A composite stacked battery and its preparation method

Abstract

This invention belongs to the field of lithium-ion battery technology, and particularly relates to a composite stacked battery and its preparation method. The battery includes a stacked cell made of a first negative electrode A (selected from single-particle graphite), a second negative electrode B (selected from secondary-particle graphite), and a positive electrode C. The positive and negative electrodes in the stacked cell are stacked in an arrangement of A / C / A / C / A / C…A / C / B / C / B / C… / B / C / A / C…A / C / A and separated by a separator. The single-particle graphite and the secondary-particle graphite have the same specific capacity. This invention not only simplifies the battery manufacturing process but also improves cell wettability and reduces material costs to a certain extent.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and in particular relates to a composite stacked battery and its preparation method. Background Technology

[0002] Lithium-ion batteries, as a new type of rechargeable battery, have seen their applications expand due to their high energy density and long cycle life. They are widely used in portable electronic devices, energy storage, and electric vehicles, especially with the rapid development of the new energy industry. However, as lithium-ion battery thickness and energy density increase, the problem of electrolyte wetting remains during manufacturing. Currently, the most widely adopted wetting processes by lithium-ion battery manufacturers involve high-temperature settling and extended settling time. High-temperature settling increases production costs, while extended settling time reduces production line efficiency, indirectly increasing battery costs and reducing market competitiveness. Furthermore, even with these methods, the wetting problem in high-energy-density battery systems remains unresolved.

[0003] In view of the difficulties in wetting caused by the increase in the thickness and energy density of lithium batteries, this invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a composite stacked battery and its preparation method. The main method is to solve the technical problem of difficulty in wetting caused by the increase in thickness and energy density of lithium-ion batteries by setting the outer layer of the negative electrode sheet of the stacked battery cell to be single-particle graphite and the inner layer to be secondary-particle graphite.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, a composite stacked battery includes a stacked cell made of a first negative electrode A selected from single-particle graphite, a second negative electrode B selected from secondary-particle graphite, and a positive electrode C. The positive and negative electrodes in the stacked cell are stacked in an arrangement of A / C / A / C / A / C……A / C / B / C / B / C…… / B / C / A / C……A / C / A and separated by a separator. The single-particle graphite and the secondary-particle graphite have the same specific capacity.

[0007] Furthermore, the D50 of the single-particle graphite is 8-15 μm;

[0008] And / or, the D50 of the secondary particle graphite is 15-16 μm;

[0009] And / or, the specific capacity of both the single-particle graphite and the secondary-particle graphite is 335-355 mAh / g.

[0010] Furthermore, the first negative electrode A and the second negative electrode B have the same compaction density, ingredient mass ratio, and areal density;

[0011] And / or, the number of the first negative electrode A and the second negative electrode B are positive integers m and n, respectively, and the number of the positive electrode C is m+n-1.

[0012] Furthermore, the compaction density of both the first negative electrode A and the second negative electrode B is 1.50-1.65 g / cm³. 3 ;

[0013] And / or, the mass ratio of the first negative electrode A and the second negative electrode B is 94-97:0.5-2:3.0-4.5, calculated as negative electrode active material: conductive agent: binder.

[0014] And / or, the areal density of both the first negative electrode A and the second negative electrode B is 150–175 g / m³. 2 ;

[0015] And / or, the ratio of the number m of the first negative electrode A to the number n of the second negative electrode B is 1:4 to 1.5:1.

[0016] Furthermore, the compaction density of both the first negative electrode A and the second negative electrode B is 1.50-1.55 g / cm³. 3 The ratio of the number m of the first negative electrode A to the number n of the second negative electrode B is 1:4 to 3:7.

[0017] And / or, the compaction density of both the first negative electrode A and the second negative electrode B is 1.55-1.65 g / cm³. 3 The ratio of the number m of the first negative electrode A to the number n of the second negative electrode B is 1:1 to 3:2.

[0018] Furthermore, the mass ratio of the positive electrode C to the positive electrode active material is 96-98: 0.5-2.0: 1.5-3.0, calculated as positive electrode active material: conductive agent: binder.

[0019] And / or, the positive electrode active material of the positive electrode C is lithium iron phosphate.

[0020] Furthermore, the diaphragm is a single-sided coated ceramic diaphragm.

[0021] Furthermore, the thickness of the laminated battery cell is 25–35 mm.

[0022] Furthermore, the energy density of the battery is 165–175 Wh / kg.

[0023] In a second aspect, a method for preparing the battery described in the first aspect includes the steps of material preparation, coating, rolling, die cutting, stacking, baking, electrolyte injection, formation, and capacity testing. During material preparation, single-particle graphite is prepared in the slurry of the first negative electrode A, and secondary-particle graphite is prepared in the slurry of the second negative electrode B. The specific capacity of the single-particle graphite and the secondary-particle graphite is the same. During stacking, the first negative electrode A, the second negative electrode B, and the positive electrode C are stacked in an arrangement of A / C / A / C / A / C…A / C / B / C / B / C… / B / C / A / C…A / C / A and separated by a separator.

[0024] Compared with existing technologies, this invention mainly discloses a novel composite stacked battery and its preparation method, which not only simplifies the battery manufacturing process but also improves cell wettability and reduces material costs to a certain extent. It has at least the following beneficial effects:

[0025] 1. This invention employs a composite stacking configuration of A / C / A / C / A / C…A / C / B / C / B / C… / B / C / A / C…A / C / A, which, compared to the traditional single-anode stacking configuration of B / C / B / C… / B / C, adds a single-particle graphite anode A. This not only possesses the high capacity and rate capability advantages of secondary particles but also the stable structure and long cycle life of single particles. Furthermore, under the same coating areal density and compaction density, the electrolyte absorption rate of the single-particle graphite electrode is faster than that of the secondary-particle graphite electrode. By placing the single-particle graphite anode on the outer layer of the stack and the secondary-particle graphite anode on the inner layer, the faster electrolyte absorption allows for rapid diffusion to the inner layer, shortening the electrolyte wetting time and solving the problem of wetting difficulties caused by increased thickness and energy density in lithium-ion batteries.

[0026] 2. Compared to graphite mixed with single-stage and secondary-stage particles, it reduces uneven mixing of the slurry and can improve the consistency of coating.

[0027] 3. With the same raw materials, single-particle graphite requires less granulation than double-particle graphite, giving it a cost advantage in production. Furthermore, using single-particle graphite reduces the need for double-particle graphite, further lowering material costs. Attached Figure Description

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1This is a schematic diagram of the battery stacking method of the present invention;

[0030] Figure 2 At 45℃, it is 1.52 g / cm³. 3 Liquid absorption diagram of the compacted core stack;

[0031] Figure 3 At 45℃, it is 1.60 g / cm³. 3 Liquid absorption diagram of the compacted core stack;

[0032] Figure 4 1.52 g / cm 3 Chart showing the rate-charge capacity retention rate of the compacted stacked cores;

[0033] Figure 5 1.52 g / cm 3 Rate discharge capacity retention diagram of compacted stacked cores;

[0034] Figure 6 1.60 g / cm 3 Chart showing the rate-charge capacity retention rate of the compacted stacked cores;

[0035] Figure 7 It is 1.60 g / cm 3 Rate discharge capacity retention diagram of compacted stacked cores. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions.

[0037] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0038] Given the difficulties in wetting caused by the increased thickness and energy density of lithium batteries, this patent invention provides a composite stacked battery and its preparation method. Details are as follows:

[0039] A composite stacked battery includes a stacked cell made of a first negative electrode A selected from single-particle graphite, a second negative electrode B selected from secondary-particle graphite, and a positive electrode C. The positive and negative electrodes in the stacked cell are stacked in an arrangement of A / C / A / C / A / C……A / C / B / C / B / C…… / B / C / A / C……A / C / A and separated by a separator. The single-particle graphite and the secondary-particle graphite have the same specific capacity.

[0040] Traditional stacked battery technology uses a single negative electrode A or B and a positive electrode C, stacked in the form of A / C / A / C...A / C or B / C / B / C...B / C, with the positive and negative electrodes separated by a separator to form a stacked core. In contrast, the battery of this invention uses two types of negative electrodes. With the same negative electrode ratio and areal density, and ensuring the same excess ratio (excess ratio = negative electrode specific capacity × active material percentage × coating areal density / (positive electrode specific capacity × active material percentage × coating areal density)) and roll-forming thickness, one negative electrode uses a single-particle graphite as its active material, and the other uses a secondary-particle graphite. The secondary particles and single particles have the same specific capacity. The materials are mixed in the same ratio, coated, rolled, and die-cut to obtain a first negative electrode A (A) using a single-particle graphite and a second negative electrode B (B) using a secondary-particle graphite. The positive electrode is manufactured using a normal process to obtain a positive electrode C (C). The positive and negative electrode sheets are stacked in the following arrangement: A / C / A / C / A / C…A / C / B / C / B / C… / B / C / A / C…A / C / A. The positive and negative electrode sheets are separated by a separator, resulting in the final stacked cell (referred to as a stacked cell). The number of A and B electrodes in the negative electrode is a positive integer m and n, respectively, and the number of positive electrode sheets is m+n-1. The stacked cells then undergo baking, electrolyte filling, and other processes to obtain the finished battery.

[0041] This invention employs a composite stacked structure, which, compared to the traditional single-layer stacked structure of B / C / B / C... / B / C, offers several advantages. First, it adds a single-particle graphite anode sheet, combining the high capacity and rate capability of secondary particles with the structural stability and long cycle life of single-particle sheets. Furthermore, under the same coating areal density and compaction density, the single-particle graphite electrode has a faster electrolyte absorption rate than the secondary-particle graphite electrode. By placing the single-particle graphite anode sheet on the outer layer of the stack and the secondary-particle graphite anode sheet on the inner layer, the faster electrolyte absorption allows for rapid diffusion of the electrolyte to the inner layer, shortening the electrolyte wetting time and solving the problem of wetting difficulties caused by increased thickness and energy density in lithium-ion batteries. Second, compared to a mixture of single and secondary graphite particles as an anode active material, it reduces uneven mixing in the slurry, improving coating consistency. Third, with the same raw materials, single-particle graphite eliminates the need for a granulation process compared to secondary-particle graphite, resulting in a cost advantage in production. Furthermore, the use of single particles reduces the need for secondary particles, thus lowering material costs.

[0042] In this invention, single-particle graphite, or primary-particle graphite, refers to the primary particles prepared from raw materials through multiple steps such as crushing, graphitization, and sieving; while secondary-particle graphite refers to the final particles made by granulating primary-particle graphite. For example, secondary particles are generally made by adding asphalt as a binder and bonding primary particles into clumps at high temperature to become secondary particles.

[0043] As an optional embodiment of the battery of the present invention, the D50 of the single-particle graphite is 8-15μm;

[0044] And / or, the D50 of the secondary particle graphite is 15-16 μm;

[0045] And / or, the specific capacity of both the single-particle graphite and the secondary-particle graphite is 335-355 mAh / g.

[0046] The graphite used in the battery of this invention can be from BTR New Materials Group Co., Ltd. (BTR), Shanshan New Energy Co., Ltd. (Shanshan), or Xiangfenghua New Energy Materials Co., Ltd. (Xiangfenghua). Specifically, the single-particle graphite can be from BTR or Shanshan, with a D50 of 8-12μm, no carbon coating, and a compaction density of 1.55g / cm³. 3 The capacity is around 340mAh / g, and the secondary granular graphite is made from materials from Shanshan or BTR. The D50 is 15-16μm, with no carbon coating, and the compaction density is 1.55g / cm³. 3 Around 340mAh / g; or, using products from BTR, Shanshan, or Xiangfenghua for individual particles, with a D50 of 9-14μm, no carbon coating, and a compaction density of 1.65g / cm³. 3The capacity is around 350mAh / g, and the secondary particles are made from materials from Shanshan, BTR, or Xiangfenghua. The D50 is 15-16μm, with no carbon coating, and the compaction density is 1.65g / cm³. 3 The density is around 350 mAh / g. Optionally, the D50 of single-particle graphite can typically, but is not limited to, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, etc.; the D50 of secondary-particle graphite can typically, but is not limited to, 15.1 μm, 15.2 μm, 15.3 μm, 15.4 μm, 15.5 μm, etc. 5μm, 15.6μm, 15.7μm, 15.8μm, 15.9μm, etc.; the specific capacity of single-particle graphite and secondary-particle graphite can typically, but not exclusively, be 336mAh / g, 338mAh / g, 340mAh / g, 342mAh / g, 344mAh / g, 346mAh / g, 348mAh / g, 350mAh / g, 352mAh / g, 354mAh / g, etc.

[0047] In one optional embodiment of the battery of the present invention, the compaction density of both the first negative electrode A and the second negative electrode B is 1.50-1.65 g / cm³. 3 (e.g., 1.51 g / cm³) 3 1.53g / cm 3 1.55g / cm 3 1.57g / cm 3 1.59g / cm 3 1.61 g / cm 3 1.63g / cm 3 wait);

[0048] And / or, the mass ratio of the first negative electrode A and the second negative electrode B is 94-97:0.5-2:3.0-4.5 (e.g., 94:2:4, 94.5:1.6:3.9, 95:1.3:3.7, 95.5:1:3.5, 96:0.7:3.3, 96.5:0.5:3, etc.) based on the ratio of negative electrode active material: conductive agent: binder.

[0049] And / or, the areal density of both the first negative electrode A and the second negative electrode B is 150–175 g / m³. 2 (e.g., 155g / cm) 3 160g / cm 3 165g / cm 3 170g / cm 3 174g / cm 3 wait);

[0050] And / or, the ratio of the number m of the first negative electrode A to the number n of the second negative electrode B is 1:4 to 1.5:1 (e.g., 1:3.8, 1.5:3.5, 2:3, 2.5:2.5, 3:2.1, etc.).

[0051] In this invention, the negative electrode active material refers to single-particle graphite or secondary-particle graphite.

[0052] Furthermore, when the negative electrode sheet is compacted to 1.50-1.55 g / cm³... 3 The ratio of single-particle to secondary-particle electrode sheets can be selected from 1:4 to 3:7 (e.g., 2:7, 9:28, 5:14, 11:28, etc.); when the negative electrode sheet is compacted to 1.55-1.65 g / cm³. 3 For single-particle negative electrodes, the ratio of single-particle to secondary-particle electrode number can be selected from 1:1 to 3:2 (such as 2.1:2, 2.3:2, 2.5:2, 2.7:2, 2.9:2, etc.).

[0053] In this invention, no particular limitations are placed on the binders, conductive agents, and positive active materials in the positive and negative electrode materials. Existing conventional materials can be used, such as those commonly used in existing lithium batteries: positive active materials / substances include lithium iron phosphate, etc.; binders include PVDF (polyvinylidene fluoride), CMC (sodium carboxymethyl cellulose), and SBR (styrene-butadiene rubber), etc.; and conductive agents include SP (carbon black), graphene, carbon nanotubes, and VGCF (carbon nanofibers), etc.

[0054] As an optional embodiment of the battery of the present invention, the mass ratio of the positive electrode sheet C is 96-98:0.5-2.0:1.5-3.0 according to the ratio of positive electrode active material: conductive agent: binder (e.g., 96:1:3, 96.5:1.1:2.4, 97:1.2:1.8, 97.2:1.3:1.5, etc.);

[0055] And / or, the positive electrode active material of the positive electrode C is lithium iron phosphate.

[0056] As an optional embodiment of the battery of the present invention, the separator is a single-sided coated ceramic separator.

[0057] As an optional embodiment of the battery of the present invention, the thickness of the stacked cells is 25-35mm (e.g., 26mm, 28mm, 30mm, 32mm, 34mm, etc.).

[0058] As an optional embodiment of the battery of the present invention, the energy density of the battery is 165-175Wh / kg (e.g., 166Wh / kg, 168Wh / kg, 170Wh / kg, 172Wh / kg, 174Wh / kg, etc.).

[0059] A method for preparing the battery includes the steps of material preparation, coating, rolling, die cutting, stacking, baking, electrolyte injection, formation, and capacity testing. During material preparation, single-particle graphite is prepared in the slurry of the first negative electrode A, and secondary-particle graphite is prepared in the slurry of the second negative electrode B. The specific capacity of the single-particle graphite and the secondary-particle graphite is the same. During stacking, the first negative electrode A, the second negative electrode B, and the positive electrode C are stacked in an arrangement of A / C / A / C / A / C…A / C / B / C / B / C… / B / C / A / C…A / C / A and separated by a separator.

[0060] The present invention will be further described below with reference to specific embodiments and comparative examples.

[0061] Example 1

[0062] A composite laminated battery includes a laminated cell made of a first negative electrode A using single-particle graphite, a second negative electrode B using secondary-particle graphite, and a positive electrode C. The positive and negative electrodes in the laminated cell are stacked in an arrangement of A / C / A / C / A / C…A / C / B / C / B / C… / B / C / A / C…A / C / A and separated by a separator. The specific stacking method is as follows: Figure 1 As shown in the figure. The specific capacity of single-particle graphite and secondary-particle graphite is the same, both being 340 mAh / g; the D50 of single-particle graphite is 8–12 μm, without carbon coating, and the compaction density is 1.55 g / cm³. 3 The secondary particulate graphite has a D50 of 15–16 μm, no carbon coating, and a compacted density of 1.55 g / cm³. 3 The graphite particles are both single-particle and double-particle graphite, both of which are products from Shanshan New Energy Co., Ltd.

[0063] The compaction density of the first negative electrode A and the second negative electrode B is 1.52 g / cm³. 3 The areal density of the electrode sheets is 150–175 g / m³. 2 The number of the first negative electrode A and the second negative electrode B are set according to the ratio of A:B = m:n = 3:7, which are 21pcs and 49pcs respectively, and the number of the positive electrode C is 69pcs.

[0064] The mass ratio of the first negative electrode A and the second negative electrode B is 95.6:1:3.4, calculated as negative electrode active material: conductive agent: binder; wherein the binder is CMC:SBR = 1.4:2, and the conductive agent is SP.

[0065] The mass ratio of the positive electrode C to the positive electrode active material is 97.5:1:1.5:1.5, based on the ratio of positive electrode active material to conductive agent to binder. The positive electrode active material is lithium iron phosphate, the binder is PVDF, and the conductive agent is SP.

[0066] The diaphragm is a single-sided coated ceramic diaphragm;

[0067] In this embodiment, the thickness of the stacked cells is 30mm, and the energy density of the battery is 165-175Wh / kg.

[0068] The above-mentioned battery preparation method includes steps such as material preparation, coating, rolling, die cutting, stacking, baking, electrolyte injection, formation, and capacity testing. In the material preparation process, single-particle graphite is prepared into the slurry of the first negative electrode A, and secondary-particle graphite is prepared into the slurry of the second negative electrode B. Specifically, the positive electrode is prepared according to the ratio of lithium iron phosphate: SP:PVDF = 97.5:1:1.5, and the negative electrode is prepared according to the ratio of single-particle / secondary-particle graphite: SP:CMC:SBR = 95.6:1:1.4:2. After homogenization, coating and rolling are performed.

[0069] Coating roller pressing: Control the areal density of the positive electrode C to be 300-360 g / m³ 2 The compacted density is 2.40–2.45 g / cm³. 3 The areal density of both the first negative electrode A and the second negative electrode B is 150–175 g / m³. 2 The compacted density is 1.52 g / cm³. 3 ;

[0070] When stacking the pieces, it is as shown in the diagram. Figure 1 The arrangement shown follows the sequence A / C / A / C / A / C……A / C / B / C / B / C…… / B / C / A / C……A / C / A and is separated by a diaphragm, which is a single-sided coated ceramic diaphragm.

[0071] After baking and ensuring the moisture content is within acceptable limits, the battery is injected with electrolyte. After injection, it is placed at 45°C for 12-24 hours for formation. After formation, it is aged for 12-48 hours, then capacity is assessed, and the battery is taken off the production line for performance testing.

[0072] Example 2

[0073] A composite laminated battery includes a laminated cell made of a first negative electrode A using single-particle graphite, a second negative electrode B using secondary-particle graphite, and a positive electrode C. The positive and negative electrodes in the laminated cell are stacked in an arrangement of A / C / A / C / A / C…A / C / B / C / B / C… / B / C / A / C…A / C / A and separated by a separator. The specific stacking method is as follows: Figure 1 As shown in the figure. The specific capacity of single-particle graphite and secondary-particle graphite is the same, both being 350 mAh / g; the D50 of single-particle graphite is 9–14 μm, without carbon coating, and the compaction density is 1.65 g / cm³. 3 The secondary particulate graphite has a D50 of 15–16 μm, no carbon coating, and a compacted density of 1.65 g / cm³. 3 The single-particle graphite is a product of BTR New Materials Group Co., Ltd., while the secondary-particle graphite is a product of Xiangfenghua New Energy Materials Co., Ltd.

[0074] The compaction density of the first negative electrode A and the second negative electrode B is 1.60 g / cm³. 3 The areal density of the electrode is 180–200 g / m³. 2 The number of the first negative electrode A and the second negative electrode B are set according to the ratio of A:B = m:n = 1:1, which are 32pcs and 32pcs respectively, and the number of the positive electrode C is 63pcs.

[0075] The mass ratio of the first negative electrode A and the second negative electrode B is 95.6:1:3.4, calculated as negative electrode active material: conductive agent: binder; wherein the binder is CMC:SBR = 1.4:2, and the conductive agent is SP.

[0076] The mass ratio of the positive electrode C to the positive electrode active material is 97.5:1:1.5:1.5, based on the ratio of positive electrode active material to conductive agent to binder. The positive electrode active material is lithium iron phosphate, the binder is PVDF, and the conductive agent is SP.

[0077] The diaphragm is a single-sided coated ceramic diaphragm;

[0078] In this embodiment, the thickness of the stacked cells is 30mm, and the energy density of the battery is 165-175Wh / kg.

[0079] The above-mentioned battery preparation method includes steps such as material preparation, coating, rolling, die cutting, stacking, baking, electrolyte injection, formation, and capacity testing. In the material preparation process, single-particle graphite is prepared into the slurry of the first negative electrode A, and secondary-particle graphite is prepared into the slurry of the second negative electrode B. Specifically, the positive electrode is prepared according to the ratio of lithium iron phosphate: SP:PVDF = 97.5:1:1.5, and the negative electrode is prepared according to the ratio of single-particle / secondary-particle graphite: SP:CMC:SBR = 95.6:1:1.4:2. After homogenization, coating and rolling are performed.

[0080] Coating roller pressing: Control the areal density of the positive electrode C to be 350-400 g / m³ 2 The compacted density is 2.45–2.55 g / cm³. 3 The areal density of both the first negative electrode A and the second negative electrode B is 180–200 g / m³. 2 The compacted density is 1.60 g / cm³. 3 ;

[0081] When stacking the pieces, it is as shown in the diagram. Figure 1 The arrangement shown follows the sequence A / C / A / C / A / C……A / C / B / C / B / C…… / B / C / A / C……A / C / A, and is separated by a diaphragm, which is a single-sided coated ceramic diaphragm.

[0082] After baking and ensuring the moisture content is within acceptable limits, the battery is injected with electrolyte. After injection, it is placed at 45°C for 24-36 hours for formation. After formation, it is aged for 12-48 hours, then capacity is assessed, and the battery is taken off the production line for performance testing.

[0083] Comparative Example 1

[0084] A conventional stacked battery and its preparation method differ from Example 1 only in that there is only a first negative electrode A, and the number of first negative electrode A is 70 pcs. That is, the positive and negative electrode sheets in the stacked cell are stacked in the arrangement of A / C / A / C / A / C...A / C / A. All other settings are the same as in Example 1.

[0085] Comparative Example 2

[0086] A conventional stacked battery and its preparation method differ from Example 1 only in that there is only a second negative electrode B, and the number of second negative electrode B is 70 pcs. That is, the positive and negative electrode sheets in the stacked cell are stacked in the arrangement of B / C / B / C / B / C...B / C / B. All other settings are the same as in Example 1.

[0087] Comparative Example 3

[0088] A composite laminated battery and its preparation method differ from Example 1 only in that the stacking positions of the first negative electrode A and the second negative electrode B are reversed compared to Example 1. That is, the positive and negative electrodes in the laminated cell are stacked in the following arrangement: B / C / B / C / B / C…B / C / A / C / A / C / …A / C / B / C…B / C / B, meaning the first negative electrode A is in the inner layer of the laminated cell and the second negative electrode B is in the outer layer. All other configurations are the same as in Example 1.

[0089] Comparative Example 4

[0090] A conventional stacked battery and its preparation method differ from Example 2 only in that there is only a first negative electrode A, and the number of first negative electrode A is 64 pieces. That is, the positive and negative electrode sheets in the stacked cell are stacked in the arrangement of A / C / A / C / A / C...A / C / A. All other settings are the same as in Example 2.

[0091] Comparative Example 5

[0092] A conventional stacked battery and its preparation method differ from Example 2 only in that there is only a second negative electrode B, and the number of second negative electrode B is 64 pieces. That is, the positive and negative electrode sheets in the stacked cell are stacked in the arrangement of B / C / B / C / B / C...B / C / B. All other settings are the same as in Example 2.

[0093] Comparative Example 6

[0094] A composite laminated battery and its preparation method differ from Example 2 only in that the stacking positions of the first negative electrode A and the second negative electrode B are reversed compared to Example 2. That is, the positive and negative electrodes in the laminated cell are stacked in the following arrangement: B / C / B / C / B / C…B / C / A / C / A / C / …A / C / B / C…B / C / B, meaning the first negative electrode A is in the inner layer of the laminated cell and the second negative electrode B is in the outer layer. All other configurations are the same as in Example 2.

[0095] Test and Results Analysis

[0096] The batteries obtained in Examples 1 and 2 and Comparative Examples 1-6 were tested as follows:

[0097] 1. Immersion test

[0098] The liquid absorption rate can be characterized by immersing electrodes of the same weight in an equal amount of electrolyte, weighing the electrodes after the same amount of time, and calculating the weight difference.

[0099] In the embodiments and comparative examples of this invention, an equal amount of electrolyte was injected during the injection process, and the weight of the stacked core was measured after immersion for 24 hours. The weight difference between the core and the un-immersed core was calculated.

[0100] Figure 2 , 3 The liquid absorption rates of the stacked cells under two different compaction conditions are shown. It can be seen that the liquid absorption rate of the secondary graphite anode sheet is lower than that of the single graphite anode sheet, while the liquid absorption time is equal. This indicates that the single graphite anode sheet has a higher liquid absorption rate. Introducing it into the secondary graphite anode sheet battery creates a composite stacked structure where single graphite anode sheets coexist on the outer layer of the stacked cell and secondary graphite anode sheets are on the inner layer. This significantly improves the liquid absorption rate of the secondary graphite anode sheet battery, effectively shortening the electrolyte wetting time and addressing the problem of difficult wetting. When the battery compaction reaches 1.52 g / cm³, the liquid absorption rate is significantly reduced. 3 Under compaction, adding a small amount of single-particle graphite negative electrode sheet, i.e., single-particle graphite negative electrode sheet accounting for 30% of the total number of negative electrode sheets, can increase the liquid absorption of the cell by 5% (calculated based on (mixed A on the outside - secondary particles B) / secondary particles B × 100%); when compacted to 1.60 g / cm³ 3 At that time, the single particle addition amount was 50%, and the increase was only 1.5% (calculated based on (mixed A outside - secondary particle B) / secondary particle B × 100%).

[0101] 2. Rate charge / discharge test

[0102] The rate charging test was performed by charging to 3.65V at a constant current of 0.33C / 0.5C / 1C / 2C, and discharging to 2.5V at a constant current of 0.33C. The rate charging test results for the stacked cores under different compaction conditions are shown in Tables 1 and 2.

[0103] Table 11.52 g / cm 3 Table of Rate Charging Capacity Retention Rate under Compacted Stacked Cores

[0104]

[0105] Table 21.60 g / cm 3 Table of Rate Charging Capacity Retention Rate under Compacted Stacked Cores

[0106]

[0107] The rate discharge test was performed by constant current discharge to 2.5V at 0.33C / 0.5C / 1C / 2C, and charging was performed by constant current charging to 3.65V at 0.33C, with a constant voltage cutoff current of 0.05C. The rate discharge test results of the stacked cores under different compaction conditions are shown in Tables 3 and 4.

[0108] Table 31.52 g / cm 3 Table of Rate Discharge Capacity Retention Rate under Compacted Core Stack

[0109]

[0110] Table 41.60 g / cm 3 Table of Rate Discharge Capacity Retention Rate under Compacted Core Stack

[0111]

[0112]

[0113] Table 1, Table 3 Figure 4 , 5 It is 1.52 g / cm³ 3 The rate charge and discharge capacity retention rates of the compacted stacked cores show that, when charging at no more than 1C, the rate charge performance of the single-particle-on-the-outside composite stacked group of Example 1 is comparable to that of Comparative Examples 2 and 3, but superior to that of Comparative Example 1. However, when charging at 2C, the rate charge performance of the single-particle-on-the-outside composite stacked group of Example 1 becomes inferior to that of Comparative Examples 2 and 3, but is still superior to that of Comparative Example 1. As for the discharge performance, the high rate discharge capacity retention rate of the single-particle-on-the-outside composite stacked group of Example 1 is comparable to or even slightly better than that of the secondary particle group of Comparative Example 2, and is also slightly higher than that of the other two groups.

[0114] Table 2, Table 4 Figure 6 , 7 It is 1.60 g / cm³ 3 The rate charge and discharge capacity retention rates of each group under compaction show that the rate charging performance of the composite stacked group with single particles on the outside in Example 2 is better than that of the other three groups; and the rate discharge capacity retention rate of the composite stacked group in Example 2 is comparable to that of the secondary particle group in Comparative Example 5, which is higher than that of the single particle group in Comparative Example 4.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite laminated battery, characterized in that: The battery cell comprises a first negative electrode A made of single-particle graphite, a second negative electrode B made of secondary-particle graphite, and a positive electrode C. The positive and negative electrodes in the battery cell are stacked in the arrangement A / C / A / C / A / C……A / C / B / C / B / C…… / B / C / A / C……A / C / A and separated by a separator. The specific capacity of the single-particle graphite and the secondary-particle graphite is the same.

2. The battery as described in claim 1, characterized in that: The D50 of the single-particle graphite is 8-15µm; And / or, the D50 of the secondary particle graphite is 15-16µm; And / or, the specific capacity of both the single-particle graphite and the secondary-particle graphite is 335~355mAh / g.

3. The battery as described in claim 1, characterized in that: The first negative electrode A and the second negative electrode B have the same compaction density, ingredient mass ratio and areal density; And / or, the number of the first negative electrode A and the second negative electrode B are positive integers m and n, respectively, and the number of the positive electrode C is m+n-1.

4. The battery as described in claim 3, characterized in that: The compaction density of both the first negative electrode A and the second negative electrode B is 1.50-1.65 g / cm³. 3 ; And / or, the mass ratio of the first negative electrode A and the second negative electrode B is 94~97:0.5~2:3.0~4.5, calculated as negative electrode active material: conductive agent: binder. And / or, the areal density of both the first negative electrode A and the second negative electrode B is 150~175 g / m³. 2 ; And / or, the ratio of the number m of the first negative electrode A to the number n of the second negative electrode B is 1:4 to 1.5:

1.

5. The battery as described in claim 4, characterized in that: The compaction density of both the first negative electrode A and the second negative electrode B is 1.50-1.55 g / cm³. 3 The ratio of the number m of the first negative electrode A to the number n of the second negative electrode B is 1:4 to 3:

7.

6. The battery as described in claim 4, characterized in that: The compaction density of both the first negative electrode A and the second negative electrode B is 1.55-1.65 g / cm³. 3 The ratio of the number m of the first negative electrode A to the number n of the second negative electrode B is 1:1 to 3:

2.

7. The battery as described in claim 1, characterized in that: The mass ratio of the positive electrode C to the positive electrode active material is 96~98:0.5~2.0:1.5~3.0, calculated as positive electrode active material: conductive agent: binder. And / or, the positive electrode active material of the positive electrode C is lithium iron phosphate.

8. The battery as described in claim 1, characterized in that: The diaphragm is a single-sided coated ceramic diaphragm.

9. The battery as described in claim 1, characterized in that: The thickness of the laminated battery cell is 25~35mm.

10. The battery as claimed in claim 1, characterized in that: The energy density of the battery is 165~175Wh / kg.

11. The method for preparing the battery according to any one of claims 1-10, characterized in that: The process includes steps such as batching, coating, rolling, die-cutting, stacking, baking, liquid injection, formation, and capacity separation. During batching, single-particle graphite is prepared into the slurry of the first negative electrode A, and secondary-particle graphite is prepared into the slurry of the second negative electrode B. The specific capacity of the single-particle graphite and the secondary-particle graphite is the same. During stacking, the first negative electrode A, the second negative electrode B, and the positive electrode C are stacked in the arrangement A / C / A / C / A / C……A / C / B / C / B / C…… / B / C / A / C……A / C / A and separated by a diaphragm.

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