Battery and battery module

Abstract

The invention provides a battery and a battery module. Before being assembled, the battery comprises a positive pole piece, a diaphragm, a negative pole piece and electrolyte; the negative pole piece comprises a negative current collector and a negative active material layer located on the surface of at least one side of the negative current collector, and the negative current collector comprises a first base film and a first metal layer arranged on the surface of at least one side of the first base film; the base membrane comprises a first organic framework material and a first high-molecular polymer material soluble in a polar solvent; the electrolyte comprises a lithium salt and a polar organic solvent. According to the battery disclosed by the invention, the balance of high energy density and long cycle life can be realized through the cooperation of the negative pole piece and the electrolyte, the safety performance of the battery is also improved, and the service life of the battery is also prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries and relates to a battery and a battery module. Background Art

[0002] As we all know, lithium-ion batteries have attracted widespread attention due to their high energy density, high specific power, high operating voltage, good cycle performance, no memory effect, and zero pollution. However, with the development of new energy vehicles, people have higher performance requirements for lithium-ion batteries, especially the energy density of lithium-ion batteries. Among the lithium-ion battery materials currently commercialized, ternary cathode materials have relatively high energy density. High-nickel ternary cathode materials are gradually becoming the future development direction, but the poor cycle stability caused by the mixed arrangement of cations in high-nickel ternary materials, as well as poor high-temperature and rate performance, are also in urgent need of improvement. At the same time, the thermal runaway problem of high-nickel ternary materials has become a major factor limiting their large-scale application.

[0003] Commercially available graphite anodes offer advantages such as long cycle life and good electrolyte compatibility, but their low energy density is the primary obstacle limiting their application in high-energy-density batteries. Silicon anode materials have a theoretical energy density approximately 10 times that of graphite, but their volume expansion of up to 300% during operation also limits their application.

[0004] Therefore, how to achieve both high energy density and high cycle performance is a technical problem that needs to be solved urgently. Summary of the Invention

[0005] In response to the shortcomings of the prior art, the present invention provides a battery and battery module. The battery of the present invention, through the coordinated cooperation of the negative electrode plate and the electrolyte, can achieve a balance between high energy density and long cycle life, while also improving the safety performance and service life of the battery.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a battery, which comprises a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte before being assembled;

[0008] The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector. The negative electrode current collector includes a first base film and a first metal layer provided on at least one side of the first base film. The base film includes a first organic skeleton material and a first high molecular polymer material soluble in a polar solvent.

[0009] The electrolyte includes a lithium salt and a polar organic solvent.

[0010] It should be noted that the various components of the battery in the present invention are in a state before assembly, that is, the positive electrode sheet, the separator and the negative electrode sheet have not been assembled, and the electrolyte has not been injected.

[0011] It should also be noted that when the metal layer is provided on one side in the present invention, it is provided on the side of the base film facing the negative electrode active material layer.

[0012] In the battery provided by the present invention, the structure and material of the current collector in the negative electrode sheet cooperate with the electrolyte and work together. After the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte are assembled into a battery, the electrolyte is in direct contact with the negative electrode sheet, and the first high molecular polymer material is dissolved in the polar organic solvent of the electrolyte, which improves the wettability or interfacial stability of the electrolyte and can also promote the transformation of the electrolyte from a liquid state to a gel state, thereby having better mechanical stability and lower volatility, and can effectively avoid the problems of electrolyte leakage and volatilization; after the first high molecular polymer material is dissolved, the organic skeleton material in the base film is retained, so that the base film forms a porous sponge-like structure, which can ensure the collector The mechanical strength and structural stability of the fluid can also provide a buffer space during the "breathing" process of lithium insertion and delithiation of the negative electrode active material in the negative electrode active layer, absorb the stress generated by the volume expansion of the negative electrode active material, protect the electrode structure and SEI film integrity, and improve the battery cycle performance; at the same time, the structure of the current collector also synergistically plays a role in reducing weight, increasing energy density, improving the safety of the current collector, and increasing the tensile strength of the current collector, thereby reducing the problem of current collector breaking caused by negative electrode expansion; through the coordinated cooperation of the above-mentioned structure, materials and electrolyte components, a balance between high energy density and high cycle life can be achieved, and the safety performance and service life of the battery are also improved.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0014] Preferably, the ratio of the thickness of the first base film to the thickness of the first metal layer is (4-10):(0.5-3), for example, 4:0.5, 4:1, 4:2, 4:3, 4.5:1, 5:0.5, 5:1, 5:2, 5:3, 8:0.5, 8:1, 8:2, 8:3, 10:0.5, 10:1, 10:2 or 10:3, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0015] It should be noted that, in the present invention, the thickness of the first base film and the thickness of the first metal layer are expressed in the same unit.

[0016] Preferably, the mass ratio of the first organic skeleton material to the first high molecular polymer material is (1-6):(8-15), for example, 1:8, 1:9, 1:10, 1:12, 1:15, 3:8, 3:9, 3:10, 3:12, 3:15, 5:8, 5:9, 5:10, 5:12, 5:15, 6:8, 6:9, 6:10, 6:12 or 6:15, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0017] For the present invention, a suitable mass ratio of the first organic skeleton material to the first high molecular polymer material is conducive to the excellent structural stability of the current collector; and preferably (1 to 6): (8 to 15), which can better form a rich and porous organic skeleton with buffering capacity while ensuring the mechanical strength of the current collector base film, avoiding the problem of current collector tearing during normal use.

[0018] Preferably, the first organic framework material comprises cellulose material and / or cellulose derivative material.

[0019] Cellulose materials and / or cellulose derivative materials have good transparency, flexibility and plasticity, which can improve the strength and durability of the current collector and effectively extend the service life of the current collector. When used as the first organic skeleton material, the current collector can still have a certain mechanical strength after the first high molecular polymer material is released.

[0020] In addition, the present invention does not limit the specific types of cellulose materials or cellulose derivative materials. The present invention is applicable to any type of material that is insoluble in polar organic solvents and can be used as a base membrane skeleton material; for example, it can be selected from at least one of unmodified natural cellulose, cellulose nanofibers (CNF), cellulose nanocrystals (CNC), regenerated cellulose (such as Lyocell fiber, traditional viscose fiber), and carboxymethyl cellulose (CMC).

[0021] Preferably, the first high molecular polymer material includes any one of polyethylene oxide, polyethylene glycol, polyvinyl pyrrolidone or a bio-based polymer material, or a combination of at least two thereof.

[0022] The present invention further limits the first high molecular polymer material to include at least one of polyethylene oxide, polyethylene glycol, polyvinyl pyrrolidone or a bio-based polymer material, which, while dissolving in the electrolyte, can more effectively promote the conversion of the electrolyte from a liquid state to a gel state, thereby further improving the safety and service life of the battery.

[0023] Furthermore, the bio-based polymer material refers to a polymer material prepared from renewable biomass resources (such as plants, animals, microorganisms, etc.) through biological, chemical or physical methods, including at least one of polylactic acid, bio-based polyethylene terephthalate or bio-based polyethylene.

[0024] Preferably, the negative electrode active material in the negative electrode active material layer includes a carbon-based negative electrode material and / or a silicon-based negative electrode material, preferably a silicon-based negative electrode material.

[0025] It should be noted that the carbon-based negative electrode materials and silicon-based negative electrode materials in the present invention are both conventional technical solutions, and the present invention is applicable to any specific negative electrode material types that can be known to those skilled in the art within a reasonable range; in addition to the above-mentioned carbon-based negative electrode materials and silicon-based negative electrode materials, the present invention is also applicable to other conventional types of negative electrode materials that can be used in lithium-ion battery systems.

[0026] For example, the carbon-based negative electrode material includes but is not limited to at least one of graphite, hard carbon or soft carbon; the silicon-based negative electrode material includes but is not limited to at least one of pure silicon material, silicon-oxygen material or silicon-carbon negative electrode material.

[0027] Furthermore, the present invention preferably comprises a negative electrode active material comprising a silicon-based negative electrode material. The volume expansion of the silicon material is more obvious during the process of lithium insertion and removal. In conjunction with the negative electrode current collector and electrolyte provided by the present invention, higher battery energy density and longer-lasting battery cycle capacity can be achieved.

[0028] Preferably, along the thickness direction of the negative electrode plate, the negative electrode plate has a through-hole structure.

[0029] In the present invention, by providing a through-hole structure in the negative electrode plate, on the one hand, it increases the contact area between the electrolyte and the current collector base membrane and improves the wetting effect; on the other hand, it can also increase the lithium ion transmission path and improve the battery ion conductivity.

[0030] Preferably, the equivalent diameter of the through-hole structure is 50 to 5000 μm, for example, 50 μm, 100 μm, 500 μm, 1000 μm, 1500 μm, 2000 μm, 2500 μm, 3000 μm, 3500 μm, 4000 μm, 4500 μm or 5000 μm, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0031] It should be noted that the equivalent diameter in the present invention refers to the diameter of a circular hole having the same area as the through hole.

[0032] Preferably, the porosity of the through-hole structure in the negative electrode plate is 10% to 50%, for example, 10%, 20%, 30%, 35%, 40%, 45% or 50%, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0033] Preferably, the polar organic solvent includes any one of EC, DMC, DEC or DMF, or a combination of at least two thereof.

[0034] It is understandable that the electrolyte provided by the present invention, except for the characteristic limitations of the polar organic solvent, the specific material types of lithium salts, the proportion of organic solvents, the specific volume proportion of organic solvents, etc., are all conventional technical solutions, and those skilled in the art can make adaptive selections and adjustments based on actual needs.

[0035] Optionally, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate or lithium difluorophosphate.

[0036] Optionally, the concentration of the lithium salt in the electrolyte is 0.8 to 2.5 mol / L, for example, 0.8 mol / L, 1 mol / L, 1.3 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.3 mol / L or 2.5 mol / L, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0037] Optionally, when the polar organic solvent includes at least two different solvents, the solvents can be mixed in any proportion. Those skilled in the art can make adaptive selections and adjustments based on actual needs. Preferably, the volume ratio between the solvents is (0.5-1.5):(0.5-1.5), for example, 1:1, 0.5:1, 0.5:1.5, 1:0.5 or 1:1.5, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0038] Optionally, the electrolyte may further include conventional additives with various functions, such as film-forming additives, flame-retardant additives, etc. Those skilled in the art may make adaptive selections and adjustments based on actual needs.

[0039] Optionally, the mass proportion of the additive in the electrolyte is 1% to 10%, such as 1%, 3%, 5%, 8% or 10%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] Preferably, the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer located on at least one side surface of the positive electrode current collector.

[0041] Preferably, the positive electrode active material in the positive electrode active material layer includes a high-nickel positive electrode material.

[0042] It can be understood that the high-nickel positive electrode material refers to a lithium oxide positive electrode material in which the molar amount of nickel accounts for ≥80% of the non-lithium metal elements in the positive electrode material, such as a lithium nickel cobalt manganese oxide positive electrode material or a lithium nickel cobalt aluminum oxide positive electrode material.

[0043] In the present invention, a combination of high-nickel positive electrode material and silicon-based negative electrode material is preferred, which can better exert the pressure release and buffering effect of the present solution on the expansion force of the electrode in the field of high-capacity batteries.

[0044] Preferably, the positive electrode current collector includes a second base film and a second metal layer provided on at least one surface of the second base film, and the base film includes a second organic skeleton material and a second high molecular polymer material soluble in a polar solvent.

[0045] In the present invention, it is preferred that both the positive electrode sheet and the negative electrode sheet adopt a specific current collector + electrolyte combination, which can provide more expansion space for the silicon negative electrode and better achieve a balance between high energy density and long cycle performance.

[0046] Preferably, the ratio of the thickness of the second base film to the thickness of the second metal layer is (4-10):(0.5-3), for example, 4:0.5, 4:1, 4:2, 4:3, 4.5:1, 5:0.5, 5:1, 5:2, 5:3, 8:0.5, 8:1, 8:2, 8:3, 10:0.5, 10:1, 10:2 or 10:3, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0047] Preferably, the mass ratio of the second organic skeleton material to the second high molecular polymer material is (1-6):(8-15), for example, 1:8, 1:9, 1:10, 1:12, 1:15, 3:8, 3:9, 3:10, 3:12, 3:15, 5:8, 5:9, 5:10, 5:12, 5:15, 6:8, 6:9, 6:10, 6:12 or 6:15, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0048] Preferably, the second organic framework material comprises a cellulose material and / or a cellulose derivative material.

[0049] Preferably, the second high molecular polymer material includes any one of polyethylene oxide, polyethylene glycol, polyvinyl pyrrolidone or a bio-based polymer material, or a combination of at least two thereof.

[0050] Preferably, along the thickness direction of the positive electrode plate, the positive electrode plate has a through-hole structure.

[0051] In the present invention, when the base film in the positive electrode current collector is consistent with the base film in the negative electrode current collector, a through-hole structure is also formed in the positive electrode plate, which can also increase the contact area between the electrolyte and the current collector base film and improve the wetting effect. On the other hand, it can also increase the lithium ion transmission path and improve the battery ion conductivity.

[0052] It should also be noted that:

[0053] In the battery provided by the present invention, except for the above-mentioned feature limitations, the remaining technical details are conventional technical solutions, and those skilled in the art can make adaptive selections and adjustments based on actual needs.

[0054] Optionally, the metal layer in the negative electrode current collector includes a copper layer, the metal layer in the positive electrode current collector includes an aluminum layer, or the positive electrode current collector includes a pure aluminum foil structure.

[0055] Optionally, in addition to the positive electrode active material, the positive electrode active material layer may also include a positive electrode conductor and / or a positive electrode binder; for example, the positive electrode conductor includes but is not limited to one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, carbon nanofibers and graphene; the positive electrode binder includes one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), polypropylene (PP), polyethylene (PE), styrene-butadiene rubber (SBR), nitrile rubber (NBR), sodium hydroxymethyl cellulose (CMC), polyacrylic acid, polyacrylonitrile and sodium alginate.

[0056] Optionally, in addition to the negative electrode active material, the negative electrode active material layer may also include a negative electrode conductor and / or a negative electrode binder; the negative electrode conductor includes but is not limited to one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, carbon nanofibers, and graphene; the negative electrode binder includes but is not limited to one or more of styrene-butadiene rubber, carboxymethyl cellulose, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene, polypropylene, polyethylene, and polyimide.

[0057] Optionally, the diaphragm is known to those skilled in the art, including but not limited to one or more of polypropylene, polyethylene, polyvinylidene fluoride, polyimide, and polyacrylonitrile.

[0058] Secondly, the present invention does not specifically limit the specific preparation method of the battery of the first aspect. The present invention is applicable to the method of obtaining the positive electrode sheet, the negative electrode sheet separator and the electrolyte, as well as the conventional method of assembling the above features to obtain a finished lithium-ion battery.

[0059] Exemplarily, the present invention provides a complete method for preparing a battery: (1)

[0061] a) Preparation of the base film: mixing the first organic framework material and the first high molecular polymer material, and optionally adding a plasticizer, to obtain a mixed raw material, extruding the mixed raw material for melt blending, rolling the mixed raw material into a film, and annealing to obtain the base film;

[0062] b) Preparation of the current collector: preparing a metal layer on at least one side of the base film by magnetron sputtering or evaporation;

[0063] c) Preparation of positive and / or negative electrode sheets: Mix the electrode active material, conductive agent, binder and solvent to obtain electrode slurry, apply the electrode slurry to the surface of at least one side of the current collector, dry it, and then perform laser drilling to form a through-hole structure in the electrode sheet along the thickness direction of the electrode sheet.

[0064] (2) The positive and negative electrodes and the diaphragm are stacked and injected with electrolyte to form a stacked soft-pack small battery, and a battery sample is obtained after formation.

[0065] It is understandable that the specific parameter values ​​and the ratio of raw materials in the preparation process can be adaptively selected and adjusted by those skilled in the art based on the characteristic definitions of the battery and known technical solutions.

[0066] In a third aspect, the present invention further provides a battery module, comprising at least one group of batteries as described in the first aspect.

[0067] It can be understood that a group of batteries described in the present invention is a battery structure.

[0068] Compared with the prior art, the present invention has the following beneficial effects:

[0069] In the battery provided by the present invention, the structure and material of the current collector in the negative electrode sheet cooperate with the electrolyte and work together. After the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte are assembled into a battery, the electrolyte is in direct contact with the negative electrode sheet, and the first high molecular polymer material is dissolved in the polar organic solvent of the electrolyte, which improves the wettability or interfacial stability of the electrolyte and can also promote the transformation of the electrolyte from a liquid state to a gel state, thereby having better mechanical stability and lower volatility, and can effectively avoid the problems of electrolyte leakage and volatilization; after the first high molecular polymer material is dissolved, the organic skeleton material in the base film is retained, so that the base film forms a porous sponge-like structure, which can ensure the collector The mechanical strength and structural stability of the fluid can also provide a buffer space during the "breathing" process of lithium insertion and delithiation of the negative electrode active material in the negative electrode active layer, absorb the stress generated by the volume expansion of the negative electrode active material, protect the electrode structure and SEI film integrity, and improve the battery cycle performance; at the same time, the structure of the current collector also synergistically plays a role in reducing weight, increasing energy density, improving the safety of the current collector, and increasing the tensile strength of the current collector, thereby reducing the problem of current collector breaking caused by negative electrode expansion; through the coordinated cooperation of the above-mentioned structure, materials and electrolyte components, a balance between high energy density and high cycle life can be achieved, and the safety performance and service life of the battery are also improved. DETAILED DESCRIPTION

[0070] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0071] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusions.

[0072] In the description of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0073] Example 1

[0074] This embodiment provides a battery, which includes a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte before being assembled;

[0075] The positive electrode plate includes an aluminum foil and a positive electrode active material layer provided on both sides of the aluminum foil. The positive electrode active material layer includes LiNi 0.8 Co 0.1 Mn 0.1 O2, carbon nanotubes, conductive carbon black Super P and polyvinylidene fluoride (PVDF);

[0076] The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector. The negative electrode current collector includes a first base film and copper layers provided on both sides of the first base film. The base film includes a first organic framework material (CMC) and a first high molecular polymer material (polyethylene oxide) (PEO) soluble in a polar solvent. The negative electrode plate has a through-hole structure extending through the plate in the thickness direction. The through-hole structure has an equivalent diameter of 200 μm and a porosity of 10%.

[0077] The electrolyte includes lithium salt lithium hexafluorophosphate and polar organic solvents EC and DMC.

[0078] The preparation method of the battery is as follows:

[0079] (1) Preparation of negative electrode current collector:

[0080] a) Base Film Preparation: PEO was dried in a vacuum oven at 60°C for 6 hours to prevent moisture absorption; CMC was dried in an oven at 80°C for 12 hours (CMC is hygroscopic and requires thorough removal of moisture); CMC was premixed with a plasticizer (glycerol was added in an amount of 5 wt% of the CMC) to lower the melt temperature to obtain plasticized CMC. The dried PEO and CMC were weighed to a target mass ratio of PEO:plasticized CMC = 7:3 and added to a twin-screw extruder for melt blending. The melt blending was temperature-controlled in sections: 80°C in the feeding section → 100°C in the mixing section → 90°C in the extrusion section, with a screw speed of 80 rpm. A slit die (100 cm width, 2 mm die lip gap) was used. After the melt was extruded through the die, it was quickly cooled and shaped by a cooling roller (temperature 20°C). The pulling speed matched the extrusion rate (e.g., 3 m / min) to avoid uneven film stretching. The film was annealed (50°C, 30 minutes) to eliminate internal stress, resulting in a base film with a thickness of 4.5 μm.

[0081] 2) Coating:

[0082] A copper layer was formed on both sides of the base film by magnetron sputtering and water electroplating. The thickness of the copper layer on one side was 1 micron, and a negative electrode current collector was obtained. The magnetron sputtering parameters were: argon flow rate: 500 sccm, main roller cooling temperature: -10 ° C, winding speed: 12 m / min, target-substrate distance: 120 mm, magnetron sputtering power: 80 kW, magnetic field strength: 400 GS, and a copper seed layer with a thickness of 5 nm on one side was obtained. The electroplating parameters were: electroplating temperature ≤ 25 ° C, winding speed 12 m / min, square resistance ≤ 20 μΩ, and electroplating until the copper layer reached 1 micron (on one side).

[0083] (2) Battery preparation:

[0084] a) Preparation of negative electrode sheet: A negative electrode slurry was applied to both sides of the negative electrode current collector. The components and weight percentages thereof were as follows: 95 parts of silicon-carbon material (Si content was 10%), 1 part of Super P, 2 parts of styrene-butadiene rubber (SBR), and 2 parts of CMC. The solvent was deionized water. The obtained negative electrode slurry had a solid content of 48%. After coating, the slurry was dried and then roller pressed to obtain a negative electrode sheet. The surface of the negative electrode sheet was then laser-drilled to obtain a perforated negative electrode sheet.

[0085] Preparation of positive electrode sheet: Aluminum foil was selected as the positive electrode current collector, and a positive electrode slurry was coated on both sides of the foil. The composition and weight percentage of the positive electrode slurry were: 92 parts of NCM811 positive electrode material, 3 parts of carbon nanotubes, 2 parts of Super P, and 3 parts of PVDF. The solvent was NMP, and the solid content of the positive electrode slurry was 60%. After drying, the positive electrode sheet was obtained.

[0086] b) Electrolyte preparation: The solute is LiPF6 (lithium hexafluorophosphate), the solvent is a 1:1 volume ratio of EC and DMC composite organic solvent, and the concentration of lithium salt in the electrolyte is 1 mol / L;

[0087] 3) Battery assembly: The positive electrode sheet, negative electrode sheet and separator (ceramic separator, thickness 8 μm) are stacked and injected with electrolyte to make a stacked soft-pack small battery, which is then formed to obtain a battery sample.

[0088] Example 2

[0089] The difference between this embodiment and embodiment 1 is that in the base film of this embodiment, the organic skeleton material is CNF, the first high molecular polymer material is polyvinyl pyrrolidone PVP, and the mass ratio of CNF to PVP is 5:15.

[0090] The rest of the preparation methods and parameters were the same as those in Example 1.

[0091] Example 3

[0092] The difference between this embodiment and embodiment 1 is that, except for the raw materials of the metal layer, the structures, raw materials and proportions of the positive electrode collector and the negative electrode collector of this embodiment are the same, and the metal layer in the positive electrode collector is an aluminum layer.

[0093] In the preparation method, after the base film is prepared, an aluminum layer and a copper layer are deposited respectively to obtain a positive electrode current collector and a negative electrode current collector, and the positive electrode plate is also laser-drilled;

[0094] The specific preparation of the aluminum layer is as follows: the base film is passed into the vacuum evaporation equipment chamber, the vacuum is evacuated to a vacuum degree of 5*10-3Pa, the evaporation boat is heated and the aluminum wire is fed at a wire feeding speed of 300mm / min, and the oxygen intake is turned on at the same time. The vacuum degree is controlled at 5*10-2Pa, so that a layer of aluminum oxide coating is formed on the surface of both sides of the base film, and the thickness of the aluminum oxide coating is controlled to be 10nm; then the vacuum is broken and the vacuum is evacuated to a vacuum degree of 5*10 -3 Pa, the vacuum degree is controlled at 5*10 -2 Pa, continue to plate an aluminum layer on both sides in the same way, and the thickness of the aluminum layer on one side is 1 micron.

[0095] The rest of the preparation methods and parameters were the same as those in Example 1.

[0096] Example 4

[0097] The difference between this embodiment and embodiment 1 is that the mass ratio of PEO:plasticized CMC in this embodiment is 1:8.

[0098] In the preparation method, the amount of raw materials can be adjusted adaptively.

[0099] The rest of the preparation methods and parameters were the same as those in Example 1.

[0100] Example 5

[0101] The difference between this embodiment and embodiment 1 is that the mass ratio of PEO:plasticized CMC in this embodiment is 1:15.

[0102] In the preparation method, the amount of raw materials can be adjusted adaptively.

[0103] The rest of the preparation methods and parameters were the same as those in Example 1.

[0104] Example 6

[0105] The difference between this embodiment and embodiment 1 is that the mass ratio of PEO:plasticized CMC in this embodiment is 6:8.

[0106] In the preparation method, the amount of raw materials can be adjusted adaptively.

[0107] The rest of the preparation methods and parameters were the same as those in Example 1.

[0108] Example 7

[0109] The difference between this embodiment and embodiment 1 is that the mass ratio of PEO:plasticized CMC in this embodiment is 1:8.

[0110] In the preparation method, the amount of raw materials can be adjusted adaptively.

[0111] The rest of the preparation methods and parameters were the same as those in Example 1.

[0112] Example 8

[0113] The difference between this embodiment and embodiment 1 is that the negative electrode sheet of this embodiment does not contain a through-hole structure;

[0114] In the preparation method, no laser drilling process is performed.

[0115] The rest of the preparation methods and parameters were the same as those in Example 1.

[0116] Example 9

[0117] The difference between this embodiment and embodiment 1 is that the first high molecular polymer material in this embodiment is polystyrene (PS).

[0118] In the preparation method, PEO can be replaced by PS.

[0119] Example 10

[0120] The difference between this embodiment and embodiment 1 is that the mass ratio of PEO:plasticized CMC in this embodiment is 1:1.

[0121] In the preparation method, the amount of raw materials can be adjusted adaptively.

[0122] The rest of the preparation methods and parameters were the same as those in Example 1.

[0123] Example 11

[0124] The difference between this embodiment and embodiment 1 is that the mass ratio of PEO to plasticized CMC in this embodiment is 1:20.

[0125] In the preparation method, the amount of raw materials can be adjusted adaptively.

[0126] The rest of the preparation methods and parameters were the same as those in Example 1.

[0127] Example 12

[0128] The difference between this embodiment and embodiment 1 is that the negative electrode active material in the negative electrode plate of this embodiment is artificial graphite material (Shanshan artificial graphite FSN-1).

[0129] In the preparation method, the silicon-carbon negative electrode material is replaced with an artificial graphite negative electrode material.

[0130] The rest of the preparation methods and parameters were the same as those in Example 1.

[0131] Comparative Example 1

[0132] The difference between this comparative example and Example 1 is that the base film of the negative electrode current collector in this comparative example is polyethylene terephthalate (PET).

[0133] The base film preparation process of step (1) of the preparation method is adjusted as follows: PET particles are added to a twin-screw extruder and melted. The melting process is temperature-controlled in stages: feeding section 180°C → melting section 240°C → extrusion section 220°C, and the screw speed is 50-100 rpm. A slit die (width 100 cm, die lip gap 2 mm) is used. After the melt is extruded through the die, it is rapidly cooled and shaped by a cooling roller (temperature 30°C). The pulling speed matches the extrusion rate (e.g., 3 m / min), and the film is annealed (70°C, 30 minutes) to obtain the PET base film.

[0134] The rest of the preparation methods and parameters were the same as those in Example 1.

[0135] Comparative Example 2

[0136] The difference between this comparative example and Example 1 is that the electrolyte components of this comparative example are: the lithium salt is LiPF6, the organic solvent is fluoroether (TTE), and the lithium salt concentration is 1 mol / L.

[0137] The rest of the preparation methods and parameters were the same as those in Example 1.

[0138] Comparative Example 3

[0139] The difference between this comparative example and Example 1 is that the base film of the negative electrode current collector in this comparative example does not contain CMC.

[0140] In the preparation method, no CMC is added.

[0141] The rest of the preparation methods and parameters were the same as those in Example 1.

[0142] Comparative Example 4

[0143] The difference between this comparative example and Example 1 is that the base film of the negative electrode current collector in this comparative example does not contain PEO.

[0144] In the preparation method, no PEO is added.

[0145] The rest of the preparation methods and parameters were the same as those in Example 1.

[0146] The batteries provided by Examples 1-12 and Comparative Examples 1-4 were tested for energy density, cycle performance, and safety performance.

[0147] Before the battery is formally charged and discharged, the first charge and discharge process is carried out: at 25°C, the batteries provided in the embodiment and the comparative example are charged for the first time at a rate of 0.5C. The charging is constant current and constant voltage charging. The charging termination voltage is 4.2V and the cut-off current is 0.05C. Then, the battery is discharged at a rate of 0.5C and the discharge termination voltage is 3.0V. After the first charge and discharge are completed, the battery is left for 24 hours.

[0148] ① Energy density: Measure the battery weight W0, then assemble the battery. At room temperature, the lithium-ion batteries prepared in the Examples and Comparative Examples were charged and discharged for the first time at a current of 0.33C. Charging was constant current and constant voltage charging, with a termination voltage of 4.2V, a cut-off current of 0.05C, and a discharge termination voltage of 2.5V. The batteries were left for 12 hours. Constant current and constant voltage charging was performed at a current of 1C, with a termination voltage of 4.2V, a cut-off current of 0.05C, and a discharge termination voltage of 2.5V. The discharge was performed at a current of 1C, with a discharge termination voltage of 2.5V. The discharge capacity of the cell, C0, was recorded. Battery volume energy density = discharge capacity C0 / cell mass W0.

[0149] ② Cycle performance: At 25°C and a voltage range of 3.0 to 4.2 V, charge and discharge cycle tests were performed at a rate of 1C, and the discharge capacity Cb at the first cycle and the capacity retention rate after 1000 cycles were recorded.

[0150] The test process of the above battery is shown in Table 1.

[0151] Table 1

[0152]

[0153]

[0154] Peel force test:

[0155] ① Initial peel force test: Take the negative electrode current collector structure prepared in Examples 1-12 and Comparative Examples 1-4 with a size of 15*100mm, stick 3M-9080A-15mm tape on a stainless steel plate, and then evenly stick the aluminum side of the measurement sample on the double-sided tape. Use a 2kg standard small pressure roller to squeeze back and forth twice. Then, stick 3M-9080A-14mm tape on the copper side surface of the sample and use a 2kg standard small pressure roller to squeeze back and forth twice. Then, take the pressed sample to a tensile testing machine and stretch it 180° at a speed of 100mm / min and a width of 14mm. The maximum value is taken.

[0156] ② Post-cycle peel strength test: After cycling, the battery was discharged and disassembled. The disassembled negative electrode sheet was placed in deionized water to wash away the negative electrode active material layer and dried to obtain a sample. Take the negative electrode current collector structure prepared in Examples 1-12 and Comparative Examples 1-4 with a size of 15*100mm, apply 3M-9080A-15mm tape to a stainless steel plate, then evenly apply the aluminum side of the test sample to the double-sided tape and squeeze it back and forth twice using a 2kg standard small roller. Then, apply 3M-9080A-14mm tape to the copper side of the sample and squeeze it back and forth twice using a 2kg standard small roller. Then, take the pressed sample and stretch it 180° on a tensile testing machine at a speed of 100mm / min and a width of 14mm. The maximum value is taken.

[0157] The test results of the above tests are shown in Table 2.

[0158] Table 2

[0159] Initial peel force N / m Peel force after cycle N / m Example 1 1405 694 Example 2 1552 729 Example 3 1418 701 Example 4 1478 708 Example 5 1403 672 Example 6 1451 699 Example 7 1506 711 Example 8 1491 653 Example 9 1483 640 Example 10 1489 651 Example 11 1477 642 Example 12 1459 639 Comparative Example 1 1369 788 Comparative Example 2 1424 771 Comparative Example 3 1458 312 Comparative Example 4 1124 601

[0160] Note: The qualified standard for current collector peeling force is ≥500N / m.

[0161] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A battery, characterized in that: The battery comprises a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte before being assembled; The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector. The negative electrode current collector includes a first base film and a first metal layer provided on at least one side of the first base film. The base film includes a first organic skeleton material and a first high molecular polymer material soluble in a polar solvent. The electrolyte includes a lithium salt and a polar organic solvent.

2. The battery according to claim 1, characterized in that The ratio of the thickness of the first base film to the thickness of the first metal layer is (4-10):(0.5-3).

3. The battery according to claim 1, characterized in that The mass ratio of the first organic framework material to the first high molecular polymer material is (1-6):(8-15).

4. The battery according to claim 1 or 3, characterized in that The first organic framework material includes cellulose material and / or cellulose derivative material; Preferably, the first high molecular polymer material includes any one of polyethylene oxide, polyethylene glycol, polyvinyl pyrrolidone or a bio-based polymer material, or a combination of at least two thereof.

5. The battery according to claim 1, characterized in that The negative electrode active material in the negative electrode active material layer includes a carbon-based negative electrode material and / or a silicon-based negative electrode material, preferably a silicon-based negative electrode material.

6. The battery according to claim 1, characterized in that The negative electrode sheet has a through-hole structure along the thickness direction of the negative electrode sheet; Preferably, the equivalent diameter of the through-hole structure is 50 to 5000 μm; Preferably, the porosity of the through-hole structure in the negative electrode plate is 10% to 50%.

7. The battery according to claim 1, characterized in that The polar organic solvent includes any one of EC, DMC, DEC or DMF, or a combination of at least two thereof.

8. The battery according to claim 1, characterized in that The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector; Preferably, the positive electrode active material in the positive electrode active material layer includes a high-nickel positive electrode material.

9. The battery according to claim 8, characterized in that The positive electrode current collector includes a second base film and a second metal layer provided on at least one side of the second base film, wherein the base film includes a second organic skeleton material and a second high molecular polymer material soluble in a polar solvent; Preferably, the ratio of the thickness of the second base film to the thickness of the second metal layer is (4-10):(0.5-3); Preferably, the mass ratio of the second organic framework material to the second high molecular polymer material is (1-6):(8-15); Preferably, the second organic framework material comprises a cellulose material and / or a cellulose derivative material; Preferably, the second high molecular polymer material includes any one of polyethylene oxide, polyethylene glycol, polyvinyl pyrrolidone or a bio-based polymer material, or a combination of at least two thereof.

10. A battery module, characterized in that: The battery module comprises at least one group of batteries according to any one of claims 1 to 9.

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