A fast-charging lithium battery and a preparation method thereof

Abstract

The application discloses a kind of fast charging type lithium battery and preparation method thereof, belong to lithium battery technical field.The fast charging type lithium battery, including positive pole piece, diaphragm, negative pole piece and electrolyte, the negative pole active material of negative pole piece includes 6~8 parts of N-P doped hollow silicon-carbon particles, 3~5 parts of double network binder and 2~4 parts of conductive graphite;Double network binder is polyacrylic acid-polyvinyl alcohol double network binder containing ether oxygen chain.The hollow cavity in N-P doped hollow silicon-carbon particles in negative pole active material provides buffer space for the huge volume expansion of silicon in lithium intercalation process, and shortens lithium ion diffusion path, is conducive to realizing fast ion transport.N and P doping improves the electronic conductivity of the material, reduces the charge transfer impedance, improves the lithium ion migration ability, thereby reducing the generation and accumulation of heat.Double network binder provides an additional heat conduction path, which can achieve continuous charging rate at high rate.

Description

Technical Field

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

[0002] Lithium-ion batteries have advantages such as high energy density, long cycle life and low self-discharge rate, making them key components for energy storage and conversion. They have a wide range of applications. For example, in the electronics field, lithium-ion batteries provide portable and long-lasting power support for smartphones, laptops and some portable devices. Lithium-ion batteries are also the core power source for electric vehicles and play an irreplaceable role in large-scale energy storage systems, drones, power tools and other fields.

[0003] With the continuous deepening and development of lithium-ion battery applications, especially the widespread adoption of electronic devices and the increasing demand for portability, fast charging capability is one of the key directions for the development of lithium-ion battery technology. It can greatly enhance the usability and convenience of devices and adapt to the needs of fast-paced life and work.

[0004] However, current fast-charging batteries still have shortcomings. For example, under fast-charging conditions, increased internal impedance or intensified polarization leads to the generation of a large amount of heat. The rapidly rising temperature not only accelerates the breakdown of the electrode active material structure and the decomposition of the electrolyte, causing an irreversible decrease in the battery's usable capacity, but also triggers thermal runaway, leading to battery swelling or even fire and explosion, posing significant safety hazards. Furthermore, at the high current density of fast charging, the diffusion rate of lithium ions in the battery is slow, and the diffusion of lithium ions in the negative electrode material is restricted, causing lithium metal deposition, increasing the battery's internal resistance, and reducing battery capacity. These problems not only severely restrict the improvement of the fast-charging performance of lithium-ion batteries, but also directly affect the cycle life and safety of lithium-ion batteries.

[0005] Therefore, it is of great significance to develop a fast-charging lithium-ion battery that can effectively address the problems of rapid temperature rise, easy thermal runaway, and slow lithium-ion diffusion under high-rate charging. Summary of the Invention

[0006] This invention provides a fast-charging lithium battery and its preparation method, which can solve the problems of easy thermal runaway and slow lithium-ion diffusion in existing fast-charging batteries.

[0007] In a first aspect, the present invention provides a fast-charging lithium battery, comprising a positive electrode, a separator, a negative electrode and an electrolyte, wherein the negative electrode active material of the negative electrode comprises 6 to 8 parts by weight of NP-doped hollow silicon-carbon particles, 3 to 5 parts by weight of a dual-network binder and 2 to 4 parts by weight of conductive graphite.

[0008] The dual-network adhesive is a polyacrylic acid-polyvinyl alcohol dual-network adhesive containing ether oxygen chains.

[0009] Preferably, the positive electrode active material of the positive electrode sheet includes one or more combinations of high-nickel ternary materials, lithium manganese phosphate, and spinel-type lithium manganese oxide.

[0010] By adopting the above technical solution, the negative electrode active material of the present invention mainly comprises NP-doped hollow silicon-carbon particles, which have a higher energy density than traditional pure carbon materials. Furthermore, silicon's lithium storage mechanism allows a single silicon atom to coordinate multiple lithium ions, improving lithium-ion insertion / extraction kinetics and supporting higher charging rates. This ensures high capacity while accelerating the diffusion rate of lithium ions. Since silicon undergoes significant volume expansion during charging and discharging, leading to particle pulverization and electrode structure damage, the silicon-carbon particles of the present invention have a hollow structure. This structure provides internal space for the volume expansion of silicon during lithium insertion, effectively accommodating expansion stress and preventing active material failure and conductive network damage caused by particle pulverization, thus ensuring structural stability.

[0011] Furthermore, the hollow internal structure greatly shortens the diffusion path of lithium ions from the electrolyte to the interior of the active material, providing a convenient three-dimensional channel for the rapid insertion / extraction of lithium ions, directly alleviating concentration polarization at high rates, and fundamentally solving the problem of by-product heat caused by polarization.

[0012] Meanwhile, the hollow silicon-carbon particles are also doped with N and P, which can create more defects and active sites in the carbon skeleton, significantly improve the intrinsic electronic conductivity of the material, and directly reduce the charge transfer impedance, thereby reducing the generation and accumulation of heat.

[0013] The adhesive used in the negative electrode is a polyacrylic acid-polyvinyl alcohol dual-network adhesive containing ether oxygen chains. The polyacrylic acid network provides strong mechanical strength and forms strong hydrogen bonds with the oxides on the surface of NP-doped hollow silicon-carbon particles, firmly fixing the active material and conductive agent to the current collector and ensuring the basic integrity of the electrode structure. The polyvinyl alcohol segments are soft, providing overall flexibility and elasticity. The interpenetrating dual-network structure formed by these two components combines high strength and high elasticity. Furthermore, the polyacrylic acid-polyvinyl alcohol dual-network adhesive of this invention also incorporates ether oxygen segments. The ether oxygen groups have excellent hydrophilicity, significantly improving the affinity of the negative electrode for the electrolyte, ensuring that the electrolyte can fully wet the entire electrode interior. Moreover, it itself has high lithium-ion transport capacity, further optimizing lithium-ion conduction at the SEI film on the surface of the active particles, creating transport channels for the rapid migration of lithium ions on the surface and in the pores of the active material, and improving the fast-charging performance of the lithium battery.

[0014] NP-doped hollow silicon-carbon particles, in conjunction with a dual-network binder, not only optimize electronic conductivity and ion transport paths, constructing a highly efficient and stable three-dimensional ion and electron transport network, but also utilize the elastic buffering effect of the dual-network binder to prevent rapid expansion of silicon. The negative electrode sheet can maintain structural integrity under high-rate charging conditions, suppressing the risk of thermal runaway and preventing the active material from becoming ineffective.

[0015] The selected positive electrode active material can also match the high activity and high lithium-ion diffusion rate of the negative electrode.

[0016] Preferably, NP-doped hollow silicon-carbon particles are prepared according to the following method:

[0017] Polyvinylpyrrolidone, phosphorus source and template agent are dissolved in deionized water and stirred to obtain a mixed gel solution; then 20-30% by mass of nano silica suspension is added to the mixed gel solution, and stirring is continued at room temperature for 6-8 hours, and then dried at 90-110℃ for 6-10 hours to obtain a premix.

[0018] The premix was mixed with spherical zinc oxide and ball-milled, then dried to obtain core-shell particles;

[0019] The core-shell particles are obtained by heat treatment at 800-900℃ for 2-3 hours.

[0020] Preferably, the mass ratio of polyvinylpyrrolidone, phosphorus source, template agent and nano silica is (2-2.5):(0.1-0.2):(3-3.5):(0.6-0.8).

[0021] Preferably, the phosphorus source includes one or more of lithium dihydrogen phosphate, lithium phosphate, sodium phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate; the template agent includes one or more of starch, sodium carboxymethyl cellulose, sodium alginate, konjac flour, and chitosan.

[0022] Preferably, the mass ratio of the premix to the spherical zinc oxide is (1.2 to 1.6):1.

[0023] By adopting the above technical solution, nano-silica particles are encapsulated and fixed by a polyvinylpyrrolidone gel network to form a premix. Then, after ball milling, core-shell particles with ZnO as the core and an organic polymer-SiO2 composite layer as the shell are formed. Finally, under high temperature, the organic polymer is pyrolyzed and carbonized to form an amorphous / partially graphitized carbon skeleton. Nitrogen in the polyvinylpyrrolidone molecule and phosphorus in the phosphorus source are in situ doped into the carbon network. The formed carbon can act as a reducing agent to reduce zinc oxide to metallic zinc under high temperature conditions. Finally, the zinc vapor escapes, leaving a hollow cavity. The SiO2 nanoparticles originally encapsulated in the carbon matrix may also be partially reduced by carbon to generate silicon, ultimately forming a composite structure of silicon nanoparticles embedded in an NP-doped carbon shell.

[0024] The hollow cavities inside the obtained NP-doped hollow silicon-carbon particles provide a buffer space for the huge volume expansion of silicon during lithium intercalation, effectively absorbing internal stress. Furthermore, the carbon shell can constrain the volume change of silicon and provide a continuous conductive network. Moreover, the carbon shell itself is typically porous, and together with the internal hollow cavities, they form a multi-dimensional porous network, which can increase the contact area between the electrode and the electrolyte, shorten the diffusion path of lithium ions, and facilitate rapid ion transport.

[0025] Nitrogen (N) doping provides additional free electrons to the carbon framework, significantly enhancing the electronic conductivity of carbon materials and reducing electrode resistance. P (P) doping increases the interlayer spacing of microcrystals, providing wider channels for lithium-ion insertion and extraction, and significantly improving the diffusion coefficient of lithium ions in the silicon-carbon layer. The synergistic effect of both doping and phosphorus (P) not only modulates the carbon layer structure, creating more defects and active sites, resulting in a stronger charge polarization effect than single doping, leading to more stable chemical bonds and improved structural stability, but also enhances the electronic conductivity and lithium-ion migration ability of the material.

[0026] The hollow porous structure of NP-doped hollow silicon-carbon particles, combined with the co-doping effect of NP, establishes a highly stable, highly conductive, and high-ion-flux three-dimensional network, which accelerates the diffusion of lithium ions and facilitates the uniform distribution and dissipation of heat within the electrode, thus solving the problem of thermal runaway.

[0027] Preferably, the raw materials of the polyacrylic acid-polyvinyl alcohol dual network adhesive containing ether oxygen chains include polyvinyl alcohol, polyacrylic acid and ethylene oxide macromonomers in a mass ratio of (8-10):(2-4):(0.5-1);

[0028] The ethylene oxide macromonomer is monomethacrylate-terminated polyethylene oxide with a molecular weight of 300–500 Da.

[0029] Preferably, the polyacrylic acid-polyvinyl alcohol dual-network adhesive containing ether oxide chains is prepared according to the following method:

[0030] Polyvinyl alcohol and polyacrylic acid are added to water separately and stirred to dissolve at 60-90°C. The two aqueous solutions are then mixed and stirred to disperse at 60-65°C for 1-2 hours. Then, ethylene oxide macromonomer and free radical initiator are added and stirred to react at 70-75°C for 12-24 hours. Finally, the mixture is subjected to a freeze-thaw cycle to obtain the final product.

[0031] More preferably, the free radical initiator includes ammonium persulfate; the amount of free radical initiator added is 1 to 3% of the mass of the ethylene oxide macromonomer.

[0032] While the above-mentioned technical solutions can reduce heat accumulation caused by polarization by using NP-doped hollow silicon-carbon particles, the overall thermal conductivity is generally poor, and it is difficult to form a continuous thermal conductivity network. Heat tends to accumulate inside or between the active material particles, which is not conducive to rapid heat dissipation. Moreover, although the hollow structure provides initial buffer space, the integrity of the structure may be compromised during long-term, high-rate charge-discharge cycles.

[0033] The dual-network adhesive provided by this invention uses polyvinyl alcohol and polyacrylic acid as the network backbone. When the two are mixed, they will entangle with each other through strong hydrogen bonding between molecules. Then, ethylene oxide macromonomers are added and grafted onto the carboxyl groups of polyacrylic acid, thereby introducing ether oxygen segments. Finally, after cyclic freeze-thaw cycles, a denser and more regular microcrystalline region is formed, which strengthens the network structure and ultimately yields an interpenetrating and entangled dual-network structure.

[0034] On the one hand, the binder can act as a bridge between NP-doped hollow silicon-carbon particles, filling the particle pores and providing an additional heat conduction path. This helps to more effectively conduct the heat generated inside the NP-doped hollow silicon-carbon particles to the current collector, improve the lateral thermal conductivity of the entire electrode, and alleviate local overheating.

[0035] On the other hand, the high elasticity of the dual-network binder can effectively bind and disperse the macroscopic stress transmitted to the entire electrode by the silicon volume change, reduce the local pressure on the individual hollow carbon shell, thereby protecting it from cracking and significantly improving the overall structural stability and cycle life of the electrode.

[0036] The introduced ether oxygen segments not only improve the contact between the electrolyte and the negative electrode, forming an interface phase with high ionic conductivity, but also optimize the migration process of lithium ions from the electrolyte to the porous carbon shell surface of NP-doped hollow silicon carbon particles, further reducing interfacial impedance and concentration polarization. In addition, they can further improve and maintain the long-lasting electronic conductivity necessary for fast charging.

[0037] Preferably, the electrolyte comprises 2-4% by mass of cyanoethylene compounds and 8-10% by mass of fluoroethylene carbonate.

[0038] More preferably, the electrolyte also includes the remainder of one or more combinations of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate.

[0039] By adopting the above technical solution, in addition to conventional electrolyte components, the electrolyte of the present invention also contains fluoroethylene carbonate and cyanoethylene compounds. Fluoroethylene carbonate can preferentially reduce and decompose on the negative electrode surface to generate a solid electrolyte interface film with lithium fluoride as the main inorganic component. It has high interfacial energy, high mechanical strength and high ionic conductivity, which can effectively prevent the continuous decomposition of the electrolyte and is also conducive to rapid charge transfer and adapting to the volume change of silicon.

[0040] The cyano groups in cyanoethylene compounds can form a polycyano-rich organic polymer layer on the negative electrode surface, which can homogenize the lithium-ion flow on the negative electrode surface, prevent excessive accumulation of lithium ions in local locations, effectively inhibit the nucleation and growth of lithium dendrites, and prevent damage to the solid electrolyte interface film, making the entire interface film more stable at high temperature and high potential.

[0041] The stable solid electrolyte interface film formed by adding fluoroethylene carbonate and cyanoethylene compounds to the electrolyte can tightly encapsulate the negative electrode active material. Even if the silicon carbon particles undergo volume changes inside, the interface can remain intact, and it also has good interfacial forces with the dual-network binder.

[0042] Secondly, the present invention provides a method for preparing a fast-charging lithium battery, comprising the following process steps:

[0043] S1. The positive electrode active material, binder and conductive agent are mixed and then added to N-methylpyrrolidone and stirred evenly to obtain a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying and slicing, a positive electrode sheet is obtained;

[0044] S2. Disperse the negative electrode active material in water and stir to obtain a negative electrode slurry; coat the negative electrode slurry onto the negative electrode current collector, and obtain a negative electrode sheet after drying and slicing;

[0045] S3. The positive electrode, separator and negative electrode are stacked in a Z-shape and the edges are sealed to obtain the battery cell;

[0046] S4. Electrolyte is injected into the battery cell to obtain a fast-charging lithium battery.

[0047] More preferably, in step S1, the adhesive includes one or more combinations of polyvinylidene fluoride, polyvinylidene chloride, polyacrylic acid, and sodium carboxymethyl cellulose; the conductive agent includes one or more combinations of acetylene black, carbon nanotubes, graphene, and graphene oxide.

[0048] More preferably, in step S1, the amount of binder added is 2 to 5% of the mass of the positive electrode active material; and the amount of conductive agent added is 1 to 3% of the mass of the positive electrode active material.

[0049] More preferably, in step S1, the solid content of the positive electrode slurry is 50-70%.

[0050] More preferably, in step S1, the positive current collector includes aluminum foil.

[0051] More preferably, in step S2, the solid content of the negative electrode slurry is 40-55%.

[0052] More preferably, in step S2, the negative current collector includes copper foil.

[0053] More preferably, the separator is a polyolefin separator; polyolefin separators include any one of polyethylene separators, polypropylene separators, polyethylene / polypropylene composite separators, and polypropylene / polyethylene / polypropylene composite separators.

[0054] More preferably, the thickness of the battery cell is 10-11 mm; the width is 100-110 mm; and the length is 220-240 mm.

[0055] The beneficial effects of this invention are:

[0056] 1. In the fast-charging lithium battery of the present invention, the negative electrode active material includes NP-doped hollow silicon-carbon particles. The hollow cavity inside the particles provides a buffer space for the huge volume expansion of silicon during lithium intercalation and shortens the diffusion path of lithium ions, which is conducive to achieving rapid ion transport. The doping of N and P can create more defects and active sites in the carbon framework, significantly improve the intrinsic electronic conductivity of the material, directly reduce the charge transfer impedance, improve the lithium ion migration ability, and thus reduce the generation and accumulation of heat.

[0057] 2. In the fast-charging lithium battery of the present invention, a dual-network binder is used as the negative electrode binder in the negative electrode active material. This binder forms strong hydrogen bonds with the oxides on the surface of the NP-doped hollow silicon-carbon particles, providing an additional heat conduction path and helping to more effectively dissipate the heat generated inside the NP-doped hollow silicon-carbon particles to the current collector. The introduced ether-oxygen segments optimize the migration process of lithium ions from the electrolyte to the porous carbon shell surface of the NP-doped hollow silicon-carbon particles, improving overall elasticity and providing stress buffer margin.

[0058] 3. The fast-charging battery prepared by this invention can achieve continuous charging at high rates with high charging efficiency. It also effectively maintains the overall structural stability of the lithium battery, extends the cycle life, fundamentally reduces heat generation and accumulation, and improves safety. Detailed Implementation

[0059] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0060] Preparation Example 1

[0061] Preparation Example 1-1: An NP-doped hollow silicon-carbon particle was prepared according to the following method:

[0062] 2g of polyvinylpyrrolidone, 0.2g of disodium hydrogen phosphate and 3g of sodium alginate were dissolved in deionized water and stirred to obtain a mixed gel solution; then, a 20% (w / w) nano silica suspension was added to the mixed gel solution, with the amount of nano silica added being 0.7g, and the mixture was stirred and mixed at room temperature for 8 hours, and then dried at 110℃ for 6 hours to obtain a premix.

[0063] The premix obtained above was mixed with spherical zinc oxide and ball-milled, wherein the mass ratio of the premix to spherical zinc oxide was 1.4:1, and after drying, core-shell particles were obtained.

[0064] The core-shell particles are obtained by heat treatment at 850℃ for 2 hours.

[0065] Preparation Examples 1-2: NP-doped hollow silicon-carbon particles were prepared according to the following method:

[0066] 2.5g of polyvinylpyrrolidone, 0.1g of disodium hydrogen phosphate and 3.5g of sodium alginate were dissolved in deionized water and stirred to obtain a mixed gel solution; then, a 20% (w / w) nano silica suspension was added to the mixed gel solution, with the amount of nano silica added being 0.6g. The mixture was stirred and mixed at room temperature for 8 hours and then dried at 110℃ for 6 hours to obtain a premix.

[0067] The premix obtained above was mixed with spherical zinc oxide and ball-milled, wherein the mass ratio of the premix to spherical zinc oxide was 1.2:1, and after drying, core-shell particles were obtained.

[0068] The core-shell particles are obtained by heat treatment at 850℃ for 2 hours.

[0069] Preparation Examples 1-3 are N-doped hollow silicon-carbon particles, which differ from Preparation Example 1-1 only in that disodium hydrogen phosphate is not added.

[0070] Preparation Examples 1-4: A P-doped hollow silicon-carbon particle, differing from Preparation Example 1-1 only in that an equal amount of glucose is used instead of polyvinylpyrrolidone.

[0071] Preparation Examples 1-5: Hollow silicon-carbon particles were prepared according to the following method:

[0072] 2g of glucose and 3g of sodium alginate were dissolved in deionized water and stirred to obtain a mixed gel solution; then, 20% by mass of nano silica suspension was added to the mixed gel solution, and the amount of nano silica added was 0.7g. The mixture was stirred and mixed at room temperature for 8 hours, and then dried at 110℃ for 6 hours to obtain a premix.

[0073] The premix obtained above was mixed with spherical zinc oxide and ball-milled, wherein the mass ratio of the premix to spherical zinc oxide was 1.4:1, and after drying, core-shell particles were obtained.

[0074] The core-shell particles are obtained by heat treatment at 850℃ for 2 hours.

[0075] Preparation Examples 1-6: An NP-doped hollow carbon particle was prepared according to the following method:

[0076] 2g of polyvinylpyrrolidone, 0.2g of disodium hydrogen phosphate and 3g of sodium alginate were dissolved in deionized water and stirred to obtain a mixed gel solution, which was dried at 110℃ for 6h to obtain a premix.

[0077] The premix obtained above was mixed with spherical zinc oxide and ball-milled, wherein the mass ratio of the premix to spherical zinc oxide was 1.4:1, and after drying, core-shell particles were obtained.

[0078] The core-shell particles are obtained by heat treatment at 850℃ for 2 hours.

[0079] Preparation Examples 1-7: An NP-doped silicon-carbon particle was prepared according to the following method:

[0080] 2g of polyvinylpyrrolidone, 0.2g of disodium hydrogen phosphate and 3g of sodium alginate were dissolved in deionized water and stirred to obtain a mixed gel solution. Then, a 20% (w / w) nano silica suspension was added to the mixed gel solution, with the amount of nano silica added being 0.7g. The mixture was stirred and mixed at room temperature for 8 hours and dried at 110℃ for 6 hours to obtain a premix. The premix was then heat-treated at 850℃ for 2 hours to obtain the final product.

[0081] Preparation Examples 1-8: A silicon-carbon particle was prepared according to the following method:

[0082] 2g of glucose and 3g of sodium alginate were dissolved in deionized water and stirred to obtain a mixed gel solution. Then, a 20% (w / w) nano silica suspension was added to the mixed gel solution, with an addition amount of 0.7g of nano silica. The mixture was stirred and mixed at room temperature for 8 hours and dried at 110℃ for 6 hours to obtain a premix. The premix was then heat-treated at 850℃ for 2 hours to obtain the final product.

[0083] Preparation Example 2

[0084] Preparation Example 2-1: A dual-network adhesive was prepared according to the following method:

[0085] Add 8g of polyvinyl alcohol and 2g of polyacrylic acid to water respectively, stir and dissolve at 80℃, then mix the two aqueous solutions and stir and disperse at 60℃ for 1h. Then add 0.5g of ethylene oxide macromonomer, namely monomethacrylate-terminated polyethylene oxide (molecular weight of 500Da) and 0.005g of ammonium persulfate, stir and react at 75℃ for 20h, and finally repeat the freeze-thaw cycle from -20℃ to room temperature 3 times to obtain the final product.

[0086] Preparation Example 2-2: A dual-network adhesive was prepared according to the following method:

[0087] 10g of polyvinyl alcohol and 4g of polyacrylic acid were added to water and stirred at 80°C to dissolve. The two aqueous solutions were then mixed and stirred at 60°C for 1 hour. Then, 1g of ethylene oxide macromonomer, namely monomethacrylate-terminated polyethylene oxide (molecular weight of 500 Da), and 0.01g of ammonium persulfate were added and stirred at 75°C for 20 hours. Finally, the mixture was subjected to three freeze-thaw cycles from -20°C to room temperature to obtain the final product.

[0088] Preparation Example 2-3 is a dual-network adhesive, which differs from Preparation Example 2-1 only in that the amount of ethylene oxide macromonomer added is 0.2g.

[0089] Preparation Example 2-4 is a dual-network adhesive, which differs from Preparation Example 2-1 only in that the amount of ethylene oxide macromonomer added is 1.5g.

[0090] Preparation Examples 2-5: A dual-network adhesive was prepared according to the following method:

[0091] Add 8g of polyvinyl alcohol and 2g of polyacrylic acid to water respectively, stir and dissolve at 80℃, then mix the two aqueous solutions, stir and disperse at 60℃ for 1 hour, and repeat the freeze-thaw cycle from -20℃ to room temperature 3 times to obtain the final product.

[0092] Example

[0093] Example 1: A fast-charging lithium battery was prepared according to the following method:

[0094] S1. A mixture of high-nickel ternary material, polyvinylidene fluoride (PVDF), and carbon nanotubes is added to N-methylpyrrolidone and stirred until homogeneous to obtain a positive electrode slurry. 100g of high-nickel ternary material is used, with 3g of PVDF added as 3% of the mass of the high-nickel ternary material and 2g of carbon nanotubes added as 2% of the mass of the high-nickel ternary material. The resulting positive electrode slurry with a solid content of 60% is coated onto a positive electrode current collector aluminum foil (12μm thick), and then dried and sliced ​​to obtain a positive electrode sheet.

[0095] S2. Disperse the negative electrode active material in water, wherein the negative electrode active material includes 42g of NP-doped hollow silicon-carbon particles prepared in Preparation Example 1-1, 24g of double-network binder prepared in Preparation Example 2-1 and 18g of conductive graphite, and stir to obtain a negative electrode slurry with a solid content of 45%.

[0096] The negative electrode slurry is coated onto the negative electrode current collector copper foil (8 μm thick), and then dried and sliced ​​to obtain the negative electrode sheet;

[0097] S3. The positive electrode sheet, Celgard2400 polypropylene separator and negative electrode sheet obtained above are stacked in a Z-shape and sealed to obtain the battery cell; the thickness of the battery cell is 10.23 mm; the width is 104.48 mm; and the length is 228.13 mm.

[0098] S4. The electrolyte is injected into the cell to obtain a fast-charging lithium battery, wherein the electrolyte includes 3% of cyanoethylene compound 2-cyanoethyl acetate, 9% of fluoroethylene carbonate, and the balance being a mixture of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate in a mass ratio of 3:5:2.

[0099] Example 2, a fast-charging lithium battery, differs from Example 1 only in that the negative electrode active material includes 36g of NP-doped hollow silicon-carbon particles prepared in Preparation Example 1-1, 18g of dual-network binder prepared in Preparation Example 2-1, and 24g of conductive graphite.

[0100] The electrolyte comprises 2% 2-cyanoethyl acetate, 10% fluoroethylene carbonate, and the balance being a mixture of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in a mass ratio of 3:5:2.

[0101] Example 3, a fast-charging lithium battery, differs from Example 1 only in that the negative electrode active material includes 48g of NP-doped hollow silicon-carbon particles prepared in Preparation Example 1-1, 30g of dual-network binder prepared in Preparation Example 2-1, and 12g of conductive graphite.

[0102] The electrolyte comprises 4% 2-cyanoethyl acetate, 8% fluoroethylene carbonate, and the balance being a mixture of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in a mass ratio of 3:5:2.

[0103] Example 4, a fast-charging lithium battery, differs from Example 1 only in that the NP-doped hollow silicon-carbon particles prepared in Example 1-1 are replaced with an equal amount of NP-doped hollow silicon-carbon particles prepared in Example 1-2.

[0104] Example 5, a fast-charging lithium battery, differs from Example 1 only in that an equal amount of the dual-network adhesive prepared in Preparation Example 2-2 is used to replace the dual-network adhesive prepared in Preparation Example 2-1.

[0105] Example 6, a fast-charging lithium battery, differs from Example 1 only in that 2-cyanoethyl acetate is not added to the electrolyte.

[0106] Example 7, a fast-charging lithium battery, differs from Example 1 only in that fluoroethylene carbonate is not added to the electrolyte.

[0107] Example 8, a fast-charging lithium battery, differs from Example 1 only in that 2-cyanoethyl acetate and fluoroethylene carbonate are not added to the electrolyte.

[0108] Example 9, a fast-charging lithium battery, differs from Example 1 only in that an equal amount of the dual-network adhesive prepared in Preparation Examples 2-3 is used to replace the dual-network adhesive prepared in Preparation Example 2-1.

[0109] Example 10, a fast-charging lithium battery, differs from Example 1 only in that an equal amount of the dual-network adhesive prepared in Preparation Examples 2-4 is used to replace the dual-network adhesive prepared in Preparation Example 2-1.

[0110] Comparative Example

[0111] Comparative Example 1 is a fast-charging lithium battery, which differs from Example 1 only in that an equal amount of N-doped hollow silicon-carbon particles prepared in Examples 1-3 are used to replace the NP-doped hollow silicon-carbon particles prepared in Example 1-1.

[0112] Comparative Example 2 is a fast-charging lithium battery, which differs from Example 1 only in that the NP-doped hollow silicon-carbon particles prepared in Example 1-1 are replaced with an equal amount of P-doped hollow silicon-carbon particles prepared in Example 1-4.

[0113] Comparative Example 3 is a fast-charging lithium battery, which differs from Example 1 only in that the NP-doped hollow silicon-carbon particles prepared in Example 1-1 are replaced with an equal amount of hollow silicon-carbon particles prepared in Example 1-5.

[0114] Comparative Example 4 is a fast-charging lithium battery, which differs from Example 1 only in that the NP-doped hollow silicon-carbon particles prepared in Example 1-1 are replaced with an equal amount of NP-doped hollow carbon particles prepared in Examples 1-6.

[0115] Comparative Example 5 is a fast-charging lithium battery, which differs from Example 1 only in that the NP-doped hollow silicon-carbon particles prepared in Example 1-1 are replaced with an equal amount of NP-doped silicon-carbon particles prepared in Examples 1-7.

[0116] Comparative Example 6 is a fast-charging lithium battery, which differs from Example 1 only in that the NP-doped hollow silicon-carbon particles prepared in Example 1-1 are replaced with an equal amount of silicon-carbon particles prepared in Examples 1-8.

[0117] Comparative Example 7 is a fast-charging lithium battery, which differs from Example 1 only in that an equal amount of the dual-network adhesive prepared in Preparation Examples 2-5 is used to replace the dual-network adhesive prepared in Preparation Example 2-1.

[0118] Comparative Example 8 is a fast-charging lithium battery, which differs from Example 1 only in that an equal amount of polyacrylic acid adhesive is used to replace the dual-network adhesive prepared in Preparation Example 2-1.

[0119] Performance testing

[0120] 1. Rate discharge test: At 25℃, charge at 5C and discharge at 10C, with a voltage range of 3.0~4.35V, test the capacity retention rate during charging and the maximum discharge temperature at this rate;

[0121] 2. Cyclic performance test: At 25℃, with 5C charging and 10C discharging, and a voltage range of 3.0~4.35V, the battery capacity retention rate and maximum cycle temperature are tested when the cycle period is 999 cycles.

[0122] The results of the above experiments are shown in Table 1:

[0123] Table 1 Performance test results

[0124]

[0125] According to Table 1, and in conjunction with Examples 1, 6 to 8, it can be seen that the capacity retention rate of Examples 6 to 8 is lower than that of the Examples 1, while the maximum temperature is higher. This may be because, in Example 6, no cyanoethylene compounds were added, so a uniform elastic interface layer could not be formed on the negative electrode surface, resulting in a decrease in the ability to suppress lithium dendrites, a significant increase in discharge temperature, and accelerated capacity decay during long-term cycling. In Example 7, no fluoroethylene carbonate was added, so a stable interface film with high mechanical strength and ionic conductivity could not be formed, leading to a significant decrease in both fast-charging capacity retention rate and cycle capacity retention rate. In Example 8, neither cyanoethylene compounds nor fluoroethylene carbonate were added to the electrolyte, resulting in a more significant performance degradation.

[0126] Based on Examples 1, 9, and 10, and Comparative Examples 7 and 8, it can be seen that the performance indicators of Examples 9, 10, 7, and 8 are lower than those of Example 1. This may be because Examples 9 and 10 varied the content of ether oxygen segments in the dual-network binder. When the content decreases, the binder becomes more rigid, resulting in weak ion transport capacity, reduced buffering capacity for volume changes, and accelerated long-term cycling degradation. When the content increases, excessive flexible segments may sacrifice the mechanical strength of the binder, affecting long-term cycling stability. Comparative Example 7, lacking ether oxygen segments, significantly reduces ionic conductivity and increases internal ion transport resistance, leading to decreased fast-charging performance and increased temperature rise. In Comparative Example 8, a conventional binder was used to replace the dual-network binder, which is prone to cracking and failure under silicon volume expansion, causing the conductive network to collapse, active material to detach, and performance to significantly decrease.

[0127] Based on Examples 1 and Comparative Examples 1 to 6, it can be seen that the performance indicators of Comparative Examples 1 to 6 are lower than those of Example 1. This may be because Comparative Examples 1 to 3 adjusted the doping elements in the hollow silicon-carbon particles. The absence of nitrogen (N) reduces the electronic conductivity of the carbon framework and increases charge transfer impedance, leading to fast-charging capacity loss and temperature increase. The absence of phosphorus (P) does not effectively widen the carbon interlayer spacing, resulting in slow lithium-ion solid-phase diffusion, large concentration polarization, and more severe heat generation. The performance degradation is even more pronounced when both elements are absent. Comparative Example 4, lacking silicon, has low specific capacity of the carbon particles, resulting in reduced power and safety. Comparative Example 5, lacking a hollow structure, has no outlet for the volume expansion stress of silicon, leading to particle structure damage, a long internal diffusion path during fast charging, and a significantly reduced cycle life. Comparative Example 6, lacking both element doping and a hollow structure, exhibits an even more significant performance degradation.

[0128] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A fast-charging lithium battery, comprising a positive electrode, a separator, a negative electrode, and an electrolyte, characterized in that, The negative electrode active material of the negative electrode sheet includes 6 to 8 parts by weight of NP-doped hollow silicon-carbon particles, 3 to 5 parts by weight of double-network binder and 2 to 4 parts by weight of conductive graphite. The dual-network adhesive is a polyacrylic acid-polyvinyl alcohol dual-network adhesive containing ether oxygen chains; The NP-doped hollow silicon-carbon particles were prepared according to the following method: Polyvinylpyrrolidone, phosphorus source and template agent are dissolved in deionized water and stirred to obtain a mixed gel solution; then 20-30% by mass of nano silica suspension is added to the mixed gel solution, and stirring is continued at room temperature for 6-8 hours, and then dried at 90-110℃ for 6-10 hours to obtain a premix. The premix was mixed with spherical zinc oxide and ball-milled, then dried to obtain core-shell particles; The core-shell particles are obtained by heat treatment at 800-900℃ for 2-3 hours.

2. The fast-charging lithium battery according to claim 1, characterized in that, The mass ratio of polyvinylpyrrolidone, phosphorus source, template agent and nano silica is (2-2.5):(0.1-0.2):(3-3.5):(0.6-0.8).

3. The fast-charging lithium battery according to claim 1, characterized in that, The phosphorus source includes one or more of lithium dihydrogen phosphate, lithium phosphate, sodium phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate; the template agent includes one or more of starch, sodium carboxymethyl cellulose, sodium alginate, konjac flour, and chitosan.

4. The fast-charging lithium battery according to claim 1, characterized in that, The mass ratio of the premix to spherical zinc oxide is (1.2–1.6):

1.

5. The fast-charging lithium battery according to claim 1, characterized in that, The raw materials of the polyacrylic acid-polyvinyl alcohol dual network adhesive containing ether oxygen chains include polyvinyl alcohol, polyacrylic acid and ethylene oxide macromonomers in a mass ratio of (8-10):(2-4):(0.5-1). The ethylene oxide macromonomer is monomethacrylate-terminated polyethylene oxide with a molecular weight of 300–500 Da.

6. The fast-charging lithium battery according to claim 5, characterized in that, The polyacrylic acid-polyvinyl alcohol dual-network adhesive containing ether oxide chains is prepared according to the following method: Polyvinyl alcohol and polyacrylic acid are added to water separately and stirred to dissolve at 60-90°C. The two aqueous solutions are then mixed and stirred to disperse at 60-65°C for 1-2 hours. Then, ethylene oxide macromonomer and free radical initiator are added and stirred to react at 70-75°C for 12-24 hours. Finally, the mixture is subjected to a freeze-thaw cycle to obtain the final product.

7. The fast-charging lithium battery according to claim 1, characterized in that, The electrolyte contains 2-4% by mass of cyanoethylene compounds and 8-10% by mass of fluoroethylene carbonate.

8. The fast-charging lithium battery according to claim 1, characterized in that, The positive electrode active material of the positive electrode sheet includes one or more combinations of high-nickel ternary materials, lithium manganese phosphate, and spinel-type lithium manganese oxide.

9. A method for preparing a fast-charging lithium battery, used to prepare the fast-charging lithium battery according to any one of claims 1 to 8, characterized in that, The process includes the following steps: S1. The positive electrode active material, binder and conductive agent are mixed and then added to N-methylpyrrolidone and stirred evenly to obtain a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying and slicing, a positive electrode sheet is obtained; S2. Disperse the negative electrode active material in water and stir to obtain a negative electrode slurry; coat the negative electrode slurry onto the negative electrode current collector, and obtain a negative electrode sheet after drying and slicing; S3. The positive electrode, separator and negative electrode are stacked in a Z-shape and the edges are sealed to obtain the battery cell; S4. Electrolyte is injected into the battery cell to obtain a fast-charging lithium battery.

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