Lithium ion battery and application thereof

Abstract

The application relates to the technical field of batteries, and provides a lithium ion battery and application thereof. The lithium ion battery comprises a positive electrode sheet and a negative electrode sheet, the negative electrode sheet comprises a negative electrode material layer, and the negative electrode material layer comprises a negative electrode material; the lithium ion battery satisfies 0 < (a x b x c / 100)-d < 4; wherein a is the area density of the negative electrode sheet, the unit is g / m 2 ; b is the compacted density of the negative electrode sheet, the unit is g / cm 3 ; c is the particle size gradient distribution coefficient of the negative electrode material; and d is the ratio of the liquid-phase diffusion impedance of the negative electrode sheet to the liquid-phase diffusion impedance of the positive electrode sheet. By establishing a mathematical formula of a, b, c and d and limiting the value range, a balance mechanism of lithium ion migration rate of the positive electrode and the negative electrode is established, and the fast-charging performance and the cycle performance of the lithium ion battery are synergistically optimized.

Description

Technical Field

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

[0002] Lithium-ion batteries, with their ultra-high energy density and low self-discharge rate, are considered one of the key candidate materials in the current energy storage and power supply fields, and are widely used in new energy vehicles, portable electronic devices, large-scale energy storage systems and other fields.

[0003] To optimize the fast-charging and cycle performance of lithium-ion batteries in practical applications, current technologies primarily focus on multifaceted material design. Common strategies include modifying the surface and bulk structure of the cathode material through doping and coating to isolate the electrolyte from the cathode material and reduce surface side reactions; and adding functional additives to the electrolyte system to improve SEI film stability. However, despite these various approaches, current lithium-ion batteries still face the challenge of synergistic optimization of fast-charging and cycle performance, making it difficult to achieve a balance among multiple performance indicators.

[0004] Therefore, there is an urgent need to develop more precise and efficient material designs to synergistically improve its fast-charging and cycle performance. Summary of the Invention

[0005] This application provides a lithium-ion battery that achieves the technical effect of synergistically optimizing fast charging performance and cycle performance.

[0006] This application also provides an electrical device that includes the aforementioned lithium-ion battery, which has excellent fast-charging performance and cycle performance.

[0007] The first aspect of this application provides a lithium-ion battery, the lithium-ion battery including a positive electrode and a negative electrode, the negative electrode including a negative electrode material layer, the negative electrode material layer including a negative electrode material;

[0008] The lithium-ion battery satisfies: 0 < (a × b × c / 100) - d < 4;

[0009] Wherein, 'a' represents the areal density of the negative electrode, in g / m³. 2 ; b is the compaction density of the negative electrode sheet, in g / cm³. 3 ; c is the particle size gradient distribution coefficient of the negative electrode material; d is the ratio of the liquid phase diffusion resistance of the negative electrode to the liquid phase diffusion resistance of the positive electrode.

[0010] The lithium-ion battery as described above, wherein 100 ≤ a ≤ 300; and / or,

[0011] 1.4 ≤ b ≤ 1.7; and / or,

[0012] 0.5≤c≤2; and / or,

[0013] 0.2≤d≤6.2.

[0014] The lithium-ion battery as described above, wherein 140 ≤ a ≤ 220; and / or,

[0015] 1.5 ≤ b ≤ 1.65; and / or,

[0016] 0.7≤c≤1.8; and / or, 0.7≤d≤2.6.

[0017] In the lithium-ion battery described above, the liquid phase diffusion resistance of the negative electrode is 0.1mΩ~100Ω, and the liquid phase diffusion resistance of the positive electrode is 0.1mΩ~100Ω.

[0018] In the lithium-ion battery described above, the negative electrode material includes a negative electrode active material, which includes at least one of graphite, hard carbon, soft carbon, mesophase carbon microspheres, silicon-based negative electrode material, and tin-based negative electrode material.

[0019] In the lithium-ion battery described above, the porosity of the negative electrode material is 0.05~0.2; and / or,

[0020] The OI value of the negative electrode material is 9~30.

[0021] In the lithium-ion battery described above, the negative electrode material D 50 The value is 10~25μm, D 10 The value is 5~20μm, D 90 It is 26~40μm.

[0022] In the lithium-ion battery described above, the negative electrode material further includes a first conductive agent and a first binder. The first conductive agent includes at least one of carbon black, acetylene black, Ketjen black, carbon fiber, and graphene. The first binder includes at least one of styrene-butadiene rubber, sodium carboxymethyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, and polyvinyl fluoride.

[0023] In the lithium-ion battery described above, the positive electrode includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, the positive electrode active material includes a core and a coating layer covering at least a portion of the surface of the core, and the chemical composition of the core is LiFe. q Mn x PO4,

[0024] Wherein, 0 < q ≤ 0.5, 0.5 ≤ x ≤ 1, and the coating layer includes at least one of C, Al2O3, MgO, TiO2, and LATP.

[0025] In the lithium-ion battery described above, the thickness of the coating layer is <1 nm, and the mass percentage of the coating layer in the positive electrode active material is <5%.

[0026] In the lithium-ion battery described above, the porosity of the positive electrode active material is 0.02~0.2; and / or,

[0027] The positive electrode active material D 50 The range is 0.8~6μm.

[0028] In the lithium-ion battery described above, the positive electrode active material layer further includes a second conductive agent and a second binder. The second conductive agent includes at least one of carbon black, carbon nanotubes, acetylene black, Ketjen black, carbon fiber, and graphene. The second binder includes at least one of polyvinylidene fluoride, polyurethane, polytetrafluoroethylene, polyethylene, and polypropylene.

[0029] The lithium-ion battery described above further includes an electrolyte comprising a lithium salt, an additive, and a solvent. The lithium salt comprises at least one of LiPF6, LiBF4, and LiFSI. The additive comprises at least one of VC and FEC. The solvent comprises at least one of EC, EMC, and DEC.

[0030] In the lithium-ion battery described above, the solvent comprises EC, EMC and DEC, and the mass ratio of EC, EMC and DEC is 10~40:10~40:10~40.

[0031] In the lithium-ion battery described above, the lithium salt has a mass percentage content of 5-15% in the electrolyte, the additive has a mass percentage content of 0.5-5% in the electrolyte, and the solvent has a mass percentage content of 80-95% in the electrolyte.

[0032] In the lithium-ion battery described above, the viscosity of the electrolyte is 0.3~3 cP; and / or,

[0033] The conductivity of the electrolyte is 1~12 mS / cm.

[0034] The lithium-ion battery as described above further includes a separator, the separator comprising a separator substrate and a separator functional layer disposed on at least a portion of the surface of the separator substrate, the separator substrate comprising at least one of PE, PP, and PI, the separator functional layer comprising at least one of Al2O3 and PVDF, and the ratio of the thickness of the separator substrate to the thickness of the separator functional layer being 1 to 16.

[0035] In the lithium-ion battery described above, the thickness of the separator substrate is 5~16 μm; and / or,

[0036] The thickness of the diaphragm functional layer is 1~3μm.

[0037] A second aspect of this application provides an electrical device including the lithium-ion battery of the first aspect.

[0038] The lithium-ion battery of this application includes a positive electrode and a negative electrode. The negative electrode includes a negative electrode material layer, and the negative electrode material layer includes a negative electrode material. The lithium-ion battery satisfies: 0 < (a × b × c / 100) - d < 4; where a is the areal density of the negative electrode, in g / m³. 2 ; b is the compaction density of the negative electrode sheet, in g / cm³. 3 Where c is the particle size gradient distribution coefficient of the negative electrode material; and d is the ratio of the liquid phase diffusion impedance of the negative electrode to that of the positive electrode. This application establishes a balance mechanism for the lithium-ion migration rates of the positive and negative electrodes by mathematically relating the areal density (a), compaction density (b), particle size gradient distribution coefficient (c), and the ratio of the liquid phase diffusion impedance of the negative electrode to that of the positive electrode (d). By limiting the range of values ​​in the mathematical formula, the wettability of the electrolyte is improved, enhancing fast-charging performance, while avoiding side reactions between the negative electrode material and the electrolyte, thus improving cycle performance. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0040] Lithium-ion batteries, as high-energy-density energy storage devices, are widely used in consumer electronics, electric vehicles, and large-scale energy storage systems. However, existing lithium-ion batteries struggle to achieve synergistic optimization of fast-charging and cycle performance in practical applications. The inventors investigated this issue and concluded that the mismatch between the lithium-ion migration capabilities of the positive and negative electrodes is a key factor limiting the battery's fast-charging and cycle performance.

[0041] Furthermore, the inventors believe that the above problems are mainly related to the areal density of the negative electrode, the compaction density of the negative electrode, the particle size gradient distribution coefficient of the negative electrode material, and the ratio of the liquid phase diffusion impedance of the negative electrode to the liquid phase diffusion impedance of the positive electrode. By achieving a dynamic balance relationship in which these four parameters are matched and mutually constrained, it is expected to synergistically improve the fast charging performance and cycle performance of lithium-ion batteries.

[0042] Based on this, this application provides a lithium-ion battery, which includes a positive electrode and a negative electrode. The negative electrode includes a negative electrode material layer, and the negative electrode material layer includes a negative electrode material.

[0043] Lithium-ion batteries satisfy the following condition: 0 < (a × b × c / 100) - d < 4;

[0044] Where 'a' is the areal density of the negative electrode, in g / m³. 2 b represents the compaction density of the negative electrode, in g / cm³. 3 c is the particle size gradient distribution coefficient of the negative electrode material; d is the ratio of the liquid phase diffusion resistance of the negative electrode to the liquid phase diffusion resistance of the positive electrode.

[0045] In the fast charging process of lithium-ion batteries, electrolyte wetting and lithium-ion diffusion are key factors restricting performance improvement. By synergistically controlling four parameters—the areal density and compaction density of the negative electrode, the particle size gradient distribution coefficient of the negative electrode material, and the ratio of the liquid phase diffusion impedance of the negative electrode to that of the positive electrode—an optimized match can be achieved at the physical and electrochemical levels, thereby comprehensively improving wettability, ion transport rate, and interface stability.

[0046] Specifically, the areal density of the negative electrode sheet mainly determines the migration path of lithium ions in the solid phase; the compaction density, while ensuring the compactness of the negative electrode structure, can also retain the necessary pore network, providing sufficient penetration channels for the electrolyte and accelerating overall wetting; the particle size gradient distribution coefficient of the negative electrode material reflects the combination of particles of different sizes, and while changing the electrode compaction density and energy density, it also helps to construct ion transport channels, thus determining the distribution of the electrolyte and the rapid migration kinetics of lithium ions; the ratio of the liquid phase diffusion resistance of the negative electrode sheet to that of the positive electrode sheet is essentially adjusting the balance of liquid phase transport resistance of lithium ions inside the porous electrodes of the positive and negative electrodes.

[0047] During fast charging, battery performance is determined by the synergy of multiple physical fields. By ensuring that 0 < (a × b × c / 100) - d < 4, the capillary wetting rate of the electrolyte and the lithium-ion liquid phase transport rate within the pores during fast charging can be balanced with the lithium-ion insertion rate on the surface of the negative electrode solid phase particles. This ensures that the total number of active sites provided by the macroscopic mass load and microstructural compactness of the negative electrode is precisely matched with the electrolyte's ability to penetrate and supply through optimized pores.

[0048] This matching avoids kinetic imbalances during fast charging. The inventors discovered that if the formula value is too low, it often means poor pore structure or obstructed liquid phase transport, insufficient electrolyte wetting, and an ion supply rate lower than the electron conduction rate, leading to increased local polarization and triggering lithium plating and side reactions. If the formula value is too high, it may mean that the electrode is too thick or too dense, and the migration path of ions in the solid phase is too long, becoming a new rate-limiting step, which also leads to increased polarization and rapid capacity decay.

[0049] Therefore, controlling the above coupling formula within the target range essentially means pre-coordinating the rates of the three key steps—liquid phase transport, solid phase diffusion, and electrochemical reaction—at the electrode design level. This ensures that, under the high current density of fast charging, lithium ions can be rapidly transported to the vicinity of each active particle through a low-resistance, unobstructed liquid phase network and synchronously and uniformly embedded into the particles. This simultaneously improves the lithium ion embedding rate, reduces interfacial side reactions, and achieves synergistic performance optimization.

[0050] During parameter testing, the negative electrode, positive electrode, and negative electrode material can be from any of the following sources:

[0051] The sample obtained directly;

[0052] Components removed from fresh batteries after formation;

[0053] Components disassembled from batteries whose capacity remains between 60% and 98% after cycling.

[0054] In one specific embodiment, 100 ≤ a ≤ 300. Optionally, a can be 100, 125, 150, 175, 200, 225, 250, 275, 300, or any two of the above values. The areal density 'a' of the negative electrode directly affects the diffusion path length of lithium ions in the solid phase. Controlling 'a' within the above range can balance lithium ion transport efficiency and electrode structure stability.

[0055] In one specific embodiment, 1.4 ≤ b ≤ 1.7. Optionally, b can be 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, or any two of the above values. By controlling the compaction density b of the negative electrode within the above range, the electrode porosity can be changed, thereby optimizing the liquid phase diffusion resistance.

[0056] In one specific embodiment, 0.5 ≤ c ≤ 2. Optionally, c can be 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2, or any two of the above values. By controlling the particle size gradient distribution coefficient c of the negative electrode material within the above range, a multi-level porous structure is formed through the gradient design of the main material particle size on the negative electrode surface side and the foil side, thereby maintaining a fast diffusion channel for lithium ions while ensuring high areal density.

[0057] In one specific embodiment, 0.2 ≤ d ≤ 6.2. Optionally, d can be 0.2, 1, 1.8, 2.6, 3.4, 4.2, 5, 6.2, or any two of the above values. By adjusting the ratio d of the liquid phase diffusion impedance of the negative electrode to that of the positive electrode, the transport resistance of lithium ions in the electrolyte is matched with the solid phase diffusion capability, thus avoiding the accumulation of overpotential due to diffusion impedance imbalance.

[0058] Furthermore, 140 ≤ a ≤ 220. Optionally, a can be 140, 160, 180, 200, 220, or any range between two of the above values.

[0059] Furthermore, 1.5 ≤ b ≤ 1.65. Optionally, b can be 1.5, 1.55, 1.6, 1.65, or a range between any two of the above values.

[0060] Furthermore, 0.7 ≤ c ≤ 1.8. Optionally, c can be 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 or a range between any two of the above values.

[0061] Furthermore, 0.7 ≤ d ≤ 2.6. Optionally, d can be 0.7, 1.0, 1.3, 1.6, 1.9, 2.0, 2.6, or a range between any two of the above values.

[0062] By controlling a, b, c, and d within the aforementioned ranges, the capacity retention rate of lithium-ion batteries can be effectively improved. While increasing the areal density of the negative electrode will lengthen the lithium-ion diffusion path, increasing the compaction density can reduce porosity, thereby improving the electrolyte wetting efficiency. Simultaneously, the particle size gradient design of the negative electrode material can form a gradient porosity structure, reducing the diffusion resistance of lithium ions in the electrode thickness direction. Furthermore, adjusting the ratio of the liquid phase diffusion resistance of the negative electrode to that of the positive electrode can prevent overpotential damage to the positive electrode structure.

[0063] Furthermore, the liquid phase diffusion resistance of both the negative electrode and the positive electrode is 0.1 mΩ to 100 Ω. Controlling the liquid phase diffusion resistance of the negative electrode within this range accelerates lithium-ion transport within the negative electrode pores, reduces concentration polarization, improves the capacity retention of the lithium-ion battery under fast charging conditions, and maintains electrode reaction uniformity, reducing stress concentration and uneven consumption of active materials. Similarly, controlling the liquid phase diffusion resistance of the positive electrode within this range promotes uniform lithium-ion insertion / extraction within the positive electrode, reduces localized stress, and improves structural stability.

[0064] It should be noted that the anode material includes the anode active material, which includes at least one of graphite, hard carbon, soft carbon, mesophase carbon microspheres, silicon-based anode materials, and tin-based anode materials. Graphite has good cycle stability, low cost, and good conductivity, making it a widely used anode active material. Hard carbon has high specific capacity (400~500mAh / g) and stable structure, making it suitable for fast charge and discharge. Mesophase carbon microspheres have high compaction density and excellent cycle performance, making them suitable for high-energy-density battery designs. The anode material is coated with amorphous carbon, and the coating thickness is <1nm. Coating the amorphous carbon surface of the anode material and controlling the coating thickness can accelerate the lithium-ion insertion / extraction rate, which is beneficial to improving the fast-charging performance of the battery.

[0065] In one specific embodiment, the porosity of the negative electrode material is 0.05~0.2. Optionally, the porosity of the negative electrode material can be 0.05, 0.1, 0.15, 0.2, or any two of the above values. By controlling the porosity of the negative electrode material within the above range, on the one hand, internal space can be provided to accommodate the huge volume expansion of the negative electrode material during charging and discharging, effectively preventing electrode structure pulverization and significantly improving cycle stability; on the other hand, it can ensure the wetting of the electrolyte and ensure that the active material participates in the reaction.

[0066] It should be noted that the OI value of the anode material is 9~30. Optionally, the OI value of the anode material can be 9, 10, 15, 20, 25, 30, or any two of the above values. The OI value is the orientation index, used to quantify the degree of order in the anode material. An OI value of 9~30 ensures a moderate level of oxygen participation during SEI film formation, avoiding excessive lithium ion consumption that could lead to a decrease in the initial coulombic efficiency, while also maintaining the mechanical stability of the SEI film.

[0067] In addition, the D of the negative electrode material 50 The value is 10~25μm, D 10 The value is 5~20μm, D 90 The diameter is 26~40μm. Optionally, the D of the negative electrode material... 50 D can be 10μm, 15μm, 20μm, 25μm, or any two of the above values. 10 It can be 5μm, 10μm, 15μm, 20μm, or any range between two of the above values, D 90 The particle size can be 26μm, 30μm, 34μm, 38μm, 40μm, or any two of the above values. Through the particle size gradient distribution design, the electrode maintains sufficient pore connectivity even at high areal density, thereby improving the bulk diffusion efficiency of lithium ions.

[0068] It should be added that the negative electrode material also includes a first conductive agent and a first binder. The first conductive agent includes at least one of carbon black, acetylene black, Ketjen black, carbon fiber, and graphene. The first binder includes at least one of styrene-butadiene rubber, sodium carboxymethyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, and polyvinyl fluoride. SP (carbon black) is a nano-sized particle with a high specific surface area and a branched structure, which can form a conductive network of "point-line" contact between active material particles. SBR (styrene-butadiene rubber) is a water-based binder with excellent elasticity and flexibility, which can well adapt to the small volume expansion and contraction of the negative electrode active material during the lithium insertion / delithiation process, maintaining the integrity of the electrode. CMC (sodium carboxymethyl cellulose) serves as a binder with good dispersibility and thixotropy, which can keep the slurry uniform and stable and prevent sedimentation.

[0069] In one specific embodiment, the positive electrode sheet includes a positive electrode active material layer, which includes a positive electrode active material. The positive electrode active material includes a core and a coating layer covering at least a portion of the surface of the core. The core has a chemical composition of LiFe. q Mn x PO4,

[0070] Where 0 < q ≤ 0.5, 0.5 ≤ x ≤ 1, and the coating layer includes at least one of C, Al2O3, MgO, TiO2, and LATP.

[0071] Introducing manganese (Mn) can achieve higher operating voltages, thereby improving the gravimetric and volumetric energy densities of lithium-ion batteries. Introducing iron (Fe) can significantly improve the intrinsic electronic conductivity of the cathode active material and create more pathways for lithium-ion diffusion, which is beneficial for improving the fast-charging performance of lithium-ion batteries.

[0072] Meanwhile, the coating layer forms a protective layer on the surface of the positive electrode active material, which can effectively inhibit the erosion of the positive electrode active material by electrolyte decomposition products. Coating C on the surface of the positive electrode active material can greatly enhance the electron conduction between particles, which is one of the key means to improve the rate performance of lithium-ion batteries. As a coating element, Al's oxide Al2O3 can strongly anchor the surface Mn-O bonds, effectively inhibiting the dissolution of Mn and lattice distortion, thereby significantly improving the cycle stability of lithium-ion batteries at high temperatures.

[0073] Furthermore, the thickness of the coating layer covering at least a portion of the core surface is <1 nm, and the mass percentage of this coating layer in the positive electrode active material is <5%. Controlling the thickness of this coating layer within this range ensures electronic conductivity while preventing excessive coating that could lead to an extended lithium-ion diffusion path. Maintaining a mass percentage of <5% in the positive electrode active material helps preserve the overall mass energy density and volumetric energy density of the electrode material.

[0074] Furthermore, the porosity of the positive electrode active material is 0.02~0.2. Optionally, the porosity of the positive electrode active material can be 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, or any two of the above values. A porosity design of 0.02~0.2 means that the positive electrode active material particles can be closely packed, achieving a high electrode compaction density after electrode rolling, which directly determines the volumetric energy density of the lithium-ion battery. In addition, this porosity design ensures rapid lithium-ion replenishment at high rates, avoiding capacity reduction and voltage polarization caused by slow ion diffusion.

[0075] In addition, the D of the positive electrode active material 50 The diameter is 0.8~6μm. Optionally, the D of the positive electrode active material... 50 The value can be 0.8 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, or any two of the above values. This is achieved by adjusting the D of the positive electrode active material. 50 By controlling the lithium-ion solid-state diffusion path within the above range, the rate performance can be improved.

[0076] This application does not limit the second conductive agent and the second binder in the positive electrode active material layer. In one specific embodiment, the second conductive agent includes at least one of carbon black, carbon nanotubes, acetylene black, Ketjen black, carbon fiber, and graphene, and the second binder includes at least one of polyvinylidene fluoride, polyurethane, polytetrafluoroethylene, polyethylene, and polypropylene. CNTs (carbon nanotubes), as the second conductive agent, have an extremely high aspect ratio, allowing them to penetrate multiple active material particles to form a "long-range, three-dimensional conductive framework," significantly improving the electronic conductivity and mechanical toughness of the electrode. PVDF (polyvinylidene fluoride) provides sufficient bonding force and has a certain degree of elasticity to accommodate the small volume changes of the active material during charging and discharging. Furthermore, it is very stable in high-potential environments and organic electrolyte environments, and is not easily oxidized or decomposed.

[0077] In one specific embodiment, the lithium-ion battery further includes an electrolyte, which comprises a lithium salt, an additive, and a solvent. The lithium salt includes at least one selected from LiPF6, LiBF4, and LiFSI; the additive includes at least one selected from VC and FEC; and the solvent includes at least one selected from EC, EMC, and DEC. In the electrolyte system, the lithium salt provides high ionic conductivity, the additive forms a stable SEI film on the negative electrode surface, and the solvent reduces the viscosity of the electrolyte, thereby improving the transport efficiency of lithium ions in the liquid phase.

[0078] LiPF6, as a lithium salt, exhibits excellent ionic conductivity balance in organic carbonate solvents and forms a stable passivation film on the aluminum current collector surface to prevent corrosion. VC (ethylene carbonate), as an additive, forms a flexible and dense SEI film on the negative electrode surface, effectively inhibiting the continuous decomposition of the electrolyte and significantly improving the cycle life of lithium-ion batteries. FEC (fluoroethylene carbonate) participates in the formation of a stable, LiF-containing SEI film; the LiF component facilitates rapid lithium-ion transport and provides high mechanical strength.

[0079] Ethylene carbonate (EC) can effectively dissociate lithium salts, providing a high lithium-ion concentration. Furthermore, it can preferentially reduce and decompose on the negative electrode surface, forming a dense and stable solid electrolyte interface film. Eethyl methyl carbonate (EMC) and diethyl carbonate (DEC) primarily reduce the overall viscosity of the electrolyte, increasing the migration rate of lithium ions, thereby improving the rate performance and low-temperature performance of lithium-ion batteries. Simultaneously, when mixed with EC, they lower the freezing point of the electrolyte, widening the operating temperature range.

[0080] Furthermore, the solvents include EC, EMC, and DEC, and the mass ratio of EC, EMC, and DEC is 10~40:10~40:10~40. This mass ratio design can reduce the adsorption energy of solvent molecules on the electrode surface, thereby reducing interfacial impedance.

[0081] Furthermore, the lithium salt content in the electrolyte is 5-15% by mass, the additive content is 0.5-5% by mass, and the solvent content is 80-95% by mass. Controlling the lithium salt content within these ranges provides sufficient free lithium ions while maintaining an optimal balance between ion association and electrolyte viscosity, resulting in the highest ionic conductivity. This is the physical basis for supporting fast charging and discharging and ensuring battery power output. By adjusting the proportion of additives, a dense and stable solid electrolyte interface film can be formed, completely covering the positive and negative electrode surfaces. The solvent ensures the dissolution and uniform distribution of lithium salts and additives, provides a site for lithium ion solvation and desolvation, and directly determines the physicochemical properties of the electrolyte, such as viscosity, boiling point, freezing point, and dielectric constant.

[0082] It should be added that the viscosity of the electrolyte is 0.3~3 cP. Optionally, the viscosity of the electrolyte can be 0.3 cP, 0.9 cP, 1.5 cP, 2.1 cP, 2.7 cP, 3 cP, or any two of the above values. Viscosity is very sensitive to temperature, reflecting the internal frictional resistance of the electrolyte as a fluid. Controlling the viscosity of the electrolyte within the above range can ensure the wetting of the active material particles and guarantee sufficient ion migration ability at low temperatures.

[0083] Furthermore, the conductivity of the electrolyte is 1~12 mS / cm. Optionally, the conductivity of the electrolyte can be 1 mS / cm, 3 mS / cm, 6 mS / cm, 9 mS / cm, 12 mS / cm, or any two of the above values. Conductivity directly measures the electrolyte's ability to conduct current; it comprehensively reflects the lithium-ion concentration and ion migration rate. Controlling the electrolyte conductivity within the above range allows for the instantaneous delivery of large currents and effective power output.

[0084] In one specific embodiment, the lithium-ion battery further includes a separator, which comprises a separator substrate and a separator functional layer disposed on at least a portion of the surface of the separator substrate. The separator substrate includes at least one of PE, PP, and PI, and the separator functional layer includes at least one of Al2O3 and PVDF. The ratio of the thickness of the separator substrate to the thickness of the separator functional layer is 1 to 16. In the separator system, the separator substrate is the skeleton of the separator, mainly providing electrical insulation, mechanical strength, and basic thermal shut-off characteristics. The separator functional layer refers to a functional layer coated on one or both sides of the substrate, designed to address inherent defects in the substrate and improve overall performance.

[0085] Al2O3 has a high melting point, and as a functional layer in a separator, it can significantly improve the separator's resistance to heat shrinkage. Even if the substrate melts at high temperatures, the Al2O3 ceramic layer can maintain its skeletal structure, preventing large-area contact between positive and negative electrodes and resisting thermal runaway. PVDF (polyvinylidene fluoride) has good affinity for electrodes and electrolytes. During battery filling or cycling, the PVDF layer can partially swell or dissolve, forming a bond with the electrode, reducing interfacial impedance, and suppressing interfacial separation caused by electrode expansion.

[0086] It should be added that the thickness of the membrane substrate is 5~16μm. The thickness of the membrane substrate is the core of the trade-off between safety and energy density. Controlling the thickness of the membrane substrate within the above range can improve the volumetric energy density and reduce ion transport resistance.

[0087] Furthermore, the thickness of the membrane functional layer is 1~3μm. The thickness of the membrane functional layer determines the strength of the additional functions. Controlling the thickness of the membrane functional layer within the above range can provide basic wettability improvement and slight adhesion and thermal stability.

[0088] This application also provides a method for preparing the above-mentioned lithium-ion battery, comprising the following steps:

[0089] The above-mentioned positive electrode sheet, separator, and negative electrode sheet are wound to obtain a bare cell. The bare cell is placed in an outer packaging foil, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, shaping, and sorting, a lithium-ion battery is obtained.

[0090] In the specific preparation of the positive electrode sheet, for example, the above-mentioned positive electrode active material can be uniformly mixed with the positive electrode conductive agent and the positive electrode binder, and dispersed in N-methylpyrrolidone (NMP) to obtain a positive electrode slurry; the positive electrode slurry is coated on aluminum foil and dried in a vacuum furnace; then rolled and cut to obtain the positive electrode sheet. In one specific embodiment, the positive electrode active layer comprises, by weight percentage, 70-99 wt% of positive electrode active material, 0.5-15 wt% of positive electrode conductive agent, and 0.5-15 wt% of positive electrode binder; more specifically, it comprises 80-98 wt% of positive electrode active material, 1-10 wt% of positive electrode conductive agent, and 1-10 wt% of positive electrode binder. Furthermore, the drying temperature is 80-120°C.

[0091] In the specific preparation of the negative electrode sheet, for example, the aforementioned negative electrode active material can be uniformly mixed with the negative electrode conductive agent and the negative electrode binder, and dispersed in deionized water to obtain a negative electrode slurry; the negative electrode slurry is then coated onto copper foil and dried in a vacuum furnace; subsequently, it is rolled and cut to obtain the negative electrode sheet. In one specific embodiment, the negative electrode active layer comprises, by mass percentage, 70-99 wt% of the negative electrode active material, 0.5-15 wt% of the negative electrode conductive agent, and 0.5-15 wt% of the negative electrode binder; more specifically, it comprises 80-98 wt% of the negative electrode active material, 1-10 wt% of the negative electrode conductive agent, and 1-10 wt% of the negative electrode binder. Furthermore, the drying temperature is 80-120°C.

[0092] In the specific preparation of the electrolyte, for example, the lithium salt and additives mentioned above can be dissolved in a solvent to obtain the electrolyte. In one specific embodiment, the concentration of the lithium salt is 0.7~1.5 mol / L.

[0093] It should be noted that the formation temperature is 45℃, and the formation steps are: 0.01~0.05C to 10% SOC, 0.02~0.1C to 20% SOC, 0.05~0.2C to 50% SOC, and 0.1~1C to 100% SOC.

[0094] This application also provides an electrical device including the aforementioned lithium-ion battery. The term "electrical device" broadly refers to various devices or systems that rely on electrical energy for operation, particularly including mobile or stationary equipment that uses electricity as a power source for all or part of its operation. Exemplarily, the device can be a transportation vehicle, such as a conventional internal combustion engine vehicle, a gas-powered vehicle, or a vehicle driven by new energy sources, wherein new energy vehicles can further include pure electric vehicles, hybrid vehicles, range-extended electric vehicles, etc.

[0095] Besides vehicles, this electrical equipment can also encompass other terminal products that rely on energy storage devices for operation, such as communication terminals (e.g., mobile phones), portable computing devices (e.g., tablets and laptops), consumer electronics (e.g., digital media players, electric toys), work tools (e.g., power tools), and various vehicles (e.g., electric ships, drones). Furthermore, in the aerospace field, this equipment can also include aircraft, launch vehicles, spacecraft, and other devices that require high-energy-density power systems.

[0096] By adopting the lithium-ion battery provided in this application, the above-mentioned electrical equipment can achieve significant improvements in cycle performance and fast charging performance, which is conducive to improving the overall performance and reliability of the equipment and is suitable for diversified application scenarios with high requirements for power systems.

[0097] The present application will be further described below through specific embodiments.

[0098] Example 1

[0099] The method for preparing a lithium-ion battery in this embodiment includes the following steps:

[0100] 1) Preparation of positive electrode sheet: The positive electrode active material, SP, CNT and PVDF are mixed evenly in a mass ratio of 97:1:0.5:1.5 and dispersed in NMP to obtain positive electrode slurry; the positive electrode slurry is coated on aluminum foil and dried in a vacuum furnace at 100°C; then rolled and cut to obtain positive electrode sheet;

[0101] The positive electrode active material includes a core and a coating layer covering at least a portion of the surface of the core. The core has a chemical composition of LiFe. 0.4 Mn 0.6 PO4, with a C coating layer of 0.5 nm thickness, the coating layer accounts for 3% of the mass of the positive electrode active material, and the porosity of the positive electrode active material is 0.2. D 50 It is 1.5μm;

[0102] 2) Preparation of negative electrode sheet: Graphite, SP and CMC are mixed evenly in a mass ratio of 96.4:1:2.6 and dispersed in deionized water to obtain negative electrode slurry; the negative electrode slurry is coated on copper foil and dried in a vacuum furnace at 100°C; then it is rolled and cut to obtain negative electrode sheet;

[0103] The coating amount of the negative electrode paste on the copper foil is 0.115g / 1257mm. 2 The rolling pressure is 2500 kgf; the D of the negative electrode material used on the surface of the negative electrode sheet and 1 μm away from the copper foil is... 50 The particle size ratio is 1;

[0104] 3) Preparation of electrolyte: EC, EMC and DEC are mixed in a mass ratio of 1:1:1 to obtain a solvent, and then LiPF6, VC and FEC are dissolved in the solvent to obtain the electrolyte;

[0105] The electrolyte contains 12% LiPF6, 0.5% VC, 0.5% FEC, and 87% solvent.

[0106] The electrolyte has a viscosity of 1.2 cP and a conductivity of 6 mS / cm.

[0107] 4) Assembly and formation: The positive electrode, separator and negative electrode are wound to obtain the bare cell; the bare cell is placed in the outer packaging foil, dried and injected with electrolyte, and then subjected to vacuum sealing, standing, formation, shaping and sorting processes to obtain the lithium-ion battery;

[0108] The membrane substrate is PE with a thickness of 12μm, the membrane functional layer is Al2O3 with a thickness of 2μm, the formation temperature is 45℃, and the formation steps are: 0.02C to 10%SOC, 0.05C to 20%SOC, 0.1C to 50%SOC, and 0.2C to 100%SOC.

[0109] Example 2

[0110] The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2), the coating amount of the negative electrode paste on the copper foil is 0.112 g / 1257 mm. 2 The rolling pressure in step 2) is 2800 kgf; the D of the negative electrode material used on the surface of the negative electrode sheet and 1 μm away from the copper foil in step 2) is... 50 The particle size ratio is 1.2; the conductivity of the electrolyte in step 3) is 6.8 mS / cm.

[0111] Example 3

[0112] The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2), the coating amount of the negative electrode paste on the copper foil is 0.188g / 1257mm. 2 The rolling pressure in step 2) is 2100 kgf; the D of the negative electrode material used on the surface of the negative electrode sheet and 1 μm away from the copper foil in step 2) is... 50 The particle size ratio is 0.5; the conductivity of the electrolyte in step 3) is 6.5 mS / cm.

[0113] Example 4

[0114] The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2), the coating amount of the negative electrode paste on the copper foil is 0.156g / 1257mm. 2 The rolling pressure in step 2) is 3000 kgf; the D of the negative electrode material used on the surface of the negative electrode sheet and 1 μm away from the copper foil in step 2) is... 50 The particle size ratio is 2; the conductivity of the electrolyte in step 3) is 11 mS / cm.

[0115] Example 5

[0116] The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2), the coating amount of the negative electrode paste on the copper foil is 0.113g / 1257mm. 2 The rolling pressure in step 2) is 2300 kgf; the D of the negative electrode material used on the surface of the negative electrode sheet and 1 μm away from the copper foil in step 2) is... 50 The particle size ratio is 1.5; the conductivity of the electrolyte in step 3) is 9 mS / cm.

[0117] Example 6

[0118] The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2), the coating amount of the negative electrode paste on the copper foil is 0.156g / 1257mm. 2 The rolling pressure in step 2) is 2650 kgf; the D of the negative electrode material used on the surface of the negative electrode sheet and 1 μm away from the copper foil in step 2) is... 50 The particle size ratio is 1.4; the conductivity of the electrolyte in step 3) is 10.2 mS / cm.

[0119] Example 7

[0120] The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2), the coating amount of the negative electrode paste on the copper foil is 0.176 g / 1257 mm. 2 The rolling pressure in step 2) is 2950 kgf; the D of the negative electrode material used on the surface of the negative electrode sheet and 1 μm away from the copper foil in step 2) is... 50 The particle size ratio is 0.6; the conductivity of the electrolyte in step 3) is 5.4 mS / cm.

[0121] Example 8

[0122] The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2), the coating amount of the negative electrode paste on the copper foil is 0.174 g / 1257 mm. 2 The rolling pressure in step 2) is 2700 kgf; the D of the negative electrode material used on the surface of the negative electrode sheet and 1 μm away from the copper foil in step 2) 50The particle size ratio is 1.8; the conductivity of the electrolyte in step 3) is 10.6 mS / cm.

[0123] Example 9

[0124] The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2), the coating amount of the negative electrode paste on the copper foil is 0.095g / 1257mm. 2 The rolling pressure in step 2) is 2950 kgf; the D of the negative electrode material used on the surface of the negative electrode sheet and 1 μm away from the copper foil in step 2) is... 50 The particle size ratio is 1.7; the conductivity of the electrolyte in step 3) is 5 mS / cm.

[0125] Example 10

[0126] The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2), the coating amount of the negative electrode paste on the copper foil is 0.185g / 1257mm. 2 The rolling pressure in step 2) is 2980 kgf; the D of the negative electrode material used on the surface of the negative electrode sheet and 1 μm away from the copper foil in step 2) is... 50 The particle size ratio is 1.5; the conductivity of the electrolyte in step 3) is 10 mS / cm.

[0127] Example 11

[0128] The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2), the coating amount of the negative electrode paste on the copper foil is 0.154 g / 1257 mm. 2 The rolling pressure in step 2) is 2960 kgf; the D of the negative electrode material used on the surface of the negative electrode sheet and 1 μm away from the copper foil in step 2) is... 50 The particle size ratio is 1.5; the conductivity of the electrolyte in step 3) is 8.5 mS / cm.

[0129] Example 12

[0130] The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2), the coating amount of the negative electrode paste on the copper foil is 0.156g / 1257mm. 2 The rolling pressure in step 2) is 2400 kgf; the D of the negative electrode material used on the surface of the negative electrode sheet and 1 μm away from the copper foil in step 2) is... 50 The particle size ratio is 2; the conductivity of the electrolyte in step 3) is 8.8 mS / cm.

[0131] Comparative Example 1

[0132] The preparation method of this comparative example is basically the same as that of Example 1, except that in step 2), the coating amount of the negative electrode paste on the copper foil is 0.188 g / 1257 mm. 2 In step 2), the D of the negative electrode material used on the surface of the negative electrode sheet and at a distance of 1 μm from the copper foil 50 The particle size ratio is 1.2; the conductivity of the electrolyte in step 3) is 8.6 mS / cm.

[0133] Comparative Example 2

[0134] The preparation method of this comparative example is basically the same as that of Example 1, except that in step 2), the coating amount of the negative electrode paste on the copper foil is 0.174 g / 1257 mm. 2 The rolling pressure in step 2) is 2800 kgf; the D of the negative electrode material used on the surface of the negative electrode sheet and 1 μm away from the copper foil in step 2) is... 50 The particle size ratio is 1.8; the conductivity of the electrolyte in step 3) is 9.5 mS / cm.

[0135] Comparative Example 3

[0136] The preparation method of this comparative example is basically the same as that of Example 1, except that in step 2), the coating amount of the negative electrode paste on the copper foil is 0.188 g / 1257 mm. 2 The rolling pressure in step 2) is 3000 kgf; the D of the negative electrode material used on the surface of the negative electrode sheet and 1 μm away from the copper foil in step 2) is... 50 The particle size ratio is 1.9; the conductivity of the electrolyte in step 3) is 10.9 mS / cm.

[0137] Experimental Example 1

[0138] The areal density (a), compaction density (b), particle size gradient distribution coefficient (c), ratio of liquid phase diffusion resistance of negative electrode to liquid phase diffusion resistance of positive electrode (d), porosity and OI value of negative electrode material were tested for all embodiments and comparative examples. The negative electrode, positive electrode and negative electrode material were components disassembled from fresh batteries after formation. The results are shown in Table 1.

[0139] The areal density 'a' of the negative electrode: A negative electrode is punched into a 1cm diameter disc, dried, and its mass is m1; the undried 1cm disc is washed with water to remove electrode components, yielding a current collector foil, which is then dried and weighed to obtain m2; a (g / m 2 = (m1-m2) / area of ​​the circle.

[0140] The compaction density b of the negative electrode: The areal density a is obtained using the above testing method. The negative electrode thickness d1 and the foil thickness d2 are obtained using a micrometer. b (g / cm²) 3 = a / (d1-d2).

[0141] The particle size gradient distribution coefficient c of the negative electrode material: The negative electrode sheet is punched into a disc with a diameter of 1 cm. The electrode material is dispersed with water, the foil is removed, and the particle size distribution coefficient c is obtained using a Malvern particle size analyzer. 50 D 10 and D 90 c=(D 90 -D 10 ) / D 50 .

[0142] Liquid phase diffusion impedance of the negative electrode and the positive electrode: The impedance spectra of the positive and negative electrodes of the three-electrode battery were measured using an electrochemical impedance spectroscopy (EIS) with a bias voltage of 0.5V and a frequency range of 0.01~10^6Hz. The frequency f and the real part of the impedance Z' were obtained. The frequency range of 0~0.01Hz in f and the corresponding real part of the impedance were processed. Z' = Warburg coefficient × (2pi × f)^(-0.5), where the slope of the linear part is the Warburg coefficient. The Warburg coefficient of the positive electrode is w1 and the Warburg coefficient of the negative electrode is w2. w1 is the liquid phase diffusion impedance of the positive electrode and w2 is the liquid phase diffusion impedance of the negative electrode.

[0143] The ratio of the liquid phase diffusion resistance of the negative electrode to that of the positive electrode is d: d = w2 / w1.

[0144] Porosity of negative electrode material: Porosity of negative electrode material = (1-(ρ)) / (ρ) bulk / ρ true ))×100%, where ρ bulk It is the compaction density of the negative electrode material, ρ true It is the true density of the negative electrode material (tested using the gas specific gravity bottle method).

[0145] OI value of negative electrode material: The negative electrode material was scanned using an X-ray diffractometer in θ-2θ symmetric scanning mode; the diffraction intensity of the (002) crystal plane in the normal direction and the plane direction was measured using an accessory, and OI=I(002) / I(110).

[0146] Table 1

[0147]

[0148] Experimental Example 2

[0149] The cycle performance of the lithium-ion batteries in all examples and comparative examples was tested. At 25°C, the batteries were charged at a constant current of 1C to 4.25V, then charged at a constant voltage of 4.25V until the current dropped to 0.05C, and then discharged at a rate of 1C to 2.5V. This charge-discharge cycle was repeated 500 times. The discharge capacity Q1 at the first cycle and the discharge capacity Q at the 500th cycle were measured. 500 Capacity retention rate Q = Q 500 / Q1×100%, the results are shown in Table 2.

[0150] Table 2

[0151]

[0152] As shown in Table 2, the lithium-ion battery of this application has excellent cycle performance.

[0153] Experimental Example 3

[0154] The fast-charging performance of the lithium-ion batteries in all embodiments and comparative examples was tested. A three-electrode battery was used, charged at a constant current of 0.33C to 4.30V, then charged at a constant voltage of 4.30V until the current dropped to 0.05C, and then discharged at a rate of 0.33C to 3.0V. This charge-discharge cycle was repeated three times. Based on the battery's third discharge capacity, the current was set to 0.33C to charge to 10% SOC. A step-by-step charging method was then employed: a larger current was used at low SOC, and the charging current was reduced at high SOC, with the current decreasing sequentially from 5C, 4.8C, and 4.6C to 0.33C. The charging rate was reduced when the negative parameter of the three-electrode battery dropped to 5mV. The test temperature was 25±2℃. The results are shown in Table 3.

[0155] Table 3

[0156]

[0157] As shown in Table 3, the lithium-ion battery of this application has excellent fast charging performance.

[0158] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode and a negative electrode, the negative electrode includes a negative electrode material layer, and the negative electrode material layer includes a negative electrode material; The lithium-ion battery satisfies: 0 < (a × b × c / 100) - d < 4; Wherein, 'a' represents the areal density of the negative electrode, in g / m³. 2 ; b is the compaction density of the negative electrode sheet, in g / cm³. 3 ; c is the particle size gradient distribution coefficient of the negative electrode material; d is the ratio of the liquid phase diffusion resistance of the negative electrode to the liquid phase diffusion resistance of the positive electrode.

2. The lithium-ion battery according to claim 1, characterized in that, 100≤a≤300; and / or, 1.4 ≤ b ≤ 1.7; and / or, 0.5≤c≤2; and / or, 0.2≤d≤6.2。 3. The lithium-ion battery according to claim 1 or 2, characterized in that, 140≤a≤220; and / or, 1.5 ≤ b ≤ 1.65; and / or, 0.7≤c≤1.8 and / or, 0.7≤d≤2.6。 4. The lithium-ion battery according to claim 1 or 2, characterized in that, The liquid phase diffusion resistance of the negative electrode is 0.1mΩ~100Ω, and the liquid phase diffusion resistance of the positive electrode is 0.1mΩ~100Ω.

5. The lithium-ion battery according to claim 1 or 2, characterized in that, The negative electrode material includes a negative electrode active material, which includes at least one of graphite, hard carbon, soft carbon, mesophase carbon microspheres, silicon-based negative electrode material, and tin-based negative electrode material.

6. The lithium-ion battery according to claim 1 or 2, characterized in that, The porosity of the negative electrode material is 0.05~0.2; and / or, The OI value of the negative electrode material is 9~30.

7. The lithium-ion battery according to claim 1 or 2, characterized in that, The negative electrode material D 50 The value is 10~25μm, D 10 The value is 5~20μm, D 90 It is 26~40μm.

8. The lithium-ion battery according to claim 5, characterized in that, The negative electrode material further includes a first conductive agent and a first binder. The first conductive agent includes at least one of carbon black, acetylene black, Ketjen black, carbon fiber, and graphene. The first binder includes at least one of styrene-butadiene rubber, sodium carboxymethyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, and polyvinyl fluoride.

9. The lithium-ion battery according to claim 1 or 2, characterized in that, The positive electrode sheet includes a positive electrode active material layer, which includes a positive electrode active material. The positive electrode active material includes a core and a coating layer covering at least a portion of the surface of the core. The core has a chemical composition of LiFe. q Mn x PO4, Wherein, 0 < q ≤ 0.5, 0.5 ≤ x ≤ 1, and the coating layer includes at least one of C, Al2O3, MgO, TiO2, and LATP.

10. The lithium-ion battery according to claim 9, characterized in that, The thickness of the coating layer is <1 nm, and the mass percentage of the coating layer in the positive electrode active material is <5%.

11. The lithium-ion battery according to claim 9, characterized in that, The porosity of the positive electrode active material is 0.02~0.2; and / or, The positive electrode active material D 50 The range is 0.8~6μm.

12. The lithium-ion battery according to claim 9, characterized in that, The positive electrode active material layer further includes a second conductive agent and a second binder. The second conductive agent includes at least one of carbon black, carbon nanotubes, acetylene black, Ketjen black, carbon fiber, and graphene. The second binder includes at least one of polyvinylidene fluoride, polyurethane, polytetrafluoroethylene, polyethylene, and polypropylene.

13. The lithium-ion battery according to claim 1 or 2, characterized in that, The lithium-ion battery further includes an electrolyte, which comprises a lithium salt, an additive, and a solvent. The lithium salt includes at least one of LiPF6, LiBF4, and LiFSI. The additive includes at least one of VC and FEC. The solvent includes at least one of EC, EMC, and DEC.

14. The lithium-ion battery according to claim 13, characterized in that, The solvent includes EC, EMC and DEC, and the mass ratio of EC, EMC and DEC is 10~40:10~40:10~40.

15. The lithium-ion battery according to claim 13, characterized in that, The lithium salt has a mass percentage content of 5-15% in the electrolyte, the additive has a mass percentage content of 0.5-5% in the electrolyte, and the solvent has a mass percentage content of 80-95% in the electrolyte.

16. The lithium-ion battery according to claim 13, characterized in that, The viscosity of the electrolyte is 0.3~3 cP; and / or, The conductivity of the electrolyte is 1~12 mS / cm.

17. The lithium-ion battery according to claim 1 or 2, characterized in that, The lithium-ion battery further includes a separator, which includes a separator substrate and a separator functional layer disposed on at least a portion of the surface of the separator substrate. The separator substrate includes at least one of PE, PP, and PI, and the separator functional layer includes at least one of Al2O3 and PVDF. The ratio of the thickness of the separator substrate to the thickness of the separator functional layer is 1 to 16.

18. The lithium-ion battery according to claim 17, characterized in that, The thickness of the diaphragm substrate is 5~16μm; and / or, The thickness of the diaphragm functional layer is 1~3μm.

19. An electrical appliance, characterized in that, Including the lithium-ion battery according to any one of claims 1-18.

Images