Patent Application
20230307633
The present application claims priority under 35 U.S.C. § 119(a) to Korean patent application number 10-2022-0035904 filed on Mar. 23, 2022, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated by reference herein.
The present disclosure relates to a secondary battery and a battery module including the same.
With development of electronics, communications, and space industries, the demand for secondary batteries as an energy power source is rapidly increasing. In particular, as importance of global eco-friendly policies is emphasized, the electric vehicle market is growing by leaps and bounds, and research and development on secondary batteries are actively carried out at home and abroad.
Recently, the demand for batteries with high energy density for electric vehicles (EVs) is increasing, and therefore, development of secondary batteries to which high-Ni-based cathodes are applied is essential. However, the voltage for phase transition from H2 to H3 becomes low with continuous increases in the Ni content in cathode active materials. This causes generation of a large amount of gas upon charging/discharging and storage evaluation at high SOC, and thus problems arise such as venting of a pouch, posing difficulties and limitations in application to an actual battery design.
Embodiments provide a secondary battery which has improved high temperature storage performance and fast charging performance such that a design with high energy density may be applied and different current intensity may be derived from a single battery, and a battery module including the same.
In accordance with an aspect of the present disclosure, there is provided a secondary battery which includes an electrode assembly including a first electrode group including a first cathode; and a second electrode group including a second cathode, wherein the first cathode includes a first cathode active material, and the second cathode includes a first cathode active material and a second cathode active material, and wherein the first cathode active material is a lithium-nickel composite oxide having primary particles whose particle diameter is less than or equal to 1 μm, and the second cathode active material is a lithium-nickel composite oxide having primary particles whose particle diameter is greater than 1 μm.
A battery module in accordance with an embodiment of the present disclosure includes the secondary battery in accordance with an embodiment of the present disclosure as a unit battery.
A device in accordance with an embodiment of the present disclosure includes the battery module in accordance with an embodiment of the present disclosure as a power source.
In accordance with an embodiment of the present disclosure, it is possible to provide a secondary battery which has improved high temperature storage performance and fast charging performance such that a design with high energy density may be applied and different current intensity may be derived from a single battery, and a battery module including the same.
Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the example embodiments to those skilled in the art.
In the drawing figures, dimensions may be exaggerated for clarity of illustration. It will be understood that when an element is referred to as being “between” two elements, it can be the only element between the two elements, or one or more intervening elements may also be present. Like reference numerals refer to like elements throughout.
The specific structural or functional description disclosed herein is merely illustrative for the purpose of describing embodiments in accordance with the concept of the present disclosure. The embodiments in accordance with the concept of the present disclosure can be implemented in various forms, and cannot be construed as limited to the embodiments set forth herein.
Herein, “first” or “second” is used to distinguish each component but not to limit location or order relationship.
The present disclosure provides a secondary battery which includes an electrode assembly including a first electrode group and a second electrode group, wherein a first cathode includes a first cathode active material, and a second cathode includes a first cathode active material and a second cathode active material, and wherein the first cathode active material is a lithium-nickel composite oxide having primary particles whose particle diameter is less than or equal to 1 μm, and the second cathode active material is a lithium-nickel composite oxide having primary particles whose particle diameter is greater than 1 μm.
The electrode group includes a cathode, an anode, and a separator interposed between the cathode and the anode, wherein in the present disclosure, the first electrode group includes a first cathode, a first anode, and a first separator, and the second electrode group includes a second cathode, a second anode, and a second separator. Unless otherwise disclosed, in the present disclosure, the first anode and the second anode, the first separator, and the second separator may be the same anode and separator, respectively.
As described above, when a high-Ni-based cathode active material is used, the voltage for phase transition from H2 to H3 decreases with a continuous increase in the Ni content in the cathode active material, such that a large amount of gas may be generated upon charge/discharge and storage evaluation at high SOC.
The secondary battery in accordance with the present disclosure includes two types of cathode active materials, that are, the first cathode active material which is a lithium-nickel composite oxide having primary particles whose particle diameter is less than or equal to 1 μm for deriving cell capacity and the second cathode active material which is a lithium-nickel composite oxide having primary particles whose particle diameter is greater than 1 μm to increase high temperature structural stability.
In accordance with an embodiment, the first cathode active material and the second cathode active material are lithium-nickel composite oxides, specifically represented by LiaNixMyO2 (x+y=1, 0.6<x<0.95, 0.95<a<1.3), wherein M may typically be Mn, Co, Al, Ti, Zr, Sr, Y, and Mg, such as lithium-nickel-manganese-cobalt composite oxides. Since the first cathode active material has primary particles whose particle diameter is greater than or equal to 1 μm, the moving rate of lithium ions is fast upon charging and discharging, and there are many grain boundaries on which lithium may move between the primary particles, so the capacity and output are satisfactory, but an area for side reactions with electrolytes is also widened, which may cause shortcomings such as generation of a large amount of gas during phase transition from H2 to H3 under high temperature and high SOC conditions. On the contrary, the second cathode active material has primary particles whose particle diameter is greater than 1 μm and the area in which the side reaction occurs is Small, such that the amount of gas generated is small at high SOC. Therefore, by applying the second cathode active material together to the electrode group to which the first cathode active material having a high Ni composition is applied, it is possible to overcome the shortcomings concerning a large amount of gas generated at a high SOC. In addition, it is possible to overcome inferiority in the energy density when the second cathode active material is solely used, and also improve high temperature storage performance and fast charging performance.
Specifically, the first cathode includes the first cathode active material, the second cathode includes the first cathode active material and the second cathode active material, and a mass ratio of the first cathode active material and the second cathode active material in the second cathode may be less than or equal to 9:1, less than or equal to 8.5:1.5, less than or equal to 8:2, or less than or equal to 7:3, and may be greater than or equal to 1:9, greater than or equal to 1.5:8.5, greater than or equal to 2:8, or greater than or equal to 3:7. In accordance with an embodiment, the mass ratio of the first cathode active material and the second cathode active material in the second cathode may be 3:7 to 9:1 and 5:5 to 9:1.
When the mass ratio of the first cathode active material and the second cathode active material in the second cathode deviates from the above value, generation of a large amount of gas at high SOC may not be reduced, or the desired capacity and output may not be attained.
In accordance with an embodiment, the ratio of the numbers of stacks of the first cathode included in the first electrode group and the second cathode included in the second electrode group may be greater than or equal to 1:10, greater than or equal to 1:9.5, greater than or equal to 1:9, greater than or equal to 1:8.5, or greater than or equal to 1:8 and may be less than or equal to 10:1, less than or equal to 9.5:1, less than or equal to 9:1, less than or equal to 8.5:1, or less than or equal to 8:1, for example, it may be 1:10 to 10:1, 1:9.5 to 9.5:1, or 1:8 to 8:1. In accordance with an embodiment, the ratio of the numbers of stacks of the first cathode included in the first electrode group and the second cathode included in the second electrode group may be 1:1 to 10:1, and more specifically, 1:1 to 1:9. If the ratio of the numbers of stacks is too small or too large, it may be difficult to obtain improved energy density compared to the secondary battery in which the cathode active material is solely used, or the high temperature storage performance or fast charging performance may deteriorate.
In accordance with an embodiment, the first electrode group 100_1 may be disposed below the second electrode group 100_2, or the second electrode group 100_2 may be disposed below the first electrode group 100_1. Alternatively, the first electrode group 100_1 and the second electrode group 100_2 may be disposed alternately. In addition, the first cathode tab formed to extend from the first cathode in the first electrode group may be located on a left or right side of the electrode assembly, and the second cathode tab formed to extend from the second cathode in the second electrode group may be located on a right or left side of the electrode assembly. The left and right sides of the electrode assembly are based on views from a direction in which each cathode tab protrudes. Alternatively, the first cathode tab formed to extend from the first cathode in the first electrode group and the second cathode tab formed to extend from the second cathode in the second electrode group may extend in each different direction from the ends in each different direction.
In the front cross-sectional view of the secondary battery in accordance with the present disclosure in
Referring to
Since the first cathode tab 10_1 and the second cathode tab 10_2 are connected to each independent electrode lead, when the secondary battery in accordance with the present disclosure is applied to a module, different intensity of current may be derived from a single battery at the same time depending on the purpose of a design.
Here, the first electrode lead 200_1 and the second electrode lead 200_2 may be arranged in parallel and interposed in a single lead film 400 together.
Referring to
In accordance with an embodiment, the widths of the first cathode tab 10_1 and the second cathode tab 10_2 may be the same or different from each other.
Referring to
In the case of the electrode assembly included in the secondary battery in accordance with the present disclosure, the cathode in the first electrode group and the cathode in the second electrode group should each be connected through the cathode tab extending in each different direction, such that all forms of electrode structures that may be connected through the separate cathode tab may be applied for each electrode group. For example, rather than a wound electrode assembly that is formed by winding one extending cathode and anode, it may be desirable that a stacked electrode assembly that is formed by stacking a plurality of cathodes and anodes is used. The stacked electrode assembly may refer to all structures in a form in which a plurality of electrode groups including the cathode, the separator, and the anode are stacked, and is not limited to a particular stacking method. For example, the stacked electrode assembly may be an electrode assembly formed using various stacking methods such as lamination and stacking, stacking and folding, and Z-folding.
Referring to
Referring to
Referring to
It may be formed by winding or bending the separation film after arranging a plurality of electrode groups including the cathode and anode on the separation film. At this time, instead of being disposed in the separator in the form of the electrode group including the cathode and the anode as in the stacked and folded type in
The cathode tabs 10_1 and 10_2 and the anode tabs 20_1 and 20_2 may extend from the ends in each different direction in the electrode assembly, and the first cathode tab 10_1 in the first electrode group 100_1 and the second cathode tab 10_2 in the second electrode group 100_2 may extend from the ends in the same direction in the electrode assembly but may be disposed in different positions at the ends. For example, when the assembled electrode assembly is viewed form the top as shown in
In the case of the electrode assemblies disclosed in
A battery module in accordance with an embodiment of the present disclosure includes the secondary battery in accordance with an embodiment of the present disclosure as a unit battery.
A device in accordance with an embodiment of the present disclosure includes the battery module in accordance with an embodiment of the present disclosure as a power source.
Hereinafter, the present disclosure will be described in more detail based on Examples and Comparative Examples. However, the following Examples and Comparative Examples are only for explaining the present disclosure in more detail, and the present disclosure is not limited by the following Examples and Comparative Examples.
1. Evaluation on Energy Density
A secondary battery in Examples 1 to 5 and Comparative Examples 1 to 2 was prepared, which includes a stacked electrode assembly including a first electrode group having a stack number of first cathodes and a second electrode group having a stack number of second cathodes as described in Table 1 below, then the energy density was evaluated, wherein the results are shown in Table 1 below.
The prepared electrode assembly was placed in a pouch case and sealed on three sides except a main liquid surface of an electrolyte. Here, a part where an electrode tab exists was included in the sealing portion. The electrolyte was injected through remaining surfaces except the sealing portion, and the remaining surface was sealed and impregnated for more than 12 hours.
Used as the electrolyte was a mixture obtained by dissolving 1M LiPF6 in a mixed solvent of EC/EMC/DEC (25/45/30; volume ratio) and then adding 1 wt % of vinylene carbonate (VC), 0.5 wt % of 1,3-profensultone (PRS) and 0.5 wt % of lithium bis(oxalate)borate (LiBOB).
Thereafter, pre-charging was performed at a current corresponding to 0.25 C for 36 minutes. After 1 hour, degassing was performed, followed by aging for more than 24 hours and then the formation charging and discharging (charging condition CC-CV 0.2 C 4.2V 0.05 C CUT-OFF, discharge condition CC 0.2 C 2.5V CUTOFF).
Subsequently, the standard charging and discharging was performed (charging condition CC-CV 0.5 C 4.2V 0.05 C CUT-OFF, discharge condition CC 0.5 C 2.5V CUT-OFF).
The total number of stacks in the cathode was 45, wherein the first cathode includes a first cathode active material that is a lithium-nickel composite oxide having primary particles whose particle diameter is less than or equal to 1 μm, and in the second cathode, the first cathode active material and a second cathode active material which is a lithium-nickel composite oxide having primary particles whose particle diameter is greater than 1 μm was included in a mass ratio of 7:3.
As a result of evaluation on energy density, compared to the energy density of 724 Wh/L in Comparative Example 1 to which the electrode group including the second cathode was solely applied, it was found that the energy density in Examples 1 to 5 was improved.
2. Evaluation on High Temperature Storage Performance
After charging to 4.2V (charging condition CC-CV 0.3 C 4.2V 0.05 C CUT-OFF) for the secondary battery in accordance with Examples 1, 3, and 4 and Comparative Examples 1 and 2, the secondary battery was discharged to a voltage corresponding to SC96% (discharge condition CC 0.3 C) and then stored in a chamber at 60° C., and then a week in which cell venting occurs was measured and evaluated.
Results of evaluation are shown in Table 2 below.
As a result of evaluation on high temperature storage performance, compared to the vent occurred at 24th week in Comparative Example 2 that solely includes the electrode group including the first cathode, in Examples 1, 3, and 4, occurrence of the vent delayed by more then 4 to 8 weeks, with more improved effects observed.
3. Evaluation on Fast Charging Performance
The fast charging performance was evaluated with respect to Examples 1, 3, and 4 and Comparative Examples 1 and 2.
After preparing the secondary battery using the cathode and all the same anode prepared in accordance with the Examples and Comparative Examples, charging was performed to reach DOD72 within 25 minutes in accordance with the step charging method at c-rate of 2.0 C/1.75 C/1.5 C/1.25 C/1.0 C/0.75 C/0.5 C, and then discharging was performed at c-rate of 1/3 C to conduct fast charging evaluation in a chamber where a constant temperature (25° C.) set within the range of DOD72 (SOC8-80) is maintained. After repeating 50/100/150/200/250/300 cycles with a rest time of 10 minutes between charge/discharge cycles, the fast charging capacity retention rate was measured, and the results are shown in Table 3 and
As a result of evaluation on the fast charging performance, compared to Comparative Example 2, which solely includes an electrode assembly group including the first cathode, it was found that the fast charging evaluation characteristics in Examples 1, 3, and 4 were improved.
While the present disclosure has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents. Therefore, the scope of the present disclosure should not be limited to the above-described exemplary embodiments but should be determined by not only the appended claims but also the equivalents thereof.
In the above-described embodiments, all steps may be selectively performed or part of the steps and may be omitted. In each embodiment, the steps are not necessarily performed in accordance with the described order and may be rearranged. The embodiments disclosed in this specification and drawings are only examples to facilitate an understanding of the present disclosure, and the present disclosure is not limited thereto. That is, it should be apparent to those skilled in the art that various modifications can be made on the basis of the technological scope of the present disclosure.
Meanwhile, the exemplary embodiments of the present disclosure have been described in the drawings and specification. Although specific terminologies are used here, those are only to explain the embodiments of the present disclosure. Therefore, the present disclosure is not restricted to the above-described embodiments and many variations are possible within the spirit and scope of the present disclosure. It should be apparent to those skilled in the art that various modifications can be made on the basis of the technological scope of the present disclosure in addition to the embodiments disclosed herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2022-0035904 | Mar 2022 | KR | national |
