared by the preparation method of the multilayer composite electrode sheet 100 in the above embodiment, the energy storage apparatus prepared by the above preparation method of the energy storage apparatus has a high energy density and better overall performance.
Exemplarily, in the electrode sheet performance test, the button battery is assembled for testing. The specific process of assembling the button battery is as follows: first, the positive electrode sheet and the negative electrode sheet are put into a press machine respectively to be pressed, so that the vacuum bubbles in the positive electrode sheet and the negative electrode sheet are eliminated. Then, the pressed positive electrode sheet and negative electrode sheet are cut to form a positive electrode disc with a first preset diameter and a negative electrode disc with a second preset diameter (where the first preset diameter is smaller than the second preset diameter). The positive electrode sheet and the negative electrode sheet are cut by using a punch machine, respectively. Exemplarily, the diameter of the positive electrode disc is 15 mm, i.e., the first preset diameter is 15 mm, and the diameter of the negative electrode disc is 18 mm, i.e., the second preset diameter is 18 mm. Finally, the positive electrode disc and negative electrode disc are assembled in a glove box filled with protective gas (e.g., argon), and the positive electrode disc, negative electrode disc, polyethylene separator and other components are assembled together and then injected with electrolyte to form an energy storage apparatus. The electrolyte refers to a solution obtained by using 1 mol/L lithium hexafluorophosphate dissolved in a mixed solvent of ethylene carbonate and diethyl carbonate with a molar ratio of 1:1. By having the first preset diameter smaller than the second preset diameter, lithium deposition on the negative electrode sheet can be avoided, thereby ensuring the performance of the prepared energy storage apparatus.
An embodiment of the present application further provides an energy storage apparatus, which includes the multilayer composite electrode sheet 100 in the above embodiment.
It can be noted that the energy storage apparatus may be a lithium battery, a button battery, a power battery and the like. The above-mentioned energy storage apparatus may also be prepared and formed by using the above-mentioned preparation method of the energy storage apparatus.
As a result, the energy storage apparatus has a high energy density and good overall performance.
Finally, it can be noted that the above embodiments are only used to illustrate the technical solutions of the present disclosure, but not to limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art can understand that they may still modify the technical solutions recorded in the foregoing embodiments, or make equivalent substitutions for part or all of the technical features therein. However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202310681246.9 | Jun 2023 | CN | national |
