CN115632106B - Composite negative plate and secondary battery - Google Patents

Composite negative plate and secondary battery Download PDF

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Publication number
CN115632106B
CN115632106B CN202211267611.3A CN202211267611A CN115632106B CN 115632106 B CN115632106 B CN 115632106B CN 202211267611 A CN202211267611 A CN 202211267611A CN 115632106 B CN115632106 B CN 115632106B
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silicon
composite
negative
lithium
negative electrode
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CN115632106A (en
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唐文
张传健
张�浩
黄海旭
于清江
江柯成
钟应声
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Jiangsu Zenio New Energy Battery Technologies Co Ltd
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Jiangsu Zenio New Energy Battery Technologies Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Composite Materials (AREA)
  • Inorganic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Secondary Cells (AREA)

Abstract

The invention belongs to the technical field of secondary batteries, and particularly relates to a composite negative plate, which comprises a negative current collector and a negative coating arranged on at least one surface of the negative current collector, wherein the negative coating contains a silicon material and a lithium material, and the composite negative plate meets the following relational expression: k rho is more than or equal to 0.003 and less than or equal to 17.2 (1-eta). According to the composite negative plate, the porosity, the lithium/silicon mass ratio and the plate resistance are designed, so that the composite negative plate with good conductivity, low volume expansion rate, high discharge capacity, high initial coulombic efficiency, low resistivity and good high-temperature cycle performance is obtained.

Description

Composite negative plate and secondary battery
Technical Field
The invention belongs to the technical field of secondary batteries, and particularly relates to a composite negative plate and a secondary battery.
Background
With the rapid development of electric vehicles and portable electronic devices, commercial graphite negative electrodes having relatively low theoretical capacity have failed to meet the high energy density requirements of electrochemical secondary batteries. Therefore, there is an urgent need to explore advanced anode materials having high specific capacities to meet the increasing demands. Among the emerging candidate anode materials, silicon anode materials have higher theoretical capacity (reaching 3500mAh/g, li 3.75 Si in the form of Si), the earth crust is rich in the earth crust, has a low lithium intercalation potential, is low in cost, and is environmentally friendly in the synthesis process, so that the earth crust is widely used.
Unfortunately, commercial negative electrode applications of silicon suffer from multiple serious challenges including poor intrinsic conductivity, severe volume expansion during charge and discharge, and secondary growth of the interfacing solid electrolyte films, resulting in capacity fade, low first coulombic efficiency, rapid increase in DCR (direct current resistance) at high temperatures, and poor high temperature cycling performance. Therefore, a solution to the above-mentioned problems is needed.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the composite negative plate is provided, and the composite negative plate with good conductivity, low volume expansion rate, higher discharge capacity, higher initial coulombic efficiency, lower resistivity and good high-temperature cycle performance is obtained by designing the porosity of the negative material, the mass ratio of lithium to silicon and the resistance of the negative coating.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the composite negative plate comprises a negative current collector and a negative coating arranged on at least one surface of the negative current collector, wherein the negative coating contains a silicon material and a lithium material, and the composite negative plate meets the following relational expression: k rho is more than or equal to 0.003 and less than or equal to 17.2 (1-eta); wherein eta is the porosity in the anode coating, k is the mass ratio of lithium to silicon in the anode coating, and rho is the resistance of the composite anode plate.
Preferably, the value range of eta is 0.18 to 0.48.
Preferably, the value range of k is 0.02-0.8.
Preferably, the value range of rho is 0.12-32 mΩ.
Preferably, the negative electrode coating comprises a negative electrode material, a conductive agent and a binder, wherein the mass ratio of the negative electrode material to the conductive agent to the binder is 80-99: 0.3 to 10:0.2 to 10.
Preferably, the anode material further comprises a carbon material.
Preferably, the silicon material is contained in the anode material in an amount of 1 to 30%, and the silicon material has a particle diameter of 0.15 to 20 μm.
Preferably, the silicon material is silicon oxide. The chemical formula of the silicon oxide is SiOx, wherein the value of X satisfies the following conditions: x is more than 0 and less than 2.
More preferably, the silicon material is obtained by pre-lithiation or pre-magnesia.
Preferably, the anode material further comprises one or more elements of aluminum, selenium, nitrogen, phosphorus, boron, tin, magnesium, sodium, potassium, calcium, beryllium, gallium, germanium, strontium, zirconium, vanadium, titanium, boron, nickel, cobalt, copper, zinc, silver and fluorine.
The second object of the present invention is: aiming at the defects of the prior art, the secondary battery has higher energy density, lower volume expansion rate, lower resistivity, higher first coulombic efficiency and higher high-temperature cycle performance.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a secondary battery comprises the composite negative plate.
Preferably, the secondary battery further includes a positive electrode sheet, a separator for separating the negative electrode sheet from the positive electrode sheet, an electrolyte, and a case for packaging the positive electrode sheet, the separator, the electrolyte, and the negative electrode sheet.
The secondary battery has good conductivity, lower resistivity, higher initial coulombic efficiency and good cycle performance.
Compared with the prior art, the invention has the beneficial effects that: according to the composite negative plate, the composite negative plate with good conductivity, low volume expansion rate, high discharge capacity, high initial coulombic efficiency, low resistivity and good high-temperature cycle performance is obtained by designing the porosity, the lithium/silicon mass ratio and the negative coating resistance.
Detailed Description
The present invention will be described in further detail with reference to the following specific embodiments, but the embodiments of the present invention are not limited thereto.
The composite negative plate comprises a negative current collector and a negative coating arranged on at least one surface of the negative current collector, wherein the negative coating contains a silicon material and a lithium material, and the composite negative plate meets the following relational expression: k rho is more than or equal to 0.003 and less than or equal to 17.2 (1-eta); wherein eta is the porosity in the anode coating, k is the mass ratio of lithium to silicon in the anode coating, and rho is the resistance of the composite anode plate.
According to the invention, the porosity eta of the membrane is designed to be 0.18-0.48, the mass ratio of lithium/silicon is controlled to be 0.02-0.80, the membrane resistance rho is controlled to be 0.12-32 mΩ, and when the k rho of 0.003-eta is less than or equal to (1-eta) and less than or equal to 17.2, the volume space required by membrane expansion can be met, the apparent structure change is small, the negative influence of the volume expansion is reduced to be lower, the problems of particle pulverization, falling and the like caused by the volume expansion are better relieved, more effective reaction area can be provided, the higher discharge capacity and lower resistivity are maintained, the first coulomb efficiency is improved, the DCR at the high temperature (40-60 ℃) is reduced, and the high-temperature cycle performance is better.
In the present invention, the inventors consider that the porosity is closely related to the capacity of the pole piece, and may have a certain influence on the membrane structure, the rate of the battery, and the cycle performance. For the composite negative plate containing silicon oxide, if the porosity of the membrane is too large, the compaction density is low, the membrane structure is easy to be broken, even if the particle size expansion of particles is relatively reduced, the expansion degree of the membrane is reduced, the effective reaction area of electrolyte and active materials is increased, and the migration efficiency of lithium ions is improved, but the contact between active particles in unit volume is less, the discharge capacity of a battery is gradually reduced, and the cycle performance of the membrane is affected; if the porosity of the membrane is designed to be too small, the mechanical stress generated by volume expansion of the membrane is difficult to release, cracks are easy to generate, poor contact of the current collector is caused by crack expansion, and finally the multiplying power and the cycle performance of the battery are reduced.
In addition, when lithium is contained in the negative electrode coating of the composite negative electrode plate, inert substances such as lithium silicate, lithium oxide and the like are formed in the silicon oxide in the silicon-containing composite negative electrode plate when lithium is intercalated, so that the volume expansion of silicon can be restrained, and the silicon-containing composite negative electrode plate has better cycle performance than silicon. The inventor finds that by designing the lithium/silicon mass ratio reasonably, when the lithium/silicon mass ratio in the membrane is in the range of 0.02-0.80, the silicon oxide intercalates lithium to compensate irreversible lithium loss caused by the formation of the first SEI membrane, and the first coulomb efficiency and the cycle life of the lithium battery can be improved better. However, when the mass ratio of lithium/silicon in the membrane is too low (< 0.02), the lithium content is low, and the first coulombic efficiency cannot be sufficiently improved; when the mass ratio of lithium to silicon in the membrane is too high (> 0.8), the high lithium content can cause high activity and high pH of the silicon-containing material, and the gas production amount is increased in the preparation process of the cathode slurry and in the charge-discharge cycle process of the battery, so that the prepared membrane has poor quality and potential safety hazard.
Finally, the pole piece resistance reflects the advantages and disadvantages of the electrode material performance and the formula, so that the reasonable pole piece resistance and the electrode conductivity are improved, and the capacity, the power size, the cycle life and the safety performance of the lithium ion battery are facilitated. Moreover, by setting the pole pieces with lower resistance and proper range, the method can be used for improving the homogenate coating process and the formula, can screen and sort pole pieces with larger resistance values in time, does not flow into the process of monomer manufacturing, and improves the quality of terminal products.
In summary, the inventor finds that when the porosity eta of the membrane is controlled to be 0.18-0.48, the mass ratio of lithium/silicon is controlled to be 0.02-0.80, the resistance rho of the negative electrode coating is controlled to be 0.12-32 mΩ, and the (1-eta) krho is satisfied to be less than or equal to 17.2, the volume space required by the expansion of the pole piece can be satisfied, the apparent structure change is not large, the negative influence of the volume expansion is reduced to be lower, the pulverization and the shedding of particles caused by the volume expansion are better relieved, more effective reaction area can be provided, the higher discharge capacity and the lower resistivity are maintained, the first coulombic efficiency is improved, and the DCR (direct current collector) at high temperature (40-60 ℃) and the high-temperature cycle performance are better.
In some embodiments, the η ranges from 0.18 to 0.48. The method for testing the porosity eta comprises the following steps: taking a rectangular negative electrode coating to be measured, measuring the overall appearance length and width of the negative electrode coating, and calculating to obtain the volume number V1; placing the diaphragm in a sample tank of a true density instrument, and measuring to obtain the true volume V2 of the diaphragm; the membrane porosity η= (V1-V2)/V1 is obtained by calculation. Specifically, η ranges from 0.18, 0.2, 0.24, 0.26, 0.28, 0.3, 0.34, 0.38, 0.4, 0.45, 0.48.
In some embodiments, the value of k ranges from 0.02 to 0.8. Preferably, k has a value ranging from 0.02 to 0.1, from 0.1 to 0.2, from 0.2 to 0.3, and from 0.04 to 0.36. Specifically, the value of k ranges from 0.04, 0.06, 0.08, 0.1, 0.15, 0.17, 0.18, 0.2, 0.22, 0.25, 0.27, 0.28, 0.3, 0.34, 0.36, 0.4, 0.45, 0.5, 0.55, 0.6.
In some embodiments, the ρ is in the range of 0.12 to 32mΩ. The resistance rho testing method comprises the following steps: cutting a flat and wrinkle-free composite silicon-containing negative electrode plate into a size of 5cm or 5cm, placing the composite silicon-containing negative electrode plate between an upper test probe and a lower test probe of a negative electrode coating resistance tester, connecting the two test probes with a resistor meter through two polar posts, extruding the pole piece by the two test probes under stable pressure (0.005-0.5 t), controlling the pressure by a pressure meter, and reading resistance data of the resistor meter within a time period of 0.1s after the pressure is more than or equal to 0.4t, wherein the data is rho. Specifically, ρ has a value range of 0.12mΩ, 0.18mΩ, 0.2mΩ, 0.6mΩ, 0.8mΩ, 0.9mΩ, 1mΩ, 5mΩ, 9mΩ, 10mΩ, 11mΩ, 12mΩ, 16mΩ, 17mΩ, 19mΩ, 20mΩ, 21mΩ, 23mΩ, 28mΩ, 30mΩ, 32mΩ.
In some embodiments, the negative electrode coating comprises a negative electrode material, a conductive agent and a binder, wherein the mass ratio of the negative electrode material, the conductive agent and the binder is 80-99: 0.3 to 10:0.2 to 10. Preferably, the mass ratio of the anode material, the conductive agent and the binder is 80-99: 0.3 to 3: 0.2-10, 80-90: 0.3 to 3: 0.2-10, 80-99: 0.3 to 3: 0.2-3, 80-99: 0.3 to 3: 0.2-3, 90-99: 8-10: 3-10, specifically, the mass ratio of the anode material, the conductive agent and the binder is 80:0.5:0.5, 82:2:5, 85:6:8, 90:8:10, 92:10:12, 95:7:8, 96:7:8, 97:7:8, 92:7:8, 93:7:8.
In some embodiments, the negative electrode material further comprises a carbon material. Wherein the carbon material comprises one or more of natural graphite, artificial graphite and graphitized carbon fibers. The silicon material has higher gram capacity, can provide higher energy density, the carbon material can provide higher deintercalation efficiency, the lithium material contains lithium ions, compared with silicon ions, has higher conductivity, and inert substances such as lithium silicate, lithium oxide and the like can be formed in the silicon oxide during lithium intercalation, so that the volume expansion of silicon can be restrained, the silicon material has better cycle performance than silicon, and a certain amount of lithium is added, so that the lithium/silicon mass ratio in a negative electrode coating is within a certain reasonable interval, the lithium intercalation of the silicon oxide can compensate the formation of a first SEI film to cause irreversible lithium loss, and the first coulombic efficiency and the cycle life of a lithium battery can be better improved. Preferably, the silicon material is pre-lithiated to improve first-time efficiency and conductivity.
In some embodiments, the silicon material is present in the negative electrode material in an amount of 1 to 30% and the silicon material has a particle size of 0.15 to 20 μm. Preferably, the content of the silicon material in the anode material is 1 to 10%, 10 to 20%, 20 to 30%, and the content of the silicon material in the anode material is 1%, 2%, 5%, 6%, 8%, 9%, 10%, 12%, 15%, 16%, 18%, 19%, 20%, 24%, 26%, 28%, 30%. The particle size of the silicon material was 0.15 μm, 0.18 μm, 0.25 μm, 0.28 μm, 0.38 μm, 0.45 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 4 μm, 5 μm, 7 μm, 9 μm, 10 μm, 12 μm, 15 μm, 17 μm, 19 μm, 20 μm.
Preferably, the silicon material is silicon oxide, and the chemical formula of the silicon oxide is SiOx, wherein the value range of X satisfies: x is more than 0 and less than 2. More preferably, the silicon material is obtained by pre-lithiation or pre-magnesia. The silicon material subjected to pre-lithiation or pre-magnesia has more stable structure and better electrochemical performance.
Wherein the negative electrode material also comprises one or more elements of oxygen, aluminum, selenium, nitrogen, phosphorus, boron, tin, magnesium, sodium, potassium, calcium, beryllium, gallium, germanium, strontium, zirconium, vanadium, titanium, nickel, cobalt, copper, zinc, silver and fluorine. The stability of the material can be improved by various elements in the anode material, so that the cycle performance is improved.
A secondary battery has higher energy density, lower volume expansion rate, lower resistivity, higher first coulombic efficiency and higher high-temperature cycle performance.
The secondary battery also comprises a positive plate, a separation membrane, electrolyte and a shell, wherein the separation membrane is used for separating the negative plate from the positive plate, and the shell is used for packaging the positive plate, the separation membrane, the electrolyte and the negative plate.
The positive plate comprises one or more than two of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese phosphate and lithium iron phosphate.
The isolating film is one or more of a medium single film, a double composite film or a multi-composite film of polyethylene, polypropylene, polyacrylonitrile, polyamide acid, polyamide, polyarylethersulfone, polyvinylidene fluoride, polyethylene glycol terephthalate, polyester, a non-woven fabric film and a cellulose paper-based isolating film.
The electrolyte contains one or more lithium salts of lithium hexafluorophosphate, lithium difluorosulfimide, lithium bistrifluoromethylsulfonimide, lithium tetrafluoroborate, lithium dioxalate borate, lithium trifluoromethane sulfonate, lithium oxalyldifluoroborate, lithium difluorophosphate, lithium 4, 5-dicyano-2-trifluoromethylimidazole, lithium difluorodioxalate and lithium tetrafluorooxalate.
Further, the electrolyte contains an organic solvent, which may be a cyclic carbonate, including PC, EC, FEC; chain carbonates are also possible, including DEC, DMC, or EMC; carboxylic esters, including MF, MA, EA, MP, and the like, are also contemplated.
Further, the electrolyte contains one or more of additives fluoroethylene carbonate, vinylene carbonate, ethylene sulfate, methylene methane disulfonate, tris (trimethylsilane) boron/phosphate, the additives including, but not limited to, at least one of film forming additives, conductive additives, flame retardant additives, overcharge preventing additives, additives to control the H2O and HF content of the electrolyte, additives to improve high temperature performance, multifunctional additives.
The binder is one or more of monomers, polymers or copolymers of acrylonitrile, vinylidene fluoride, sodium carboxymethyl cellulose, acrylic acid, acrylamide, amide, imide, acrylic ester, styrene-butadiene rubber, vinyl alcohol, sodium alginate, lithium carboxymethyl cellulose, dopamine and the like.
The negative electrode current collector is one or more of copper foil, porous copper foil, foam nickel/copper foil, zinc plating, nickel, titanium, gold, silver, indium and other copper foils, carbon-coated copper foil and polymer composite current collector, preferably copper foil, foam copper foil and nickel-plated copper foil.
The stripping force between the negative electrode coating and the negative electrode current collector is 0.10-1.2N; preferably, the peel force between the anode coating and the anode current collector is 0.1N, 0.5N, 0.8N, 1.1N, 1.2N.
Further, in the case where the coating weight per unit area of the composite silicon-containing negative electrode sheet is constant, the magnitude of the peeling force between the composite silicon-containing membrane and the current collector is related to factors such as the content of the binder in the composite silicon-containing membrane, the type of the binder, the compaction density of the composite silicon-containing membrane, and the like, and a person skilled in the art can select a known method to adjust the magnitude of the peeling force (0.10 to 1.2N) between the composite silicon-containing membrane and the current collector according to the actual situation.
A secondary battery comprises the composite negative plate.
The following secondary battery is exemplified by a lithium ion battery including a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, and a case for housing the positive electrode sheet, the negative electrode sheet, the separator, and the electrolyte. The negative plate is the composite negative plate.
Positive electrode
The positive plate comprises a positive current collector and a positive active material layer arranged on at least one surface of the positive current collector, wherein the positive active material layer comprises a positive active material, and the positive active material can be a compound with a chemical formula as Li a Ni x Co y M z O 2-b N b (wherein 0.95.ltoreq.a.ltoreq.1.2, x)>0, y.gtoreq.0, z.gtoreq.0, and x+y+z.ltoreq.1, 0.ltoreq.b.ltoreq.1, M is selected from combinations of one or more of Mn, al, N is selected from combinations of one or more of F, P, S), the positive electrode active material may also be a combination of one or more of compounds including but not limited to LiCoO 2 、LiNiO 2 、LiVO 2 、LiCrO 2 、LiMn 2 O 4 、LiCoMnO 4 、Li 2 NiMn 3 O 8 、LiNi 0.5 Mn 1.5 O 4 、LiCoPO 4 、LiMnPO 4 、LiFePO 4 、LiNiPO 4 、LiCoFSO 4 、CuS 2 、FeS 2 、MoS 2 、NiS、TiS 2 And the like. The positive electrode active material may be further subjected to a modification treatment, and a method for modifying the positive electrode active material should be known to those skilled in the art, for example, the positive electrode active material may be modified by coating, doping, or the like, and the material used for the modification treatment may be one or more combinations including, but not limited to, al, B, P, zr, si, ti, ge, sn, mg, ce, W, or the like. The positive current collector is usually a structure or a part for collecting current, and the positive current collector may be various materials suitable for being used as a positive current collector of a lithium ion battery in the field, for example, the positive current collector may be a metal foil, and the like, and more particularly may include, but is not limited to, an aluminum foil, and the like.
Negative electrode
The negative electrode sheet is the composite negative electrode sheet, and the negative electrode current collector is usually a structure or a part for collecting current, and the negative electrode current collector can be various materials suitable for being used as a negative electrode current collector of a lithium ion battery in the field, for example, the negative electrode current collector can be a metal foil or the like, and more particularly can be a copper foil or the like.
Electrolyte solution
The lithium ion battery also includes an electrolyte comprising an organic solvent, an electrolyte lithium salt, and an additive. Wherein the electrolyte lithium salt can be LiPF used in high-temperature electrolyte 6 And/or LiBOB; liBF used in the low-temperature electrolyte may be used 4 、LiBOB、LiPF 6 At least one of (a) and (b); liBF used in the overcharge-preventing electrolyte may also be used 4 、LiBOB、LiPF 6 At least one of LiTFSI; liClO may also be 4 、LiAsF 6 、LiCF 3 SO 3 、LiN(CF 3 SO 2 ) 2 At least one of them. And the organic solvent may be a cyclic carbonate, including PC, EC; can also be in a chain shapeCarbonates, including DFC, DMC, or EMC; carboxylic esters, including MF, MA, EA, MP, and the like, are also contemplated. And the additive includes, but is not limited to, at least one of a film forming additive, a conductive additive, a flame retardant additive, an overcharge preventing additive, an additive for controlling the contents of H2O and HF in the electrolyte, an additive for improving low temperature performance, and a multifunctional additive.
And the separator may be a variety of materials suitable for lithium ion battery separators in the art, for example, may be a combination of one or more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fibers, and the like.
Preferably, the shell is made of one of stainless steel and aluminum plastic film. More preferably, the housing is an aluminum plastic film.
The secondary battery of the invention specifically comprises the following preparation methods: r1: and winding the composite silicon-containing negative electrode plate, the isolating film and the positive electrode plate to obtain a battery cell, injecting electrolyte, packaging the battery cell, standing, forming and capacity-dividing to obtain the electrochemical secondary battery.
Example 1
Preparing a composite silicon-containing negative electrode sheet:
t1: the composite silicon-containing anode material (composed of particles with a particle diameter D 50 Pre-lithiated silicon oxide (SiO) of 5 μm, particle size D 50 Artificial graphite of 12 μm according to 15:85 mass ratio), conductive carbon nanotubes, and a binder (sodium carboxymethylcellulose, styrene-butadiene rubber according to 90:10 mass ratios mixed) was 95:1.5:2.5, mixing and pulping to obtain composite silicon-containing slurry;
t2: coating the composite silicon-containing slurry on a copper foil, cold pressing, drying and cutting to obtain eta=0.28 and k=0.36, thus obtaining the composite silicon-containing negative plate.
Preparing an electrochemical secondary battery:
r1: composite silicon-containing negative electrode plate, isolating film, lithium nickel cobalt manganese oxide (LiNi 0.6 Co 0.2 Mn 0.2 O 2 ) Winding the positive electrode sheet to obtain a battery core, and injecting 1mol/L lithium hexafluorophosphate (dissolved inEMC, EC, DMC in the solution with the volume ratio of 1:1:1) electrolyte (the injection amount is 3.2 g/Ah), cell packaging, standing, forming and capacity division, and obtaining the electrochemical secondary battery.
Example 2
Preparing a composite silicon-containing negative electrode sheet:
t1: the composite silicon-containing anode material (prepared by mixing silicon oxide (SiO) with the granularity of 6 mu m and artificial graphite with the granularity of 12 mu m according to the mass ratio of 15:85), conductive carbon nano tubes and a binder (prepared by mixing sodium carboxymethyl cellulose and styrene-butadiene rubber according to the mass ratio of 90:10) with the mass ratio of 95:1.5:2.5, mixing and pulping to obtain composite silicon-containing slurry;
t2: coating the composite silicon-containing slurry on a copper foil, cold pressing, drying and cutting to obtain eta=0.23 and k=0.36, thus obtaining the composite silicon-containing negative plate.
Preparing an electrochemical secondary battery:
r1: composite silicon-containing negative electrode plate, isolating film, lithium nickel cobalt manganese oxide (LiNi 0.6 Co 0.2 Mn 0.2 O 2 ) Winding the positive plate to obtain a battery core, injecting 1mol/L lithium hexafluorophosphate (dissolved in a solution with a volume ratio of EMC, EC, DMC of 1:1:1) electrolyte (the injection amount is 3.2 g/Ah), packaging the battery core, standing, forming and separating the battery core to obtain the electrochemical secondary battery.
Example 3
T1: the composite silicon-containing anode material (prepared by mixing silicon oxide with the granularity of 3 mu m and artificial graphite with the granularity of 20 mu m according to the mass ratio of 15:85), conductive carbon nano tubes and a binder (prepared by mixing sodium carboxymethyl cellulose, styrene-butadiene rubber and polyacrylonitrile according to the mass ratio of 80:10:10) with the mass ratio of 95:1.5:2.5, mixing and pulping to obtain composite silicon-containing slurry;
t2: coating the composite silicon-containing slurry on a copper foil, cold pressing, drying and cutting to obtain eta=0.31 and k=0.37, thus obtaining the composite silicon-containing negative plate.
Preparing an electrochemical secondary battery:
r1: composite silicon-containing negative electrode plate, isolating film, lithium nickel cobalt manganese oxide (LiNi 0.6 Co 0.2 Mn 0.2 O 2 ) Winding the positive plate to obtainAnd (3) injecting 1mol/L lithium hexafluorophosphate (dissolved in EMC, EC, DMC solution according to the volume ratio of 1:1:1) electrolyte (the injection amount is 3.2 g/Ah) into the battery cell, packaging the battery cell, standing, forming and separating the capacity to obtain the electrochemical secondary battery.
Example 4
Preparing a composite silicon-containing negative electrode sheet:
t1: the composite silicon-containing anode material (prepared by mixing silicon oxide with the granularity of 4 mu m and artificial graphite with the granularity of 13 mu m according to the mass ratio of 20:80), conductive carbon nano tubes and a binder (prepared by mixing sodium carboxymethyl cellulose, styrene-butadiene rubber and polyacrylonitrile according to the mass ratio of 80:10:10) with the mass ratio of 90:1.5:3.5, mixing and pulping to obtain composite silicon-containing slurry;
t2: coating the composite silicon-containing slurry on a copper foil, cold pressing, drying and cutting to obtain eta=0.33 and k=0.34, thus obtaining the composite silicon-containing negative plate.
Preparing an electrochemical secondary battery:
r1: composite silicon-containing negative electrode plate, isolating film, lithium nickel cobalt manganese oxide (LiNi 0.6 Co 0.2 Mn 0.2 O 2 ) Winding the positive plate to obtain a battery core, injecting 1mol/L lithium hexafluorophosphate (dissolved in a solution with a volume ratio of EMC, EC, DMC of 1:1:1) electrolyte (the injection amount is 3.2 g/Ah), packaging the battery core, standing, forming and separating the battery core to obtain the electrochemical secondary battery.
Example 5
Preparing a composite silicon-containing negative electrode sheet:
t1: the composite silicon-containing anode material (prepared by mixing silicon oxide with the granularity of 2.5 mu m and artificial graphite with the granularity of 13 mu m according to the mass ratio of 15:85), conductive carbon nano tubes and a binder (prepared by mixing sodium carboxymethyl cellulose, styrene butadiene rubber and polyacrylonitrile according to the mass ratio of 80:10:10) has the mass ratio of 90:1.5:2.5, mixing and pulping to obtain composite silicon-containing slurry;
t2: coating the composite silicon-containing slurry on a copper foil, cold pressing, drying and cutting to obtain eta=0.38 and k=0.46, thus obtaining the composite silicon-containing negative plate.
Preparing an electrochemical secondary battery:
r1: will be compounded to containSilicon negative electrode sheet, separator, lithium nickel cobalt manganese oxide (LiNi 0.6 Co 0.2 Mn 0.2 O 2 ) Winding the positive plate to obtain a battery core, injecting 1mol/L lithium hexafluorophosphate (dissolved in a solution with a volume ratio of EMC, EC, DMC of 1:1:1) electrolyte (the injection amount is 3.2 g/Ah), packaging the battery core, standing, forming and separating the battery core to obtain the electrochemical secondary battery.
Example 6
Preparing a composite silicon-containing negative electrode sheet:
t1: the composite silicon-containing anode material (prepared by mixing silicon oxide (SiO) with the granularity of 4 mu m and artificial graphite with the granularity of 6 mu m according to the mass ratio of 20:80), conductive carbon nano tubes and a binder (prepared by mixing sodium carboxymethyl cellulose, styrene butadiene rubber and polyacrylonitrile according to the mass ratio of 80:10:10) with the mass ratio of 85:1.5:3.5, mixing and pulping to obtain composite silicon-containing slurry;
t2: coating the composite silicon-containing slurry on a copper foil, cold pressing, drying and cutting to obtain eta=0.41 and k=0.39, thus obtaining the composite silicon-containing negative plate.
Preparing an electrochemical secondary battery:
r1: composite silicon-containing negative electrode plate, isolating film, lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.15 Mn 0.05 O 2 ) Winding the positive plate to obtain a battery core, injecting 1mol/L lithium hexafluorophosphate (dissolved in a solution with a volume ratio of EMC, EC, DMC of 1:1:1) electrolyte (the injection amount is 3.2 g/Ah), packaging the battery core, standing, forming and separating the battery core to obtain the electrochemical secondary battery.
Example 7
The difference from example 1 is that: η=0.18, k=0.02, ρ=3.4 were measured.
The remainder is the same as in example 1 and will not be described again here.
Example 8
The difference from example 1 is that: η=0.28, k=0.24, ρ=13.7 were measured.
The remainder is the same as in example 1 and will not be described again here.
Example 9
The difference from example 1 is that: η=0.33, k=0.41, ρ=19.6 were measured.
The remainder is the same as in example 1 and will not be described again here.
Example 10
The difference from example 1 is that: η=0.41, k=0.62, ρ=17.9 were measured.
The remainder is the same as in example 1 and will not be described again here.
Example 11
The difference from example 1 is that: η=0.45, k=0.7, ρ=23.7 were measured.
The remainder is the same as in example 1 and will not be described again here.
Example 12
The difference from example 1 is that: η=0.48, k=0.8, ρ=27.5 were measured.
The remainder is the same as in example 1 and will not be described again here.
Comparative example 1
The difference from example 1 is that: t2: and (3) coating the composite silicon-containing slurry on a copper foil, cold pressing, drying and cutting to obtain eta=0.13 and k=0.36, thus obtaining the composite silicon-containing negative plate.
The remainder is the same as in example 1 and will not be described again here.
Comparative example 2
The difference from example 3 is that: t2: coating the composite silicon-containing slurry on a copper foil, cold pressing, drying and cutting to obtain eta=0.29 and k=0.03, thus obtaining the composite silicon-containing negative plate.
The remainder is the same as in example 3, and a detailed description thereof will be omitted.
Comparative example 3:
the difference from example 5 is that: t2: and (3) cold pressing, drying and cutting to obtain eta=0.22 and k=0.85, thus obtaining the composite silicon-containing negative plate.
The remainder is the same as in example 5, and a detailed description thereof will not be given here.
The parameters of the above examples and comparative examples are listed in table 1 below, and the secondary batteries described above were subjected to a first coulombic efficiency test, a DCR increase rate at 45 ℃ and a capacity retention rate at 45 ℃, and the test results are recorded in table 2.
TABLE 1
TABLE 2
Table 1, the values of eta and k and the values of (1-eta) and k/rho in comparative examples 1-3 and examples 1-12 are designed in different ranges, and the data of comparative examples 1-3 and examples 1-12 are combined in Table 2, so that the initial coulombic efficiency of each group in comparative examples 1-3 is lower, the DCR increase speed is faster at high temperature (40-60 ℃), the high-temperature cycle performance is poorer, the capacity retention rate of the 100 th circle and the 400 th circle is lower, and the DCR increase rate is higher, and the dynamic performance of lithium removal and lithium intercalation is higher when the eta, k and rho values of the composite silicon-containing negative plate are designed in a reasonable range, so that the lithium ion secondary battery has higher initial coulombic efficiency, lower DCR increase rate and better capacity retention rate.
Variations and modifications of the above embodiments will occur to those skilled in the art to which the invention pertains from the foregoing disclosure and teachings. Therefore, the present invention is not limited to the above-described embodiments, but is intended to be capable of modification, substitution or variation in light thereof, which will be apparent to those skilled in the art in light of the present teachings. In addition, although specific terms are used in the present specification, these terms are for convenience of description only and do not limit the present invention in any way.

Claims (7)

1. The composite negative plate comprises a negative current collector and a negative coating arranged on at least one surface of the negative current collector, and is characterized in that the negative coating contains a silicon material and a lithium material, and the composite negative plate meets the following relational expression: k rho is more than or equal to 0.003 and less than or equal to 17.2 (1-eta); wherein, eta is the porosity in the cathode coating, and the value range of eta is 0.18 to 0.48; the k is the mass ratio of lithium to silicon in the anode coating, and the value range of the k is 0.02-0.8; ρ is the resistance of the composite negative plate, and the value range of ρ is 0.12-32 mΩ.
2. The composite negative plate according to claim 1, wherein the negative coating comprises a negative material, a conductive agent and a binder, and the mass ratio of the negative material, the conductive agent and the binder is 80-99: 0.3 to 10:0.2 to 10.
3. The composite negative electrode sheet of claim 1, wherein the negative electrode material further comprises a carbon material.
4. The composite negative electrode sheet according to claim 1, wherein the silicon material has a content of 1 to 30% in the negative electrode material, and a particle diameter of 0.15 to 20 μm.
5. The composite negative electrode sheet of claim 4, wherein the silicon material is silicon oxide.
6. The composite negative electrode sheet according to claim 1, wherein the negative electrode material further comprises one or more elements of aluminum, selenium, nitrogen, phosphorus, boron, tin, magnesium, sodium, potassium, calcium, beryllium, gallium, germanium, strontium, zirconium, vanadium, titanium, boron, nickel, cobalt, copper, zinc, silver, fluorine.
7. A secondary battery comprising the composite negative electrode sheet of any one of claims 1-6.
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Publication number Priority date Publication date Assignee Title
CN104538591A (en) * 2014-12-30 2015-04-22 天津巴莫科技股份有限公司 Pre-lithiation method of lithium ion battery negative electrode material
CN115101711A (en) * 2022-06-09 2022-09-23 江苏正力新能电池技术有限公司 Negative plate, preparation method thereof and secondary battery
CN115117347A (en) * 2022-06-20 2022-09-27 深圳新宙邦科技股份有限公司 Negative plate and secondary battery

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Publication number Priority date Publication date Assignee Title
JP6256855B2 (en) * 2014-07-15 2018-01-10 川上 総一郎 Negative electrode material for secondary battery, electrode structure, secondary battery, and production method thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104538591A (en) * 2014-12-30 2015-04-22 天津巴莫科技股份有限公司 Pre-lithiation method of lithium ion battery negative electrode material
CN115101711A (en) * 2022-06-09 2022-09-23 江苏正力新能电池技术有限公司 Negative plate, preparation method thereof and secondary battery
CN115117347A (en) * 2022-06-20 2022-09-27 深圳新宙邦科技股份有限公司 Negative plate and secondary battery

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