Lithium ion battery and preparation method thereof

Abstract

The invention discloses a lithium ion battery and a preparation method thereof. The lithium ion battery comprises a positive plate, a negative plate, a diaphragm and electrolyte. A positive electrode material layer of the positive plate comprises the following components in parts by mass: 95 to 99 parts of lithium nickel cobalt manganese oxide (Li (Ni < 0.90 > Co < 0.06 > Mn < 0.04 >) O2), 0.2 to 0.5 part of conductive carbon black Super P, 0.3 to 0.6 part of multi-walled carbon nanotube conductive slurry and 0.2 to 0.4 part of lithium carbonate; a negative electrode material layer of the negative electrode plate comprises 85 to 90 parts of natural graphite, 6 to 9 parts of a silica material, 0.5 to 1.0 part of conductive carbon black Super P and 0.05 to 0.1 part of single-walled carbon nanotube conductive slurry; the diaphragm is a ceramic coated diaphragm; the electrolyte comprises a lithium salt, an organic solvent and an additive. By optimizing the positive plate, the negative plate, the diaphragm and the preparation process, the discharge capacity and the cycle life of the lithium ion battery can be effectively improved, and the safety of the lithium ion battery under high-rate discharge can be effectively improved.

Description

Technical Field

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

[0002] As a core component in the current energy storage and power fields, the performance improvement of lithium-ion batteries has always revolved around key indicators such as energy density, cycle life, safety, and cost. Among these, increasing energy density to extend device range or increase effective load is the primary goal continuously pursued by the industry. Cathode materials, as a key factor determining the energy density of lithium-ion batteries, have clearly reflected this trend in their development history: from early lithium cobalt oxide (LCO) and lithium manganese oxide (LMO), to the more stable lithium iron phosphate (LFP), and then to the ternary material lithium nickel cobalt manganese oxide (NCM) with more balanced overall performance.

[0003] In ternary material systems, energy density is strongly positively correlated with nickel (Ni) content. Increasing the nickel content can effectively improve the specific capacity and operating voltage platform of the material, which is a key path to achieving breakthroughs in the energy density of single battery cells. As a result, the industry's technical route has rapidly evolved from NCM523 and NCM622 to NCM811 and even higher nickel content (Ni≥90%) ternary materials. However, with the sharp increase in nickel content, a series of severe technical challenges have also emerged, especially the inherent contradiction between "ultra-high energy density" and "long cycle life": although high-nickel cathode materials can significantly improve energy density, their structure is unstable, interfacial side reactions are severe, and irreversible phase transitions and transition metal dissolution are prone to occur, leading to accelerated decay of active materials and a surge in interfacial impedance during cycling; at the same time, high-capacity silicon-based anodes introduced to match high-capacity cathodes face challenges such as huge volume expansion and continuous SEI film reconstruction. The capacity decay and interfacial degradation of the cathode and anode exacerbate each other, forming a vicious cycle. Traditional single-optimization strategies often suffer from trade-offs—increasing energy density often comes at the cost of sacrificing cycle life, while pursuing longer cycle life forces a reduction in energy density targets. This fundamental contradiction has become a core bottleneck restricting the development of next-generation high-energy-density batteries. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention provides a lithium-ion battery and a method for preparing the same, which can effectively improve the discharge capacity and cycle life of the lithium-ion battery, as well as its safety under high-rate discharge.

[0005] A lithium-ion battery according to a first aspect of the present invention includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The positive electrode material layer includes lithium nickel cobalt manganese oxide (Li(Ni)2)2)2).0.90 Co 0.06 Mn 0.04 O2), the first composite conductive agent and lithium carbonate, wherein the lithium nickel cobalt manganese oxide (Li(Ni) 0.90 Co 0.06 Mn 0.04 The mass ratio of the first composite conductive agent to the lithium carbonate is 95-99:0.5-1.1:0.2-0.4; the first composite conductive agent includes conductive carbon black Super P and multi-walled carbon nanotube conductive paste. The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The negative electrode material layer includes natural graphite, silicon oxide material, a second composite conductive agent, and a liquid retainer. The mass ratio of the natural graphite, the silicon oxide material, the second composite conductive agent, and the liquid retainer is 85-90:6-9:0.55-1.1:0.2-0.4. The second composite conductive agent includes conductive carbon black Super P and single-walled carbon nanotube conductive paste. The diaphragm includes a base membrane and a ceramic coating applied to the upper surface of the base membrane, wherein the base membrane is at least one of polypropylene and polyethylene; The electrolyte includes lithium salt, organic solvent and additives.

[0006] According to some embodiments of the present invention, the solid content of the multi-walled carbon nanotube conductive paste is 3%-6%, the viscosity is less than 3500 mPa·s, and the moisture content is less than 1000 ppm; the solid content of the single-walled carbon nanotube conductive paste is 0.1%-0.5%, and the viscosity is less than 2500 mPa·s.

[0007] According to some embodiments of the present invention, the positive electrode material layer further includes a binder, polyvinylidene fluoride (PVDF).

[0008] According to some embodiments of the present invention, the negative electrode material layer further includes a dispersant sodium carboxymethyl cellulose (CMC) and a binder styrene-butadiene rubber (SBR).

[0009] According to some embodiments of the present invention, the silicon-oxygen material is silicon suboxide.

[0010] According to some embodiments of the present invention, the thickness of the positive electrode sheet is 139-142 μm, and the compaction density is 3.2-3.5 g / cm³. 3 The negative electrode sheet has a thickness of 135-138 μm and a compaction density of 2.7-3.4 g / cm³. 3 .

[0011] According to some embodiments of the present invention, the thickness of the positive current collector is 12-16 μm, and the thickness of the negative current collector is 6-10 μm.

[0012] According to some embodiments of the present invention, in the first composite conductive agent, the mass ratio of the conductive carbon black Super P to the multi-walled carbon nanotube conductive slurry is 2-5:3-6.

[0013] According to some embodiments of the present invention, in the second composite conductive agent, the mass ratio of the conductive carbon black Super P to the single-walled carbon nanotube conductive slurry is 5-10:0.5-1.

[0014] A method for preparing a lithium-ion battery according to a second aspect embodiment of the present invention includes the following steps: Preparation of the positive electrode: 95-99 parts by mass of lithium nickel cobalt manganese oxide (Li(Ni)) 0.90 Co 0.06 Mn 0.04 The following components are mixed in an organic solvent: 0.2-0.5 parts of conductive carbon black Super P, 0.3-0.6 parts of multi-walled carbon nanotube conductive paste, 1.0-1.2 parts of binder polyvinylidene fluoride (PVDF), and 0.2-0.4 parts of lithium carbonate, to form a uniform positive electrode paste with a solid content of 64%-70% and a viscosity of 4000-6000 mPa·s. The positive electrode paste is then weighed to a surface density of 208-212 mg / cm³. 2 The coating is uniformly applied to a positive electrode current collector with a thickness of 12-16 μm, and then dried, rolled, and sheared to obtain a thickness of 139-142 μm and a compacted density of 3.2-3.5 g / cm³. 3 The positive electrode plate; Preparation of the negative electrode sheet: By weight, 85-90 parts of natural graphite, 6-9 parts of silicon oxide material, 0.5-1.0 parts of conductive carbon black Super P, 0.05-0.1 parts of multi-walled carbon nanotube conductive slurry, 0.2-0.4 parts of liquid retainer, 1.0-1.5 parts of dispersant sodium carboxymethyl cellulose (CMC), and 2.0-2.2 parts of binder styrene-butadiene rubber (SBR) are mixed in deionized water to form a uniform negative electrode slurry with a solid content of 44%-50% and a viscosity of 2500-5500 mPa·s. The negative electrode slurry is then weighed to a single-sided dry weight areal density of 205-210 mg / cm³. 2 The coating is uniformly applied to a 6-10 μm thick negative electrode current collector, and then dried, rolled, and sheared to obtain a thickness of 135-138 μm and a compacted density of 2.7-3.4 g / cm³. 3 The negative electrode plate; Preparation of the diaphragm: The base membrane of the diaphragm is a 9 μm thick polypropylene and / or polyethylene membrane prepared by wet method. A 3 μm ceramic coating is applied to the upper surface of the base membrane to obtain a diaphragm with a total thickness of 12 μm. Preparation of electrolyte: Lithium salt, organic solvent and additives are mixed in a mass ratio of 10-15:80-90:1-5; After assembling the positive electrode, the negative electrode, and the separator, the electrolyte is injected, followed by encapsulation, formation, and capacity separation operations.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The lithium-ion battery of this invention uses an ultra-high nickel ternary cathode material, lithium nickel cobalt manganese oxide (Li(Ni)2), in its cathode. 0.90 Co 0.06 Mn 0.04 O2), with a specific capacity far exceeding that of traditional NCM523 or NCM811 materials, is the foundation for achieving high energy density. By introducing the first composite conductive agent (conductive carbon black Super P and multi-walled carbon nanotube conductive slurry), a stable and efficient three-dimensional conductive network is constructed inside the positive electrode. This not only significantly reduces the battery's internal resistance and improves rate performance, but more importantly, the network plays a good role in binding and supporting the high-nickel active material particles, effectively suppressing particle breakage and active material peeling caused by lattice stress during cycling, thereby greatly alleviating the inherent cycle decay problem of high-nickel materials. In the negative electrode, a composite active material composed of natural graphite and silicon oxide is introduced, and synergistically combined with a second composite conductive agent (conductive carbon black Super P and single-walled carbon nanotube conductive slurry) and a liquid retainer, thereby improving the negative electrode capacity while ensuring the stability of the electrode structure under lithium insertion and delithiation volume changes. Simultaneously, the electrolyte reservoir formed by the negative electrode liquid retainer continuously and stably supplies electrolyte to the negative electrode interface, maintaining a stable solid electrolyte interphase (SEI) film and mitigating the continuous consumption of electrolyte by high-nickel positive electrode side reactions. Through the synergistic design of the positive and negative electrode material systems and functional additives, the lithium-ion battery of this invention achieves a capacity of over 3.3 Ah at 0.2C discharge, and maintains a capacity retention of over 89% after 700 cycles under 1C charge / 1C discharge conditions, exhibiting excellent performance in both high energy density and long cycle life.

[0016] Furthermore, by adding lithium carbonate to the positive electrode, active lithium can be replenished in the early stages of cycling, alleviating gas generation from interfacial side reactions; by adding a liquid retainer to the negative electrode to achieve uniform electrolyte distribution, it helps to form a dense and stable SEI film, effectively inhibiting the growth of lithium dendrites and fundamentally reducing the risk of internal short circuits; a polypropylene and / or polyethylene composite separator coated with a ceramic coating is used. This separator has good ion conductivity, and its ceramic coating gives the separator excellent high-temperature resistance and mechanical strength, which can effectively inhibit separator shrinkage under high-temperature conditions, prevent direct contact between the positive and negative electrodes, and construct a reliable "thermal safety barrier"; through this multi-layered synergistic protection mechanism, the battery still has excellent safety performance at high energy density.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a rate discharge curve of the lithium-ion battery at 25°C in an embodiment of the present invention; Figure 2 This is a constant current discharge curve of the lithium-ion battery at -20°C in an embodiment of the present invention; Figure 3 This is a cycle curve of the lithium-ion battery in this embodiment of the invention, showing 1C charging / 1C discharging at 25°C. Detailed Implementation

[0019] To make the objectives and technical solutions of this invention clearer and easier to understand, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0020] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0021] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are all available from conventional commercial sources or can be obtained by existing known methods.

[0022] In a first aspect, embodiments of the present invention provide a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte; The positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector, wherein the positive electrode material layer includes lithium nickel cobalt manganese oxide (Li(Ni)2)2). 0.90 Co 0.06 Mn 0.04 O2), the first composite conductive agent and lithium carbonate, lithium nickel cobalt manganese oxide (Li(Ni)O ... 0.90 Co 0.06 Mn 0.04 The mass ratio of O2, the first composite conductive agent, and lithium carbonate is 95-99:0.5-1.1:0.2-0.4; the first composite conductive agent includes conductive carbon black Super P and multi-walled carbon nanotube conductive paste. The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The negative electrode material layer includes natural graphite, silicon oxide material, a second composite conductive agent, and a liquid retainer. The mass ratio of natural graphite, silicon oxide material, second composite conductive agent, and liquid retainer is 85-90:6-9:0.55-1.1:0.2-0.4. The second composite conductive agent includes conductive carbon black Super P and single-walled carbon nanotube conductive paste. The diaphragm includes a base membrane and a ceramic coating applied to the upper surface of the base membrane, wherein the base membrane is at least one of polypropylene and polyethylene; The electrolyte consists of lithium salts, organic solvents, and additives.

[0023] Specifically, the lithium-ion battery of this invention, through the synergistic use of a material system of "ultra-high nickel cathode + first composite conductive agent + lithium carbonate" and "graphite / silicon-oxygen anode + second composite conductive agent + liquid retainer," coupled with a ceramic-coated separator, successfully solves the core contradictions of "short cycle life" and "significant safety hazards" commonly faced by high-energy-density lithium batteries. This battery system achieves a 0.2C discharge capacity ≥3.2Ah while maintaining a capacity retention rate ≥89% after 700 cycles of 1C charge / 1C discharge. Furthermore, multi-layered safety design ensures safe use under high-energy conditions, resulting in excellent overall performance and strong market competitiveness.

[0024] Furthermore, in some embodiments, the lithium-ion battery uses a ternary material with ultra-high nickel content, lithium nickel cobalt manganese oxide (Li(Ni)2)2). 0.90 Co 0.06 Mn 0.04 The nickel content of the positive electrode is ≥90%, and its extremely high specific capacity effectively ensures the high energy density of the battery in this embodiment. The addition of lithium carbonate to the positive electrode can effectively replenish the active lithium consumed by the formation of the interface film in the early stage of cycling, and improve the initial coulombic efficiency and long-term cycle capacity retention.

[0025] Furthermore, in some embodiments, the positive electrode of the lithium-ion battery adopts a first composite conductive agent of "conductive carbon black Super P + multi-walled carbon nanotube conductive slurry". The conductive carbon black Super P provides a basic "point-to-point" conductive contact, and the multi-walled carbon nanotubes construct a "linear" long-range conductive path that runs through the electrode. The two work together to form a three-dimensional conductive network. This network not only significantly reduces internal resistance and improves rate performance, but more importantly, it effectively binds and supports the high-nickel active material particles, inhibits particle breakage and peeling during cycling, and fundamentally alleviates the capacity decay of high-nickel materials.

[0026] Furthermore, in some embodiments, the lithium-ion battery anode employs a composite system of "natural graphite + silicon oxide materials". Silicon oxide materials provide high capacity, while natural graphite provides structural buffering and a good conductive substrate; the two work synergistically to create a high-capacity cathode. Simultaneously, a second composite conductive agent, "conductive carbon black Super P + single-walled carbon nanotube conductive slurry", is used to further enhance the conductivity and structural integrity of the anode. The excellent mechanical properties of single-walled carbon nanotubes effectively buffer the volume expansion of silicon oxide materials during charging and discharging, maintaining electrode structural stability. A liquid retainer is also added to the anode to store electrolyte after injection, forming an "electrolyte reservoir". During long-term cycling, especially when high-nickel cathode side reactions continuously consume electrolyte, the liquid retainer slowly releases the stored electrolyte, ensuring effective wetting of the anode interface, maintaining a stable solid electrolyte interphase (SEI) film, and reducing the surge in polarization and capacity decay caused by electrolyte drying. This is beneficial for achieving the ultra-high energy density and long cycle life of the lithium-ion battery in this embodiment.

[0027] In some embodiments, the solid content of the multi-walled carbon nanotube conductive paste is 3%-6%, the viscosity is less than 3500 mPa·s, and the moisture content is less than 1000 ppm; the solid content of the single-walled carbon nanotube conductive paste is 0.1%-0.5%, and the viscosity is less than 2500 mPa·s.

[0028] Specifically, the solid content, viscosity, and moisture content of multi-walled carbon nanotube conductive slurries and single-walled carbon nanotube conductive slurries are precisely controlled, establishing reliable quality standards for the manufacture of high-performance electrodes from the material source. This not only ensures the stability of the conductive agent's performance but also guarantees its efficient and uniform dispersion in complex multi-component slurry systems. Ultimately, this achieves controllable, predictable, and optimizable conductive network, electrode structure, and overall battery performance, which is beneficial for the high-quality and large-scale production of the lithium-ion battery of this invention.

[0029] In some embodiments, the cathode material layer further includes a binder, polyvinylidene fluoride (PVDF).

[0030] Specifically, polyvinylidene fluoride (PVDF) is used as a binder in the cathode material layer, providing an optimal balance in terms of chemical stability, bond strength, process compatibility, and electrolyte compatibility for the ultra-high nickel, high compaction density, and high-voltage operating cathode system. PVDF ensures the structural robustness and interfacial stability of the highly active lithium nickel cobalt manganese oxide cathode material under harsh electrochemical environments, which is beneficial for achieving high energy density, long cycle life, and high safety in the lithium-ion battery of this invention.

[0031] In some embodiments, the negative electrode material layer further includes a dispersant sodium carboxymethyl cellulose (CMC) and a binder styrene-butadiene rubber (SBR).

[0032] Specifically, the excellent dispersing and thickening properties of sodium carboxymethyl cellulose (CMC) work synergistically with the binder styrene-butadiene rubber (SBR) to construct a strong and elastic bonding network that can cope with the repeated volume expansion and contraction of the negative electrode active material (especially silicon suboxide). This ensures that the high-capacity, high-load negative electrode of the lithium-ion battery in this embodiment of the invention maintains structural integrity and interface stability during long-term cycling, thereby achieving an ultra-long cycle life of the battery.

[0033] In some embodiments, the silicon-oxygen material is silicon suboxide.

[0034] Specifically, the theoretical specific capacity of silicon suboxide (approximately 1200-1600 mAh / g) is significantly higher than that of traditional graphite anodes (372 mAh / g), effectively improving the energy density of both the anode and the lithium-ion battery. Simultaneously, the volume expansion of silicon suboxide is significantly reduced compared to pure silicon, greatly alleviating problems such as particle pulverization, conductive network breakage, and active material shedding caused by volume changes. The in-situ formation of the Li2O and lithium silicate inert phase during the initial lithium intercalation buffers volume changes and promotes the formation of a more stable SEI film, improving cycle stability and initial coulombic efficiency. Furthermore, silicon suboxide exhibits superior thermal stability and processing dispersibility compared to nano-silicon, exhibiting high synergy with the composite conductive agent network and liquid-retaining agent system in this invention, which is beneficial for achieving high energy density and long cycle life in the lithium-ion battery of this invention.

[0035] In some embodiments, the thickness of the positive electrode sheet is 139-142 μm, and the compaction density is 3.2-3.5 g / cm³. 3 The thickness of the negative electrode sheet is 135-138 μm, and the compaction density is 2.7-3.4 g / cm³. 3 .

[0036] Specifically, compaction density is a key parameter after electrode forming, reflecting the density of the active material packing and directly affecting the battery's energy density and structural stability. Appropriately increasing compaction density can, on the one hand, reduce the negative electrode thickness ratio, indirectly freeing up space for the positive electrode and further increasing battery capacity; on the other hand, it can reduce the gaps between active material particles, lower electron contact resistance, and improve electron transport efficiency; simultaneously, a reasonable compaction density can improve the electrode structure stability and reduce the shedding of active material during cycling.

[0037] According to some embodiments of the present invention, the thickness of the positive current collector is 12-16 μm, and the thickness of the negative current collector is 6-10 μm.

[0038] Specifically, the positive electrode current collector of a lithium-ion battery is aluminum foil, and the negative electrode current collector is copper foil. The current collector is a non-active material; the thinner the current collector, the higher the proportion of active material inside the battery. However, this can lead to insufficient mechanical strength of the electrode, making it prone to wrinkling or breakage during winding, thus affecting battery production yield. Therefore, an appropriate current collector thickness is beneficial for balancing energy density and mechanical strength, enabling the lithium-ion battery to maintain the integrity of the electrode structure during high-capacity charging cycles, delaying battery degradation, and achieving high energy density and long cycle life.

[0039] In some embodiments, the mass ratio of conductive carbon black Super P to multi-walled carbon nanotube conductive slurry in the first composite conductive agent is 2-5:3-6.

[0040] Specifically, the three-dimensional conductive network synergistically constructed by the first composite conductive agent and lithium nickel cobalt manganese oxide can effectively reduce the internal resistance of the battery, simultaneously improve the electron and ion transport efficiency, alleviate the polarization phenomenon under high current, and at the same time, the binding effect of the conductive agent on the lithium nickel cobalt manganese oxide particles reduces particle breakage and active material shedding, which is conducive to the realization of long cycle life of the battery. The lithium-ion battery of the present invention has a higher discharge capacity than the battery using a single conductive carbon black as a conductive agent, and the voltage platform is more stable during high current discharge, reducing rate decay. After 700 cycles of 1C charge / 1C discharge, the capacity retention rate can reach more than 70%.

[0041] In some embodiments, the mass ratio of conductive carbon black Super P to single-walled carbon nanotube conductive slurry in the second composite conductive agent is 5-10:0.5-1.

[0042] Specifically, conductive carbon black Super P, as a zero-dimensional point conductive agent, can fill the spaces between active material particles, providing numerous "point contacts" to quickly establish basic conductive pathways and effectively reduce contact resistance. Single-walled carbon nanotubes, as a one-dimensional linear conductive agent, have extremely high aspect ratios and intrinsic conductivity, enabling them to span multiple active material particles and construct a long-range conductive framework of "line bridging" or "surface connection." The 5-10:0.5-1 ratio ensures that, based on a sufficient amount of Super P to achieve extensive "point contacts," an appropriate but crucial amount of single-walled carbon nanotubes is introduced to construct a "conductive highway" that runs through the entire electrode. The two work together to form a three-dimensional conductive network of "point-line combination and near-far complementarity," enabling electrons to achieve rapid and uniform transmission within the negative electrode, significantly reducing negative electrode polarization, and improving the performance of the lithium-ion battery in this embodiment of the invention during high-rate discharge.

[0043] Secondly, embodiments of the present invention provide a method for preparing a lithium-ion battery, comprising the following steps: Preparation of the positive electrode: 95-99 parts by mass of lithium nickel cobalt manganese oxide (Li(Ni)) 0.90 Co 0.06 Mn 0.04 The following components are mixed in an organic solvent: 0.2-0.5 parts of conductive carbon black Super P, 0.3-0.6 parts of multi-walled carbon nanotube conductive paste, 1.0-1.2 parts of binder polyvinylidene fluoride (PVDF), and 0.2-0.4 parts of lithium carbonate, forming a uniform positive electrode paste with a solid content of 64%-70% and a viscosity of 4000-6000 mPa·s. The positive electrode paste is then weighed according to a single-sided dry weight areal density of 208-212 mg / cm³. 2 The coating is uniformly applied to a positive electrode current collector with a thickness of 12-16 μm, and then dried, rolled, and sheared to obtain a thickness of 139-142 μm and a compacted density of 3.2-3.5 g / cm³. 3 The positive electrode plate; Preparation of the negative electrode sheet: By mass, 85-90 parts of natural graphite, 6-9 parts of silicon oxide material, 0.5-1.0 parts of conductive carbon black Super P, 0.05-0.1 parts of multi-walled carbon nanotube conductive slurry, 0.2-0.4 parts of liquid retainer, 1.0-1.5 parts of dispersant sodium carboxymethyl cellulose (CMC), and 2.0-2.2 parts of binder styrene-butadiene rubber (SBR) are mixed in deionized water to form a uniform negative electrode slurry with a solid content of 44%-50% and a viscosity of 2500-5500 mPa·s. The negative electrode slurry is then measured to have a single-sided dry weight areal density of 205-210 mg / cm³. 2 The coating is uniformly applied to a 6-10 μm thick negative electrode current collector, and then dried, rolled, and sheared to obtain a thickness of 135-138 μm and a compacted density of 2.7-3.4 g / cm³.3 The negative electrode plate; Preparation of the diaphragm: The base membrane of the diaphragm is a 9 μm thick polypropylene and / or polyethylene membrane prepared by wet method. A 3 μm ceramic coating is applied to the upper surface of the base membrane to obtain a diaphragm with a total thickness of 12 μm. Preparation of electrolyte: Lithium salt, organic solvent and additives are mixed in a mass ratio of 10-15:80-90:1-5; After assembling the positive electrode, negative electrode and separator, the electrolyte is injected, followed by encapsulation, formation and capacity testing.

[0044] In the preparation of the electrolyte in some embodiments of the present invention, the lithium salt is selected from at least one of lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI), the organic solvent is selected from at least two of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), and ethyl acetate (EA), and the additive is selected from at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), 1,3-propanesulfonate lactone (PS), tris(trimethylsilane) phosphate (TMSP), lithium difluorophosphate (LiPO2F2), and trimethyl phosphate (TMP).

[0045] Specifically, the lithium-ion battery manufacturing method of this invention achieves high-quality, high-efficiency, and stable mass production of high-performance lithium-ion batteries through a comprehensive system design and precise control of the entire process, from slurry preparation, electrode forming, separator selection, and electrolyte preparation. The positive electrode employs an ultra-high nickel ternary material and a composite conductive agent system, achieving uniform dispersion in a slurry with optimized solid content and viscosity to form a three-dimensional conductive network. This not only significantly improves electron conduction efficiency but also effectively suppresses particle breakage and capacity decay of the high-nickel material. The negative electrode, through the composite of natural graphite and silicon-oxygen materials, combined with a second composite conductive agent and a liquid retainer, buffers volume expansion while ensuring high capacity, maintaining the integrity of the electrode structure. The introduction of the liquid retainer forms an electrolyte reserve, continuously and stably supplying the interface demand, significantly improving cycle life and interface stability.

[0046] Furthermore, the application of ceramic-coated membranes enhances heat resistance and mechanical strength, constructing a reliable thermal safety barrier; the scientific ratio of lithium salts, solvents, and additives in the electrolyte further optimizes ion transport and interfacial film formation behavior.

[0047] The lithium-ion battery provided by this invention is particularly suitable for applications requiring high energy density and long cycle life, including but not limited to 18650 cylindrical batteries, and can also be applied to other specifications of cylindrical batteries, prismatic batteries or pouch batteries.

[0048] The lithium-ion battery of the present invention is prepared using the 18650 cylindrical battery as an example.

[0049] Example 1 Preparation of the positive electrode: Lithium nickel cobalt manganese oxide (Li(Ni)) was prepared in a planetary dispersion vacuum mixer at a revolution frequency of 30 Hz and a rotation frequency of 1000 Hz. 0.90 Co 0.06 Mn 0.04 O2), super carbon black (SP), multi-walled carbon nanotube conductive paste (Shenzhen Kejing LB108A-44, with a solid content of 4.3%), polyvinylidene fluoride (PVDF), and lithium carbonate were mixed in N-methylpyrrolidone at a mass ratio of 97.8:0.3:0.5:1.1:0.3 to form a uniform positive electrode paste with a solid content of 64%-70% and a viscosity of 4000-6000 mPa·s. The positive electrode paste was then coated using a gap-type coating machine to a dry weight surface density of 208 mg / cm³. 2 The coating is uniformly applied to the upper and lower surfaces of a 16μm thick aluminum foil, dried at 120℃, and then rolled and sheared to obtain a positive electrode sheet with a width of 57.5mm and a thickness of 139μm. Preparation of negative electrode: Natural graphite, silicon oxide material (Lianchuang LC1676D), super carbon black (SP), and single-walled carbon nanotube conductive paste (TUBALL) were mixed in a planetary dispersion vacuum mixer at a revolution frequency of 30 Hz and a rotation frequency of 1000 Hz. TM BATT H2O (solid content 0.4%), a liquid retainer (Daoying SFC3100), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) were dissolved in deionized water at a mass ratio of 88.85:6.15:1.0:0.06:0.24:1.5:2.2 to form a uniform negative electrode slurry with a solid content of 44%-50% and a viscosity of 2500-5500 mPa·s. The negative electrode slurry was then coated using a gap-type coating machine to achieve a dry weight surface density of 205 mg / cm³. 2 The coating is uniformly applied to the upper and lower surfaces of a 10μm thick copper foil, dried at 130℃, and then rolled and sheared to obtain a negative electrode sheet with a width of 59mm and a thickness of 138μm. Preparation of the diaphragm: The base membrane of the diaphragm is a 9μm thick polyethylene membrane prepared by wet method. A 3μm ceramic coating is applied to the upper surface of the base membrane to obtain a diaphragm with a total thickness of 12μm. Preparation of electrolyte: The electrolyte is composed of lithium salt, organic solvent and additives; the lithium salt is LiPF6, the organic solvent is EC, EMC and DMC, and the additives are VC, FEC, DTD and LiPO2F2. The mass ratio of lithium salt LiPF6, organic solvent EC, EMC and DMC to additives VC, FEC and DTD is 14.5:25.5:40:15:1:2:2. The organic solvent EC, EMC and DMC are mixed evenly, and then lithium salt LiPF6 and additives VC, FEC and DTD are added and mixed evenly to obtain the electrolyte. Pre-processed battery assembly: Positive and negative electrode sheets are spot-welded with tabs, then covered with high-temperature tape and dried in a vacuum drying oven at 120°C for at least 8 hours. The positive and negative electrode sheets, along with the separator, are wound into a core on a winding machine in an environment with relative humidity less than 25%. After passing short-circuit testing and visual inspection, the core, along with the upper and lower insulating sheets, is placed in a container with a diameter of 18.4±0.1mm and a height of 65.2±0.15m. Inside the steel shell of m, the negative electrode tab is welded to the steel shell by an inverter welding machine. After grooving, it is put into an oven and baked at 85±10℃ for 20-40 hours. Then, a full short circuit test is performed. Qualified products are injected with 5.5±0.1g of electrolyte in a liquid injection room with a humidity of less than 1%. The positive electrode tab is welded to the cap by laser welding. Then the cap is fastened to the steel shell and sent to a fully sealed machine to be processed into a 18650 standard battery cell with a diameter of 18mm and a height of 65mm. Formation and capacity testing: After cleaning and applying anti-rust oil to the 18650 standard cells, the cells are aged at 25-45℃ for 36-48 hours. After baking at 60℃ in an inert gas atmosphere for 24 hours, the cells are formed in a formation cabinet. The formation process includes constant current and constant voltage charging at 0.5C, standing for 10 minutes, and then constant current discharging at 0.2C, with the capacity recorded. The cells are then sorted into different voltage and internal resistance levels using a matching machine. The qualified cells are sorted by capacity, and batteries with qualified capacity are selected in 30mAh increments to obtain 18650 lithium-ion batteries with a nominal capacity of 3.2Ah.

[0050] Example 2 Preparation of the positive electrode: Lithium nickel cobalt manganese oxide (Li(Ni)) was prepared in a planetary dispersion vacuum mixer at a revolution frequency of 30 Hz and a rotation frequency of 1000 Hz. 0.90 Co 0.06 Mn 0.04O2), super carbon black (SP), multi-walled carbon nanotube conductive paste (Shenzhen Kejing LB108A-44, with a solid content of 4.3%), polyvinylidene fluoride (PVDF), and lithium carbonate were mixed in N-methylpyrrolidone at a mass ratio of 97.8:0.2:0.6:1.1:0.3 to form a uniform positive electrode paste with a solid content of 64%-70% and a viscosity of 4000-6000 mPa·s. The positive electrode paste was coated using a gap-type coating machine to a dry weight surface density of 212 mg / cm³. 2 The coating is uniformly applied to the upper and lower surfaces of a 12μm thick aluminum foil, dried at 120℃, and then rolled and sheared to obtain a positive electrode sheet with a width of 57.5mm and a thickness of 142μm. Preparation of negative electrode: Natural graphite, silicon oxide material (Lianchuang LC1676D), super carbon black (SP), and single-walled carbon nanotube conductive paste (TUBALL) were mixed in a planetary dispersion vacuum mixer at a revolution frequency of 30 Hz and a rotation frequency of 1000 Hz. TM BATT H2O (with a solid content of 0.4%), a liquid retainer (Daoying SFC3100), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) were dissolved in deionized water at a mass ratio of 88.85:6.15:0.9:0.1:0.3:1.5:2.2 to form a uniform negative electrode slurry with a solid content of 44%-50% and a viscosity of 2500-5500 mPa·s. The negative electrode slurry was then coated using a gap-type coating machine to achieve a dry weight surface density of 210 mg / cm³. 2 The coating is uniformly applied to the upper and lower surfaces of a 6μm thick copper foil, dried at 130℃, and then rolled and sheared to obtain a negative electrode sheet with a width of 59mm and a thickness of 135μm. Preparation of the diaphragm: The base membrane of the diaphragm is a 9μm thick polyethylene membrane prepared by wet method. A 3μm ceramic coating is applied to the upper surface of the base membrane to obtain a diaphragm with a total thickness of 12μm. Preparation of electrolyte: The electrolyte is composed of lithium salt, organic solvent and additives; the lithium salt is LiFSI, the organic solvent is EC, EMC and DMC, and the additives are VC, FEC, DTD and LiPO2F2. The mass ratio of lithium salt LiFSI, organic solvent EC, EMC and DMC to additives VC, FEC, DTD and LiPO2F2 is 14.5:25.5:40:15:1:1:2:1. The organic solvent EC, EMC and DMC are mixed evenly, and then lithium salt LiFSI and additives VC, FEC, DTD and LiPO2F2 are added and mixed evenly to obtain the electrolyte. Pre-processed battery assembly: Positive and negative electrode sheets are spot-welded with tabs, then covered with high-temperature tape and dried in a vacuum drying oven at 120°C for at least 8 hours. The positive and negative electrode sheets, along with the separator, are wound into a core on a winding machine in an environment with relative humidity less than 25%. After passing short-circuit testing and visual inspection, the core, along with the upper and lower insulating sheets, is placed in a container with a diameter of 18.4±0.1mm and a height of 65.2±0.15m. Inside the steel shell of m, the negative electrode tab is welded to the steel shell by an inverter welding machine. After grooving, it is put into an oven and baked at 85±10℃ for 20-40 hours. Then, a full short circuit test is performed. Qualified products are injected with 5.5±0.1g of electrolyte in a liquid injection room with a humidity of less than 1%. The positive electrode tab is welded to the cap by laser welding. Then the cap is fastened to the steel shell and sent to a fully sealed machine to be processed into a 18650 standard battery cell with a diameter of 18mm and a height of 65mm. Formation and capacity testing: After cleaning and applying anti-rust oil to the 18650 standard cells, the cells are aged at 25-45℃ for 36-48 hours. After baking at 60℃ in an inert gas atmosphere for 24 hours, the cells are formed in a formation cabinet. The formation process includes constant current and constant voltage charging at 0.5C, standing for 10 minutes, and then constant current discharging at 0.2C, with the capacity recorded. The cells are then sorted into different voltage and internal resistance levels using a matching machine. The qualified cells are sorted by capacity, and batteries with qualified capacity are selected in 30mAh increments to obtain 18650 lithium-ion batteries with a nominal capacity of 3.2Ah.

[0051] The lithium-ion batteries prepared in Examples 1-2 were subjected to performance tests.

[0052] 1.25℃ Rate Performance Test (0.2C, 0.5C, 1C, 5A, 10A and 15A) 1.1 Place the battery in a 25°C incubator and let it stand for at least 2 hours to allow the internal and external temperatures of the battery to become uniform.

[0053] 1.2 Charge the battery to 4.2V at 0.5C constant current and constant voltage at 25℃, with a cutoff current of 0.05C. Let it stand at the test temperature for 10 minutes to ensure uniform temperature inside and outside the battery.

[0054] 1.3 At the test temperature, discharge to 2.5V at constant currents of 0.2C (0.64A), 0.5C (1.6A), 1C (3.2A), 5A, 10A and 15A respectively, and leave for 30 minutes, and record the discharge time.

[0055] 1.4 Calculation of discharge capacity at rate: Capacity (Ah) = Discharge current (A) x Discharge time (h).

[0056] 2. Low-temperature performance test 2.1 Place the battery in a -20℃ temperature chamber and let it stand for at least 2 hours to allow the internal and external temperatures of the battery to become uniform.

[0057] 2.2 Charge the battery to 4.2V at a constant current and constant voltage of 0.5C at the test temperature, with a cutoff current of 0.05C. Let it stand at the test temperature for 10 minutes to ensure that the internal and external temperatures of the battery are uniform.

[0058] 2.3 Discharge at a constant current of 0.2C to 2.0V at the test temperature and record the discharge time.

[0059] 2.4 Calculation of low-temperature discharge capacity: Capacity (Ah) = Discharge current (A) x Discharge time (h).

[0060] (2) Test results Table 1: Discharge capacity test results of Examples 1-2 2. Loop testing (1) Test method 1. 25℃ 1C charge / 1C discharge cycle test 1.1 Let the battery stand at 25°C for 4 hours to ensure uniform temperature inside and outside the battery.

[0061] 1.2 Charge to 4.2V at 25℃ with a constant current and constant voltage of 1C, cut off current of 0.05C, and let stand for 10 minutes.

[0062] 1.3 Discharge at a constant current of 1C to 2.5V at 25℃, let stand for 30 minutes; record the discharge capacity.

[0063] 1.4 Repeat steps 1.2 and 1.3 above until the set number of iterations is reached.

[0064] 1.5 Calculation of Cyclic Capacity Retention Rate: Cyclic Capacity Retention Rate = Capacity after n cycles (Cn) / Capacity after the first cycle (C1).

[0065] (2) Test results Table 2: Cyclic Test Results of Examples 1-2 Through Table 1 and Figure 1It is evident that the lithium-ion battery of this invention possesses excellent rate performance and high capacity retention. At 25°C, the battery of Example 1 achieved a discharge capacity of 3.31 Ah at a 0.2C rate. As the discharge rate increased from 0.2C (0.64A) to 15A, the battery capacity retention was extremely high. The 10A discharge capacity (3.18Ah) still reached 96.1% of the 0.2C capacity, and the 15A discharge capacity (3.16Ah) also reached 95.5%. This indicates that the battery can still maintain most of its energy output under high power output. The slight fluctuations between the 5A discharge capacity (3.13Ah) and the higher rate capacity may be due to differences in the battery polarization state and thermal management effects within different current ranges. Overall, it still reflects the successful construction of the three-dimensional composite conductive network "conductive carbon black Super P + multi-walled / single-walled carbon nanotubes" in this invention. This network significantly reduces the internal resistance and polarization of the electrodes, ensuring rapid and uniform electron transport at high rates, resulting in excellent battery performance in high-power demand scenarios.

[0066] From Table 1 and Figure 2 It is evident that the lithium-ion battery of the present invention possesses excellent low-temperature performance. In a harsh low-temperature environment of -20°C, the batteries of Examples 1 and 2, discharged at 0.2C, achieved capacities of 2.83 Ah (approximately 85.5% of their 25°C, 0.2C discharge capacity) and 2.84 Ah, respectively. This excellent low-temperature capacity retention is attributed to: (1) a composite conductive network: ensuring electronic conductivity within the electrode at low temperatures; (2) the role of a liquid retainer: maintaining sufficient and uniform distribution of the electrolyte at the negative electrode interface, mitigating mass transfer polarization caused by increased electrolyte viscosity and decreased ionic conductivity at low temperatures; and (3) an optimized electrode pore structure: a reasonable compaction density (positive electrode 3.2-3.5 g / cm³). 3 Negative electrode 2.7-3.4 g / cm 3 This ensures good wetting of the electrolyte, providing a channel for low-temperature ion transport.

[0067] From Table 2 and Figure 3 It is evident that the lithium-ion battery of the present invention possesses excellent long-term cycle stability. Under the stringent charge-discharge regime of 25°C and 1C charge / 1C discharge, the batteries of Example 1 and Example 2 maintained capacity retention rates of 88% and 89%, respectively, after 700 cycles. This directly demonstrates that the present invention effectively alleviates the inherent cycle degradation problem of high-nickel materials (Ni≥90%) through the synergistic design of the entire system of "high-nickel cathode + first composite conductive agent + lithium carbonate" and "graphite / silicon-oxygen anode + second composite conductive agent + liquid retainer".

[0068] In summary, the lithium-ion battery of the present invention, through optimization and adjustment of various aspects such as positive and negative electrodes, electrolytes, separators, and preparation methods, enables the prepared lithium-ion battery to simultaneously possess high rate performance, long cycle life, and low-temperature performance.

[0069] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The positive electrode material layer includes lithium nickel cobalt manganese oxide (Li(Ni)2)2). 0.90 Co 0.06 Mn 0.04 O2), the first composite conductive agent and lithium carbonate, wherein the lithium nickel cobalt manganese oxide (Li(Ni) 0.90 Co 0.06 Mn 0.04 The mass ratio of the first composite conductive agent to the lithium carbonate is 95-99:0.5-1.1:0.2-0.4; the first composite conductive agent includes conductive carbon black Super P and multi-walled carbon nanotube conductive paste. The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The negative electrode material layer includes natural graphite, silicon oxide material, a second composite conductive agent, and a liquid retainer. The mass ratio of the natural graphite, the silicon oxide material, the second composite conductive agent, and the liquid retainer is 85-90:6-9:0.55-1.1:0.2-0.

4. The second composite conductive agent includes conductive carbon black Super P and single-walled carbon nanotube conductive paste. The diaphragm includes a base membrane and a ceramic coating applied to the upper surface of the base membrane, wherein the base membrane is at least one of polypropylene and polyethylene; The electrolyte includes lithium salt, organic solvent and additives.

2. The lithium-ion battery according to claim 1, characterized in that, The multi-walled carbon nanotube conductive paste has a solid content of 3%-6%, a viscosity of less than 3500 mPa·s, and a moisture content of less than 1000 ppm; the single-walled carbon nanotube conductive paste has a solid content of 0.1%-0.5% and a viscosity of less than 2500 mPa·s.

3. The lithium-ion battery according to claim 1, characterized in that, The positive electrode material layer also includes a binder, polyvinylidene fluoride (PVDF).

4. The lithium-ion battery according to claim 1, characterized in that, The negative electrode material layer also includes dispersant sodium carboxymethyl cellulose (CMC) and binder styrene-butadiene rubber (SBR).

5. The lithium-ion battery according to claim 1, characterized in that, The silicon-oxygen material is silicon suboxide.

6. The lithium-ion battery according to claim 1, characterized in that, The thickness of the positive electrode sheet is 139-142 μm, and the compaction density is 3.2-3.5 g / cm³. 3 The negative electrode sheet has a thickness of 135-138 μm and a compaction density of 2.7-3.4 g / cm³. 3 .

7. The lithium-ion battery according to claim 1, characterized in that, The thickness of the positive current collector is 12-16 μm, and the thickness of the negative current collector is 6-10 μm.

8. The lithium-ion battery according to claim 1, characterized in that, In the first composite conductive agent, the mass ratio of the conductive carbon black Super P to the multi-walled carbon nanotube conductive slurry is 2-5:3-6.

9. The lithium-ion battery according to claim 1, characterized in that, In the second composite conductive agent, the mass ratio of the conductive carbon black Super P to the single-walled carbon nanotube conductive slurry is 5-10:0.5-1.

10. A method for preparing a lithium-ion battery, characterized in that, Includes the following steps: Preparation of the positive electrode: 95-99 parts by mass of lithium nickel cobalt manganese oxide (Li(Ni)) 0.90 Co 0.06 Mn 0.04 The following components are mixed in an organic solvent: 0.2-0.5 parts of conductive carbon black Super P, 0.3-0.6 parts of multi-walled carbon nanotube conductive paste, 1.0-1.2 parts of binder polyvinylidene fluoride (PVDF), and 0.2-0.4 parts of lithium carbonate, to form a uniform positive electrode paste with a solid content of 64%-70% and a viscosity of 4000-6000 mPa·s. The positive electrode paste is then weighed to a surface density of 208-212 mg / cm³. 2 The coating is uniformly applied to a positive electrode current collector with a thickness of 12-16 μm, and then dried, rolled, and sheared to obtain a thickness of 139-142 μm and a compacted density of 3.2-3.5 g / cm³. 3 The positive electrode plate; Preparation of the negative electrode sheet: By weight, 85-90 parts of natural graphite, 6-9 parts of silicon oxide material, 0.5-1.0 parts of conductive carbon black Super P, 0.05-0.1 parts of multi-walled carbon nanotube conductive slurry, 0.2-0.4 parts of liquid retainer, 1.0-1.5 parts of dispersant sodium carboxymethyl cellulose (CMC), and 2.0-2.2 parts of binder styrene-butadiene rubber (SBR) are mixed in deionized water to form a uniform negative electrode slurry with a solid content of 44%-50% and a viscosity of 2500-5500 mPa·s. The negative electrode slurry is then weighed to a single-sided dry weight areal density of 205-210 mg / cm³. 2 The coating is uniformly applied to a 6-10 μm thick negative electrode current collector, and then dried, rolled, and sheared to obtain a thickness of 135-138 μm and a compacted density of 2.7-3.4 g / cm³. 3 The negative electrode plate; Preparation of the diaphragm: The base membrane of the diaphragm is a 9 μm thick polypropylene and / or polyethylene membrane prepared by wet method. A 3 μm ceramic coating is applied to the upper surface of the base membrane to obtain a diaphragm with a total thickness of 12 μm. Preparation of electrolyte: Lithium salt, organic solvent and additives are mixed in a mass ratio of 10-15:80-90:1-5; After assembling the positive electrode, the negative electrode, and the separator, the electrolyte is injected, followed by encapsulation, formation, and capacity separation operations.

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