Battery positive plate and battery

Abstract

The utility model discloses a battery positive plate and a battery, and relates to the field of batteries. The battery positive plate comprises a current collector and a composite layer, the composite layer is arranged on at least one surface of the current collector, and the composite layer comprises a first active layer, a lithium supplementing layer and a second active layer which are sequentially stacked in the thickness direction of the current collector. The battery positive plate provided by the utility model can reduce lithium loss in the first charging and discharging process, so that the energy density and the cycle life of a lithium ion battery are improved.

Description

Technical Field

[0001] The utility model relates to the field of batteries, and in particular to a battery positive electrode sheet and a battery. Background Art

[0002] Silicon-based materials are widely used in lithium-ion batteries due to their high theoretical gram capacity.

[0003] During the first charge and discharge process, silicon-based materials will react with lithium ions in the electrochemical reaction, causing excessive loss of lithium ions, thus affecting the energy density and cycle life of lithium-ion batteries. At present, many companies can develop silicon-oxygen materials with high initial efficiency, but the process is often difficult and increases costs; another idea is to replenish lithium. Generally speaking, replenishing lithium at the positive end is safer, but the effect will be poor; replenishing lithium at the negative end is more effective, but more dangerous; therefore, how to design lithium replenishment to balance the comprehensive performance of lithium batteries is an urgent problem that needs to be solved in the industry. Utility Model Content

[0004] The utility model aims to provide a battery positive electrode sheet, which can reduce lithium loss during the first charge and discharge process, thereby improving the energy density and cycle life of the lithium-ion battery.

[0005] Another object of the utility model is to provide a battery having the characteristics of higher energy density and longer cycle life.

[0006] The embodiment of the utility model provides a technical solution:

[0007] A battery positive electrode sheet comprises a current collector and a composite layer, wherein the composite layer is arranged on at least one surface of the current collector, and the composite layer comprises a first active layer, a lithium supplement layer and a second active layer which are sequentially stacked in the thickness direction of the current collector.

[0008] In an optional embodiment, there are multiple composite layers, and multiple composite layers are sequentially stacked on at least one side surface of the current collector.

[0009] In an optional embodiment, the total number of layers N and the total thickness H of the plurality of composite layers on the same side of the current collector and the thickness h of the lithium replenishing layer of any composite layer satisfy the following relationship:

[0010] 1.5≤(H / Nh) / h≤9.

[0011] In an alternative embodiment, the total thickness of the plurality of composite layers on the same side of the current collector is in a range of 100 μm to 500 μm.

[0012] In an alternative embodiment, a value of a total thickness of the plurality of composite layers on the same side of the current collector divided by a total number of layers is in a range of 50 to 100.

[0013] In an optional embodiment, in any two adjacent composite layers on the same side of the current collector, the lithium replenishing layer closer to the current collector has a smaller thickness.

[0014] In an optional embodiment, in the plurality of composite layers on the same side of the current collector, the thicknesses of the plurality of lithium replenishing layers increase in arithmetic progression from close to to far from the current collector.

[0015] In an optional embodiment, the total number N of the plurality of composite layers on the same side of the current collector and the thickness h of the lithium replenishing layer of the nth composite layer satisfy the following equation:

[0016] hn=10*(N+n) / N.

[0017] In an optional embodiment, the thickness of the lithium replenishing layer is in the range of 10 μm to 20 μm.

[0018] An embodiment of the utility model also provides a battery, comprising the battery positive electrode sheet, wherein the battery positive electrode sheet comprises a current collector and a composite layer, wherein the composite layer is arranged on at least one surface of the current collector, and the composite layer comprises a first active layer, a lithium supplement layer and a second active layer which are sequentially stacked in the thickness direction of the current collector.

[0019] Compared with the prior art, the battery positive electrode provided by the utility model has a composite layer arranged on at least one surface of the current collector, and the composite layer includes a first active layer, a lithium supplement layer and a second active layer stacked in sequence, and the lithium supplement layer is between the first active layer and the second active layer. The first active layer and the second active layer can normally deintercalate lithium and do not affect the electrochemical cycle performance. In addition, the lithium supplement agent in the lithium supplement layer first participates in the reaction during the first charge to compensate for the lithium loss caused by the electrochemical reaction, thereby improving the energy density and cycle life of the lithium-ion battery. Therefore, the beneficial effects of the battery positive electrode provided by the utility model include: being able to reduce the lithium loss during the first charge and discharge process, thereby improving the energy density and cycle life of the lithium-ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the utility model and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative work.

[0021] Figure 1 A schematic structural diagram of a battery positive electrode sheet provided in an embodiment of the utility model.

[0022] Icon: 100 - positive electrode of battery; 110 - current collector; 120 - composite layer; 121 - first active layer; 122 - lithium supplement layer; 123 - second active layer. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the present invention to be protected, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0026] In the description of the present utility model, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the utility model product is usually placed when in use, or are directions or positional relationships that are usually understood by those skilled in the art. These directions or positional relationships are only for the convenience of describing the present utility model and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present utility model.

[0027] Furthermore, the terms “first”, “second”, etc. are merely used for distinguishing descriptions and are not to be understood as indicating or implying relative importance.

[0028] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms such as "setting" and "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] The specific implementation of the utility model is described in detail below in conjunction with the accompanying drawings.

[0030] Example

[0031] See also Figure 1 , Figure 1 FIG. 1 is a schematic structural diagram of a battery positive electrode sheet 100 provided in this embodiment.

[0032] The battery positive electrode sheet 100 provided in this embodiment is applied to a lithium-ion battery, which can reduce lithium loss during the initial charge and discharge process, thereby improving the energy density and cycle life of the lithium-ion battery.

[0033] Specifically, the battery positive electrode sheet 100 includes a current collector 110 and a composite layer 120 , the composite layer 120 is arranged on at least one surface of the current collector 110 , and the composite layer 120 includes a first active layer 121 , a lithium supplement layer 122 and a second active layer 123 stacked in sequence in the thickness direction of the current collector 110 .

[0034] The first active layer 121 and the second active layer 123 are both positive electrode active slurries, and the lithium replenishing layer 122 contains a lithium replenishing agent, such as LiNiO2, etc. When the battery positive electrode sheet 100 is applied to a lithium-ion battery, the lithium replenishing layer 122 is located between the first active layer 121 and the second active layer 123, and the first active layer 121 and the second active layer 123 can both normally deintercalate lithium and do not affect the electrochemical cycle performance.

[0035] Furthermore, when the lithium-ion battery is charged for the first time, the lithium replenishing agent in the lithium replenishing layer 122 first participates in the reaction during the first charging to compensate for the lithium loss caused by the electrochemical reaction, thereby improving the energy density and cycle life of the lithium-ion battery.

[0036] In this embodiment, there are multiple composite layers 120, and multiple composite layers 120 are stacked in sequence on at least one side surface of the current collector 110. Each composite layer 120 is composed of a first active layer 121, a lithium replenishing layer 122 and a second active layer 123 stacked in sequence.

[0037] In practical applications, if the thickness of the lithium replenishing layer 122 is too high, the thickness of the inactive layer on the same side of the current collector 110 will be reduced. At this time, the binding effect of the inactive layer on the lithium replenishing layer 122 will be reduced, and the contact impedance between the interfaces will be reduced. The polarization phenomenon in the electrochemical reaction will be aggravated, thereby affecting the power performance. At the same time, the capacity loss caused by polarization will cause a decrease in energy density.

[0038] If the thickness of the lithium replenishing layer 122 is too low, the lithium replenishing effect is poor and is insufficient to replenish the consumption of lithium ions at the negative electrode in the high silicon system. Therefore, the initial efficiency of the lithium battery is reduced, thereby affecting the energy density and cycle life.

[0039] Therefore, in this embodiment, preferably, the thickness of the lithium supplement layer 122 is in the range of 10 μm to 20 μm. The total thickness of the multiple composite layers 120 on the same side of the current collector 110 is in the range of 100 μm to 500 μm.

[0040] Furthermore, if the number of lithium replenishing layers 122 is too large, too much interface contact will be introduced, the contact impedance will be increased, the electrochemical polarization will be deteriorated, and the power performance and energy density will be affected. If the number of lithium replenishing layers 122 is too small, the transmission of lithium ions on the vertical gradient will be hindered by the enlarged path, affecting its power performance.

[0041] To solve this problem, in this embodiment, the total number N and total thickness H of the multiple composite layers 120 on the same side of the current collector 110 and the thickness h of the lithium replenishing layer 122 of any composite layer 120 satisfy the following relationship:

[0042] 1.5≤(H / Nh) / h≤9.

[0043] It is understandable that, since each composite layer 120 includes a lithium replenishing layer 122 , the numbers of the two layers correspond to each other, and therefore, the total number of the composite layers 120 is equal to the total number of the lithium replenishing layers 122 .

[0044] Furthermore, in this embodiment, the value of the total thickness of the plurality of composite layers 120 on the same side of the current collector 110 divided by the total number of layers is in the range of 50 to 100. That is, 50≤H / N≤100.

[0045] In addition, among the multiple stacked composite layers 120, in the direction from close to to far away from the current collector 110, among the multiple lithium replenishing layers 122 corresponding to the multiple composite layers 120, the lithium ion transmission path of the lithium replenishing layer 122 closer to the current collector 110 is longer and the resistance encountered is greater. Therefore, an overly thick lithium replenishing layer 122 is not conducive to the transmission of lithium ions, which will increase the transmission impedance, reduce the first efficiency, and affect the power performance and energy density.

[0046] To this end, in this embodiment, in any two adjacent composite layers 120 on the same side of the current collector 110, the thickness of the lithium replenishing layer 122 closer to the current collector 110 is smaller. In other words, on one side of the current collector 110, the thickness of the lithium replenishing layer 122 corresponding to the plurality of composite layers 120 increases from close to far from the current collector 110, ensuring that the lithium ion transfer impedance of the lithium replenishing layers 122 at different levels is balanced, thereby improving the lithium replenishing effect.

[0047] Preferably, in this embodiment, in the multiple composite layers 120 on the same side of the current collector 110 , the thicknesses of the multiple lithium replenishing layers 122 increase in arithmetic progression from close to the current collector 110 to far away from the current collector 110 .

[0048] Specifically, the total number N of the multiple composite layers 120 on the same side of the current collector 110 and the thickness h of the lithium replenishing layer 122 of the n-th composite layer 120 satisfy the following equation:

[0049] hn=10*(N+n) / N.

[0050] In other words, the difference in thickness between the two lithium replenishing layers 122 corresponding to two adjacent composite layers 120 is 10 / Nμm. The thicknesses of the multiple lithium replenishing layers 122 on the same side of the current collector 110 are set to increase in arithmetic progression, which is consistent with the resistance encountered by the lithium ions of each lithium replenishing layer 122 through different lengths of paths, thereby reducing differentiation, reducing the power performance reduction and electrochemical polarization deterioration caused by impedance differences.

[0051] It can be seen that the battery positive electrode sheet 100 provided in this embodiment ensures reliable binding force between the lithium replenishing layer 122 and the two active layers and optimizes the transmission path of lithium ions by controlling the thickness of the lithium replenishing layer 122. The contact impedance between the interfaces of the two is improved by binding the active layer, and the polarization phenomenon in the electrochemical reaction is reduced. By controlling the number of lithium replenishing layers 122, the lithium replenishing efficiency is improved, and finally the effect of balancing the comprehensive electrochemical performance of silicon-based system batteries is achieved.

[0052] The present embodiment also provides a plurality of test examples and a plurality of comparative examples to verify the effect of the battery positive electrode sheet 100 provided in the present embodiment. Specifically, a plurality of lithium-ion batteries are prepared using a plurality of battery positive electrode sheets 100 that meet the parameter ranges of the present embodiment, and a plurality of lithium-ion batteries are prepared using a plurality of battery positive electrode sheets 100 that each contain at least one parameter that does not meet the parameter range provided in the present embodiment.

[0053] Specifically, the slurry of the first active layer 121 and the second active layer 123 is obtained by fully stirring and mixing the active material, the conductive agent SP, the CNT, and the adhesive PVDF in a weight ratio of 97.2:1.2:0.6:1 in an NMP solvent system, wherein the active material is LiNi0.85Co0.1Mn0.05O2. The slurry of the lithium replenishing layer 122 is obtained by fully stirring and mixing the lithium replenishing agent, the conductive agent SP, the CNT, and the adhesive PVDF in a weight ratio of 96:2.2:0.8:1 in an NMP solvent system.

[0054] A plurality of test examples and a plurality of comparative examples were prepared respectively, and some parameters of the battery positive electrode sheet 100 in the plurality of test examples and the plurality of comparative examples are as follows:

[0055]

[0056]

[0057] It can be understood that, for multiple test examples and multiple comparative examples, parameters not appearing in the above table can be considered to be the same.

[0058] A series of tests were carried out on the above multiple test examples and multiple comparative examples, and some of the test results are shown in the following table, wherein the first effect test was carried out at a temperature of 25°C, with the first charge and discharge being carried out at a constant current and constant voltage charging at a charging current of 1.0C (i.e., the current value at which the theoretical capacity is completely discharged within 1 hour), with a charging cut-off voltage of 4.25V, and then the battery was discharged at a constant current of 1.0C, with a discharge cut-off voltage of 2.5V, and the discharge capacity of the first cycle was recorded.

[0059] The first efficiency refers to the value of the first discharge capacity divided by the total charge capacity.

[0060]

[0061]

[0062] Compared with multiple test examples, in Comparative Example 1, since the lithium replenishing layer 122 is too small, it means that the thickness of other layer structures is too large, and the other layer structures are too different from the lithium replenishing layer 122. The lithium replenisher is not enough to replenish sufficient lithium source, which may affect the initial effect, energy density and cycle life. In addition, the lithium replenishment diffusion path becomes longer, which will indirectly affect the transmission impedance and reduce the power performance.

[0063] Compared with multiple test examples, in Comparative Example 2, due to the excessive number of lithium replenishing layers 122, the contact surface of each material layer increases, the contact impedance becomes larger, the electrochemical polarization is aggravated, the power performance is affected, the capacity is inhibited and the energy density is improved, and finally the cycle performance is reduced due to polarization.

[0064] Compared with multiple test examples, in Comparative Example 3, since the thickness of the lithium replenishing layer 122 is set too large, it means that the thickness of other layer structures is relatively reduced. At this time, the binding force of other layer structures on the lithium replenishing layer 122 is reduced, and the interface contact impedance is also increased. The increased polarization leads to reduced power performance and energy density, and the cycle life is reduced due to the increased polarization.

[0065] Compared with multiple test examples, in Comparative Example 4, since the thickness of the lithium replenishing layer 122 is set too small, there are not enough lithium ions to replenish the lithium ion loss of the high-silicon system, so the first efficiency is reduced, the energy density is reduced, and the reduction in the first efficiency will also aggravate the attenuation of the cycle life.

[0066] Compared with the multiple test examples, in Comparative Examples 5 and 6, since the thickness of the multiple lithium replenishing layers 122 does not conform to the arithmetic increasing rule provided in the present application, the pole piece resistance deteriorates more seriously, the power performance decreases more, and the first-effect cycle also decreases accordingly. The lithium ion transmission of the innermost lithium replenishing layer 122 is greatly hindered, and the excessive thickness of the lithium replenishing layer 122 is not conducive to the transmission of lithium ions, thus affecting the first effect of the lithium battery, increasing the transmission impedance of the lithium battery, and resulting in a decrease in power performance and a decrease in energy density.

[0067] In summary, the battery positive electrode plate 100 provided in this embodiment can reduce lithium loss during the initial charge and discharge process, thereby improving the energy density and cycle life of the lithium-ion battery, and solves the problems of reduced power performance and deterioration of electrochemical polarization caused by impedance difference to the greatest extent, thereby balancing the comprehensive performance of the lithium battery in all aspects.

[0068] In addition, this embodiment further provides a battery, including the aforementioned battery positive electrode sheet 100. Benefiting from the beneficial effects of the battery positive electrode sheet 100, the battery provided in this embodiment has the characteristics of higher energy density and longer cycle life.

[0069] The above description is only the preferred embodiment of the utility model, and is not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

Claims

1. A positive electrode sheet for a battery, characterized in that: The invention comprises a current collector (110) and a composite layer (120), wherein the composite layer (120) is arranged on at least one surface of the current collector (110), and the composite layer (120) comprises a first active layer (121), a lithium supplement layer (122), and a second active layer (123) which are sequentially stacked in a thickness direction of the current collector (110); The number of the composite layers (120) is plural, and the plurality of composite layers (120) are sequentially stacked on at least one side surface of the current collector (110); The total number of layers N and the total thickness H of the plurality of composite layers (120) on the same side of the current collector (110) and the thickness h of the lithium replenishing layer (122) of any composite layer (120) satisfy the following relationship: 1.5≤(H / Nh) / h≤9.

2. The positive electrode sheet of a battery according to claim 1, characterized in that: The total thickness of the plurality of composite layers (120) on the same side of the current collector (110) is in the range of 100 μm to 500 μm.

3. The battery positive electrode sheet according to claim 1, characterized in that: The value of the total thickness of the plurality of composite layers (120) on the same side of the current collector (110) divided by the total number of layers is in the range of 50 to 100.

4. The positive electrode sheet of the battery according to claim 1, characterized in that: In any two adjacent composite layers (120) located on the same side of the current collector (110), the lithium replenishing layer (122) closer to the current collector (110) has a smaller thickness.

5. The battery positive electrode sheet according to claim 4, characterized in that: In the plurality of composite layers (120) located on the same side of the current collector (110), the thicknesses of the plurality of lithium replenishing layers (122) increase in arithmetic progression in a direction from close to to far from the current collector (110).

6. The battery positive electrode sheet according to claim 4, characterized in that: The total number N of the plurality of composite layers (120) on the same side of the current collector (110) and the thickness h of the lithium replenishing layer (122) of the nth composite layer (120) satisfy the following equation: hn=10*(N+n) / N.

7. The positive electrode sheet of a battery according to claim 1, characterized in that: The thickness of the lithium replenishing layer (122) is in the range of 10 μm to 20 μm.

8. A battery, characterized in that: It comprises the battery positive electrode sheet (100) as claimed in any one of claims 1 to 7.

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