CN117577803A - Composite material, negative electrode plate, preparation method of negative electrode plate, electrochemical device and electronic equipment - Google Patents

Composite material, negative electrode plate, preparation method of negative electrode plate, electrochemical device and electronic equipment Download PDF

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Publication number
CN117577803A
CN117577803A CN202311533697.4A CN202311533697A CN117577803A CN 117577803 A CN117577803 A CN 117577803A CN 202311533697 A CN202311533697 A CN 202311533697A CN 117577803 A CN117577803 A CN 117577803A
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negative electrode
composite material
hard carbon
particles
carbon particles
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李腾飞
王卫东
徐小明
杨帆
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of 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
    • 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
    • H01M2004/026—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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  • Manufacturing & Machinery (AREA)
  • Inorganic Chemistry (AREA)
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Abstract

Composite material, negative electrode plate, preparation method of negative electrode plate, electrochemical device and electronic equipment. The composite material comprises silica particles and hard carbon particles, wherein the particle diameter Dv50 of the silica particles is D1, the particle diameter Dv50 of the hard carbon particles is D2, and D1 is less than or equal to 0.414D2. According to the application, the hard carbon particles with large particle sizes are matched with the silica particles with small particle sizes, and the particle sizes D1 and D2 of the silica particles are controlled to be less than or equal to 0.414D2, so that an electrochemical device adopting the composite material as a negative electrode active material has high energy density and good cycle performance.

Description

Composite material, negative electrode plate, preparation method of negative electrode plate, electrochemical device and electronic equipment
Technical Field
The application relates to the technical field of energy storage, in particular to a composite material, a negative electrode plate, a preparation method of the negative electrode plate, an electrochemical device and electronic equipment.
Background
The further improvement of the energy density of the lithium ion battery is significant, and the adoption of the cathode material with high gram capacity is an effective means for improving the energy density of the lithium ion battery. The silicon-based anode material has a significantly high gram capacity of Yu Tanji anode material, and application of the silicon-based anode material is an important technical direction for developing next-generation high-energy-density lithium ion batteries in the industry. Silicon-based anode materials are typically used in combination with graphite due to significant volume expansion of the silicon-based anode material and reduced energy density benefits resulting from the potential rise to the anode. However, a series of problems such as loss of ionic and electronic conductive network and mismatching of lithium intercalation and lithium deintercalation potentials of the silicon-based anode material and graphite caused by volume expansion in the circulation process of the silicon-based anode material result in rapid capacity decay in the circulation process and poor circulation performance.
Disclosure of Invention
In view of the above, the present application provides a composite material, a negative electrode tab, a method for preparing the same, an electrochemical device, and an electronic apparatus, and an electrochemical device using the composite material as a negative electrode active material has both high energy density and good cycle performance.
The first aspect of the application provides a composite material which comprises silica particles and hard carbon particles, wherein the particle size Dv50 of the silica particles is D1, the particle size Dv50 of the hard carbon particles is D2, and D1 is less than or equal to 0.414D2. According to the composite material, the hard carbon particles with large particle sizes are matched with the silica particles with small particle sizes, and the particle sizes D1 and D2 of the silica particles are controlled to be smaller than or equal to 0.414D2, so that an electrochemical device adopting the composite material as a negative electrode active material has high energy density and good cycle performance.
In some embodiments, the silica particles are present in the composite at a level of M1, and the hard carbon particles are present in the composite at a level of 1-M1, 10wt% M1 35wt%. The compaction density of the pole piece can be further improved, the energy density of the electrochemical device is improved, and the cycle performance of the electrochemical device is improved.
In some embodiments, the silica particles have a specific surface area of B1, and the hard carbon particles have a specific surface area of B2, 1.25.ltoreq.B1/B2.ltoreq.4. The cycle performance of the electrochemical device can be further improved.
In some embodiments, the composite material meets at least one of the following conditions: (1) D1 is less than or equal to 1 μm and less than or equal to 15 μm; (2) D2 is less than or equal to 5 μm and less than or equal to 22.5 μm; (3) The specific surface area of the silica particles is B1,0.15m 2 /g≤B1≤15m 2 /g; (4) The specific surface area of the hard carbon particles is B2,0.15m 2 /g≤B2≤12m 2 And/g. The cycle performance of the electrochemical device can be further improved and the energy density thereof can be improved.
In some embodiments, the composite material meets at least one of the following conditions: (5) The silica particles have a compacted density of C1,1.3g/cm 3 ≤C1≤1.6g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the (6) The hard carbon particles have a compacted density of C2,0.9g/cm 3 ≤C2≤1.0g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the (7) The compaction density of the composite material is C3,1g/cm 3 ≤C3≤1.4g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the (8) The electric potential of the hard carbon particles at 25% of the lithium intercalation depth is 0.1-0.3V vs Li/Li higher than the electric potential of the silicon oxide particles at 25% of the lithium intercalation depth + The method comprises the steps of carrying out a first treatment on the surface of the (9) The electric potential of the hard carbon particles at 75% lithium removal depth is 0.1-0.3V vs Li/Li higher than the electric potential of the silicon oxide particles at 75% lithium removal depth + . The cycle performance of the electrochemical device can be further improved and the energy density thereof can be improved.
The second aspect of the application provides a negative electrode plate, which comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a conductive agent, a binder and the composite material.
In some embodiments, the compacted density of the anode active material layer is 0.96g/cm3 to 1.2g/cm3, and the porosity of the anode active material layer is 14% to 27%.
A third aspect of the present application provides a method for preparing the negative electrode piece, including:
dry-mixing the composite material and the dispersing agent to obtain a mixture;
uniformly mixing a solvent, part of binder and a conductive agent to obtain first slurry;
adding the first slurry into the mixture, and stirring and uniformly mixing to obtain second slurry;
adding a solvent into the second slurry, and uniformly stirring and mixing to obtain a third slurry;
adding the rest binder into the third slurry, adding a solvent, and stirring and uniformly mixing to obtain negative electrode slurry;
and coating the negative electrode slurry on at least one surface of a negative electrode current collector to obtain a negative electrode plate.
In the preparation method of the negative electrode plate, the required adhesive is added in two steps, wherein part of the adhesive is premixed with the conductive agent, so that the optimized distribution of the conductive agent and the adhesive can be realized, and the cycle performance of the electrochemical device is improved.
A third aspect of the present application provides an electrochemical device, including a negative electrode tab manufactured by the above manufacturing method. It has good cycle performance and high energy density.
A fourth aspect of the present application provides an electronic device comprising the above electrochemical apparatus.
Detailed Description
The following examples will allow those skilled in the art to more fully understand the present application, but are not intended to limit the present application in any way.
The application provides a composite material, which comprises silica particles and hard carbon particles, wherein the particle size Dv50 corresponding to 50% in the volume distribution of the silica particles is D1, and the particle size Dv50 corresponding to 50% in the volume distribution of the hard carbon particles is D2, and D1 is less than or equal to 0.414D2.
Hard carbon is defined as carbon that is difficult to graphitize, and is difficult to graphitize even at high temperatures above 2500 ℃. Hard carbon is usually obtained by pyrolysis of a precursor such as a high molecular polymer. The hard carbon has high reversible gram capacity, and is beneficial to improving the energy density of the lithium ion battery. The hard carbon also has a more pore structure, so that ions can be conveniently removed and embedded, but the compaction density of the hard carbon cannot be too high, and the energy density is affected. The silicon-oxygen material has high specific capacity, is beneficial to improving the energy density of the lithium ion battery, but has larger volume expansion and shrinkage in the lithium intercalation process.
According to the method, the hard carbon particles with large particle sizes are matched with the silica particles with small particle sizes, the particle sizes D1 and D2 of the silica particles are controlled to be smaller than or equal to 0.414D2, the problem that the compaction density of the hard carbon particles is low can be solved, the compaction density of the negative electrode pole piece adopting the composite material as a negative electrode active material is improved, and then the energy density of an electrochemical device (such as a lithium ion battery) applying the negative electrode pole piece is improved. Meanwhile, as the hardness of the silica particles is larger than that of the hard carbon particles, the silica particles can play a role of rollers in the cold pressing process of the negative electrode plate, so that locking of the hard carbon particles caused by the sharp edges and corners is relieved, slippage among the particles is facilitated, and the compaction density of the negative electrode plate is further improved. On the other hand, the small-particle-size silica particles are distributed at the gap positions of the large-particle-size hard carbon particles, and in the lithium intercalation process, the hard carbon particles can generate acting force on the volume-expanded silica particles, so that the problem of capacity loss of the silica particles caused by volume expansion is solved, and the cycle performance of an electrochemical device is improved.
In some embodiments, the hard carbon particles comprise at least one of resinous carbon particles, organic polymer pyrolytic carbon particles, or carbon black particles, and the silica particles comprise Si, siO, or SiO 2 At least one of them.
In some embodiments, the silica particles are present in the composite at a level of M1, and the hard carbon particles are present in the composite at a level of 1-M1, 10wt% M1 35wt%. The compaction density of the pole piece can be further improved, the energy density of the electrochemical device is improved, and the cycle performance of the electrochemical device is improved. Alternatively, M1 is 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt% is a value within a range consisting of any two of these values.
In some embodiments, 1 μm.ltoreq.D1.ltoreq.15 μm,5 μm.ltoreq.D2.ltoreq.22.5 μm. Alternatively, D1 is 1 μm, 3 μm,5 μm, 10 μm, 15 μm, or a value in the range consisting of any two of these values. Alternatively, D2 is 51 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm, 21 μm, 22.5 μm or a value in the range consisting of any two of these values.
In some embodiments, the hard carbon particles are embedded at 25%The potential at the depth of lithium is 0.1-0.3V vs Li/Li higher than that of silicon oxide particles at 25% of the depth of lithium intercalation + The electric potential of the hard carbon particles at 75% lithium removal depth is 0.1-0.3V vs Li/Li higher than that of the silicon oxide particles at 75% lithium removal depth + . The hard carbon particles have higher potential than the silica particles, and the hard carbon particles can intercalate lithium before the silica particles, so that surface stress caused by reverse delithiation of the silica particles in the charging process of the lithium ion battery can be avoided, and the surface stress can inhibit the capacity of the silica particles; in addition, in the discharging process of the lithium ion battery, the lithium ions in the silica particles can be ensured to be separated to the greatest extent, the subsequent charge capacity exertion is not limited by internal stress generated by incomplete lithium separation, meanwhile, the lithium capture caused by incomplete lithium separation of the silica particles is also limited to the greatest extent, and the cycle performance of the lithium ion battery is further improved.
In some embodiments, the silica particles have a specific surface area of B1, and the hard carbon particles have a specific surface area of B2, 1.25.ltoreq.B1/B2.ltoreq.4. The close contact between the hard carbon particles and the silica particles can be further increased, so that the expansion of the silica particles is further relieved, the problem of capacity loss of the silica particles due to volume expansion is solved, and the cycle performance of the electrochemical device is further improved. Alternatively, B1/B2 is 1.25, 1.5, 2, 2.5, 3, 3.5, 4 or a value within a range consisting of any two of these values.
In some embodiments, 0.15m 2 /g≤B1≤15m 2 /g，0.15m 2 /g≤B2≤12m 2 And/g. Alternatively, B1 is 0.15m 2 /g、0.5m 2 /g、1.5m 2 /g、2m 2 /g、4m 2 /g、5.5m 2 /g、7m 2 /g、9.5m 2 /g、13.5m 2 /g、15m 2 /g or a value within a range consisting of any two of these values. Alternatively, B2 is 0.15m 2 /g、0.5m 2 /g、1.5m 2 /g、2m 2 /g、4m 2 /g、5.5m 2 /g、7m 2 /g、9.5m 2 /g、12m 2 /g or a value within a range consisting of any two of these values.
In some embodiments, the compaction of the silica particles in the composite materialThe solid density is C1, the compacted density of hard carbon particles in the composite material is C2, and the compacted density of the composite material is C3,1.3g/cm 3 ≤C1≤1.6g/cm 3 ，0.9g/cm 3 ≤C2≤1.0g/cm 3 ，1g/cm 3 ≤C3≤1.4g/cm 3 .0 further improves the problem of low compacted density of the hard carbon material, increases the energy density of the electrochemical device, and further improves the expansion of the silica particles, enhancing the cycle performance of the electrochemical device. Alternatively, C1 is 1.3g/cm 3 、1.35g/cm 3 、1.4g/cm 3 、1.45g/cm 3 、1.5g/cm 3 、1.55g/cm 3 、1.6g/cm 3 Or a value within a range consisting of any two of these values. Alternatively, C2 is 0.9g/cm 3 、0.92g/cm 3 、0.95g/cm 3 、0.97g/cm 3 、1.0g/cm 3 Or a value within a range consisting of any two of these values. Alternatively, C3 is 1g/cm 3 、1.2g/cm 3 、1.3g/cm 3 、1.4g/cm 3 Or a value within a range consisting of any two of these values.
Negative pole piece
The application also provides a negative electrode plate, which comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a conductive agent, a binder and the composite material. The composite material is used as a negative electrode active material of the negative electrode active material layer. In other words, the anode active material of the anode active material layer includes hard carbon particles and silicon oxide particles.
The binder may improve the binding of the anode active material particles to each other and may improve the binding of the anode active material to the anode current collector. The binder may comprise any adhesive polymer. Examples of binders include, but are not limited to: polyacrylic acid, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethyleneoxy-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, or mixtures thereof.
The conductive agent is used for improving the conductivity of the negative electrode plate. The conductive agent may comprise any material that is electrically conductive but does not cause a chemical change. Examples of conductive agents include, but are not limited to: base materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fibers, etc.), metal base materials (e.g., metal powders or metal fibers including copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives, etc.), or mixtures thereof.
In some embodiments, the negative electrode active material layer has a compacted density of 0.96g/cm 3 ～1.2g/cm 3 The porosity of the anode active material layer is 14% -27%. The electrochemical device can be further ensured to have higher energy density and better cycle performance. Alternatively, the negative electrode active material layer has a compacted density of 0.96g/cm 3 、0.98g/cm 3 、0.10g/cm 3 、0.12g/cm 3 、0.14g/cm 3 、0.17g/cm 3 、1.2g/cm 3 Or a value within a range consisting of any two of these values. Alternatively, the porosity of the anode active material layer is 14%, 16%, 17%, 19%, 22%, 24%, 27% or a value in a range composed of any two of these values.
In some embodiments, the negative electrode current collector includes, but is not limited to: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, conductive metal coated polymeric substrates, and any combination thereof. In some embodiments, the negative current collector is copper foil.
In some embodiments, the structure of the negative electrode tab is a negative electrode tab structure that is well known in the art and that can be used in electrochemical devices.
In some embodiments, the method of preparing the negative electrode sheet is known in the art as a method of preparing a negative electrode sheet that can be used in an electrochemical device. Illustratively, the negative electrode sheet may be obtained by: the anode active material, the conductive agent, and the binder are mixed in a solvent, and the thickener may be heated as needed to prepare an active material composition, and the active material composition is coated on the anode current collector. In some embodiments, the solvent may include, but is not limited to, water, N-methylpyrrolidone.
The application also provides a preparation method of the negative electrode plate, which comprises the following steps: (a) Dry-mixing the composite material and the dispersing agent to obtain a mixture; (b) Uniformly mixing a solvent, part of binder and a conductive agent to obtain first slurry; (c) Adding the first slurry into the mixture, and stirring and uniformly mixing to obtain second slurry; (d) Adding a solvent into the second slurry, and uniformly stirring and mixing to obtain a third slurry; (e) Adding the rest binder into the third slurry, adding a solvent, and stirring and uniformly mixing to obtain negative electrode slurry; (f) And coating the negative electrode slurry on at least one surface of a negative electrode current collector to obtain a negative electrode plate.
In the step (a), the composite material is pre-dispersed by a dispersing agent, so that the aggregation risk of hard carbon particles and silicon oxide particles of the composite material can be reduced. In some embodiments, the dispersant comprises at least one of sodium carboxymethyl cellulose, sodium hydroxymethyl cellulose, sodium polyacrylate, acrylamide.
In the step (b), the binder in the anode active material layer is partially premixed with the conductive agent, so that the optimization of the conductive agent and the binder can be realized, and the cycle performance of the electrochemical device can be improved.
The solvents used in step (b), step (d) and step (e) may be the same or different. In some embodiments, the solvents used in step (b), step (d) and step (e) each comprise at least one of deionized water, N-methylpyrrolidone, N-dimethylformamide, dimethylsulfoxide, tetrahydrofuran.
The present application also provides an electrochemical device comprising the above composite material. Electrochemical devices include any device in which an electrochemical reaction occurs. Examples of electrochemical devices include, but are not limited to, primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including but not limited to a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
In some embodiments, the electrochemical device includes the negative electrode tab described above, a positive electrode tab, an electrolyte, and a separator disposed between the positive electrode tab and the negative electrode tab.
Positive electrode plate
In some embodiments, the positive electrode tab includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, and the specific kind of the positive electrode active material is not particularly limited and may be selected according to the need.
In some embodiments, the positive electrode active material includes a compound that reversibly intercalates and deintercalates lithium ions (i.e., lithiated intercalation compound). In some embodiments, the positive electrode active material may include a lithium transition metal composite oxide. The lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese and nickel. In some embodiments, the positive electrode active material is selected from at least one of the following: lithium cobalt oxide (LiCoO) 2 ) Lithium nickel manganese cobalt ternary material (NCM), lithium manganate (LiMn) 2 O 4 ) Lithium nickel manganese (LiNi) 0.5 Mn 1.5 O 4 ) Or lithium iron phosphate (LiFePO) 4 )。
In some embodiments, the positive electrode active material layer further includes a binder, and optionally further includes a conductive material. The binder may improve the bonding of the positive electrode active material particles to each other, and may improve the bonding of the positive electrode active material to the positive electrode current collector. In some embodiments, the binder includes, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethyleneoxy-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy, nylon, and the like.
In some embodiments, the positive electrode active material layer includes a conductive material, thereby imparting conductivity to the positive electrode sheet. The conductive material may include any conductive material as long as it does not cause a chemical change. Non-limiting examples of conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fibers, etc.), metal-based materials (e.g., metal powders, metal fibers, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.
In some embodiments, the positive electrode current collector is a metal, including but not limited to aluminum foil.
In some embodiments, the structure of the positive electrode sheet is a positive electrode sheet structure that is well known in the art and that can be used in electrochemical devices.
In some embodiments, the method of preparing the positive electrode is a method of preparing a positive electrode that can be used in an electrochemical device, as known in the art. For example, the positive electrode can be obtained by: the active material, the conductive material, and the binder are mixed in a solvent to prepare an active material composition, and the active material composition is coated on a current collector. In some embodiments, the solvent may include water, N-methylpyrrolidone, etc., but is not limited thereto.
Electrolyte solution
The electrolyte used in embodiments of the present application may be an electrolyte known in the art. The electrolyte may be classified into an aqueous electrolyte and a non-aqueous electrolyte, wherein an electrochemical device employing the non-aqueous electrolyte may operate under a wider voltage window as compared to the aqueous electrolyte, thereby achieving a higher energy density. In some embodiments, the nonaqueous electrolyte includes an organic solvent, an electrolyte, and an additive.
Electrolytes useful in the electrolytes of embodiments of the present application include, but are not limited to: inorganic lithium salts, e.g. LiClO 4 、LiAsF 6 、LiPF 6 、LiBF 4 、LiSbF 6 、LiSO 3 F、LiN(FSO 2 ) 2 Etc.; fluorine-containing organolithium salts, e.g. LiCF3SO3, liN (FSO) 2 )(CF 3 SO 2 )、LiN(CF 3 SO 2 ) 2 、LiN(C 2 F 5 SO 2 ) 2 Cyclic 1, 3-hexafluoropropane disulfonimide lithium, cyclic 1, 2-tetrafluoroethane disulfonimide lithium and LiPF 4 (CF 3 ) 2 、LiN(CF 3 SO 2 )(C 4 F 9 SO 2 )、LiC(CF 3 SO 2 ) 3 、LiPF 4 (CF 3 SO 2 ) 2 、LiPF 4 (C 2 F 5 ) 2 、LiPF 4 (C 2 F 5 SO 2 ) 2 、LiBF 2 (CF 3 ) 2 、LiBF 2 (C 2 F 5 ) 2 、LiBF 2 (CF 3 SO 2 ) 2 、LiBF 2 (C 2 F 5 SO 2 ) 2 The method comprises the steps of carrying out a first treatment on the surface of the Examples of the dicarboxylic acid-containing complex lithium salt include lithium bis (oxalato) borate, lithium difluorooxalato borate, lithium tris (oxalato) phosphate, lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate, and the like. In addition, one kind of the above-mentioned electrolyte may be used alone, or two or more kinds may be used simultaneously. For example, in some embodiments, the electrolyte includes LiPF 6 And LiBF 4 Is a combination of (a) and (b). In some embodiments, the electrolyte comprises LiPF 6 。
In some embodiments, the concentration of the electrolyte is in the range of 0.8mol/L to 3mol/L, such as in the range of 0.8mol/L to 2.5mol/L, in the range of 0.8mol/L to 2mol/L, in the range of 1mol/L to 2mol/L, and further such as 1mol/L, 1.15mol/L, 1.2mol/L, 1.5mol/L, 2mol/L, or 2.5mol/L.
Additives useful in the electrolytes of the embodiments of the present application may be additives known to those skilled in the art that can be used to enhance the electrochemical performance of a battery. In some embodiments, the additive includes, but is not limited to, at least one of a polynitrile compound, a sulfur-containing additive, fluoroethylene carbonate (FEC), 1, 3-Propane Sultone (PS), 1,4 butane sultone.
The organic solvent that may be used in the electrolyte of the embodiments of the present application may be any organic solvent known in the art. In some embodiments, the organic solvent includes, but is not limited to: carbonate compounds, ester-based compounds, ether-based compounds, ketone-based compounds, alcohol-based compounds, aprotic solvents, or combinations thereof. Examples of carbonate compounds include, but are not limited to, chain carbonate compounds, cyclic carbonate compounds, fluorocarbonate compounds, or combinations thereof.
In some embodiments the organic solvent comprises at least one of Ethylene Carbonate (EC), propylene Carbonate (PC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate, methyl acetate, or ethyl propionate.
The preparation method of the electrolyte in the embodiment of the application is not limited, and the electrolyte can be prepared in a conventional electrolyte mode. In some embodiments, the electrolytes of the present application may be prepared by mixing the components.
Isolation film
In some embodiments, a separator is provided between the positive and negative electrode sheets to prevent shorting. The material and shape of the separator are not particularly limited and may be any of the techniques disclosed in the prior art. In some embodiments, the separator comprises a polymer or inorganic, etc., formed from a material that is stable to the electrolyte of the present application.
For example, in some embodiments, the release film includes a substrate layer. The substrate layer is a non-woven fabric, a membrane or a composite membrane with a porous structure. The material of the base material layer may be at least one selected from polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, the material of the substrate layer may be selected from a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane.
The substrate layer is provided with a surface treatment layer on at least one surface thereof. The surface treatment layer may be a polymer layer, an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance. Specifically, the inorganic layer includes inorganic particles and a binder. The inorganic particles may be selected from one or more of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. The binder can be selected from one or a combination of more of polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
The application also provides electronic equipment comprising the electrochemical device. The composite material can improve the cycle performance of the electrochemical device, so that the electrochemical device manufactured by the composite material is applicable to electronic equipment in various fields, in particular to electronic equipment with long cycle working requirements.
The use of the electrochemical device of the present application is not particularly limited, and it may be used in any electronic apparatus known in the art. For example, the electronic device includes, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile machine, a portable copier, a portable printer, a headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD, a mini-compact disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable audio recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flash lamp, a camera, a household large-sized battery, a lithium ion capacitor, and the like. In addition, the electrochemical device of the present application is applicable to an energy storage power station, a marine vehicle, and an air vehicle, in addition to the above-described electronic device. The air carrier comprises an air carrier within the atmosphere and an air carrier outside the atmosphere.
The following examples are set forth to better illustrate the present application, taking lithium ion batteries as an example.
Examples 1-8 and comparative examples 1-2
1. Preparation of lithium ion batteries
1. Preparation of negative electrode plate
The negative electrode active material/composite material (Dv 50 of 8.4 μm, specific surface area of 0.88m 2 Silica particles per gram+Dv50 of 20.3. Mu.m, specific surface area of 0.83m 2 Per gram of hard carbon particles), a conductive agent, polyacrylic acid (PAA), and a thickener (sodium carboxymethylcellulose, CMC) in a weight ratio of 95.7:1.5:1.8:1 in a solvent (deionized water) by stirring and mixing thoroughly to form a uniform negative electrode slurry. And uniformly coating the negative electrode slurry on a negative electrode current collector (copper foil), drying, cold pressing to form a negative electrode active material layer, and then cutting and welding the electrode lugs to obtain a negative electrode plate.
2. Preparation of the Positive electrode
The positive electrode active material (lithium iron phosphate), the conductive agent (acetylene black) and the binder (polyvinylidene fluoride, PVDF) are mixed according to the mass ratio of 96.3:2.2:1.5 mixing in solvent (N-methyl pyrrolidone, NMP) and stirring thoroughly under vacuum stirrer to obtain positive electrode slurry. The positive electrode material is coated on a positive electrode current collector (aluminum foil), dried, cold-pressed to form a positive electrode active material layer, and then subjected to cutting and tab welding to obtain a positive electrode plate.
3. Preparation of electrolyte
In a dry argon atmosphere glove box, ethylene Carbonate (EC), propylene Carbonate (PC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) were mixed according to the mass ratio EC: PC: EMC: dec=10: 30:30:30, adding 2% fluoroethylene carbonate and 2% 1, 3-propane sultone, dissolving and stirring thoroughly, adding lithium salt LiPF 6 And (5) uniformly mixing to obtain the electrolyte. Wherein LiPF is 6 The concentration of (C) was 1mol/L.
4. Preparation of a separator film
A porous polymer film of Polyethylene (PE) was used as a separator.
5. Preparation of lithium ion batteries
Sequentially stacking the obtained positive pole piece, the isolating film and the negative pole piece, enabling the isolating film to be positioned between the positive pole piece and the negative pole piece to play a role of isolation, and then winding to obtain a bare cell; and placing the bare cell in an outer packaging aluminum plastic film, injecting electrolyte, and carrying out the technological processes of vacuum packaging, standing, formation and the like to obtain the lithium ion battery.
The main difference between examples 1-8 and comparative examples 1-2 is: the types and contents of the negative electrode active materials used are different, and refer to table 1.
2. Test method
1. Cycle performance test of lithium ion battery
The cycle performance test flow is as follows:
(1) Adjusting the furnace temperature to 25 ℃, and standing for 30min;
(2) 1C DC to 2.5V;
(3) Standing for 30min;
(4) 1C CC to 4.3V, CV to 0.05C;
(5) Standing for 5min;
(6) 1C DC to 2.5V (record discharge capacity);
(7) Standing for 5min;
(8) Step 4 to step 7 are circulated 1000 times;
(9) And (5) ending the test.
Capacity retention rate of lithium ion battery = discharge capacity per turn/discharge capacity of third turn x 100%.
2. Compact density testing of anode active material layers
The area taken from the negative electrode active material layer on the negative electrode plate to be measured along the surface of the negative electrode current collector is 1540.25mm 2 Is a sample of the active material of the small disc of (a). After the negative electrode current collector was removed, the weight of its negative electrode active material was recorded. Samples of the active material at 12 different positions were taken for each group, and the weight per unit area of the anode active material layer was calculated.
The thickness of the anode active material layer on the anode tab in the vertical direction of the anode current collector surface (collector removal thickness) was measured. Samples of the active material at different positions at 12 were taken for each group, and the compacted density of the anode active material layer was calculated. Compacted density = weight of negative electrode active material/thickness in the vertical direction of the negative electrode current collector surface.
3. Porosity test of anode active material layer
The gas substitution method is adopted for measurement, and the apparent density, the true density and the porosity of the iron ore can be measured specifically by referring to the national standard GB/T24586-2009. Porosity p= (V1-V2)/v1×100%, V1 representing apparent volume, V2 representing real volume.
3. Test results
Table 1 lists the content of the silicon oxide particles and the hard carbon particles in the anode active materials/composite materials of examples 1 to 8, the anode active material of comparative example 1 being only hard carbon particles, the anode active material of comparative example 2 being only silicon oxide particles, and the performances of the batteries corresponding to the respective examples and comparative examples.
TABLE 1
As can be seen from table 1, the negative electrode sheets of examples 1 to 8 had high compacted density, and the batteries of examples 1 to 8 had high capacity retention, i.e., the batteries of examples 1 to 8 had both high energy density and good cycle performance. This is because the hard carbon particles together with the silica particles can improve the problem of low compaction density of the hard carbon particles; meanwhile, as the hardness of the silica particles is higher than that of the hard carbon particles, the silica particles can play a role of rollers in the cold pressing process of the negative electrode plate, and the compaction density of the negative electrode plate is further improved; and the silicon oxide particles are distributed at the gap positions of the hard carbon particles, so that the hard carbon particles can generate acting force on the silicon oxide particles with volume expansion in the lithium intercalation process, the problem of capacity loss of the silicon oxide particles caused by the volume expansion is solved, and the cycle performance of the electrochemical device is improved. The negative electrode active material of comparative example 1 included only hard carbon particles resulting in the lowest compacted density, and the negative electrode active material of comparative example 2 included only silicon oxide particles resulting in the lowest capacity retention.
In examples 2 to 7, the silicon oxide particles account for 10 to 35wt% of the negative electrode active material, the negative electrode sheet has a higher compacted density, and the battery has a higher capacity retention.
Examples 9 to 14 and comparative example 3
The preparation and performance test of lithium ion batteries of examples 9 to 14 and comparative example 3 were performed with reference to example 7, with the main difference that: the particle sizes of the silica particles and the hard carbon particles are different, see in particular table 2. In examples 9 to 14 and comparative example 3, the proportion of the silicon oxide particles in the anode active material was 35wt%, and the proportion of the hard carbon particles in the anode active material was 65wt%.
Table 2 shows the particle diameters of the silicon oxide particles and the hard carbon particles in examples 7, 9 to 14 and comparative example 3, and the performances of the batteries corresponding to the respective examples and comparative examples.
TABLE 2
As is clear from Table 2, when the particle diameter D1 of the silica particles and the particle diameter D2 of the hard carbon particles satisfy D1.ltoreq. 0.414D2, the battery has both high energy density and good cycle performance. In comparative example 3, D1/D2 was greater than 0.414, while the compacted density and capacity retention were significantly reduced.
Examples 15 to 20
The preparation and performance test of the lithium ion batteries of examples 15 to 20 were performed with reference to example 7, with the main differences: the specific surface areas of the silica particles and hard carbon particles are different, see in particular Table 3. In examples 15 to 20, the proportion of the silicon oxide particles in the anode active material was 35wt%, and the proportion of the hard carbon particles in the anode active material was 65wt%.
Table 3 shows the specific surface areas of the silica particles and hard carbon particles in examples 7, 15-20, and the properties of the batteries corresponding to each example.
TABLE 3 Table 3
As can be seen from Table 3, when 1.25.ltoreq.B1/B2.ltoreq.4 is satisfied, the negative electrode tab has a higher compacted density, thereby enabling the battery to have a higher energy density and capacity retention rate.
The foregoing disclosure is merely illustrative of the presently preferred embodiments of the present application and, of course, is not intended to limit the invention thereto, but to cover modifications as fall within the scope of the present application.

Claims (10)

1. The composite material is characterized by comprising silica particles and hard carbon particles, wherein the particle size Dv50 of the silica particles is D1, and the particle size Dv50 of the hard carbon particles is D2, and D1 is less than or equal to 0.414D2.
2. The composite material according to claim 1, wherein the content of the silica particles in the composite material is M1, and the content of the hard carbon particles in the composite material is 1-M1, and M1 is 10wt% or more and 35wt% or less.
3. The composite material according to claim 1, wherein the specific surface area of the silica particles is B1, and the specific surface area of the hard carbon particles is B2, 1.25.ltoreq.b1/b2.ltoreq.4.
4. A composite material according to any one of claims 1 to 3, wherein the composite material meets at least one of the following conditions:
(1) 1μm≤D 1≤15μm；
(2) 5μm≤D2≤22.5μm；
(3) The specific surface area of the silica particles is B1,0.15m 2 /g≤B 1≤15m 2 /g；
(4) The specific surface area of the hard carbon particles is B2,0.15m 2 /g≤B2≤12m 2 /g。
5. A composite material according to any one of claims 1 to 3, wherein the composite material meets at least one of the following conditions:
(5) The silica particles have a compacted density of C1,1.3g/cm 3 ≤C 1≤1.6g/cm 3 ；
(6) The hard carbon particles have a compacted density of C2,0.9g/cm 3 ≤C2≤1.0g/cm 3 ；
(7) The compaction density of the composite material is C3,1g/cm 3 ≤C3≤1.4g/cm 3 ；
(8) The electric potential of the hard carbon particles at the lithium intercalation depth of 25% is 0.1-0.3V vs Li/Li higher than the electric potential of the silicon oxide particles at the lithium intercalation depth of 25% + ；
(9) The electric potential of the hard carbon particles at 75% lithium removal depth is 0.1-0.3V vs Li/Li higher than the electric potential of the silicon oxide particles at 75% lithium removal depth + 。
6. A negative electrode tab comprising a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a conductive agent, a binder, and the composite material of any one of claims 1-5.
7. The negative electrode sheet of claim 6, wherein the compacted density of the negative electrode active material layer is 0.96g/cm 3 ～1.2g/cm 3 The porosity of the anode active material layer is 14% -27%.
8. The negative electrode sheet according to any one of claims 6 to 7, which is produced by a process comprising:
dry-mixing the composite material and a dispersing agent to obtain a mixture;
uniformly mixing a solvent, a part of the binder and the conductive agent to obtain a first slurry;
adding the first slurry into the mixture, and stirring and uniformly mixing to obtain second slurry;
adding a solvent into the second slurry, and uniformly stirring and mixing to obtain a third slurry;
adding the rest binder into the third slurry, adding a solvent, and stirring and mixing uniformly to obtain negative electrode slurry;
and coating the negative electrode slurry on at least one surface of the negative electrode current collector to obtain the negative electrode plate.
9. An electrochemical device comprising a negative electrode sheet, wherein the negative electrode sheet comprises the negative electrode sheet of any one of claims 6-8.
10. An electronic device comprising the electrochemical device according to claim 9.
CN202311533697.4A 2023-11-16 2023-11-16 Composite material, negative electrode plate, preparation method of negative electrode plate, electrochemical device and electronic equipment Pending CN117577803A (en)

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