Negative electrode sheet, battery, preparation method, and use

Abstract

A negative electrode sheet, a battery, a preparation method, and a use, relating to the technical field of lithium-ion batteries. The structure of the negative electrode sheet comprises: a current collector; and an active material layer which is arranged on the surface of the current collector. The number of the active material layers is greater than or equal to 1, and pore slots are formed in the surface of at least one active material layer; the depth H of each pore slot and the thickness T of the active material layer satisfy the following relationship: 1 / 3T<H≤2 / 3T; and the compaction density of the active material layer is P, wherein P satisfies the following relationship: 1.55≤P≤1.75 g / cm3. When the active material layer has high compaction density, the wettability balance between the negative electrode sheet and an electrolyte is achieved, it is ensured that the battery has high energy density gains, and the battery also has good liquid retention capability and excellent high- and low- temperature cycle life.

Description

A negative electrode sheet, battery, and preparation method and application thereof Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a negative electrode sheet, a battery, and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries are a common rechargeable battery widely used in mobile devices, electric vehicles, and renewable energy storage systems. They store and release electrical energy through the electrochemical reaction of lithium ions between a positive and negative electrode. The main components of a lithium-ion battery include a positive electrode, a negative electrode, an electrolyte, and a separator. The positive electrode is typically composed of a lithium compound (such as lithium manganese oxide, lithium cobalt oxide, or lithium iron phosphate), while the negative electrode is often made of graphite. The electrolyte is a conductive solution or polymer film that conducts ions. The separator separates the positive and negative electrodes to prevent short circuits. The operating principle of a lithium-ion battery is that lithium ions intercalate and deintercalate between the positive and negative electrodes during charge and discharge. When the battery is charged, lithium ions are released from the positive electrode, move through the electrolyte to the negative electrode, and intercalate there. When the battery is discharged, lithium ions are deintercalated from the negative electrode and move back to the positive electrode. This intercalation and deintercalation process is reversible, allowing lithium-ion batteries to be charged and discharged multiple times. Lithium-ion batteries offer many advantages, such as high energy density, long cycle life, low self-discharge rate, and minimal memory effect. They are also lighter and easier to maintain than other types of rechargeable batteries and have higher voltage stability.

[0003] As market demands for battery performance continue to increase, high-performance lithium-ion batteries must not only possess high energy density but also an excellent long cycle life. To improve the energy density of lithium-ion batteries, one of the most common measures is to increase the compaction density of the positive and negative electrodes. However, increasing the compaction density has a significant negative impact on the amount and time that the electrodes and separators absorb liquid. Excessive liquid absorption by the battery cell can lead to adverse reactions such as battery drain in the later stages of the cycle.

[0004] To improve electrolyte wetting, high-temperature standing or vacuum standing after injection, or complex formation processes are usually used. In addition, some battery companies have solved the problem of electrode and diaphragm absorption by reducing the viscosity of the electrolyte and adding new wetting agents to increase the amount of liquid absorbed by the electrode and diaphragm in the battery cell and reduce the absorption time. If the electrolyte increases the content of low-melting-point, low-viscosity solvents, the wettability of the electrode will improve, but the high-temperature performance of the battery will be deteriorated. If the viscosity of the electrolyte increases, the high-temperature performance of the battery is better, but the penetration ability is weak, resulting in insufficient wetting, which in turn causes the product to malfunction.

[0005] Therefore, how to make the electrode and the electrolyte have appropriate wettability and improve the battery's liquid retention and high and low temperature cycle life has become a technical problem that needs to be solved urgently.

[0006] Summary of the Invention

[0007] The first technical problem to be solved by the present invention is:

[0008] A negative electrode sheet is provided.

[0009] The second technical problem to be solved by the present invention is:

[0010] A battery is provided.

[0011] In order to solve the first technical problem, the technical solution adopted by the present invention is:

[0012] A negative electrode sheet, the structure of the negative electrode sheet comprising:

[0013] current collector;

[0014] an active material layer disposed on the surface of the current collector;

[0015] The number of the active material layers is greater than or equal to 1, and a surface of at least one active material layer is provided with pores and grooves;

[0016] The depth H of the pores and the thickness T of the active material layer satisfy the following relationship: 1 / 3T<H≤2 / 3T;

[0017] The compacted density of the active material layer is P, and P satisfies the following relationship: 1.55≤P≤1.75g / cm 3 .

[0018] According to the embodiments of the present invention, one of the technical solutions has at least one of the following advantages or beneficial effects:

[0019] The present invention further balances the wettability between the negative electrode plate and the electrolyte when the active material layer has a high compaction density, ensuring that the battery has a high energy density while also having good liquid retention ability and excellent high and low temperature cycle life.

[0020] Specifically:

[0021] The high compaction density of the active material layer can effectively improve the energy density of the battery, but the high compaction density will reduce the gaps in the active material layer, increase the difficulty of electrolyte infiltration, easily cause poor infiltration, and cause the battery's liquid retention ability to deteriorate. Based on this, the present invention sets holes and grooves on the active material layer on the surface of the negative electrode to help the circulation of the electrolyte to improve infiltration, promote battery liquid retention, form a channel for rapid diffusion of lithium ions, and effectively alleviate the infiltration and lithium precipitation problems of high-density electrode sheets. Furthermore, by setting the depth H of the hole groove and the thickness T of the active material layer, the circulation of the electrolyte is regulated, the wettability between the negative electrode sheet and the electrolyte is balanced, and the high energy density of the battery is guaranteed, as well as good liquid retention and excellent high and low temperature cycle life.

[0022] According to one embodiment of the present invention, the active material layer is provided on the upper surface and / or lower surface of the current collector.

[0023] According to one embodiment of the present invention, the volume fraction of pores in the active material layer is η, where η satisfies the following relationship: 1% ≤ η ≤ 5%. This solution specifies that pores are provided in the active material layer on the surface of the negative electrode sheet to facilitate electrolyte flow and improve wetting. However, if the volume fraction of pores in the negative electrode sheet is too high, it will affect the N / P ratio of the positive and negative electrodes; if the volume fraction is too low, electrolyte wetting is not ideal, and the lithium ion transmission path is blocked. Therefore, the volume fraction of pores in the active material layer must be strictly controlled.

[0024] According to one embodiment of the present invention, the punching width of the pores in the active material layer is R, and R satisfies the following relationship: 50≤R≤140 μm.

[0025] According to one embodiment of the present invention, the spacing between the holes and grooves in the active material layer is L, and L satisfies the following relationship: 1.0≤L≤2.5mm.

[0026] According to one embodiment of the present invention, the angle between the holes in the conductive material layer and the negative electrode sheet is θ, where θ satisfies the following relationship: 85°≤θ≤95°. The angle between the holes and the negative electrode sheet, the spacing between the holes, the hole width, the volume ratio of the holes, and the depth H of the holes all affect the holes' control of electrolyte flow, thereby affecting electrolyte retention stability.

[0027] According to one embodiment of the present invention, the material of the negative electrode sheet includes at least one of graphite and silicon-carbon mixed graphite.

[0028] In order to solve the second technical problem, the technical solution adopted by the present invention is:

[0029] A battery comprises a positive electrode sheet, a separator, an electrolyte and the negative electrode sheet.

[0030] According to one embodiment of the present invention, the components of the electrolyte include a non-aqueous solvent, a lithium salt and an additive, wherein the non-aqueous solvent includes a first organic solvent and a second organic solvent, the mass fraction of the first organic solvent in the electrolyte is W1, and W1 satisfies the following relationship: 30wt.%≤W1≤45wt.%; the mass fraction of the second organic solvent in the electrolyte is W2, and W2 satisfies the following relationship: 15wt.%≤W2≤40wt.%, and W2≤W1≤3W2.

[0031] According to one embodiment of the present invention, the viscosity of the electrolyte is ω, and ω satisfies the following relationship: 0.4≤ω≤2mPa·s. The viscosity ω of the electrolyte is the viscosity of the electrolyte at 25°C. Too low viscosity of the electrolyte will deteriorate the high-temperature performance, and an increase in the viscosity of the electrolyte is not conducive to the performance of the low-temperature performance, and will also affect the wetting effect and liquid retention stability of the battery. By setting the ratio of the first solvent and the second solvent of the present invention to regulate the viscosity of the electrolyte, combined with the pore effect of the negative electrode sheet, the viscosity and liquid retention stability of the electrolyte can be appropriately improved while ensuring wetting, taking into account the high and low temperature performance of the battery. Therefore, the present invention reduces the requirements of high compaction density on the penetration ability of the electrolyte, broadens the selection types and ratio window of solvents and additives, and significantly improves the overall performance of the battery.

[0032] According to one embodiment of the present invention, the negative electrode sheet has a compacted density of P, includes an active material layer, and has pores in the active material layer. The volume fraction of the pores is η, and P, η, W1, and ω satisfy the following relationship: 2.8≤(P*ω) / (10*=*W1)≤50. To ensure stable liquid retention between the negative electrode sheet and the electrolyte, while taking into account the high and low temperature performance of the battery, the compacted density, pore volume fraction, and electrolyte solvent of the negative electrode sheet must satisfy the above relationship. When the compacted density is high, there are fewer gaps between the various substances in the active material layer, making it extremely difficult for the electrolyte to infiltrate and maintain liquid stability. Low electrolyte viscosity facilitates electrolyte infiltration, but in high temperature environments, the reactivity of the substances in the active material layer is also enhanced, increasing side reactions with the electrolyte, generating more byproducts and heat, and posing a significant safety risk. The presence of pores on the electrode surface facilitates good liquid retention stability of the electrode sheet and provides a path for rapid lithium ion transmission. Therefore, under high compaction density, the electrode surface is provided with holes and grooves, which can appropriately increase the viscosity of the electrolyte, so that the electrode has good liquid retention stability and excellent performance at high or low temperatures.

[0033] According to one embodiment of the present invention, the negative electrode sheet has a decompression compaction density of β, and the decompression compaction density β, the negative electrode sheet's compaction density P, and the electrolyte viscosity ω satisfy the following relationship: 0.05≤ω*(P-β) / P≤0.23. Meeting this relationship further enhances the negative electrode sheet's liquid retention stability. Furthermore, in this relationship, the various materials in the active material layer are in good contact, and the presence of pores and grooves in the active material layer on the anode sheet's surface further reduces obstacles to lithium ion transport, helping to reduce heat generation during battery charge and discharge, and improving the battery's high and low temperature performance.

[0034] According to one embodiment of the present invention, the first organic solvent includes at least one of a carbonate organic solvent and a carboxylate organic solvent; the second organic solvent includes at least one of a sulfur solvent, a fluorinated solvent, a sulfone solvent and a nitrile solvent.

[0035] According to one embodiment of the present invention, the first organic solvent includes at least one of ethylene carbonate, propylene carbonate, γ-butyrolactone L, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate.

[0036] According to one embodiment of the present invention, the mass fraction of the first organic solvent in the electrolyte is W1, and 30 wt.%≤W1≤45 wt.%.

[0037] According to one embodiment of the present invention, the second organic solvent includes at least one of CF3SO2N(CH2CH3)(CH3), CF3SO2N(CH2CH3)2, CF3SO2N(CH3)2, CF3CF2SO2N(CH3)2, sulfite, butylene sulfite, methoxyethyl methyl sulfone, tetramethylene sulfone, succinonitrile, pivalonitrile, fluorinated dioxolane, pyrrolidine, piperidine and ammonium solvents.

[0038] According to one embodiment of the present invention, the mass fraction of the second organic solvent in the electrolyte is W2, and 15 wt.%≤W2≤40 wt.%.

[0039] According to one embodiment of the present invention, the electrolyte in the battery further includes a lithium salt, and the lithium salt includes at least one of LiFSI, LiTFSI, LiBOB, and LiPO2F2.

[0040] According to one embodiment of the present invention, the mass fraction of the lithium salt in the electrolyte is 10 to 20 wt.%.

[0041] According to one embodiment of the present invention, the electrolyte in the battery further includes an additive, and the additive includes at least one of 1,3-propane sultone, 1,3-propylene sultone, 1,3,6-hexane trinitrile, 1,3-propane sultone, vinyl sulfate and 1,2-bis(cyanoethoxy)ethane.

[0042] According to one embodiment of the present invention, the mass percentage of the additive in the electrolyte is 10 to 20 wt.%.

[0043] According to one embodiment of the present invention, the material of the positive electrode plate includes at least one of lithium cobalt oxide, ternary materials and lithium-rich materials.

[0044] According to one embodiment of the present invention, the material of the diaphragm includes at least one of polyethylene, polypropylene and polyvinylidene fluoride.

[0045] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0047] FIG1 is a schematic structural diagram of the active material layer in Example 1. DETAILED DESCRIPTION

[0048] In the description of the present invention, if there is a description of first, second, etc., it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0049] In the description of the present invention, it should be understood that descriptions involving orientation, such as the orientation or positional relationship indicated by up, down, etc., are based on the orientation or positional relationship shown in the embodiment, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0050] The terms "preferably," "more preferably," and the like, used herein refer to embodiments of the present invention that may provide certain benefits under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the present invention.

[0051] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are understood to include any and all subranges subsumed therein.

[0052] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of the present invention.

[0053] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0054] In the examples and comparative examples, the first organic solvent is ethylene carbonate, the second organic solvent is methoxyethyl methyl sulfone, the lithium salt is LiPO2F2, and the additive is 1,3-propylene sultone.

[0055] In the Examples and Comparative Examples, the viscosity ω of the electrolyte is the viscosity of the electrolyte at 25°C.

[0056] Example 1

[0057] A negative electrode sheet, the structure of the negative electrode sheet comprising:

[0058] current collector;

[0059] An active material layer is provided on the surface of the current collector; a schematic structural diagram of the active material layer is shown in FIG1 ;

[0060] The number of the active material layer is 1, and the surface of the active material layer is provided with pores and grooves;

[0061] The depth H of the pores and the thickness T of the active material layer satisfy the following relationship: 1 / 3T<H≤2 / 3T;

[0062] The compacted density of the active material layer is P, which is 1.6 g / cm 3 .

[0063] The volume ratio of pores in the active material layer is η, and η is 1%.

[0064] A battery comprises a positive electrode sheet, a separator, an electrolyte and the above-mentioned negative electrode sheet.

[0065] The method for preparing the positive electrode sheet comprises the following steps:

[0066] The active material LiCoO2, conductive agent acetylene black, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed and evenly coated on the aluminum current collector in an N-methylpyrrolidone solvent system in a weight ratio of 97.6:0.5:0.6:1.3, and then cold-pressed and stripped to obtain the positive electrode sheet.

[0067] The method for preparing the above-mentioned diaphragm comprises the following steps:

[0068] The PE surface is coated with a ceramic mixture as an isolation membrane.

[0069] The preparation process of the above-mentioned negative electrode sheet includes the following steps:

[0070] The negative electrode active material, conductive agent (SP and CNT mixed, mass ratio is 0.45:0.05), binder (SBR and PAALi mixed, mass ratio is 0.5:1.8) are mixed in a weight ratio of 97.7:1.1:1.2 to prepare the negative electrode active material slurry, which is evenly coated on the composite current collector and then compacted with a density of 1.6 g / cm 3 Cold pressing and striping; using laser drilling equipment to make holes on the surface of the active material layer, with a hole volume rate of 1%, to obtain a negative electrode sheet.

[0071] The preparation process of the above electrolyte includes the following steps:

[0072] 40 wt.% of a first organic solvent, 30 wt.% of a second organic solvent, 15 wt.% of a lithium salt, and 15 wt.% of an additive are mixed and dissolved to prepare an electrolyte.

[0073] The viscosity of the electrolyte is 0.806 mPa·s.

[0074] The preparation process of the above-mentioned battery includes the following steps:

[0075] The positive electrode sheet, separator, and negative electrode sheet are wound to produce a bare cell, which is then packaged and injected with electrolyte to produce a finished battery.

[0076] Example 2

[0077] The difference between Example 2 and Example 1 is that the volume ratio of the holes and grooves is different. Specifically, the volume ratio of the holes and grooves in Example 1 is 1%, while the volume ratio of the holes and grooves in Example 2 is 3%.

[0078] A negative electrode sheet, the structure of the negative electrode sheet comprising:

[0079] current collector;

[0080] an active material layer disposed on the surface of the current collector;

[0081] The number of the active material layer is 1, and the surface of the active material layer is provided with pores and grooves;

[0082] The depth H of the pores and the thickness T of the active material layer satisfy the following relationship: 1 / 3T<H≤2 / 3T;

[0083] The compacted density of the active material layer is P, which is 1.6 g / cm 3 .

[0084] The volume ratio of pores in the active material layer is η, and η is 3%.

[0085] A battery comprises a positive electrode sheet, a separator, an electrolyte and the above-mentioned negative electrode sheet.

[0086] The method for preparing the positive electrode sheet comprises the following steps:

[0087] The active material LiCoO2, conductive agent acetylene black, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed and evenly coated on the aluminum current collector in an N-methylpyrrolidone solvent system in a weight ratio of 97.6:0.5:0.6:1.3, and then cold-pressed and stripped to obtain the positive electrode sheet.

[0088] The method for preparing the above-mentioned diaphragm comprises the following steps:

[0089] The PE surface is coated with a ceramic mixture as an isolation membrane.

[0090] The preparation process of the above-mentioned negative electrode sheet includes the following steps:

[0091] The negative electrode active material, conductive agent (SP and CNT mixed, mass ratio is 0.45:0.05), binder (SBR and PAALi mixed, mass ratio is 0.5:1.8) are mixed in a weight ratio of 97.7:1.1:1.2 to prepare the negative electrode active material slurry, which is evenly coated on the composite current collector and then compacted with a density of 1.6 g / cm 3 Cold pressing and striping; using laser drilling equipment to make holes on the surface of the active material layer, with a hole volume rate of 3%, to obtain a negative electrode sheet.

[0092] The preparation process of the above electrolyte includes the following steps:

[0093] 40 wt.% of a first organic solvent, 30 wt.% of a second organic solvent, 15 wt.% of a lithium salt, and 15 wt.% of an additive are mixed and dissolved to prepare an electrolyte.

[0094] The viscosity of the electrolyte is 0.806 mPa·s.

[0095] The preparation process of the above-mentioned battery includes the following steps:

[0096] The positive electrode sheet, separator, and negative electrode sheet are wound to produce a bare cell, which is then packaged and injected with electrolyte to produce a finished battery.

[0097] Example 3

[0098] The difference between Example 3 and Example 1 is that the volume ratio of the holes and grooves is different. Specifically, the volume ratio of the holes and grooves in Example 1 is 1%, while the volume ratio of the holes and grooves in Example 3 is 5%.

[0099] A negative electrode sheet, the structure of the negative electrode sheet comprising:

[0100] current collector;

[0101] an active material layer disposed on the surface of the current collector;

[0102] The number of the active material layer is 1, and the surface of the active material layer is provided with pores and grooves;

[0103] The depth H of the pores and the thickness T of the active material layer satisfy the following relationship: 1 / 3T<H≤2 / 3T;

[0104] The compacted density of the active material layer is P, which is 1.6 g / cm 3 .

[0105] The volume ratio of pores in the active material layer is η, and η is 5%.

[0106] A battery comprises a positive electrode sheet, a separator, an electrolyte and the above-mentioned negative electrode sheet.

[0107] The method for preparing the positive electrode sheet comprises the following steps:

[0108] The active material LiCoO2, conductive agent acetylene black, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed and evenly coated on the aluminum current collector in an N-methylpyrrolidone solvent system in a weight ratio of 97.6:0.5:0.6:1.3, and then cold-pressed and stripped to obtain the positive electrode sheet.

[0109] The method for preparing the above-mentioned diaphragm comprises the following steps:

[0110] The PE surface is coated with a ceramic mixture as an isolation membrane.

[0111] The preparation process of the above-mentioned negative electrode sheet includes the following steps:

[0112] The negative electrode active material, conductive agent (SP and CNT mixed, mass ratio is 0.45:0.05), binder (SBR and PAALi mixed, mass ratio is 0.5:1.8) are mixed in a weight ratio of 97.7:1.1:1.2 to prepare the negative electrode active material slurry, which is evenly coated on the composite current collector and then compacted with a density of 1.6 g / cm 3 Cold pressing and striping; using laser drilling equipment to make holes on the surface of the active material layer, with a hole volume rate of 5%, to obtain a negative electrode sheet.

[0113] The preparation process of the above electrolyte includes the following steps:

[0114] 40 wt.% of a first organic solvent, 30 wt.% of a second organic solvent, 15 wt.% of a lithium salt, and 15 wt.% of an additive are mixed and dissolved to prepare an electrolyte.

[0115] The viscosity of the electrolyte is 0.806 mPa·s.

[0116] The preparation process of the above-mentioned battery includes the following steps:

[0117] The positive electrode sheet, separator, and negative electrode sheet are wound to produce a bare cell, which is then packaged and injected with electrolyte to produce a finished battery.

[0118] Example 4

[0119] The difference between Example 4 and Example 2 is that the compaction density is different. The compaction density of Example 2 is 1.6 g / cm 3 , the compacted density of Example 4 is 1.55g / cm 3 .

[0120] A negative electrode sheet, the structure of the negative electrode sheet comprising:

[0121] current collector;

[0122] an active material layer disposed on the surface of the current collector;

[0123] The number of the active material layer is 1, and the surface of the active material layer is provided with pores and grooves;

[0124] The depth H of the pores and the thickness T of the active material layer satisfy the following relationship: 1 / 3T<H≤2 / 3T;

[0125] The compacted density of the active material layer is P, which is 1.55 g / cm 3 .

[0126] The volume ratio of pores in the active material layer is η, and η is 3%.

[0127] A battery comprises a positive electrode sheet, a separator, an electrolyte and the above-mentioned negative electrode sheet.

[0128] The method for preparing the positive electrode sheet comprises the following steps:

[0129] The active material LiCoO2, conductive agent acetylene black, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed and evenly coated on the aluminum current collector in an N-methylpyrrolidone solvent system in a weight ratio of 97.6:0.5:0.6:1.3, and then cold-pressed and stripped to obtain the positive electrode sheet.

[0130] The method for preparing the above-mentioned diaphragm comprises the following steps:

[0131] The PE surface is coated with a ceramic mixture as an isolation membrane.

[0132] The preparation process of the above-mentioned negative electrode sheet includes the following steps:

[0133] The negative electrode active material, conductive agent (SP and CNT mixed, mass ratio is 0.45:0.05), binder (SBR and PAALi mixed, mass ratio is 0.5:1.8) are mixed in a weight ratio of 97.7:1.1:1.2 to prepare the negative electrode active material slurry, which is evenly coated on the composite current collector and then compacted with a density of 1.55 g / cm 3 Cold pressing and striping; using laser drilling equipment to make holes on the surface of the active material layer, with a hole volume rate of 3%, to obtain a negative electrode sheet.

[0134] The preparation process of the above electrolyte includes the following steps:

[0135] 40 wt.% of a first organic solvent, 30 wt.% of a second organic solvent, 15 wt.% of a lithium salt, and 15 wt.% of an additive are mixed and dissolved to prepare an electrolyte.

[0136] The viscosity of the electrolyte is 0.806 mPa·s.

[0137] The preparation process of the above-mentioned battery includes the following steps:

[0138] The positive electrode sheet, separator, and negative electrode sheet are wound to produce a bare cell, which is then packaged and injected with electrolyte to produce a finished battery.

[0139] Example 5

[0140] The difference between Example 5 and Example 2 is that the compaction density is different. The compaction density of Example 2 is 1.6 g / cm 3 The compacted density of Example 5 is 1.65 g / cm 3 .

[0141] A negative electrode sheet, the structure of the negative electrode sheet comprising:

[0142] current collector;

[0143] an active material layer disposed on the surface of the current collector;

[0144] The number of the active material layer is 1, and the surface of the active material layer is provided with pores and grooves;

[0145] The depth H of the pores and the thickness T of the active material layer satisfy the following relationship: 1 / 3T<H≤2 / 3T;

[0146] The compacted density of the active material layer is P, which is 1.65 g / cm 3 .

[0147] The volume ratio of pores in the active material layer is η, and η is 3%.

[0148] A battery comprises a positive electrode sheet, a separator, an electrolyte and the above-mentioned negative electrode sheet.

[0149] The method for preparing the positive electrode sheet comprises the following steps:

[0150] The active material LiCoO2, conductive agent acetylene black, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed and evenly coated on the aluminum current collector in an N-methylpyrrolidone solvent system in a weight ratio of 97.6:0.5:0.6:1.3, and then cold-pressed and stripped to obtain the positive electrode sheet.

[0151] The method for preparing the above-mentioned diaphragm comprises the following steps:

[0152] The PE surface is coated with a ceramic mixture as an isolation membrane.

[0153] The preparation process of the above-mentioned negative electrode sheet includes the following steps:

[0154] The negative electrode active material, conductive agent (SP and CNT mixed, mass ratio is 0.45:0.05), binder (SBR and PAALi mixed, mass ratio is 0.5:1.8) are mixed in a weight ratio of 97.7:1.1:1.2 to prepare the negative electrode active material slurry, which is evenly coated on the composite current collector and then compacted with a density of 1.65 g / cm 3 Cold pressing and striping; using laser drilling equipment to make holes on the surface of the active material layer, with a hole volume rate of 3%, to obtain a negative electrode sheet.

[0155] The preparation process of the above electrolyte includes the following steps:

[0156] 40 wt.% of a first organic solvent, 30 wt.% of a second organic solvent, 15 wt.% of a lithium salt, and 15 wt.% of an additive are mixed and dissolved to prepare an electrolyte.

[0157] The viscosity of the electrolyte is 0.806 mPa·s.

[0158] The preparation process of the above-mentioned battery includes the following steps:

[0159] The positive electrode sheet, separator, and negative electrode sheet are wound to produce a bare cell, which is then packaged and injected with electrolyte to produce a finished battery.

[0160] Example 6

[0161] The difference between Example 6 and Example 2 is that the compaction density is different. The compaction density of Example 2 is 1.6 g / cm 3 The compacted density of Example 6 is 1.70 g / cm 3 .

[0162] A negative electrode sheet, the structure of the negative electrode sheet comprising:

[0163] current collector;

[0164] an active material layer disposed on the surface of the current collector;

[0165] The number of the active material layer is 1, and the surface of the active material layer is provided with pores and grooves;

[0166] The depth H of the pores and the thickness T of the active material layer satisfy the following relationship: 1 / 3T<H≤2 / 3T;

[0167] The compacted density of the active material layer is P, which is 1.70 g / cm 3 .

[0168] The volume ratio of pores in the active material layer is η, and η is 3%.

[0169] A battery comprises a positive electrode sheet, a separator, an electrolyte and the above-mentioned negative electrode sheet.

[0170] The method for preparing the positive electrode sheet comprises the following steps:

[0171] The active material LiCoO2, conductive agent acetylene black, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed and evenly coated on the aluminum current collector in an N-methylpyrrolidone solvent system in a weight ratio of 97.6:0.5:0.6:1.3, and then cold-pressed and stripped to obtain the positive electrode sheet.

[0172] The method for preparing the above-mentioned diaphragm comprises the following steps:

[0173] The PE surface is coated with a ceramic mixture as an isolation membrane.

[0174] The preparation process of the above-mentioned negative electrode sheet includes the following steps:

[0175] The negative electrode active material, conductive agent (SP and CNT mixed, mass ratio is 0.45:0.05), binder (SBR and PAALi mixed, mass ratio is 0.5:1.8) are mixed in a weight ratio of 97.7:1.1:1.2 to prepare the negative electrode active material slurry, which is evenly coated on the composite current collector and then compacted with a density of 1.7 g / cm 3 Cold pressing and striping; using laser drilling equipment to make holes on the surface of the active material layer, with a hole volume rate of 3%, to obtain a negative electrode sheet.

[0176] The preparation process of the above electrolyte includes the following steps:

[0177] 40 wt.% of a first organic solvent, 30 wt.% of a second organic solvent, 15 wt.% of a lithium salt, and 15 wt.% of an additive are mixed and dissolved to prepare an electrolyte.

[0178] The viscosity of the electrolyte is 0.806 mPa·s.

[0179] The preparation process of the above-mentioned battery includes the following steps:

[0180] The positive electrode sheet, separator, and negative electrode sheet are wound to produce a bare cell, which is then packaged and injected with electrolyte to produce a finished battery.

[0181] Example 7

[0182] The difference between Example 7 and Example 2 is that the compaction density is different. The compaction density of Example 2 is 1.6 g / cm 3 The compacted density of Example 7 is 1.75 g / cm 3 .

[0183] A negative electrode sheet, the structure of the negative electrode sheet comprising:

[0184] current collector;

[0185] an active material layer disposed on the surface of the current collector;

[0186] The number of the active material layer is 1, and the surface of the active material layer is provided with pores and grooves;

[0187] The depth H of the pores and the thickness T of the active material layer satisfy the following relationship: 1 / 3T<H≤2 / 3T;

[0188] The compacted density of the active material layer is P, which is 1.75 g / cm 3 .

[0189] The volume ratio of pores in the active material layer is η, and η is 3%.

[0190] A battery comprises a positive electrode sheet, a separator, an electrolyte and the above-mentioned negative electrode sheet.

[0191] The method for preparing the positive electrode sheet comprises the following steps:

[0192] The active material LiCoO2, conductive agent acetylene black, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed and evenly coated on the aluminum current collector in an N-methylpyrrolidone solvent system in a weight ratio of 97.6:0.5:0.6:1.3, and then cold-pressed and stripped to obtain the positive electrode sheet.

[0193] The method for preparing the above-mentioned diaphragm comprises the following steps:

[0194] The PE surface is coated with a ceramic mixture as an isolation membrane.

[0195] The preparation process of the above-mentioned negative electrode sheet includes the following steps:

[0196] The negative electrode active material, conductive agent (SP and CNT mixed, mass ratio is 0.45:0.05), binder (SBR and PAALi mixed, mass ratio is 0.5:1.8) are mixed in a weight ratio of 97.7:1.1:1.2 to prepare the negative electrode active material slurry, which is evenly coated on the composite current collector and then compacted with a density of 1.75 g / cm 3 Cold pressing and striping; using laser drilling equipment to make holes on the surface of the active material layer, with a hole volume rate of 3%, to obtain a negative electrode sheet.

[0197] The preparation process of the above electrolyte includes the following steps:

[0198] 40 wt.% of a first organic solvent, 30 wt.% of a second organic solvent, 15 wt.% of a lithium salt, and 15 wt.% of an additive are mixed and dissolved to prepare an electrolyte.

[0199] The viscosity of the electrolyte is 0.806 mPa·s.

[0200] The preparation process of the above-mentioned battery includes the following steps:

[0201] The positive electrode sheet, separator, and negative electrode sheet are wound to produce a bare cell, which is then packaged and injected with electrolyte to produce a finished battery.

[0202] Example 8

[0203] The differences between Example 8 and Example 5 include the following: the amounts of the first and second organic solvents, the lithium salt concentrations, the additive concentrations, and the electrolyte viscosity. In Example 5, the first organic solvent amount was 40 wt%, the second organic solvent amount was 30 wt%, the lithium salt concentration was 15 wt%, the additive concentration was 15 wt%, and the electrolyte viscosity was 0.806 mPa·s. In Example 8, the first organic solvent amount was 45 wt%, the second organic solvent amount was 40 wt%, the lithium salt concentration was 10 wt%, the additive concentration was 5 wt%, and the electrolyte viscosity was 0.400 mPa·s.

[0204] A negative electrode sheet, the structure of the negative electrode sheet comprising:

[0205] current collector;

[0206] an active material layer disposed on the surface of the current collector;

[0207] The number of the active material layer is 1, and the surface of the active material layer is provided with pores and grooves;

[0208] The depth H of the pores and the thickness T of the active material layer satisfy the following relationship: 1 / 3T<H≤2 / 3T;

[0209] The compacted density of the active material layer is P, which is 1.65 g / cm 3 .

[0210] The volume ratio of pores in the active material layer is η, and η is 3%.

[0211] A battery comprises a positive electrode sheet, a separator, an electrolyte and the above-mentioned negative electrode sheet.

[0212] The method for preparing the positive electrode sheet comprises the following steps:

[0213] The active material LiCoO2, conductive agent acetylene black, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed and evenly coated on the aluminum current collector in an N-methylpyrrolidone solvent system in a weight ratio of 97.6:0.5:0.6:1.3, and then cold-pressed and stripped to obtain the positive electrode sheet.

[0214] The method for preparing the above-mentioned diaphragm comprises the following steps:

[0215] The PE surface is coated with a ceramic mixture as an isolation membrane.

[0216] The preparation process of the above-mentioned negative electrode sheet includes the following steps:

[0217] The negative electrode active material, conductive agent (SP and CNT mixed, mass ratio is 0.45:0.05), binder (SBR and PAALi mixed, mass ratio is 0.5:1.8) are mixed in a weight ratio of 97.7:1.1:1.2 to prepare the negative electrode active material slurry, which is evenly coated on the composite current collector and then compacted with a density of 1.65 g / cm 3 Cold pressing and striping; using laser drilling equipment to make holes on the surface of the active material layer, with a hole volume rate of 3%, to obtain a negative electrode sheet.

[0218] The preparation process of the above electrolyte includes the following steps:

[0219] 45 wt.% of a first organic solvent, 40 wt.% of a second organic solvent, 10 wt.% of a lithium salt, and 5 wt.% of an additive are mixed and dissolved to prepare an electrolyte.

[0220] The viscosity of the electrolyte is 0.400 mPa·s.

[0221] The preparation process of the above-mentioned battery includes the following steps:

[0222] The positive electrode sheet, separator, and negative electrode sheet are wound to produce a bare cell, which is then packaged and injected with electrolyte to produce a finished battery.

[0223] Example 9

[0224] Example 9 differs from Example 5 in the following: the amount of the first organic solvent, the lithium salt concentration, the additive concentration, and the electrolyte viscosity. In Example 5, the first organic solvent amount is 40 wt %, the lithium salt concentration is 15 wt %, the additive concentration is 15 wt %, and the electrolyte viscosity is 0.806 mPa·s. In Example 9, the first organic solvent amount is 30 wt %, the lithium salt concentration is 20 wt %, the additive concentration is 20 wt %, and the electrolyte viscosity is 2.000 mPa·s.

[0225] A negative electrode sheet, the structure of the negative electrode sheet comprising:

[0226] current collector;

[0227] an active material layer disposed on the surface of the current collector;

[0228] The number of the active material layer is 1, and the surface of the active material layer is provided with pores and grooves;

[0229] The depth H of the pores and the thickness T of the active material layer satisfy the following relationship: 1 / 3T<H≤2 / 3T;

[0230] The compacted density of the active material layer is P, which is 1.65 g / cm 3 .

[0231] The volume ratio of pores in the active material layer is η, and η is 3%.

[0232] A battery comprises a positive electrode sheet, a separator, an electrolyte and the above-mentioned negative electrode sheet.

[0233] The method for preparing the positive electrode sheet comprises the following steps:

[0234] The active material LiCoO2, conductive agent acetylene black, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed and evenly coated on the aluminum current collector in an N-methylpyrrolidone solvent system in a weight ratio of 97.6:0.5:0.6:1.3, and then cold-pressed and stripped to obtain the positive electrode sheet.

[0235] The method for preparing the above-mentioned diaphragm comprises the following steps:

[0236] The PE surface is coated with a ceramic mixture as an isolation membrane.

[0237] The preparation process of the above-mentioned negative electrode sheet includes the following steps:

[0238] The negative electrode active material, conductive agent (SP and CNT mixed, mass ratio is 0.45:0.05), binder (SBR and PAALi mixed, mass ratio is 0.5:1.8) are mixed in a weight ratio of 97.7:1.1:1.2 to prepare the negative electrode active material slurry, which is evenly coated on the composite current collector and then compacted with a density of 1.65 g / cm 3 Cold pressing and striping; using laser drilling equipment to make holes on the surface of the active material layer, with a hole volume rate of 3%, to obtain a negative electrode sheet.

[0239] The preparation process of the above electrolyte includes the following steps:

[0240] 30 wt.% of a first organic solvent, 30 wt.% of a second organic solvent, 20 wt.% of a lithium salt, and 20 wt.% of an additive are mixed and dissolved to prepare an electrolyte.

[0241] The viscosity of the electrolyte is 2.000 mPa·s.

[0242] The preparation process of the above-mentioned battery includes the following steps:

[0243] The positive electrode sheet, separator, and negative electrode sheet are wound to produce a bare cell, which is then packaged and injected with electrolyte to produce a finished battery.

[0244] Example 10

[0245] Example 10 differs from Example 9 in the following: the amounts of the first and second organic solvents used, and the electrolyte viscosity. In Example 9, the first and second organic solvents were used in amounts of 30 wt%, 30 wt%, and 2.000 mPa·s, respectively. In Example 10, the first and second organic solvents were used in amounts of 45 wt%, 15 wt%, and 1.379 mPa·s, respectively.

[0246] A negative electrode sheet, the structure of the negative electrode sheet comprising:

[0247] current collector;

[0248] an active material layer disposed on the surface of the current collector;

[0249] The number of the active material layer is 1, and the surface of the active material layer is provided with pores and grooves;

[0250] The depth H of the pores and the thickness T of the active material layer satisfy the following relationship: 1 / 3T<H≤2 / 3T;

[0251] The compacted density of the active material layer is P, which is 1.65 g / cm 3 .

[0252] The volume ratio of pores in the active material layer is η, and η is 3%.

[0253] A battery comprises a positive electrode sheet, a separator, an electrolyte and the above-mentioned negative electrode sheet.

[0254] The method for preparing the positive electrode sheet comprises the following steps:

[0255] The active material LiCoO2, conductive agent acetylene black, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed and evenly coated on the aluminum current collector in an N-methylpyrrolidone solvent system in a weight ratio of 97.6:0.5:0.6:1.3, and then cold-pressed and stripped to obtain the positive electrode sheet.

[0256] The method for preparing the above-mentioned diaphragm comprises the following steps:

[0257] The PE surface is coated with a ceramic mixture as an isolation membrane.

[0258] The preparation process of the above-mentioned negative electrode sheet includes the following steps:

[0259] The negative electrode active material, conductive agent (SP and CNT mixed, mass ratio is 0.45:0.05), binder (SBR and PAALi mixed, mass ratio is 0.5:1.8) are mixed in a weight ratio of 97.7:1.1:1.2 to prepare the negative electrode active material slurry, which is evenly coated on the composite current collector and then compacted with a density of 1.65 g / cm 3 Cold pressing and striping; using laser drilling equipment to make holes on the surface of the active material layer, with a hole volume rate of 3%, to obtain a negative electrode sheet.

[0260] The preparation process of the above electrolyte includes the following steps:

[0261] 45 wt.% of a first organic solvent, 15 wt.% of a second organic solvent, 20 wt.% of a lithium salt, and 20 wt.% of an additive are mixed and dissolved to prepare an electrolyte.

[0262] The viscosity of the electrolyte is 1.379 mPa·s.

[0263] The preparation process of the above-mentioned battery includes the following steps:

[0264] The positive electrode sheet, separator, and negative electrode sheet are wound to produce a bare cell, which is then packaged and injected with electrolyte to produce a finished battery.

[0265] Example 11

[0266] The difference between Example 11 and Example 10 is that the pressure relief compaction density is different. Among them, the pressure relief compaction density of Example 10 is 1.44g / cm 3 The decompression compaction density of Example 11 is 1.48 g / cm 3 .

[0267] A negative electrode sheet, the structure of the negative electrode sheet comprising:

[0268] current collector;

[0269] an active material layer disposed on the surface of the current collector;

[0270] The number of the active material layer is 1, and the surface of the active material layer is provided with pores and grooves;

[0271] The depth H of the pores and the thickness T of the active material layer satisfy the following relationship: 1 / 3T<H≤2 / 3T;

[0272] The compacted density of the active material layer is P, which is 1.65 g / cm 3 .

[0273] The volume ratio of pores in the active material layer is η, and η is 3%.

[0274] A battery comprises a positive electrode sheet, a separator, an electrolyte and the above-mentioned negative electrode sheet.

[0275] The method for preparing the positive electrode sheet comprises the following steps:

[0276] The active material LiCoO2, conductive agent acetylene black, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed and evenly coated on the aluminum current collector in an N-methylpyrrolidone solvent system in a weight ratio of 97.6:0.5:0.6:1.3, and then cold-pressed and stripped to obtain the positive electrode sheet.

[0277] The method for preparing the above-mentioned diaphragm comprises the following steps:

[0278] The PE surface is coated with a ceramic mixture as an isolation membrane.

[0279] The preparation process of the above-mentioned negative electrode sheet includes the following steps:

[0280] The negative electrode active material, conductive agent (SP and CNT mixed, mass ratio is 0.45:0.05), binder (SBR and PAALi mixed, mass ratio is 0.5:1.8) are mixed in a weight ratio of 97.7:1.1:1.2 to prepare the negative electrode active material slurry, which is evenly coated on the composite current collector and then compacted with a density of 1.65 g / cm 3 Cold pressing and striping; using laser drilling equipment to make holes on the surface of the active material layer, with a hole volume rate of 3%, to obtain a negative electrode sheet.

[0281] The preparation process of the above electrolyte includes the following steps:

[0282] 45 wt.% of a first organic solvent, 15 wt.% of a second organic solvent, 20 wt.% of a lithium salt, and 20 wt.% of an additive are mixed and dissolved to prepare an electrolyte.

[0283] The viscosity of the electrolyte is 1.379 mPa·s.

[0284] The preparation process of the above-mentioned battery includes the following steps:

[0285] The positive electrode sheet, separator, and negative electrode sheet are wound to produce a bare cell, which is then packaged and injected with electrolyte to produce a finished battery.

[0286] Example 12

[0287] The difference between Example 12 and Example 10 includes: a different pore volume ratio, wherein the pore volume ratio of Example 10 is 3%, and the pore volume ratio of Example 12 is 1%.

[0288] A negative electrode sheet, the structure of the negative electrode sheet comprising:

[0289] current collector;

[0290] an active material layer disposed on the surface of the current collector;

[0291] The number of the active material layer is 1, and the surface of the active material layer is provided with pores and grooves;

[0292] The depth H of the pores and the thickness T of the active material layer satisfy the following relationship: 1 / 3T<H≤2 / 3T;

[0293] The compacted density of the active material layer is P, which is 1.65 g / cm 3 .

[0294] The volume ratio of pores in the active material layer is η, and η is 1%.

[0295] A battery comprises a positive electrode sheet, a separator, an electrolyte and the above-mentioned negative electrode sheet.

[0296] The method for preparing the positive electrode sheet comprises the following steps:

[0297] The active material LiCoO2, conductive agent acetylene black, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed and evenly coated on the aluminum current collector in an N-methylpyrrolidone solvent system in a weight ratio of 97.6:0.5:0.6:1.3, and then cold-pressed and stripped to obtain the positive electrode sheet.

[0298] The method for preparing the above-mentioned diaphragm comprises the following steps:

[0299] The PE surface is coated with a ceramic mixture as an isolation membrane.

[0300] The preparation process of the above-mentioned negative electrode sheet includes the following steps:

[0301] The negative electrode active material, conductive agent (SP and CNT mixed, mass ratio is 0.45:0.05), binder (SBR and PAALi mixed, mass ratio is 0.5:1.8) are mixed in a weight ratio of 97.7:1.1:1.2 to prepare the negative electrode active material slurry, which is evenly coated on the composite current collector and then compacted with a density of 1.65 g / cm 3 Cold pressing and striping; using laser drilling equipment to make holes on the surface of the active material layer, with a hole volume rate of 1%, to obtain a negative electrode sheet.

[0302] The preparation process of the above electrolyte includes the following steps:

[0303] 45 wt.% of a first organic solvent, 15 wt.% of a second organic solvent, 20 wt.% of a lithium salt, and 20 wt.% of an additive are mixed and dissolved to prepare an electrolyte.

[0304] The viscosity of the electrolyte is 1.379 mPa·s.

[0305] The preparation process of the above-mentioned battery includes the following steps:

[0306] The positive electrode sheet, separator, and negative electrode sheet are wound to produce a bare cell, which is then packaged and injected with electrolyte to produce a finished battery.

[0307] Example 13

[0308] Example 13 differs from Example 7 in the following: the mass percentage of the first organic solvent, the lithium salt concentration, the additive concentration, and the electrolyte viscosity. In Example 7, the mass percentage of the first organic solvent was 40 wt.%, the lithium salt concentration was 15 wt.%, the additive concentration was 15 wt.%, and the electrolyte viscosity was 0.806 wt.%. In Example 13, the mass percentage of the first organic solvent was 30 wt.%, the lithium salt concentration was 20 wt.%, the additive concentration was 20 wt.%, and the electrolyte viscosity was 2.000 mPa·s.

[0309] A negative electrode sheet, the structure of the negative electrode sheet comprising:

[0310] current collector;

[0311] an active material layer disposed on the surface of the current collector;

[0312] The number of the active material layer is 1, and the surface of the active material layer is provided with pores and grooves;

[0313] The depth H of the pores and the thickness T of the active material layer satisfy the following relationship: 1 / 3T<H≤2 / 3T;

[0314] The compacted density of the active material layer is P, which is 1.75 g / cm 3 .

[0315] The volume ratio of pores in the active material layer is η, and η is 3%.

[0316] A battery comprises a positive electrode sheet, a separator, an electrolyte and the above-mentioned negative electrode sheet.

[0317] The method for preparing the positive electrode sheet comprises the following steps:

[0318] The active material LiCoO2, conductive agent acetylene black, conductive carbon nanotubes, and binder polyvinylidene fluoride (PVDF) are fully dispersed and evenly coated on the aluminum current collector in an N-methylpyrrolidone solvent system in a weight ratio of 97.6:0.5:0.6:1.3, and then cold-pressed and stripped to obtain the positive electrode sheet.

[0319] The method for preparing the above-mentioned diaphragm comprises the following steps:

[0320] The PE surface is coated with a ceramic mixture as an isolation membrane.

[0321] The preparation process of the above-mentioned negative electrode sheet includes the following steps:

[0322] The negative electrode active material, conductive agent (SP and CNT mixed, mass ratio is 0.45:0.05), binder (SBR and PAALi mixed, mass ratio is 0.5:1.8) are mixed in a weight ratio of 97.7:1.1:1.2 to prepare the negative electrode active material slurry, which is evenly coated on the composite current collector and then compacted with a density of 1.75 g / cm 3 Cold pressing and striping; using laser drilling equipment to make holes on the surface of the active material layer, with a hole volume rate of 3%, to obtain a negative electrode sheet.

[0323] The preparation process of the above electrolyte includes the following steps:

[0324] 30 wt.% of a first organic solvent, 30 wt.% of a second organic solvent, 20 wt.% of a lithium salt, and 20 wt.% of an additive are mixed and dissolved to prepare an electrolyte.

[0325] The viscosity of the electrolyte is 2.000 mPa·s.

[0326] The preparation process of the above-mentioned battery includes the following steps:

[0327] The positive electrode sheet, separator, and negative electrode sheet are wound to produce a bare cell, which is then packaged and injected with electrolyte to produce a finished battery.

[0328] Comparative Example 1

[0329] The difference between Comparative Example 1 and Example 5 is that there are no pores in the active material layer in Comparative Example 1.

[0330] Comparative Example 2

[0331] Comparative Example 2 differs from Example 9 in the following: the amounts of the first and second organic solvents used, and the electrolyte viscosity. In Example 9, the first and second organic solvents were used in amounts of 30 wt%, 30 wt%, and 2.000 mPa·s, respectively. In Comparative Example 2, the first and second organic solvents were used in amounts of 25 wt%, 35 wt%, and 2.291 mPa·s, respectively.

[0332] Comparative Example 3

[0333] The difference between Comparative Example 3 and Example 5 is that the pressure relief compaction density is different. Among them, the pressure relief compaction density of Example 5 is 1.44 g / cm 3 The decompression compaction density of comparative example 3 is 1.60 g / cm3 .

[0334] Comparative Example 4

[0335] The difference between Comparative Example 4 and Example 5 includes: a different pore volume ratio, wherein the pore volume ratio of Example 5 is 3%, while the pore volume ratio of Comparative Example 4 is 6%.

[0336] Some parameter settings of Examples 1-13 and Comparative Examples 1-4 are shown in Table 1-2.

[0337] Table 1

[0338] In Table 1, the values ​​of the first organic solvent W1, the second organic solvent W2, the lithium salt concentration, and the additive concentration mainly affect the electrolyte viscosity ω.

[0339] Table 2

[0340] The parameters recorded in Table 2 are mainly the parameters of the pores and slots, which affect the pore volume ratio η in Table 1. When the parameters in Table 2 are adjusted, the corresponding pore volume ratio η in Table 1 will be affected.

[0341] Based on the parameters listed in Table 1, calculate whether P, η, W1, and ω satisfy the following relationship: 2.8 ≤ (P * ω) / (10 * η * W1) ≤ 50. Also calculate whether β, P, and ω satisfy the following relationship: 0.05 ≤ ω * (P - β) / P ≤ 0.23. The calculation results are shown in Table 3.

[0342] Table 3

[0343] It can be seen from Table 3 that Example 12, Comparative Example 1 and Comparative Example 2 do not satisfy 2.8≤(P*ω) / (10*η*W1)≤50; Example 13, Comparative Example 1, Comparative Example 2 and Comparative Example 3 do not satisfy 0.05≤ω*(P-β) / P≤0.23.

[0344] Performance testing:

[0345] The batteries prepared in Examples 1-13 and Comparative Examples 1-4 were subjected to the following tests. The test results are shown in Table 4.

[0346] Decompression compaction density: Weigh 1.00g ± 0.05g of negative electrode active material powder and place the sample in a powder compaction density instrument at a test pressure of 5 tons. The decompression compaction density is β, the mass of the negative electrode active material is M, the force-bearing area of ​​the negative electrode active material is S, and the thickness of the powder sample after decompression is H. The decompression compaction density is calculated as follows: β = M / (S × H).

[0347] Liquid retention range: After vacuum drying for a period of time, the battery is filled with electrolyte and the initial injection volume is recorded. After a period of electrolyte infiltration, the excess electrolyte inside the battery is extracted and the amount of electrolyte extracted is recorded. Therefore, the liquid retention range = injection volume - electrolyte extraction volume, and the values ​​are calculated for 100 batteries.

[0348] Cyclic test method:

[0349] Cycling tests were conducted at 25°C / 45°C using the following method: Charge mode: 3.5C CC-4.25V, 2.8C CC-4.35V, CV-1.8C, 1.8C CC-4.4V, CV-1.5C, 1.5C CC-4.5V, CV-1.2C, 1.2C CC-4.55V, CV-0.26C; Discharge mode: 0.7C DC-3.0V. 500-cycle capacity retention = discharge capacity at 500th cycle / discharge capacity at 1st cycle * 100%; 300-cycle capacity retention = discharge capacity at 300th cycle / discharge capacity at 1st cycle * 100%;

[0350] -10°C low-temperature discharge test: At 25°C, charge to 4.5V at 0.5C, cutoff current 0.02C, hold for 5 minutes, and discharge to 3.0V at 0.2C. Next, charge to 4.5V at 0.5C, cutoff current 0.02C. Set the test temperature to -10°C, hold for 120 minutes, and discharge to 3.0V at 0.2C. Low-temperature discharge capacity ratio = -10°C discharge capacity / 25°C discharge capacity * 100%.

[0351] Table 4

[0352] As can be seen from Examples 1 to 10, when the battery parameters P, ω, η, W1, and β satisfy the relationship: 2.8≤(P*ω) / (10*η*W1)≤50, and 0.05≤ω*(P-β) / P≤0.23, and each parameter is within the scope of this application, the battery can have a more stable liquid retention capability, and at the same time, the battery has better high and low temperature performance. The selection window of the electrolyte type is expanded to ensure good liquid retention stability of the battery while taking into account the comprehensive high and low temperature performance. If the parameters do not meet the above relationship range, the electrolyte retention is unstable and the high and low temperature performance is also poor.

[0353] It can be seen from Examples 1 to 10 and Comparative Examples 1 to 4 that the provision of holes and grooves on the surface of the electrode is beneficial for the electrode to have good liquid retention stability, and at the same time provides a path for rapid transmission of lithium ions. Therefore, under high compaction density, the provision of holes and grooves on the surface of the electrode can appropriately improve the viscosity of the electrolyte, so that the electrode has good liquid retention stability and has excellent performance at high or low temperatures. If the holes are not punched, the stability and mean of the electrolyte's liquid retention amount will drop significantly, and the high and low temperature performance will be severely attenuated. If the hole volume ratio of the negative electrode is set too high, it will affect the N / P ratio of the positive and negative electrodes, and the high and low temperature cycle life will be significantly reduced. The high hole volume ratio will reduce the active material more, and more free electrolyte will be stored in the hole. When the excess electrolyte is vacuum-extracted, a large amount of electrolyte will be lost, and it will also lead to unstable liquid retention.

[0354] It can be seen from Examples 1 to 10 and Comparative Example 2 that the low viscosity leads to poor high-temperature performance, mainly because the side reactions are aggravated at high temperatures due to low viscosity. If the viscosity is too high, the electrolyte viscosity is too high, the lithium ion conduction is blocked, lithium precipitation is easy, and the wettability is poor, which affects the liquid retention stability, low-temperature discharge, and high-low temperature cycle performance.

[0355] It can be seen from Examples 1 to 10 and Comparative Example 3 that the pressure relief compaction density is between 1.37 and 1.52 g / cm 3 When the pressure relief and compaction density are within this range, the contact between the active material layers is good, the active material structure is stable, and the gaps between the particles are fixed, which is conducive to improving the stability of the electrolyte retention volume. In combination with the compaction density and electrolyte viscosity, the stability of the electrolyte volume and high and low temperature cycling performance are further maintained. When the pressure relief and compaction density are too large, the active material structure is less stable, and the liquid retention stability and high and low temperature performance are also reduced.

[0356] As can be seen from Examples 1-12, when the parameters P, ω, η, and W1 are within the ranges of this application but do not satisfy the relationship 2.8 ≤ (P*ω) / (10*η*W1) ≤ 50, electrolyte stability and high-low temperature cycling performance will also be reduced. The parameters P, ω, η, and W1 must be coordinated to improve electrolyte stability and high-low temperature cycling performance.

[0357] It can be seen from Examples 1 to 13 that if the parameters P, ω, and β are within the range of this application but do not satisfy the relationship: 0.05≤ω*(P-β) / P≤0.23, the liquid retention stability and high and low temperature cycle performance will also decrease. The P, ω, and β parameters need to cooperate with each other to improve the liquid retention stability of the electrolyte and improve the high and low temperature cycle performance.

[0358] In this solution, the pores and grooves in the active layer of the anode surface not only facilitate electrolyte flow, effectively improving the wettability of the high-pressure solid electrode, reducing the electrolyte penetration requirements of the high-pressure solid electrode, and broadening the selection and ratio window of solvents and additives; they also form channels for rapid lithium ion transmission, alleviating the problem of lithium ion precipitation caused by the low porosity of the high-pressure solid electrode. By appropriately adjusting the solvent ratio in the electrolyte based on the volume ratio of the pores and grooves in the active material layer of the anode, while ensuring wettability, it helps to balance the high and low temperature performance of the battery, thereby improving the overall battery capacity and meeting market demand.

[0359] The above are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention specification, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A negative electrode sheet, characterized in that: The structure of the negative electrode sheet includes: Current collector; Active material layer, which is disposed on the surface of the current collector; The number of the active material layers is greater than or equal to 1, and at least one surface of the active material layer is provided with pore grooves; The depth H of the pore groove and the thickness T of the active material layer satisfy the following relationship: 1 / 3T < H ≤ 2 / 3T; The compaction density of the active material layer is P, and P satisfies the following relationship: 1.55 ≤ P ≤ 1.75 g / cm 3 .

2. The negative electrode sheet according to claim 1, characterized in that: The volume ratio of the pore grooves in the active material layer is η, and η satisfies the following relationship: 1% ≤ η ≤ 5%.

3. A negative electrode sheet according to claim 1, characterized in that: The punching width of the pore grooves in the active material layer is R, and R satisfies the following relationship: 50 ≤ R ≤ 140 μm.

4. A negative electrode sheet according to claim 1, characterized in that: The spacing between the pore grooves in the active material layer is L, and L satisfies the following relationship: 1.0 ≤ L ≤ 2.5 mm.

5. A negative electrode sheet according to claim 1, characterized in that: The angle between the pore grooves in the active material layer and the negative electrode sheet is θ, and θ satisfies the following relationship: 85° ≤ θ ≤ 95°.

6. A battery, characterized in that: It includes a positive electrode sheet, a separator, an electrolyte, and the negative electrode sheet according to any one of claims 1 to 5.

7. A battery according to claim 6, characterized in that: The components of the electrolyte include a non-aqueous solvent, a lithium salt, and an additive. Among them, the non-aqueous solvent includes a first organic solvent and a second organic solvent. The mass fraction of the first organic solvent in the electrolyte is W1, and W1 satisfies the following relationship: 30 wt.% ≤ W1 ≤ 45 wt.%; the mass fraction of the second organic solvent in the electrolyte is W2, and W2 satisfies the following relationship: 15 wt.% ≤ W2 ≤ 40 wt.%, and W2 ≤ W1 ≤ 3W2.

8. A battery according to claim 7, characterized in that: The viscosity of the electrolyte is ω, and ω satisfies the following relationship: 0.4 ≤ ω ≤ 2 mPa·s.

9. A battery according to claim 8, wherein: The compaction density of the negative electrode sheet is P. The negative electrode sheet includes an active material layer, and pore grooves are provided in the active material layer. The volume ratio of the pore grooves is η. P, η, W1, and ω satisfy the following relationship: 2.8 ≤ (P * ω) / (10 * η * W1) ≤ 50.

10. A battery according to claim 8, characterized in that: The pressure relief compaction density of the negative electrode sheet is β, where 1.37 ≤ β ≤ 1.52 g / cm 3 .

11. A battery according to claim 8, characterized in that: Between the pressure relief compaction density β of the negative electrode sheet, the compaction density P of the negative electrode sheet, and the viscosity ω of the electrolyte, the following relational formula is satisfied: 0.05 ≤ ω * (P - β) / P ≤ 0.

23.

12. A battery according to claim 7, wherein: The first organic solvent includes at least one of carbonate organic solvents and carboxylate organic solvents; the second organic solvent includes at least one of sulfur solvents, fluorinated solvents, sulfone solvents, and nitrile solvents.

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