Positive active slurry of lithium ion battery, positive pole piece and lithium ion battery

Abstract

The invention provides lithium ion battery positive active slurry, a positive pole piece and a lithium ion battery, and relates to the field of batteries. The positive active slurry comprises the following raw materials: an LMFP positive active material, a conductive agent, a binder, a lithium supplement agent, a lithium supplement auxiliary agent and a solvent; the lithium supplement agent comprises at least one of lithium-rich transition metal oxide and lithium sulfide. According to the lithium ion battery positive electrode slurry provided by the invention, a positive electrode material can keep a stable crystal structure in a circulation process, and the dissolution amount of manganese ions is remarkably reduced. And the reversibility of the electrode reaction is maintained by continuous supplement of the active lithium, and capacity fading is inhibited. The optimization of the conductive network reduces the occurrence probability of interface side reactions, and protects the integrity of the solid electrolyte interface.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to a lithium-ion battery positive electrode active slurry, a positive electrode sheet and a lithium-ion battery. Background Art

[0002] Lithium manganese iron phosphate (LiMn x Fe 1-x As a new generation of lithium-ion battery cathode materials, lithium iron phosphate (LMFP) combines the high safety and high voltage platform advantages of lithium iron phosphate (LFP), making it an ideal choice for increasing battery energy density. However, LMFP is prone to manganese ion dissolution during long-term cycling, a technical bottleneck that has seriously restricted its commercial application.

[0003] The source of manganese dissolution is Mn in the crystal structure of the material. 3 + Jahn-Teller distortion and disproportionation reaction in acidic electrolyte (2Mn 3+ →Mn 2+ Mn 4+ ), resulting in Mn 2+ This process triggers multiple negative effects: 1) loss of positive electrode active material leading to rapid capacity decay; 2) dissolved Mn 2+ Migrate to the negative electrode to cause reduction deposition, destroy the solid electrolyte interface (SEI film) and catalyze the growth of lithium dendrites, causing the risk of thermal runaway; 3) Free manganese ions intensify the decomposition of the electrolyte and increase the internal resistance of the battery.

[0004] Existing methods to inhibit manganese dissolution mainly include surface coating (such as carbon layer, metal oxide) and bulk doping (Al, Mg, etc.). However, traditional coatings are prone to cracking and failure due to interface stress, while bulk doping can stabilize the lattice but sacrifice the material specific capacity. In addition, although electrolyte additives can partially complex Mn 2+ However, this will introduce side reactions and increase costs. Therefore, it is urgent to develop a method for inhibiting manganese dissolution that takes into account the material structure stability, electrochemical performance and economy. Summary of the Invention

[0005] The purpose of this application is to provide a lithium-ion battery positive electrode active slurry, a positive electrode sheet and a lithium-ion battery to solve the above problems.

[0006] To achieve the above objectives, this application adopts the following technical solutions:

[0007] The present application provides a positive electrode active slurry for lithium-ion batteries, wherein the raw materials of the positive electrode active slurry include: LMFP positive electrode active material, conductive agent, binder, lithium replenisher, lithium replenishing auxiliary agent, and solvent;

[0008] The lithium supplement comprises at least one of lithium-rich transition metal oxides and lithium sulfides.

[0009] Optionally, the lithium-rich transition metal oxide includes at least one of Li5FeO4 and Li2NiO2.

[0010] Optionally, the lithium sulfide includes Li2S.

[0011] Optionally, the lithium supplementing agent includes ZrO2.

[0012] Optionally, the ratio of the lithium-rich transition metal oxide to the lithium sulfide is 1:2-4.

[0013] Optionally, the amount of the lithium supplement agent is 1-5 wt % of the positive electrode active material.

[0014] Optionally, the amount of the lithium supplementing agent used is 1-4 wt% of the mass of the lithium supplementing agent.

[0015] Optionally, the usage ratio of the LMFP positive electrode active material, the conductive agent, the binder, and the lithium supplement agent is 90-94:2-5:1-4:2-5.

[0016] Optionally, the conductive agent includes Super P.

[0017] Optionally, the binder comprises PVDF.

[0018] Optionally, the solvent comprises NMP.

[0019] The present application also provides a lithium-ion battery positive electrode plate, which includes a positive electrode collector and a positive electrode active layer; the positive electrode collector includes aluminum foil; and the raw material of the positive electrode active layer is the lithium-ion battery positive electrode active slurry.

[0020] Optionally, the compaction density of the positive electrode active layer is 2.1-2.4 g / cm 3 .

[0021] The present application also provides a lithium-ion battery, wherein the raw materials of the lithium-ion battery include the lithium-ion battery positive electrode sheet.

[0022] Optionally, the raw materials of the lithium-ion battery further include a graphite negative electrode, a Celgard 2400 separator, and an electrolyte;

[0023] The electrolyte includes a first solution, an additive, and a lithium salt complexing agent;

[0024] The solute of the first solution includes LiPF6; the solvent includes EC, EMC, and DMC; the volume ratio of the EC, the EMC, and the DMC is 2-4:4-6:1-4; Li in the first solution + The concentration is 1.2 mol / L;

[0025] The additive includes FEC, and the amount of the additive added is 1-4 wt% of the mass of the first solution;

[0026] The lithium salt complexing agent includes LiBOB, and the addition amount of the lithium salt complexing agent is 0.1-0.8 wt % of the mass of the first solution.

[0027] Compared with the prior art, the advantages of this application include:

[0028] The positive electrode active material provided in this application acts as the main body for lithium ion deintercalation and extraction, and the stability of its crystal structure directly affects the degree of manganese dissolution. The lithium supplement works through a dual mechanism: on the one hand, the lithium-rich transition metal oxide gradually releases lithium ions during the charge and discharge process, continuously filling lithium vacancies to alleviate lattice distortion; on the other hand, the sulfur atoms in the lithium sulfide fix the transition metal ions through strong electronegativity, inhibiting the dissolution of Mn. 3+ Disproportionation reaction. Conductive carbon black forms a three-dimensional network structure, reducing charge transfer impedance and avoiding abnormal fluctuations in manganese valence caused by local overpotential. The positive electrode material maintains a stable crystal structure during the cycle, significantly reducing the amount of manganese ion dissolution. The continuous replenishment of active lithium maintains the reversibility of the electrode reaction and inhibits capacity decay. The optimization of the conductive network reduces the probability of interfacial side reactions and protects the integrity of the solid electrolyte interface. The synergistic effect of each component improves the battery cycle stability and safety while ensuring high energy density.

[0029] The positive electrode sheet provided in this application can effectively inhibit the structural degradation of the positive electrode material during cycling, reducing the probability of manganese ions detaching from the crystal lattice. The stable interface layer formed on the electrode surface reduces electrolyte erosion of the active material, thus controlling the risk of SEI film damage and lithium dendrite growth caused by manganese dissolution, thereby improving both battery cycle life and safety performance.

[0030] The lithium-ion battery provided in this application has excellent battery cycle life and safety performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0032] Figure 11 is a comparison chart of the capacity retention rate and recovery rate of the batteries of Example 1 and Comparative Example 1 after storage at 60° C. for 7 days;

[0033] Figure 2 This is a comparison chart of the capacity retention of Example 1 and Comparative Example 1 at 45°C and 1C / 1C cycles after 500 cycles;

[0034] Figure 3 This is a comparison chart of the ICP test results of manganese dissolution from the negative electrode sheets after cycling of Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0035] As used herein:

[0036] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0037] The conjunction "consisting of" excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed, excluding materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim, rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0038] When an amount, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed alone. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including the range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0039] In these examples, parts and percentages are by mass unless otherwise indicated.

[0040] "Parts by mass" refers to the basic unit of measurement used to express the mass ratio of multiple components. One part can represent any unit of mass, such as 1g or 2.689g. If we say that the mass of component A is a parts and the mass of component B is b parts, this means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, we could say that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number representing a multiplication factor). It's important to note that, unlike parts by mass, the sum of the mass of all components is not limited to 100 parts.

[0041] "And / or" is used to indicate that one or both of the stated situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0042] In order to better explain the technical solution provided by this application, an overall statement of the technical solution is first made before the specific implementation method.

[0043] In a first aspect, the present application provides a positive electrode active slurry for a lithium-ion battery, wherein the raw materials of the positive electrode active slurry include: LMFP positive electrode active material, conductive agent, binder, lithium replenisher, lithium replenishing auxiliary agent, and solvent;

[0044] The lithium supplement comprises at least one of lithium-rich transition metal oxides and lithium sulfides.

[0045] This application focuses on how to achieve material self-stabilization through optimization of positive electrode slurry components. For the manganese dissolution mechanism, it is necessary to work synergistically from three levels: lithium vacancy compensation, transition metal valence regulation, and interface protection. After screening a variety of lithium-supplementing materials, it was found that lithium-rich transition metal oxides and lithium sulfides can stabilize the lattice structure through metal-oxygen bonds or the strong electronegativity of sulfur while replenishing active lithium. By optimizing the conductive network to reduce electrode polarization, the change of manganese valence caused by local potential anomalies can be suppressed. Compared with the existing technology, traditional surface coating can only form a physical barrier on the surface of the material, while this application achieves lattice stabilization through the chemical action of the lithium supplement agent to form an intrinsic anti-dissolution property. Compared with the capacity loss caused by bulk doping, the lithium supplement agent does not change the main component of the material while replenishing active lithium. Compared with the exogenous complexation of electrolyte additives, this application realizes a self-protection mechanism by optimizing the positive electrode components to avoid the introduction of additional side reactions.

[0046] In an optional embodiment, the lithium-rich transition metal oxide includes at least one of Li5FeO4 and Li2NiO2.

[0047] In an alternative embodiment, the lithium sulfide comprises Li2S.

[0048] In an optional embodiment, the lithium supplementing agent includes ZrO2.

[0049] Lithium-rich transition metal oxides refer to transition metal oxides containing excess lithium elements, which can be specifically achieved by using Li5FeO4 with a layered structure or Li2NiO2 with a spinel structure. The transition metal elements maintain lattice stability through redox reactions. Lithium sulfide refers to an inorganic lithium compound containing sulfur elements, which can be specifically achieved by using Li2S with high reactivity, and its decomposition products can react with the acidic components of the electrolyte to neutralize. Specifically, Li5FeO4 releases excess lithium ions during the charge and discharge process to replenish the lithium loss of the positive electrode active material. At the same time, the reversible redox reaction of the iron element effectively inhibits the migration of manganese ions caused by lattice distortion. The nickel element of Li2NiO2 enhances the integrity of the crystal structure by forming a stable Ni-O bond network, reducing the probability of manganese ions leaving the lattice. Li2S releases sulfide ions when the electrolyte decomposes, preferentially reacting with H + The reaction generates H2S gas that is discharged from the system, thereby reducing the corrosive effect of the acidic environment of the electrolyte on manganese ions. At the same time, the sulfide forms a dense passivation layer on the surface of the positive electrode to block the diffusion path of manganese ions. Through the above technical solution, the present application effectively inhibits the dissolution behavior of manganese ions in the positive electrode active material and improves the cycle stability and safety of the battery. The structural stabilization effect of the transition metal oxide reduces the migration power of manganese ions, and the environmental regulation effect of the sulfide blocks the dissolution path. The synergistic effect of the two significantly reduces the electrolyte decomposition side reaction and extends the battery life.

[0050] In an optional embodiment, the ratio of the lithium-rich transition metal oxide to the lithium sulfide is 1:2-4.

[0051] Optionally, the ratio of the lithium-rich transition metal oxide to the lithium sulfide is 1:2, 1:2.5, 1:3, 1:3.5, 1:4, or any value between 1:2 and 4.

[0052] Lithium-rich transition metal oxides serve as the main lithium replenishment component, compensating for the loss of active lithium during the cycle by releasing lithium ions, while lithium sulfides inhibit lattice collapse through the coordination of sulfur and transition metal ions. Lithium-rich oxides can provide sufficient lithium source supplementation, while sulfides effectively constrain the migration path of manganese ions. If the proportion of lithium-rich oxides is too high, the sulfide's fixation of manganese ions will be weakened due to insufficient dispersion; if the sulfide ratio is too high, excess sulfur will trigger side reactions on the electrode surface to form polysulfides. Within this range, both the lithium replenishment capacity is guaranteed and the dissolution of transition metals is suppressed.

[0053] In an optional embodiment, the amount of the lithium supplement agent is 1-5 wt % of the positive electrode active material.

[0054] Optionally, the amount of the lithium supplement agent can be 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt% of the positive electrode active material, or any value between 1-5wt%.

[0055] When the lithium replenisher content is controlled between 1% and 5% of the mass of the positive electrode active material, lithium loss caused by side reactions on the active material surface is effectively compensated, while avoiding particle agglomeration caused by excessive lithium replenisher. Amounts below 1% fail to cover the reaction sites on the active material surface, resulting in a decrease in the initial coulombic efficiency. Above 5%, the interaction between the lithium replenisher particles increases, disrupting the continuity of the conductive network and reducing the uniformity of the slurry coating. This ratio range balances the lithium compensation requirements with the slurry rheological properties, allowing the electrode to maintain high capacity while maintaining processing stability.

[0056] In an optional embodiment, the amount of the lithium supplementing auxiliary agent is 1-4 wt % of the mass of the lithium supplementing agent.

[0057] Optionally, the amount of the lithium supplementing agent may be 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt% or any value between 1-4 wt% of the mass of the lithium supplementing agent.

[0058] In an optional embodiment, the usage ratio of the LMFP positive electrode active material, the conductive agent, the binder, and the lithium supplement agent is 90-94:1-4:1-3:1-3.

[0059] Optionally, the usage ratio of the LMFP positive electrode active material, the conductive agent, the binder, and the lithium supplement agent can be 90:1:1:1, 91:1:1:1, 92:1:1:1, 93:1:1:1, 94:1:1:1, 90:2:1:1, 90:3:1:1, 90:4:1:1, 90:1:2:1, 90:1:3:1, 90:1:1:2, 90:1:1:3, 91:2:2:2, 93:3:3:3, 94:4:3:3, or any ratio of 90-94:1-4:1-3:1-3.

[0060] In an optional embodiment, the conductive agent includes Super P.

[0061] In an alternative embodiment, the binder comprises PVDF.

[0062] In an alternative embodiment, the solvent comprises NMP.

[0063] In a second aspect, the present application also provides a lithium-ion battery positive electrode plate, which includes a positive electrode collector and a positive electrode active layer; the positive electrode collector includes aluminum foil; and the raw material of the positive electrode active layer is the lithium-ion battery positive electrode active slurry.

[0064] In an optional embodiment, the compaction density of the positive electrode active layer is 2.1-2.4 g / cm 3 .

[0065] Optionally, the compaction density of the positive electrode active layer can be 2.1 g / cm 3 , 2.15g / cm 3 , 2.2g / cm 3 , 2.25g / cm 3 , 2.3g / cm 3 , 2.35g / cm 3 , 2.4g / cm 3 , or 2.1-2.4g / cm 3 Any value in between.

[0066] The compaction density refers to the mass per unit volume of the positive electrode active layer, which can be achieved by adjusting the roller pressing process parameters. The active material particles are tightly packed by controlling the roller pressing pressure and the gap distance. This density range maintains a reasonable porosity while ensuring the integrity of the electrode structure, which is beneficial to electrolyte infiltration and ion transport. Among them, the dense arrangement can limit the relative displacement between the active material particles and reduce the accumulation of lattice stress during the cycle; moderate pores can buffer the mechanical damage caused by volume expansion and inhibit the formation of manganese dissolution channels caused by particle breakage. The surface of the aluminum foil current collector is electrochemically polished to form an aluminum oxide passivation layer, which blocks the contact between the electrolyte and the aluminum substrate and inhibits the formation of interfacial corrosion products. The lithium replenisher in the positive electrode active layer continuously releases lithium ions during the cycle, compensates for the loss of active lithium caused by the formation of the SEI film, and maintains the integrity of the lattice structure of the positive electrode material. The compaction density is controlled at 2.1-2.4g / cm 3 In the range of 0.5, moderate contact stress is formed between the material particles, which not only prevents the lithium ion diffusion channel from being overly compressed, but also avoids excessive local current density caused by excessive interparticle gaps. Chemical adsorption is formed at the interface between the active layer and the current collector through hydrogen bonding, which inhibits interlayer delamination caused by volume expansion during charge and discharge.

[0067] The present application also provides a lithium-ion battery, wherein the raw materials of the lithium-ion battery include the lithium-ion battery positive electrode sheet.

[0068] In an optional embodiment, the raw materials of the lithium-ion battery further include a graphite negative electrode, a Celgard 2400 separator, and an electrolyte;

[0069] The electrolyte includes a first solution, an additive, and a lithium salt complexing agent;

[0070] The solute of the first solution includes LiPF6; the solvent includes EC, EMC, and DMC; the volume ratio of the EC, the EMC, and the DMC is 2-4:4-6:1-4; the Li + The concentration is 1.2 mol / L;

[0071] Optionally, the volume ratio of the EC, the EMC, and the DMC may be 2:4:1, 2:5:1, 2:6:1, 2:5:2, 2:5:3, 2:5:4, 3:5:2, 3:6:3, 3:6:4, 4:6:4, or any ratio between 2-4:4 and 6:1-4.

[0072] The additive includes FEC, and the amount of the additive added is 1-3 wt% of the mass of the first solution;

[0073] Optionally, the amount of the additive added may be 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt% of the mass of the first solution, or any value between 1-3 wt%.

[0074] The lithium salt complexing agent includes LiBOB, and the addition amount of the lithium salt complexing agent is 0.1-0.8wt% of the mass of the first solution;

[0075] Optionally, the added amount of the lithium salt complexing agent can be 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt% of the mass of the first solvent, or any value between 0.1-0.8wt%.

[0076] Among them, the volume ratio of EC, EMC, and DMC refers to the mixing ratio of the three carbonate solvents, which can be achieved by mixing them in proportion using the volumetric measurement method. This ratio can balance the viscosity and dielectric constant of the electrolyte. The concentration of LiPF6 refers to the molar concentration of the solute in the solvent, which can take into account both ionic conductivity and electrolyte stability. The amount of FEC added refers to its percentage of the mass of the first solution, which can be achieved by dissolving it after weighing. FEC can preferentially decompose on the electrode surface to form a protective film. The amount of LiBOB added refers to its percentage of the mass of the first solution, which can be achieved by pre-dissolving and then adding it. LiBOB can simultaneously complex free metal ions and adsorb on the positive electrode surface. Celgard 2400 membrane refers to a polypropylene microporous membrane material, and its pore size distribution can physically block the migration of manganese ions.

[0077] Specifically, in the ternary carbonate solvent system, the high dielectric constant of EC promotes the dissociation of LiPF6, the low viscosity of EMC and DMC reduces the resistance to ion migration, and the volume ratio of 3:5:2 enables the solvent to form a stable solvation structure. The LiPF6 concentration of 1.2 mol / L ensures the efficiency of lithium ion transmission while avoiding excessive viscosity of the electrolyte caused by excessive concentration. FEC decomposes before the solvent in the early stage of charge and discharge, forming a dense CEI film on the positive electrode surface to block the contact between manganese ions and the electrolyte; forming a stable SEI film on the negative electrode surface to inhibit the reduction and deposition of manganese ions. LiBOB combines with Mn through its boron center empty orbital 2+ It forms a chelate, reducing the concentration of free manganese ions. It also adsorbs onto the surface of the cathode material, inhibiting the dissolution of manganese from the crystal lattice. The microporous structure of the separator forms a physical barrier, working in conjunction with the additives in the electrolyte to restrict the transelectrode movement of manganese ions.

[0078] Compared to existing technologies, traditional solutions typically use a single carbonate solvent or a binary solvent mixture, which fails to balance dielectric constant and viscosity. Electrolyte additives often use single-functional substances, such as VC or PS as film-forming additives, which lack the ability to complex manganese ions. This solution, however, optimizes solvation capacity through a ternary solvent ratio, combining the dual functions of FEC and LiBOB to suppress manganese dissolution while maintaining electrode interface stability. Existing separators primarily focus on lithium dendrite blocking.

[0079] Through the above technical solution, the present application can effectively reduce the amount of manganese ions dissolved in the positive electrode active material, reduce the destructive effect of dissolved manganese ions on the negative electrode SEI film, and inhibit the decomposition side reactions caused by manganese ions in the electrolyte. The CEI film formed on the positive electrode surface and the LiBOB adsorption layer work together to stabilize the material crystal structure. The dense SEI film formed on the negative electrode surface prevents the reduction and deposition of manganese ions. The chelated manganese ions in the electrolyte reduce the possibility of their participation in side reactions. The physical barrier effect of the diaphragm extends the migration path of manganese ions. The multi-dimensional protection mechanism works together to extend the battery cycle life and improve safety.

[0080] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0081] Example 1

[0082] This embodiment provides a positive electrode active slurry for a lithium ion battery:

[0083] The raw materials are LMFP positive electrode active material, Super P, PVDF, Li5FeO4, ZrO2, and NMP. The ratio of LMFP positive electrode active material, Super P, PVDF, and Li5FeO4 is 93:3:2:2. The ratio of Mn to Fe in the LMFP positive electrode active material is 7:3. The amount of ZrO2, a lithium supplement, is 2% by weight of the Li5FeO4 mass. Based on a total mass of 100% by weight of the positive electrode active slurry, the amount of NMP solvent is 60% by weight.

[0084] This embodiment also provides a lithium-ion battery positive electrode plate:

[0085] The current collector of the positive electrode sheet is aluminum foil. The lithium-ion battery positive electrode active slurry is coated on the aluminum foil, and after drying and roller pressing, the positive electrode active layer has a compaction density of 2.2g / cm 3 Lithium-ion battery positive electrode plate.

[0086] This embodiment also provides a lithium-ion battery:

[0087] The raw materials of lithium-ion batteries include graphite negative electrode, Celgard 2400 separator, and electrolyte.

[0088] The electrolyte includes a first solution, an additive, and a lithium salt complexing agent.

[0089] In the first solution, Li + The concentration is 1.2 mol / L, the solute in the first solution is LiPF6, and the solvent is a mixture of EC, EMC, and DMC in a volume ratio of 3:5:2; the additive is FEC, and the addition amount is 2 wt% of the mass of the first solution; the lithium salt complexing agent is LiBOB, and the addition amount is 0.5 wt% of the mass of the first solution.

[0090] The positive electrode sheet, graphite negative electrode and Celgard 2400 separator were assembled into a cylindrical battery, which was sealed after liquid injection, charged and discharged three times at 0.1C, and left to stand at 45°C for 24 hours to obtain a lithium-ion battery.

[0091] Example 2

[0092] This embodiment provides a positive electrode active slurry for a lithium ion battery:

[0093] The raw materials are LMFP positive electrode active material, Super P, PVDF, Li5FeO4, Li2NiO2, ZrO2, and NMP. The ratio of LMFP positive electrode active material, Super P, PVDF, Li5FeO4, and Li2NiO2 is 93:3:2:1.5:0.5. The ratio of Mn:Fe in the LMFP positive electrode active material is 7:3. The amount of ZrO2, a lithium supplementing agent, is 3% by weight of the Li5FeO4 mass. Based on a total mass of 100% by weight of the positive electrode active slurry, the amount of NMP solvent is 60% by weight.

[0094] This embodiment also provides a lithium-ion battery positive electrode plate:

[0095] The current collector of the positive electrode sheet is aluminum foil. The lithium-ion battery positive electrode active slurry is coated on the aluminum foil, and after drying and roller pressing, the positive electrode active layer has a compaction density of 2.2g / cm 3 Lithium-ion battery positive electrode plate.

[0096] This embodiment also provides a lithium-ion battery:

[0097] The raw materials of lithium-ion batteries include graphite negative electrode, Celgard 2400 separator, and electrolyte.

[0098] The electrolyte includes a first solution, an additive, and a lithium salt complexing agent.

[0099] In the first solution, Li + The concentration is 1.2 mol / L, the solute in the first solution is LiPF6, and the solvent is a mixture of EC, EMC, and DMC in a volume ratio of 3:5:2; the additive is FEC, and the addition amount is 2 wt% of the mass of the first solution; the lithium salt complexing agent is LiBOB, and the addition amount is 0.5 wt% of the mass of the first solution.

[0100] The positive electrode sheet, graphite negative electrode and Celgard 2400 separator were assembled into a cylindrical battery, which was sealed after liquid injection, charged and discharged three times at 0.1C, and left to stand at 45°C for 24 hours to obtain a lithium-ion battery.

[0101] Example 3

[0102] This embodiment provides a positive electrode active slurry for a lithium ion battery:

[0103] The raw materials are LMFP positive electrode active material, Super P, PVDF, Li5FeO4, ZrO2, and NMP. The ratio of LMFP positive electrode active material, Super P, PVDF, and Li5FeO4 is 93:3:2:0.5. The ratio of Mn to Fe in the LMFP positive electrode active material is 7:3. The amount of ZrO2, a lithium supplement, is 0.5 wt% of the mass of Li5FeO4. Based on a total mass of 100 wt% positive electrode active material, the amount of NMP solvent is 50 wt%.

[0104] This embodiment also provides a lithium-ion battery positive electrode plate:

[0105] The current collector of the positive electrode sheet is aluminum foil. The lithium-ion battery positive electrode active slurry is coated on the aluminum foil, and after drying and roller pressing, the positive electrode active layer has a compaction density of 2.1g / cm 3 Lithium-ion battery positive electrode plate.

[0106] This embodiment also provides a lithium-ion battery:

[0107] The raw materials of lithium-ion batteries include graphite negative electrode, Celgard 2400 separator, and electrolyte.

[0108] The electrolyte includes a first solution, an additive, and a lithium salt complexing agent.

[0109] In the first solution, Li + The concentration is 1.2 mol / L, the solute in the first solution is LiPF6, and the solvent is a mixture of EC, EMC, and DMC in a volume ratio of 3:5:2; the additive is FEC, and the addition amount is 2 wt% of the mass of the first solution; the lithium salt complexing agent is LiBOB, and the addition amount is 0.5 wt% of the mass of the first solution.

[0110] The positive electrode sheet, graphite negative electrode and Celgard 2400 separator were assembled into a cylindrical battery, which was sealed after liquid injection, charged and discharged three times at 0.1C, and left to stand at 45°C for 24 hours to obtain a lithium-ion battery.

[0111] Comparative Example 1

[0112] This comparative example provides a lithium-ion battery positive electrode active slurry:

[0113] The raw materials are LMFP positive electrode active material, Super P, PVDF, and NMP. The ratio of LMFP positive electrode active material, Super P, and PVDF is 93:3:2. The ratio of Mn to Fe in the LMFP positive electrode active material is 7:3. Based on 100 wt% of the total mass of the positive electrode active slurry, the amount of NMP solvent used is 60 wt%.

[0114] This comparative example also provides a lithium-ion battery positive electrode sheet:

[0115] The current collector of the positive electrode sheet is aluminum foil. The lithium-ion battery positive electrode active slurry is coated on the aluminum foil, and after drying and roller pressing, the positive electrode active layer has a compaction density of 2.2g / cm 3 Lithium-ion battery positive electrode plate.

[0116] This comparative example also provides a lithium-ion battery:

[0117] The raw materials of lithium-ion batteries include graphite negative electrode, Celgard 2400 separator, and electrolyte.

[0118] The electrolyte includes a first solution, an additive, and a lithium salt complexing agent.

[0119] In the first solution, Li + The concentration is 1.2 mol / L, the solute in the first solution is LiPF6, and the solvent is a mixture of EC, EMC, and DMC in a volume ratio of 3:5:2; the additive is FEC, and the addition amount is 2 wt% of the mass of the first solution; the lithium salt complexing agent is LiBOB, and the addition amount is 0.5 wt% of the mass of the first solution.

[0120] The positive electrode sheet, graphite negative electrode and Celgard 2400 separator were assembled into a cylindrical battery, which was sealed after liquid injection, charged and discharged three times at 0.1C, and left to stand at 45°C for 24 hours to obtain a lithium-ion battery.

[0121] Comparative Example 2

[0122] This comparative example provides a lithium-ion battery positive electrode active slurry:

[0123] The raw materials are LMFP positive electrode active material, Super P, PVDF, Li5FeO4, ZrO2, and NMP. The ratio of LMFP positive electrode active material, Super P, PVDF, and Li5FeO4 is 93:3:2:2. The ratio of Mn to Fe in the LMFP positive electrode active material is 7:3. The amount of ZrO2, a lithium supplement, is 2% by weight of the Li5FeO4 mass. Based on a total mass of 100% by weight of the positive electrode active slurry, the amount of NMP solvent is 60% by weight.

[0124] This comparative example also provides a lithium-ion battery positive electrode sheet:

[0125] The current collector of the positive electrode sheet is aluminum foil. The lithium-ion battery positive electrode active slurry is coated on the aluminum foil, and after drying and roller pressing, the positive electrode active layer has a compaction density of 2.2g / cm 3 (2.1-2.3) lithium-ion battery positive electrode sheet.

[0126] This comparative example also provides a lithium-ion battery:

[0127] The raw materials of lithium-ion batteries include graphite negative electrode, Celgard 2400 separator, and electrolyte.

[0128] The electrolyte is a conventional electrolyte, including LiPF6, LIFSI, EC, EMC, DMC, FEC, DTD, LiDFOB, and CHB.

[0129] The positive electrode sheet, graphite negative electrode and Celgard 2400 separator were assembled into a cylindrical battery, which was sealed after liquid injection, charged and discharged three times at 0.1C, and left to stand at 45°C for 24 hours to obtain a lithium-ion battery.

[0130] Comparative Example 3

[0131] This comparative example provides a lithium-ion battery positive electrode active slurry:

[0132] The raw materials are LMFP positive electrode active material, Super P, PVDF, Li5FeO4, and NMP. The ratio of LMFP positive electrode active material, Super P, PVDF, and Li5FeO4 is 93:3:2:2. The ratio of Mn to Fe in the LMFP positive electrode active material is 7:3. Based on 100wt% of the total mass of the positive electrode active slurry, the amount of NMP solvent used is 60wt%.

[0133] This comparative example also provides a lithium-ion battery positive electrode sheet:

[0134] The current collector of the positive electrode sheet is aluminum foil. The lithium-ion battery positive electrode active slurry is coated on the aluminum foil, and after drying and roller pressing, the positive electrode active layer has a compaction density of 2.2g / cm 3 (2.1-2.3) lithium-ion battery positive electrode sheet.

[0135] This comparative example also provides a lithium-ion battery:

[0136] The raw materials of lithium-ion batteries include graphite negative electrode, Celgard 2400 separator, and electrolyte.

[0137] The electrolyte includes a first solution, an additive, and a lithium salt complexing agent.

[0138] In the first solution, Li + The concentration is 1.2 mol / L, the solute in the first solution is LiPF6, and the solvent is a mixture of EC, EMC, and DMC in a volume ratio of 3:5:2; the additive is FEC, and the addition amount is 2 wt% of the mass of the first solution; the lithium salt complexing agent is LiBOB, and the addition amount is 0.5 wt% of the mass of the first solution.

[0139] The positive electrode sheet, graphite negative electrode and Celgard 2400 separator were assembled into a cylindrical battery, which was sealed after liquid injection, charged and discharged three times at 0.1C, and left to stand at 45°C for 24 hours to obtain a lithium-ion battery.

[0140] The capacity retention and recovery rates of the batteries of Example 1 and Comparative Example 1 after storage at 60°C for 7 days are as follows: Figure 1 The capacity retention of Example 1 and Comparative Example 1 at 45°C and 1C / 1C for 500 cycles is shown in the figure. Figure 2 The ICP test results of the manganese dissolution of the negative electrode sheet after the cycle of Example 1 and Comparative Example 1 are as follows: Figure 3 shown.

[0141] The performance of the lithium-ion batteries provided in the embodiments and comparative examples is shown in Table 1:

[0142] Table 1 Performance of lithium-ion batteries provided by Example 1 and Comparative Example

[0143]

[0144] In Comparative Example 1, only no lithium supplement agent and lithium supplement auxiliary agent were added, in Comparative Example 2, conventional electrolyte was used, and in Comparative Example 3, lithium supplement auxiliary agent was further added; as can be seen from Table 1:

[0145] In Examples 1-3, all performance indicators are significantly better than the comparative example. This shows that the technical solution provided in the present application is a whole solution. In the prepared lithium ion battery, the positive electrode active layer formed by the positive electrode active slurry and the synergistic effect of the electrolyte effectively improves the battery cycle stability and reduces manganese dissolution. The amount of manganese dissolution is strongly negatively correlated with battery performance. The lower the amount of manganese dissolution, the higher the capacity retention rate, recovery rate and cycle life. Manganese dissolution is a common degradation mechanism in lithium ion batteries (manganese ions dissolve from the positive electrode and deposit at the negative electrode, resulting in SEI film damage and capacity decay), and the above embodiment data also verifies this.

[0146] As can be seen, the Example group achieved significant improvements in capacity retention, recovery rate, and manganese dissolution control compared to Comparative Examples 1-3. This demonstrates that the technical solution provided by this application successfully improved the high-temperature cycling performance and structural stability of the battery. This is because the application controls the amount of manganese dissolution, which becomes the key driver of the performance difference.

[0147] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

[0148] Furthermore, those skilled in the art will appreciate that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and to form distinct embodiments. For example, in the claims above, any of the claimed embodiments may be used in any combination. The information disclosed in this background section is intended solely to enhance understanding of the overall background of this application and should not be construed as an admission or any implication that such information constitutes prior art known to those skilled in the art.

Claims

1. A positive electrode active slurry for a lithium ion battery, characterized in that: The raw materials of the positive electrode active slurry include: LMFP positive electrode active material, conductive agent, binder, lithium supplement agent, lithium supplement auxiliary agent, and solvent; The lithium supplement comprises at least one of lithium-rich transition metal oxides and lithium sulfides.

2. The positive electrode active slurry for lithium-ion batteries according to claim 1, characterized in that: At least one of the following conditions is met: a. The lithium-rich transition metal oxide includes at least one of Li5FeO4 and Li2NiO2; b. The lithium sulfide includes Li2S; c. The lithium supplementing agent includes ZrO2.

3. The positive electrode active slurry for lithium-ion batteries according to claim 2, characterized in that: The ratio of the lithium-rich transition metal oxide to the lithium sulfide is 1:12-4.

4. The positive electrode active slurry for lithium-ion batteries according to claim 1, characterized in that: At least one of the following conditions is met: c. The amount of the lithium supplement agent is 1-5wt% of the positive electrode active material; d. The amount of the lithium supplementing agent is 1-4wt% of the mass of the lithium supplementing agent.

5. The positive electrode active slurry for lithium-ion batteries according to claim 1, characterized in that: The usage ratio of the LMFP positive electrode active material, the conductive agent, the binder, and the lithium supplement agent is 90-94:2-5:1-4:2-5.

6. The positive electrode active slurry for lithium-ion batteries according to any one of claims 1 to 5, characterized in that: At least one of the following conditions is met: e. The conductive agent includes Super P; f. The binder comprises PVDF; g. The solvent includes NMP.

7. A positive electrode plate for a lithium-ion battery, characterized in that: The lithium-ion battery positive electrode plate includes a positive electrode collector and a positive electrode active layer; the positive electrode collector includes aluminum foil; and the raw material of the positive electrode active layer is the lithium-ion battery positive electrode active slurry according to any one of claims 1 to 6.

8. The positive electrode plate of a lithium-ion battery according to claim 7, characterized in that: The compaction density of the positive electrode active layer is 2.1-2.4 g / cm 3 .

9. A lithium-ion battery, characterized in that: The raw materials of the lithium-ion battery include the lithium-ion battery positive electrode sheet according to claim 7 or 8.

10. The lithium-ion battery according to claim 9, characterized in that The raw materials of the lithium-ion battery include a graphite negative electrode, a Celgard 2400 separator, and an electrolyte; The electrolyte includes a first solution, an additive, and a lithium salt complexing agent; The solute of the first solution includes LiPF6; the solvent includes EC, EMC, and DMC; the volume ratio of the EC, the EMC, and the DMC is 2-4:4-6:1-4; the Li + The concentration is 1.2 mol / L; The additive includes FEC, and the amount of the additive added is 1-3 wt% of the mass of the first solution; The lithium salt complexing agent includes LiBOB, and the addition amount of the lithium salt complexing agent is 0.1-0.8 wt % of the mass of the first solution.

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