Patent Application
20160043361
The present application claims priority to Chinese patent application No. CN201410381717.5, filed on Aug. 5, 2014, which is incorporated herein by reference in its entirety.
The present disclosure relates to a field of an electrochemistry technology, and more specifically to an electrochemical energy storage device.
Due to advantages, such as a high operating voltage, a small volume, a light weight, a high specific capacity, non-memory effect, non-pollution, a small self-discharge and a long cycle life, a lithium-ion secondary battery has been widely applied in various fields, such as communication, electrical appliance, electronic information, power device, storage device and the like, and as the society develops rapidly, people present higher requirements on the lithium-ion secondary battery in energy density, charge-discharge rate, cycle life and safety performance.
Drop test is a relatively strict safety test of the lithium-ion secondary battery. Problems, that top sealing is burst out, electrolyte is leaked, separator wrinkles, internal short circuit is established, tab is broken, and so on, easily occur when the lithium-ion secondary battery is dropped. At present, using an adhesive tap to tie a cell up or enlarging a region for the top sealing may resolve the problems, that top sealing is burst out, electrolyte is leaked and tab is broken, but the above two methods will decrease the energy density of the lithium-ion secondary battery, and cannot resolve the problems that separator shrinks and wrinkles and internal short circuit is established when the lithium-ion secondary battery is dropped. By adhering the conventional double-sided adhesive paper to a position between the cell and a package may resolve the above problems when the lithium-ion secondary battery is dropped, but because the two surfaces of the adhesive paper are all adhesive, it is more difficult to put the cell into the package.
In view of the problems existing in the background of the present disclosure, an object of the present disclosure is to provide an electrochemical energy storage device, the electrochemical energy storage device of the present disclosure can not only fixedly connect the cell to the package so as to resolve the problems during the drop test, but also can resolve the problem that the cell is difficult to put into the package because the two surfaces of the binding material are all adhesive.
In order to achieve the above object, the present disclosure provides an electrochemical energy storage device, which comprises a cell, an electrolyte and a package. The cell comprises a positive electrode plate, a negative electrode plate and a separator positioned between the to positive electrode plate and the negative electrode plate; the electrolyte immerses the cell; the package accommodates the cell and the electrolyte. The electrochemical energy storage device further comprises a binding material positioned between the cell and the package. The binding material comprises a first adhesive layer and a second functional layer. The first adhesive layer is directly or indirectly adhered and positioned on an outer surface of the cell; the second functional layer is positioned on a side of the first adhesive layer opposite to a surface of the first adhesive layer directly or indirectly adhered on the cell, the second functional layer is not adhered to the package before a pressure is applied on the electrochemical energy storage device, and the second functional layer is adhered to the package after the pressure is applied on the electrochemical energy storage device.
The present disclosure has following beneficial effects:
1. The second functional layer of the binding material of the present disclosure is not adhered to the package before a pressure is applied on the electrochemical energy storage device, therefore the problem that the cell is difficult to put into the package because of the two adhesive surfaces of the binding material is resolved.
2. After the binding material of the present disclosure is put into the package, and the second functional layer is adhered to the package under a pressure, therefore the cell can be fixedly connected to the package and the problems during the drop test can be resolved.
Reference numerals of the embodiments are represented as follows:
Hereinafter an electrochemical energy storage device and examples, comparative examples and testing processes and test results according to the present disclosure will be described in detail.
Firstly, an electrochemical energy storage device according to a first aspect of the present disclosure will be described. Referring to
In the electrochemical energy storage device according to the first aspect of the present disclosure, the second functional layer 31 of the binding material 3 of the present disclosure is not adhered to the package 2 before a pressure is applied on the electrochemical energy storage device, therefore the problem that the cell is difficult to put into the package 2 because of the two adhesive surfaces of the binding material 3 can be resolved; after the binding material 3 of the present disclosure is put into the package 2, and the second functional layer 32 is adhered to the package 2 under the pressure, therefore the cell 1 can be fixedly connected to the package 2 and the problems during the drop test can be resolved.
In the electrochemical energy storage device according to the first aspect of the present disclosure, the electrochemical energy storage device may be one selected from lithium-ion secondary battery, super capacitor, fuel cell and solar battery.
In the electrochemical energy storage device according to the first aspect of the present disclosure, the cell 1 may be a wound cell, a laminated cell, or a laminated-wound cell.
In the electrochemical energy storage device according to the first aspect of the present disclosure, the binding material 3 may be provided at any position between the cell 1 and the package 2. For example, the binding material 3 may be adhered and positioned at an ending 11 of the wound cell 1, or the binding material 3 may be adhered and positioned at any position of the outer surface of the cell 1 facing the package 2, the binding materials 3 may be adhered and positioned respectively across and surround the top and the bottom of the cell 1 and perpendicular to the width direction of the cell 1 at the same time, and any edge or corner of the cell 1 may be adhered with the binding material 3, or several positions each may be adhered with the binding material 3 at the same time. An area of the binding material 3 may be not more than a surface area of the cell 1, a shape of the binding material 3 may be any shapes, such as rectangular shape, circular shape, diamond shape, triangular shape, annular shape, gyrose shape, porous shape and the like.
In the electrochemical energy storage device according to the first aspect of the present disclosure, the package 2 may be one selected from soft package and hard package.
In the electrochemical energy storage device according to the first aspect of the present disclosure, referring to
In the electrochemical energy storage device according to the first aspect of the present disclosure, a base material of the adhesive paper 4 having single adhesive surface or double adhesive surfaces may be at least one selected from a group consisting of polyethylene terephthalate (PET), oriented polypropylene (PP) and polyimide (PI); an adhesive of the adhesive paper 4 having single adhesive surface or double adhesive surfaces may be at least one selected from a group consisting of acrylic resin, thermosetting polyurethane, silicone, natural rubber and synthetic rubber.
In the electrochemical energy storage device according to the first aspect of the present disclosure, a thickness of the adhesive paper 4 may be 3 μm˜20 μm.
In the electrochemical energy storage device according to the first aspect of the present disclosure, a thickness of the first adhesive layer 31 may be 3 μm˜40 μm.
In the electrochemical energy storage device according to the first aspect of the present disclosure, a thickness of the second functional layer 32 may be 3 μm˜40 μm.
In the electrochemical energy storage device according to the first aspect of the present disclosure, the pressure applied on the electrochemical energy storage device may be 0.2 MPa˜1.5 MPa.
In the electrochemical energy storage device according to the first aspect of the present disclosure, the electrochemical energy storage device is at the room temperature or a temperature above the room temperature when the pressure is applied on the electrochemical energy storage device.
In the electrochemical energy storage device according to the first aspect of the present disclosure, at least one of the first adhesive layer 31 and the second functional layer 32 may have flowability. Take the first adhesive layer 31 may have flowability as an example, in this situation, after the cell 1 is put into the package 2, and under the pressure, since the first adhesive layer 31 has flowability, therefore a part of the adhesive material in the first adhesive layer 31 such as the temperature sensitive adhesive and pressure sensitive adhesive having initial adhesion later described, is extruded and overflowed out from the outer peripheral of the initial position of the first adhesive layer 31 under the pressure, thereby not only decreasing the thickness of the binding material 3, but also increasing the adhesive area, so the cell 1 and the package 2 are more fixedly connected.
In the electrochemical energy storage device according to the first aspect of the present disclosure, the first adhesive layer 31 may be at least one selected from a group consisting of a temperature sensitive adhesive and a pressure sensitive adhesive having initial adhesion. The temperature sensitive adhesive may be at least one selected from a group consisting of terpine resin, petroleum resin, naphthenoid oil, polyolefine, polyvinyl butyral, polyamide, ethylene-vinyl acetate copolymer (EVA), styrene-isopentadiene-styrene block copolymer (SIS) and polyester, the naphthenoid oil cannot be used independently. The polyolefine may be at least one selected from a group consisting of polypropylene (PP), polybutylene (PB), polyisoprene (PI) and polystyrene (PS). The polyamide may be at least one selected from a group consisting of polyacrylamide (PAM), polycaprolactam (PA-6) and epoxy polyamide. The polyester may be at least one selected from a group consisting of thermoplastic polyurethane (TPU), nitrile butadiene rubber-phenol formaldehyde and ethylene-phenol formaldehyde. The pressure sensitive adhesive having initial adhesion may be at least one selected from a group consisting of acrylic resin, thermosetting polyurethane, silicone, natural rubber and synthetic rubber. The pressure sensitive adhesive having initial adhesion refers to that at room temperature, when a brief contact is formed between an object and a pressure sensitive adhesive under an acupressure, the pressure sensitive adhesive will perform adhesive fuction on the object.
In the electrochemical energy storage device according to the first aspect of the present disclosure, the first adhesive layer 31 may further comprise an inorganic additive. The inorganic additive may be at least one selected from a group consisting of Al2O3 and SiO2.
In the electrochemical energy storage device according to the first aspect of the present disclosure, the second functional layer 32 may be selected from a pressure sensitive adhesive having no initial adhesion or a composite material composited by the pressure sensitive adhesive having no initial adhesion and a temperature sensitive adhesive having no adhesion at room temperature. The pressure sensitive adhesive having no initial adhesion may be at least one selected from a group consisting of ethylene-butylenes-styrene linear triblock copolymer (SEBS), styrene-butadiene block copolymer (SEPS) and epoxidized styrene-isopentadiene-styrene block copolymer (ESIS). The temperature sensitive adhesive having no adhesion at room temperature may be at least one selected from a group consisting of polyolefine, polyvinyl butyral, polyamide, ethylene-vinyl acetate copolymer (EVA), styrene-isopentadiene-styrene block copolymer (SIS) and polyester. The polyolefine may be at least one selected from a group consisting of polypropylene (PP), polybutylene (PB), polyisoprene (PI) and polystyrene (PS). The polyamide may be at least one selected from a group consisting of polyacrylamide (PAM), polycaprolactam (PA-6) and epoxy polyamide. The polyester may be at least one selected from a group consisting of thermoplastic polyurethane (TPU), nitrile butadiene rubber-phenol formaldehyde and ethylene-phenol formaldehyde. The pressure sensitive adhesive having no initial adhesion refers to that at room temperature, when a brief contact is formed between an object and a pressure sensitive adhesive under an acupressure, the pressure sensitive adhesive doesn't perform adhesive function on the object.
In the electrochemical energy storage device according to the first aspect of the present disclosure, the second functional layer 32 may further comprise an inorganic additive. The inorganic additive may be at least one selected from a group consisting of Al2O3 and SiO2.
In the electrochemical energy storage device according to the first aspect of the present disclosure, the binding material 3 may further comprise a substrate 33 positioned between the first adhesive layer 31 and the second functional layer 32, referring to
In the electrochemical energy storage device according to the first aspect of the present disclosure, a thickness of the substrate 33 may be not more than 20 μm.
In the electrochemical energy storage device according to the first aspect of the present disclosure, the substrate 33 may be at least one selected from a group consisting of polyethylene terephthalate (PET), oriented polyolefine and polyimide (PI). The oriented polyolefine may be at least one selected from a group consisting of oriented polyethylene (PE), oriented polypropylene (PP), oriented polybutylene (PB), oriented ethylene-propylene copolymer and oriented polystyrene (PS).
In the electrochemical energy storage device according to the first aspect of the present disclosure, referring to
In the electrochemical energy storage device according to the first aspect of the present disclosure, the covering layer 34 may be at least one selected from a group consisting of Al2O3, MgO and Mg3N2.
In the electrochemical energy storage device according to the first aspect of the present disclosure, a thickness of the covering layer 34 may be 2 μm˜10 μm.
In the electrochemical energy storage device according to the first aspect of the present disclosure, the use of the inorganic additive may effectively control the homogeneous flow of the first adhesive layer 31 and the second functional layer 32, therefore the binding material 3 will not flow to a sealing edge of the cell 1 under heating and pressing, thereby resolving the problem of poor sealing caused by the inhomogeneous flow of the binding material 3.
Then examples and comparative examples of electrochemical energy storage devices according to the present disclosure would be described, the first binding material and the second binding material were two different types of the binding material 3 of the present disclosure.
1. Preparation of a Positive Electrode Plate
LiCoO2, conductive carbon and polyvinylidene fluoride according to a weight ratio of 96:1:3 were uniformly mixed with N-methyl pyrrolidone to form a positive electrode slurry, then the positive electrode slurry was coated, dried and pressed to form a positive electrode plate with a thickness of 100 μm.
2. Preparation of a Negative Electrode Plate
Graphite, conductive carbon, sodium carboxymethyl cellulose and styrene butadiene rubber according to a weight ratio of 97:1:1:1 were uniformly mixed with deionized water to form a negative electrode slurry, then the negative electrode slurry was coated, dried and pressed to form a negative electrode plate with a thickness of 90 μm.
3. Preparation of an Electrolyte
Ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) according to a weight ratio of 20:20:50:10 were uniformly mixed to form a non-aqueous organic solvent, LiPF6 was added with a concentration of 1.0 mol/L, finally an electrolyte was completed.
4. Preparation of a Cell
The prepared positive electrode plate, a PP separator and the negative electrode plate were wound together to form a wound cell with a thickness of 3.5 mm, a width of 48 mm and a length of 80 mm.
5. Preparation of a Binding Material
A length of the binding material was 75 mm, and a width of the binding material was 8 mm;
the first adhesive layer was polybutylene (PB) having added terpine resin, the thickness of the first adhesive layer was 20 μm;
the second functional layer was a mixture of ethylene-vinyl acetate copolymer (EVA) and ethylene-butylenes-styrene linear triblock copolymer (SEBS) according to a mass ratio of 9:1, the thickness of the second functional layer was 3 μm;
the substrate was oriented polypropylene (PP), the substrate was positioned between the first adhesive layer and the second functional layer, the thickness of the substrate was 10 μm.
6. Preparation of a Lithium-Ion Secondary Battery
The first adhesive layer of the binding material was directly adhered at an ending of the wound cell, and then the wound cell was put into a package, the electrolyte was injected, then at 60° C., a 1 MPa surface pressure was applied on a surface of the package of the wound cell corresponding to a position where the binding material was adhered, to make the second functional layer adhered with the inner surface of the package, finally a lithium-ion secondary battery was completed.
The lithium-ion secondary battery was prepared the same as that in example 1 except the following:
5. Preparation of a Binding Material
The thickness of the second functional layer was 20 μm.
The lithium-ion secondary battery was prepared the same as that in example 1 except the following:
5. Preparation of a Binding Material
The thickness of the second functional layer was 40 μm.
The lithium-ion secondary battery was prepared the same as that in example 1 except the following:
5. Preparation of a binding material (referring to
(1) First Binding Material
The length of the first binding material was 75 mm, the width of the first binding material was 8 mm;
the first adhesive layer was polybutylene (PB) having added terpine resin, the thickness of the first adhesive layer was 20 μm;
the second functional layer was a mixture of ethylene-vinyl acetate copolymer (EVA) and ethylene-butylenes-styrene linear triblock copolymer (SEBS) according to a mass ratio of 9:1, the thickness of the second functional layer was 20 μm;
the substrate was oriented polypropylene (PP), the substrate was positioned between the first adhesive layer and the second functional layer, the thickness of the substrate was 10 μm.
(2) Second Binding Material
The length of the second binding material was 30 mm, the width of the second binding material was 8 mm;
the first adhesive layer was polybutylene (PB) having added terpine resin, the thickness of the first adhesive layer was 20 μm;
the second functional layer was a mixture of ethylene-vinyl acetate copolymer (EVA) and ethylene-butylenes-styrene linear triblock copolymer (SEBS) according to a mass ratio of 9:1, the thickness of the second functional layer was 20 μm;
the substrate was oriented polypropylene (PP), the substrate was positioned between the first adhesive layer and the second functional layer, the thickness of the substrate was 10 μm.
6. Preparation of a Lithium-Ion Secondary Battery
Referring to
The lithium-ion secondary battery was prepared the same as that in example 4 except the following:
5. Preparation of a Binding Material
(1) First Binding Material
The length of the first binding material was 75 mm, the width of the first binding material was 8 mm;
the first adhesive layer was polybutylene (PB) having added terpine resin, the thickness of the first adhesive layer was 20 μm;
the second functional layer was a mixture of ethylene-vinyl acetate copolymer (EVA) and ethylene-butylenes-styrene linear triblock copolymer (SEBS) according to a mass ratio of 9:1, the thickness of the second functional layer was 20 μm;
the substrate was oriented polypropylene (PP), the substrate was positioned between the first adhesive layer and the second functional layer, the thickness of the substrate was 10 μm.
(2) Second Binding Material
The length of the second binding material was 30 mm, the width of the second binding material was 8 mm;
the first adhesive layer was polybutylene (PB) having added terpine resin, the thickness of the first adhesive layer was 20 μm;
the second functional layer was a mixture of ethylene-vinyl acetate copolymer (EVA) and ethylene-butylenes-styrene linear triblock copolymer (SEBS) according to a mass ratio of 9:1, the thickness of the second functional layer was 20 μm;
the substrate was oriented polypropylene (PP), the substrate was positioned between the first adhesive layer and the second functional layer, the thickness of the substrate was 10 μm.
(3) Green Glue
The length of the green glue was 75 mm, the width of the green glue was 8 mm, the green glue comprised polyethylene terephthalate (PET) and acrylic resin, the thickness of the polyethylene terephthalate (PET) was 7 μm, the thickness of the acrylic resin was 8 μm.
6. Preparation of a Lithium-Ion Secondary Battery
Referring to
The lithium-ion secondary battery was prepared the same as that in example 4 except the following:
5. Preparation of a Binding Material
(1) First Binding Material
The second functional layer was a mixture of ethylene-vinyl acetate copolymer (EVA) and epoxidized styrene-isopentadiene-styrene block copolymer (ESIS) according to a mass ratio of 9:4.
(2) Second Binding Material
The second functional layer was a mixture of ethylene-vinyl acetate copolymer (EVA) and epoxidized styrene-isopentadiene-styrene block copolymer (ESIS) according to a mass ratio of 9:4.
6. Preparation of a Lithium-Ion Secondary Battery
Then the wound cell having the first binding material and the second binding materials was put into the package, the electrolyte was injected, then at 25° C., a 1 MPa surface pressure was applied respectively on surfaces of the package of the wound cell corresponding to positions where the first binding material and the second binding materials were adhered, to make the second functional layer adhered with the inner surface of the package, finally a lithium-ion secondary battery was completed.
The lithium-ion secondary battery was prepared the same as that in example 4 except the following:
5. Preparation of a Binding Material
(1) First Binding Material
The first adhesive layer was styrene-isopentadiene-styrene block copolymer (SIS) having added terpine resin, the thickness of the first adhesive layer was 30 μm;
the second functional layer was a mixture of styrene-isopentadiene-styrene block copolymer (SIS) and styrene-butadiene block copolymer (SEPS) according to a mass ratio of 1:1, the thickness of the second functional layer was 40 μm;
the substrate was polyethylene terephthalate (PET).
(2) Second Binding Material
The first adhesive layer was styrene-isopentadiene-styrene block copolymer (SIS) having added terpine resin, the thickness of the first adhesive layer was 30 μm;
the second functional layer was a mixture of styrene-isopentadiene-styrene block copolymer (SIS) and styrene-butadiene block copolymer (SEPS) according to a mass ratio of 1:1, the thickness of the second functional layer was 40 μm; the substrate was polyethylene terephthalate (PET).
6. Preparation of a Lithium-Ion Secondary Battery
Then the wound cell having the first binding material and the second binding materials was put into the package, the electrolyte was injected, then at 85° C., a 1 MPa surface pressure was applied respectively on surfaces of the package of the wound cell corresponding to positions where the first binding material and the second binding materials were adhered, to make the second functional layer adhered with the inner surface of the package, finally a lithium-ion secondary battery was completed.
The lithium-ion secondary battery was prepared the same as that in example 7 except the following:
5. Preparation of a Binding Material
(1) First Binding Material
The first adhesive layer was styrene-isopentadiene-styrene block copolymer (SIS) having added terpine resin and Al2O3;
the second functional layer was a mixture of styrene-isopentadiene-styrene block copolymer (SIS) having added Al2O3 and styrene-butadiene block copolymer (SEPS).
(2) Second Binding Material
The first adhesive layer was styrene-isopentadiene-styrene block copolymer (SIS) having added terpine resin and Al2O3;
the second functional layer was a mixture of styrene-isopentadiene-styrene block copolymer (SIS) having added Al2O3 and styrene-butadiene block copolymer (SEPS).
The lithium-ion secondary battery was prepared the same as that in example 4 except the following:
5. Preparation of a Binding Material
(1) First Binding Material
The second functional layer was styrene-butadiene block copolymer (SEPS);
the substrate was polyethylene terephthalate (PET).
(2) Second Binding Material
The second functional layer was styrene-butadiene block copolymer (SEPS);
the substrate was polyethylene terephthalate (PET).
6. Preparation of a Lithium-Ion Secondary Battery
Then the wound cell having the first binding material and the second binding materials was put into the package, the electrolyte was injected, then at 25° C., a 0.2 MPa surface pressure was applied respectively on surfaces of the package of the wound cell corresponding to positions where the first binding material and the second binding materials were adhered, to make the second functional layer adhered with the inner surface of the package, finally a lithium-ion secondary battery was completed.
The lithium-ion secondary battery was prepared the same as that in example 9 except the following:
6. Preparation of a Lithium-Ion Secondary Battery
The surface pressure applied was 0.6 MPa.
The lithium-ion secondary battery was prepared the same as that in example 9 except the following:
6. Preparation of a Lithium-Ion Secondary Vattery
The surface pressure applied was 0.8 MPa.
The lithium-ion secondary battery was prepared the same as that in example 4 except the following:
5. Preparation of a Binding Material
(1) First Binding Material
The width of the first binding material was 11 mm;
the first adhesive layer was polybutylene (PB) having added petroleum resin, the thickness of the first adhesive layer was 10 μm;
the second functional layer was a mixture of thermoplastic polyurethane (TPU) and styrene-butadiene block copolymer (SEPS) according to a mass ratio of 8:2, the thickness of the second functional layer was 10 μm;
the substrate was polyimide (PI), the thickness of the substrate was 8 μm.
(2) Second Binding Material
The first adhesive layer was polyacrylamide (PAM) having added petroleum resin;
the second functional layer was a mixture of ethylene-vinyl acetate copolymer (EVA) and styrene-butadiene block copolymer (SEPS) according to a mass ratio of 8:2, the thickness of the second functional layer was 40 μm;
the thickness of the substrate was 8 μm.
6. Preparation of a Lithium-Ion Secondary Battery
Then the wound cell having the first binding material and the second binding materials was put into the package, the electrolyte was injected, then at 60° C., a 1.5 MPa surface pressure was applied respectively on surfaces of the package of the wound cell corresponding to positions where the first binding material and the second binding materials were adhered, to make the second functional layer adhered with the inner surface of the package, finally a lithium-ion secondary battery was completed.
The lithium-ion secondary battery was prepared the same as that in example 12 except the following:
5. Preparation of a Binding Material
(1) First Binding Material
The first adhesive layer was polybutylene (PB) having added naphthenoid oil;
there was no substrate.
(2) Second Binding Material
The width of the second binding material was 11 mm;
the thickness of the second functional layer was 20 μm;
there was no substrate.
6. Preparation of a Lithium-Ion Secondary Battery
Then the wound cell having the first binding material and the second binding materials was put into the package, the electrolyte was injected, then at 85° C., a 0.2 MPa surface pressure was applied respectively on surfaces of the package of the wound cell corresponding to positions where the first binding material and the second binding materials were adhered, to make the second functional layer adhered with the inner surface of the package, finally a lithium-ion secondary battery was completed.
The lithium-ion secondary battery was prepared the same as that in example 4 except the following:
5. Preparation of a Binding Material
(1) First Binding Material
The width of the first binding material was 11 mm;
the first adhesive layer was polycaprolactam (PA-6) having added naphthenoid oil, the thickness of the first adhesive layer was 10 μm;
the second functional layer was styrene-butadiene block copolymer (SEPS), the thickness of the second functional layer was 10 μm;
the substrate was polyethylene terephthalate (PET);
the covering layer was Al2O3, the thickness of the covering layer was 5 μm.
(2) Second Binding Material
The first adhesive layer was polyacrylamide (PAM) having added petroleum resin, the thickness of the first adhesive layer was 10 μm;
the second functional layer was a mixture of ethylene-vinyl acetate copolymer (EVA) and styrene-butadiene block copolymer (SEPS) according to a mass ratio of 8:2;
the substrate was polyethylene terephthalate (PET);
the covering layer was MgO, the thickness of the covering layer was 10 μm.
6. Preparation of a Lithium-Ion Secondary Battery
Then the wound cell having the first binding material and the second binding materials was put into the package, the electrolyte was injected, then at 75° C., a 1.5 MPa surface pressure was applied respectively on surfaces of the package of the cell corresponding to positions where the first binding material and the second binding materials were adhered, to make the second functional layer adhered with the inner surface of the package, finally a lithium-ion secondary battery was completed.
The lithium-ion secondary battery was prepared the same as that in example 4 except the following:
5. Preparation of a Binding Material
(1) First Binding Material
The width of the first binding material was 12 μm;
the first adhesive layer was polyisoprene (PI) having added naphthenoid oil;
the second functional layer was polypropylene (PP) having added petroleum resin;
the substrate was polyethylene terephthalate (PET), the thickness of the substrate was 20 μm;
the covering layer was Al2O3, the thickness of the covering layer was 5 μm.
(2) Second Binding Material
The width of the second binding material was 12 μm;
the first adhesive layer was polyisoprene (PI) having added naphthenoid oil;
the second functional layer was polypropylene (PP) having added petroleum resin;
the substrate was polyethylene terephthalate (PET), the thickness of the substrate was 20 μm;
the covering layer was Mg3N2, the thickness of the covering layer was 5 μm.
6. Preparation of a Lithium-Ion Secondary Battery
Then the wound cell having the first binding material and the second binding materials was put into the package, the electrolyte was injected, then at 25° C., a 1.0 MPa surface pressure was applied respectively on surfaces of the package of the wound cell corresponding to positions where the first binding material and the second binding materials were adhered, to make the second functional layer adhered with the inner surface of the package, finally a lithium-ion secondary battery was completed.
The lithium-ion secondary battery was prepared the same as that in example 4 except the following:
4. Preparation of a Cell
The prepared positive electrode plate, a PP separator and the negative electrode plate were laminated together to form a laminated cell with a thickness of 3.5 mm, a width of 48 mm and a length of 80 mm.
5. Preparation of a Binding Material
(1) First Binding Material
The first adhesive layer was polyisoprene (PI) having added naphthenoid oil;
the second functional layer was a mixture of polypropylene (PP) and styrene-butadiene block copolymer (SEPS) according to a mass ratio of 8:2;
the substrate was polyethylene terephthalate (PET), the thickness of the substrate was 20 μm.
(2) Second Binding Material
The first adhesive layer was polyisoprene (PI) having added naphthenoid oil;
the second functional layer was a mixture of polypropylene (PP) and styrene-butadiene block copolymer (SEPS) according to a mass ratio of 8:2;
the substrate was polyethylene terephthalate (PET), the thickness of the substrate was 20 μm.
6. Preparation of a Lithium-Ion Secondary Battery
Referring to
The lithium-ion secondary battery was prepared the same as that in example 4 except the following:
5. Preparation of a binding material
(1) First Binding Material
The first adhesive layer was terpine resin;
the second functional layer was a mixture of ethylene-vinyl acetate copolymer (EVA) and epoxidized styrene-isopentadiene-styrene block copolymer (ESIS) according to a mass ratio of 9:4.
(2) Second Binding Material
The first adhesive layer was terpine resin;
the second functional layer was a mixture of ethylene-vinyl acetate copolymer (EVA) and epoxidized styrene-isopentadiene-styrene block copolymer (ESIS) according to a mass ratio of 9:4.
The lithium-ion secondary battery was prepared the same as that in example 4 except the following:
5. Preparation of a Binding Material
(1) First Binding Material
The first adhesive layer was polyisoprene (PI) having added naphthenoid oil;
the second functional layer was a mixture of ethylene-vinyl acetate copolymer (EVA) and styrene-butadiene block copolymer (SEPS) according to a mass ratio of 8:2;
the substrate was polyethylene terephthalate (PET), the thickness of the substrate was 20 μm
(2) Second Binding Material
The first adhesive layer was polyisoprene (PI) having added naphthenoid oil;
the second functional layer was a mixture of ethylene-vinyl acetate copolymer (EVA) and styrene-butadiene block copolymer (SEPS) according to a mass ratio of 8:2;
the substrate was polyethylene terephthalate (PET), the thickness of the substrate was 20 μm.
6. Preparation of an Adhesive Paper
The adhesive paper was a green glue with a length of 75 mm and a width of 8 mm, the green glue comprised polyethylene terephthalate (PET) as base material and acrylic resin as adhesive, the thickness of the polyethylene terephthalate (PET) was 7 μm, the thickness of the acrylic resin was 8 μm.
7. Preparation of a Lithium-Ion Secondary Battery
Referring to
The lithium-ion secondary battery was prepared the same as that in example 2 except the following:
5. Preparation of a Binding Material
A width of the binding material was 20 mm;
the first adhesive layer was acrylic resin;
the second functional layer was acrylic resin;
the substrate was polyethylene terephthalate (PET).
6. Preparation of a Lithium-Ion Secondary Battery
The wound cell having the binding material was put into the package, the electrolyte was injected, then at 25° C., a 1.0 MPa surface pressure was applied on a surface of the package of the wound cell corresponding to a position where the binding material was adhered, to make the second functional layer adhered with the inner surface of the package, finally a lithium-ion secondary battery was completed.
Next testing processes and test results of lithium-ion secondary batteries of the present disclosure would be described.
1. Testing of the Thickness of the Lithium-Ion Secondary Batteries
The main body of the lithium-ion secondary battery was put into a thickness tester, the tabs were exposed, the value of the thickness of the main body of the lithium-ion secondary battery was read and recorded, the thickness of the main body of the lithium-ion secondary battery was the thickness of the position where the thickness of the lithium-ion secondary battery was the biggest (that was the overlap area of the tab and the cell).
2. Testing of the Drop Test of the Lithium-Ion Secondary Batteries
The lithium-ion secondary battery was fixed into a drop test clamp with double-sided adhesive, the initial voltage of the lithium-ion secondary battery was tested and recorded as V0, the six surfaces of the drop test clamp was sequentially numbered as No. 1, No. 2, No. 3, No. 4, No. 5 and No. 6, and the four corners of the drop test clamp was sequentially numbered as No. C1, No. C2, No. C3 and No. C4.
At 25° C., the drop test clamp was positioned on a test platform with a height of 1.5 m, the lithium-ion secondary battery was dropped sequentially according to Nos. 1-6, then the lithium-ion secondary battery was dropped sequentially according to Nos. C1-C4, six cycles were conducted, then the drop test was completed, after standing for 1 h, the final voltage of the lithium-ion secondary battery was tested and recorded as V1.
(1) the voltage drop of the drop test was recorded as ΔV=V0−V1;
(2) observing whether the package of the lithium-ion secondary battery was demaged or top sealing was burst out;
(3) disassembling the lithium-ion secondary battery apart and observing whether the tabs of the cell were broken;
(4) disassembling the lithium-ion secondary battery apart and observing whether the separator on the two sides along the wide direction of the cell was shifted or wrinkled;
(5) disassembling the lithium-ion secondary battery apart and observing whether the positive electrode plate and the negative electrode plate were contacted with each other to establish internal short circuit;
(6) testing of the maximum adhesive overflow width
The dropped lithium-ion secondary battery sample was disassembled, the package was removed, the maximum adhesive overflow width was measured on the side of the cell having the binding material with a ruler, ten values were recorded along the lengh direction of the cell, an avarage value of the ten values was taken as the the maximum adhesive overflow width of the cell.
3. Testing of the Cycle Performance of the Lithium-Ion Secondary Batteries
The lithium-ion secondary battery was put into a thermostat oven under 25° C., the lithium-ion secondary battery was charged to 4.35V at a constant current of 0.5 C, then the lithium-ion secondary battery was charged to 0.025 C at a constant voltage of 4.35V, then the lithium-ion secondary battery was standed for 3 min, then the lithium-ion secondary battery was discharged to 3.0V at a constant current of 0.5 C, which was a charge-discharge cycle, the charge-discharge cycle was repeated for 800 times, observing whether there was a short circuit, 50 lithium-ion secondary batteries were tested for each of examples and comparative examples, and the pass rate of the lithium-ion secondary battery was calculated.
Table 1 illustrated parameters of examples 1-18 and comparative example 1.
Table 2 illustrated test results of examples 1-18 and comparative example 1.
It could be seen from a comparison between examples 1-18 and comparative example 1, the lithium-ion secondary battery of the present disclosure had a smaller thickness, a higher pass rate of the drop test, and a higher pass rate of none short circuit after the cycle test. This was because comparative example 1 used a normnal double-sided acrylic resin adhesive, the two surfaces all were adhesive at room temperature, causing the position between the cell adhered with the normnal double-sided acrylic resin adhesive and the package was difficult to adjust when they were adhered with each other, and also the adhesive strength of the normnal double-sided acrylic resin adhesive was relatively small, therefore it must increase the width of the normnal double-sided acrylic resin adhesive in order to achieve a better adhesive strength, so as to increase the adhesive area, and in turn increase the adhesive strength. Because the region of the maximum thickness of the lithium-ion secondary battery was the overlap region of the tab and the cell, and as the width of the normnal double-sided acrylic resin adhesive was bigger, the distance to this region was smaller, and would have a bigger effect on the whole thickness of the lithium-ion secondary battery, moreover, the normnal double-sided acrylic resin adhesive was unable to realize the adhesive overflow, which would also increase the whole thickness of the lithium-ion secondary battery.
It could be seen from a comparison among examples 1-3, the maximum adhesive overflow width of the binding material after heat pressing increased as the thickness of the second functional layer increased, and as the maximum adhesive overflow width increased, the adhesive strength between the cell and the package increased, the pass rate of none package demaged or none top sealing burst was increased. It could be seen from a comparison among example 2 and examples 4-5, example 4 added three binding materials on the top and bottom of the cell, which not only increased the adhesive strength between the cell and the package, improved the pass rate of none package damaged or none top sealing burst, but also the binding materials on the top and bottom and the overflowed adhesive thereof might effectively adhere the separator respectively on the top and the bottom of the cell, therefore the separator would not be shifted or wrinkled after the lithium-ion secondary battery was dropped, the electrode plates would not be contacted to each other to cause an internal short circuit and the cell would not cause a short circuit after the cycle test. Moreover, example 5 further added the green glue at the ending of the cell, which could also bring the same effect as that in example 4.
It could be seen from a comparison between example 4 and example 6, because example 6 was pressed at room temperature, no binding material was softened to extrude out (that was the maximum adhesive overflow width was 0), the adhesive area between the cell and the package was smaller, the adhesive effect of the separator on the top and bottom of the cell was worsen, therefore a part of the separator was shifted or wrinkled after the lithium-ion secondary battery was dropped.
It could be seen from a comparison between example 7 and example 8, the first adhesive layer and the second functional layer of example 8 were all added with inorganic additive Al2O3, so the maximum adhesive overflow width was smaller than that of example 7 under the same condition, and the first adhesive layer and the second functional layer would not flow to the sealing edge to cause a poor sealing. This was because the use of the inorganic additive Al2O3 might effectively control the homogeneous flow of the first adhesive layer and the second functional layer. At the same time, because the maximum adhesive overflow width was the biggest, the distance between region of the adhesive overflow and the overlap region of the tab and cell was smaller, which easily caused the thickness of the main body of the lithium-ion secondary battery to be bigger.
It could be seen from a comparison among examples 9-11, when the second functional layer was only pressure sensitive adhesive, as the pressure applied on the second functional layer increased, the pass rate of the lithium-ion secondary battery passed the drop test and the pass rate of the lithium-ion secondary battery with none short circuit after the cycle test increased. This was because as the pressure applied on the second functional layer increased, the adhesive force of the second functional layer correspondingly increased.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201410381717.5 | Aug 2014 | CN | national |
