Manganese-based secondary battery aid and use thereof

Abstract

The application discloses an additive for a manganese-based secondary battery and application thereof. The additive formula I compound contains a hetero-oxygen double bond, can participate in positive electrode interface film forming, form a polymer containing a hetero-oxygen double bond, can effectively combine metal manganese ions, reduce dissolution of the metal manganese ions, and meanwhile, the additive partially free in an electrolyte or a separator can effectively complex the metal manganese ions, so that reduction and precipitation of the metal manganese ions at a negative electrode interface is reduced, and then the degree of a side reaction is greatly reduced and loss of active lithium is reduced.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, and more specifically, to additives for manganese-based secondary batteries and their applications. Background Technology

[0002] In recent years, with global warming, countries around the world have attached increasing importance to carbon peaking and carbon emission reduction tasks. According to the Paris Agreement, in the future, countries will be required to take carbon emissions as an important economic indicator. Various renewable energy sources will rise accordingly, and wind power and solar power will receive much attention. At the same time, lithium-ion batteries and other small electronic device components are becoming more and more accepted. Their convenience and practicality are gradually being accepted and recognized, and they have become an indispensable part of people's lives.

[0003] However, at the same time, people's requirements for lithium-ion batteries have also increased, such as long battery life, high capacity, fast charging, wide operating temperature range, and high safety performance, so that lithium-ion rechargeable batteries can provide greater convenience and a better experience in people's daily lives.

[0004] Lithium-ion rechargeable batteries mainly consist of positive and negative electrode materials containing lithium intercalation and deintercalation capabilities, and a non-aqueous electrolyte containing lithium salts and non-aqueous solvents. The positive electrode material, as a crucial component, directly affects the battery's kinetics, cycle life, calendar life, and safety during abuse. Ternary materials with high specific capacity are less acceptable compared to lithium iron phosphate due to their lower safety profile. Lithium manganese iron phosphate (LFP) material, by replacing some Fe ions with a certain amount of Mn ions in the structure of lithium iron phosphate without altering the original olivine structure, offers lower cost, higher thermal stability, better safety, and significantly improved energy density and a wider operating voltage window. However, while LFP offers many advantages, it also has several drawbacks. This material exhibits the Jahn-Teller effect; polarization factors such as high currents during charging and discharging cause manganese ions to readily undergo disproportionation and dissolution on the surface of the positive electrode particles. This easily damages the SEI film of the negative electrode, triggering more side reactions and leading to accelerated loss of active lithium. As side reactions at the negative electrode interface intensify, the negative electrode potential continuously rises, thus deteriorating the cell performance. Meanwhile, due to the dissolution effect of manganese ions, cathode material particles are prone to lattice distortion and structural collapse, which greatly compromises the olivine stability of the material and shortens the cycle life and high-temperature storage life of the secondary battery. The metal ion dissolution problem is particularly prominent in lithium manganese iron phosphate materials under conventional electrolytes, and this bottleneck urgently needs further resolution.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide an additive for manganese-based secondary batteries and its application, thereby solving the problem that manganese ions are easily dissolved in the positive electrode material of manganese-based secondary batteries, which leads to the destruction of the SEI film of the negative electrode and the reduction of the stability of the positive electrode material.

[0007] This invention is implemented as follows:

[0008] In a first aspect, the present invention provides a manganese-based additive for secondary batteries, comprising a compound of formula I, the structure of which is as follows;

[0009]

[0010] In Equation I, X and Y are independently selected from one of C, P, S, and Se, n1 is 1 or 2, and n2 is 1 or 2; where,

[0011] R1 and R2 are independently selected from one of hydrogen, halogen, C1-C10 straight-chain alkyl, C1-C10 cyclic alkyl, C1-C10 haloalkyl, C1-C10 straight-chain alkenyl, C1-C10 cyclic alkenyl, C1-C10 straight-chain alkynyl, C1-C10 cyclic alkynyl, phenyl, substituted phenyl, benzyl, and substituted benzyl.

[0012] R3 and R4 are independently selected from one of the following: halogen, C1-C10 alkyl, C1-C10 substituted alkyl, C1-C10 alkenyl, C1-C10 substituted alkenyl, C1-C10 alkynyl, C1-C10 substituted alkynyl, phenyl, substituted phenyl, benzyl or substituted benzyl.

[0013] In an optional embodiment, a compound of formula II is also included, the structure of which is as follows;

[0014]

[0015] In Formula II, R' is independently selected from one of the following: halogen, alkane-containing amine, unsaturated hydrocarbon-containing amine, C1-C10 alkyl, C1-C10 substituted alkyl, C1-C10 alkenyl, C1-C10 substituted alkenyl, C1-C10 alkynyl, C1-C10 substituted alkynyl, phenyl, substituted phenyl, benzyl or substituted benzyl.

[0016] In an optional embodiment, the compound of formula I includes at least one of compounds 1 to 7, the structures of which are as follows:

[0017]

[0018] In an optional embodiment, the compound of formula II includes at least one of compounds 8 to 13, the structures of which are as follows:

[0019]

[0020]

[0021] In an optional embodiment, the molar ratio of the compound of formula I to the compound of formula II is 1:0.8 to 1:1.2.

[0022] In a second aspect, the present invention provides a manganese-based secondary battery, comprising a negative electrode, a positive electrode, a separator, and a non-aqueous electrolyte, wherein at least one of the positive electrode, the separator, or the non-aqueous electrolyte comprises the additive for manganese-based secondary batteries described in any one of the preceding claims.

[0023] In an optional embodiment, the content of compound I in the non-aqueous electrolyte is 0.05 wt% to 15 wt%; preferably, the content of compound I in the non-aqueous electrolyte is 0.05 wt% to 6 wt%.

[0024] And / or, the content of compound of formula I in the positive electrode sheet is 0.05wt% to 15wt%; preferably, the content of compound of formula I in the positive electrode sheet is 0.05wt% to 6wt%.

[0025] And / or, the content of compound I in the diaphragm is 0.05 wt% to 15 wt%; preferably, the content of compound I in the diaphragm is 0.05 wt% to 6 wt%.

[0026] In an optional embodiment, the positive electrode sheet includes a positive electrode active material, which includes at least one of lithium manganese iron phosphate or nickel cobalt manganese ternary materials;

[0027] Preferably, the lithium manganese iron phosphate has the general formula LiMn m Fe 1-m PO4, where 0.95 ≥ m ≥ 0.05

[0028] Preferably, the nickel-cobalt-manganese ternary material has the general formula Li a Ni x Co y Mn z M w O2, where 0.9≤a≤1.1, y≤0.2, z>0, x+y+z+w=1, and M includes Al.

[0029] In an optional embodiment, the non-aqueous electrolyte includes an organic solvent, a lithium salt, and additives;

[0030] Preferably, the additive comprises at least one selected from vinyl sulfate, fluoroethylene carbonate, difluoroethylene carbonate, vinylene carbonate, 1,3-propanesulfonate lactone, 1-propylene-1,3-sulfonate lactone, methanedisulfonate, tris(trimethylsilyl) phosphate and tris(trimethylsilyl) phosphite, lithium difluorodioxolane phosphate, lithium difluorophosphate, lithium difluorooxolane borate, and fluorobenzene; more preferably, the concentration of the additive in the non-aqueous electrolyte is 0.1 wt% to 3 wt%.

[0031] Preferably, the lithium salt includes LiFSI and C4BLi3O. 11 LiPF 6-n (CF3) n , LiN[(FSO2C6F4)(CF3SO2)], LiSO3CF3, LiTFSI, LiCH(SO2CF3)2, LiTFSM, LiPF6, LiBF4, LiBOB, LiDFOB, LiAsF6, LiPO2F2, LiN(CF3SO2)2, LiCF3SO3, LiClO4 and LiN(C b F 2b+1 SO2)(C c F 2c+1 At least one of SO2, wherein n is an integer from 0 to 6, and b and c are natural numbers; more preferably, the lithium ion molar concentration in the non-aqueous electrolyte is 0.1 to 3 mol / L;

[0032] Preferably, the organic solvent is at least one selected from carbonates, carboxylic acid esters, sulfates, phosphates, amides, nitriles, and ethers; more preferably, the organic solvent is ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, ethyl acetate, acid anhydride, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, acetonitrile, or cyclobutanediol. At least one of the following: sulfone, dimethyl sulfoxide, ethylene sulfite, propylene sulfite, triethyl phosphate, methyl ethyl phosphite, dimethyl sulfide, diethyl sulfite, dimethyl sulfite, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, fluorinated cyclic organic esters, and sulfur-containing cyclic organic esters; more preferably, the organic solvent content in the non-aqueous electrolyte is 60 wt% to 80 wt%.

[0033] Preferably, the non-aqueous electrolyte further includes lithium bisfluorosulfonylimide; more preferably, the concentration of lithium bisfluorosulfonylimide in the non-aqueous electrolyte is 0.02wt% to 25wt%; even more preferably, the concentration of lithium bisfluorosulfonylimide in the non-aqueous electrolyte is 0.2wt% to 19wt%.

[0034] Thirdly, the present invention provides an electrical device comprising the manganese-based secondary battery described in any of the preceding claims.

[0035] The present invention has the following beneficial effects:

[0036] The additives in this application contain a compound of formula I, which can participate in the film formation at the positive electrode interface to form a polymer containing heterooxy double bonds. This compound can effectively bind manganese ions and reduce the dissolution of manganese ions. At the same time, the compound of formula I, which is partially free on the electrolyte or the separator, can effectively complex manganese ions, thereby reducing the reduction and precipitation of manganese ions at the negative electrode interface, and thus greatly reducing the degree of side reactions and the loss of active lithium. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 SEM image of the positive electrode interface of the battery cell in Comparative Example 1 (without added Compound I) after 825 cycles at 25°C.

[0039] Figure 2 The image shows a SEM image of the positive electrode sheet after being disassembled at 25°C for 1312 cycles.

[0040] Figure 3 This is a SEM image of the negative electrode interface after 1312 cycles at 25°C in Example 3.

[0041] Figure 4 The negative electrode sheet of the first set of cells before cycling is shown in Comparative Example 1. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0043] This embodiment provides a manganese-based additive for secondary batteries, comprising a compound of formula I, the structure of which is as follows;

[0044]

[0045] In Formula I, X and Y are independently selected from one of C, P, S and Se, n1 is 1 or 2, and n2 is 1 or 2; specifically, when X is a P atom, n1 = 2; when X is C, S or Se, n1 = 1; when Y is a P atom, n2 = 2; when Y is C, S or Se, n2 = 1.

[0046] in,

[0047] R1 and R2 are independently selected from one of hydrogen, halogen, C1-C10 straight-chain alkyl, C1-C10 cyclic alkyl, C1-C10 haloalkyl, C1-C10 straight-chain alkenyl, C1-C10 cyclic alkenyl, C1-C10 straight-chain alkynyl, C1-C10 cyclic alkynyl, phenyl, substituted phenyl, benzyl, and substituted benzyl.

[0048] R3 and R4 are independently selected from one of the following: halogen, C1-C10 alkyl, C1-C10 substituted alkyl, C1-C10 alkenyl, C1-C10 substituted alkenyl, C1-C10 alkynyl, C1-C10 substituted alkynyl, phenyl, substituted phenyl, benzyl or substituted benzyl.

[0049] Compound I participates in the film formation at the positive electrode interface, forming a polymer containing heterogeneous double bonds. This effectively binds manganese ions, reducing their dissolution. Simultaneously, some of the free compounds of Formula I on the electrolyte or membrane can effectively complex manganese ions, forming complexed metal ions as described below (where M is manganese). This reduces the reduction and precipitation of manganese ions at the negative electrode interface, thereby greatly reducing the degree of side reactions and minimizing the loss of active lithium.

[0050]

[0051] In some embodiments, a compound of formula II is also included, the structure of which is as follows;

[0052]

[0053] In Formula II, R' is independently selected from one of the following: halogen, alkane-containing amine, unsaturated hydrocarbon-containing amine, C1-C10 alkyl, C1-C10 substituted alkyl, C1-C10 alkenyl, C1-C10 substituted alkenyl, C1-C10 alkynyl, C1-C10 substituted alkynyl, phenyl, substituted phenyl, benzyl or substituted benzyl.

[0054] The compound of Formula II of this invention can greatly reduce the problems of increased impedance caused by the film formation of the compound of Formula I. By regulating the electrochemical mechanism of the initial film-forming components, the interfacial compatibility is increased. At the same time, the solvation effect at the positive and negative electrode interface is adjusted, the desolvation potential of the carbonate solvent is reduced, the high polarization effect caused by the high current charge and discharge of lithium-ion batteries is greatly reduced, and the charge and discharge capacity of lithium batteries is further improved.

[0055] In some embodiments, the compound of formula I includes at least one of compounds 1 to 7, the structures of which are as follows:

[0056]

[0057]

[0058] In some embodiments, the compound of formula II includes at least one of compounds 8 to 13, the structures of which are as follows:

[0059]

[0060] In some embodiments, the molar ratio of the compound of formula I to the compound of formula II is 1:0.8 to 1:1.2.

[0061] In a second aspect, the present invention provides a manganese-based secondary battery, comprising a negative electrode, a positive electrode, a separator, and a non-aqueous electrolyte, wherein at least one of the positive electrode, the separator, or the non-aqueous electrolyte comprises the additive for manganese-based secondary batteries described in any one of the preceding claims.

[0062] This invention introduces compounds of formula I and formula II into lithium-ion batteries, aiming to further improve side reactions such as metal ion dissolution and deposition at the negative electrode in manganese-based cathode or manganese-based mixed ternary material systems through synergistic effects, thereby enhancing the cycle life of the battery system. It is important to emphasize that compound I participates in the film formation at the cathode interface, forming a polymer interface film rich in carbonyl functional groups. This film can efficiently complex metal Mn ions, reducing their dissolution. Furthermore, partially free compounds of formula I on the electrolyte or separator can effectively complex metal Mn ions, thereby reducing their reduction and precipitation at the negative electrode interface, and significantly reducing the rapid loss of active lithium under high current conditions. Compound II can significantly reduce the high impedance effect caused by the film formation of compound I, while simultaneously catalytically regulating the solvation effect at the solid-liquid interface of the cathode and negative electrodes, reducing desolvation potential energy, decreasing polarization, and improving high-current charge-discharge capacity.

[0063] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0064] In some embodiments, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the opposite surfaces of the negative electrode current collector. The negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0065] In some embodiments, the negative electrode active material may be one or a combination of several of the following: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, with a particle size D value ≥ 0.1 μm. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys; the tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.

[0066] In some embodiments, the negative electrode film layer may optionally include an adhesive. The adhesive may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0067] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0068] In some embodiments, the positive electrode includes a positive current collector and a layer of positive active material disposed on at least one surface of the positive current collector. For example, the positive current collector includes two opposing surfaces in its thickness direction, and the positive active material is stacked on either or both of the two surfaces of the positive current collector.

[0069] In some embodiments, the present invention does not impose any particular limitation on the separator membrane, and can select known porous structure separator membranes with electrochemical and chemical stability, such as one or more single-layer or multi-layer films of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP) and polyvinylidene fluoride (PVDF).

[0070] In some embodiments, the content of compound I in the non-aqueous electrolyte is 0.05 wt% to 15 wt%; preferably, the content of compound I in the non-aqueous electrolyte is 0.05 wt% to 6 wt%.

[0071] And / or, the content of compound of formula I in the positive electrode sheet is 0.05wt% to 15wt%; preferably, the content of compound of formula I in the positive electrode sheet is 0.05wt% to 6wt%.

[0072] And / or, the content of compound I in the diaphragm is 0.05 wt% to 15 wt%; preferably, the content of compound I in the diaphragm is 0.05 wt% to 6 wt%.

[0073] When the content of the compounds shown in Formula I and Formula II is less than 0.05%, the concentration is too low to effectively form a uniform and dense passivation film on the surface of the cathode material particles. This cannot effectively improve the manganese dissolution effect caused by the poor conductivity of the cathode lithium manganese iron material, and cannot fundamentally improve the problems of high-temperature cycle life and rapid decay of high-temperature storage capacity. When the content of the compounds shown in Formula I or Formula II is greater than 6%, the improvement effect produced by the additive will not increase exponentially with the increase of the addition amount. In summary, the optimal content of the compounds in Formula I and Formula II is 0.05wt% to 6wt%.

[0074] In some embodiments, the positive electrode sheet includes a positive electrode active material, which includes at least one of lithium manganese iron phosphate or nickel cobalt manganese ternary materials;

[0075] Preferably, the lithium manganese iron phosphate has the general formula LiMn m Fe 1-m PO4, where 0.95 ≥ m ≥ 0.05

[0076] Preferably, the nickel-cobalt-manganese ternary material has the general formula Li a Ni x Co y Mn z M w O2, where 0.9≤a≤1.1, y≤0.2, z>0, x+y+z+w=1, and M includes Al.

[0077] In some embodiments, the non-aqueous electrolyte includes an organic solvent, a lithium salt, and additives;

[0078] Preferably, the additive comprises at least one selected from vinyl sulfate, fluoroethylene carbonate, difluoroethylene carbonate, vinylene carbonate, 1,3-propanesulfonate lactone, 1-propylene-1,3-sulfonate lactone, methanedisulfonate, tris(trimethylsilyl) phosphate and tris(trimethylsilyl) phosphite, lithium difluorodioxolane phosphate, lithium difluorophosphate, lithium difluorooxolane borate, and fluorobenzene; more preferably, the concentration of the additive in the non-aqueous electrolyte is 0.1 wt% to 3 wt%.

[0079] Preferably, the lithium salt includes LiFSI and C4BLi3O. 11 LiPF 6-n (CF3) n , LiN[(FSO2C6F4)(CF3SO2)], LiSO3CF3, LiTFSI, LiCH(SO2CF3)2, LiTFSM, LiPF6, LiBF4, LiBOB, LiDFOB, LiAsF6, LiPO2F2, LiN(CF3SO2)2, LiCF3SO3, LiClO4 and LiN(C b F 2b+1 SO2)(C c F 2c+1 At least one of SO2, wherein n is an integer from 0 to 6, and b and c are natural numbers; more preferably, the lithium ion molar concentration in the non-aqueous electrolyte is 0.1 to 3 mol / L. Higher lithium salt concentrations result in less dissociation of the lithium salt in the solvent system; lower lithium salt concentrations result in more dissociated Li2 ions. + The quantity is too small, and the conductivity is too low.

[0080] Preferably, the organic solvent is at least one selected from carbonates, carboxylic acid esters, sulfates, phosphates, amides, nitriles, and ethers; more preferably, the organic solvent is ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, ethyl acetate, acid anhydride, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, acetonitrile, or cyclobutanediol. At least one of the following: sulfone, dimethyl sulfoxide, ethylene sulfite, propylene sulfite, triethyl phosphate, methyl ethyl phosphite, dimethyl sulfide, diethyl sulfite, dimethyl sulfite, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, fluorinated cyclic organic esters, and sulfur-containing cyclic organic esters; more preferably, the organic solvent content in the non-aqueous electrolyte is 60 wt% to 80 wt%.

[0081] Preferably, the non-aqueous electrolyte further includes lithium bisfluorosulfonylimide; more preferably, the concentration of lithium bisfluorosulfonylimide in the non-aqueous electrolyte is 0.02 wt% to 25 wt%; even more preferably, the concentration of lithium bisfluorosulfonylimide in the non-aqueous electrolyte is 0.2 wt% to 19 wt%. Lithium bisfluorosulfonylimide exhibits good high-temperature cycling performance and low-temperature discharge capability when used in non-aqueous electrolytes.

[0082] Thirdly, the present invention provides an electrical device comprising the manganese-based secondary battery described in any of the preceding claims.

[0083] The features and performance of the present invention will be further described in detail below with reference to the embodiments, wherein the concentration unit % refers to mass fraction unless otherwise specified.

[0084] Examples 1-25

[0085] The batteries in Examples 1-25 were prepared according to the following method:

[0086] Electrolyte: In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), weigh organic solvent (ethylene carbonate, diethyl carbonate, methyl ethyl carbonate (mass ratio 3:2:5)) into a sample bottle. Add 12.5% ​​LiPF6 and 1% vinylene carbonate (VC) of the total mass to the sample bottle, then add the compounds shown in Formula I and Formula II, and mix well to obtain the prepared electrolyte.

[0087] Positive electrode: The positive electrode active material is lithium manganese iron phosphate (LiMn). 0.6 Fe 0.4 PO4 and conductive agent acetylene black (Super P) are mixed evenly in a mixing tank. Then, N-methylpyrrolidone (NMP) and binder polyvinylidene fluoride (PVDF) are added and stirred evenly to obtain a black slurry. This slurry is coated on aluminum foil, baked, rolled, and cut into sheets to obtain the positive electrode sheet. The mass ratio of the positive electrode active material, conductive agent, and binder is (96.5:1.5:2).

[0088] Negative electrode sheet: The negative electrode active material graphite and the conductive agent acetylene black (Super P) are mixed evenly in a mixing tank. Then, the binder SBR and deionized water are added and stirred evenly to obtain a black slurry. This slurry is coated on copper foil, baked, rolled, and cut into sheets to obtain the negative electrode sheet. The ratio of active material, conductive agent and binder is (96.5:1.5:2).

[0089] Separator: PE substrate, 12um thickness, double-sided PCS treatment (applying adhesive containing PVDF binder to both sides of the substrate).

[0090] Battery cell manufacturing:

[0091] The obtained positive electrode sheet, negative electrode sheet, and separator are stacked in the order of positive electrode, separator, and negative electrode. After winding, hot pressing and shaping, and electrode tab welding, a bare cell is obtained. The top and side are sealed with aluminum-plastic film. After completion, the cell is placed in an oven at 85±10℃ for 24h±12h to ensure that the water content of the electrode sheet is qualified. Then, electrolyte is injected. After depressurization packaging, standing, formation, shaping and other processes, the battery is obtained.

[0092] The battery performance obtained in Examples 1 to 25 was tested using the following methods, and the results are shown in Tables 1-3.

[0093] I. Loop Testing:

[0094] Room temperature cycling: The batteries obtained in Examples 1 to 25 were subjected to charge-discharge cycle tests at 25°C with a charge-discharge rate of 1C / 1C in the range of 2.8 to 4.30V. The initial discharge capacity and the discharge capacity after each cycle were recorded. The capacity retention rate was calculated as: discharge capacity per cycle / initial discharge capacity of the battery * 100%. The cycle termination condition was 80% SOC. The recorded data are shown in Tables 1-3.

[0095] High-temperature cycling: The batteries obtained in Examples 1 to 25 were placed in a 45°C chamber for 120 minutes, and then subjected to charge-discharge cycle tests in a 45°C constant temperature chamber at a charge-discharge rate of 1C / 1C within the range of 2.8 to 4.30V. The initial discharge capacity and the discharge capacity after each cycle were recorded. The capacity retention rate was calculated as: discharge capacity per cycle / initial discharge capacity of the battery * 100%. The cycle termination condition was 80% SOC. The recorded data are shown in Tables 1-3.

[0096] II. High-temperature storage:

[0097] The batteries obtained in Examples 1-25 were fully charged and stored in a 60°C constant temperature chamber. Every 10 days, they were taken out, fully charged again, and then stored in the 60°C constant temperature chamber for another 120 days. After 120 days, their recoverable capacity was tested. The method for testing the recoverable capacity is as follows:

[0098] 1. Discharge at a constant current of 1C to 2.8V, then let stand for 10 minutes;

[0099] 2. Charge the 1C CC-CV to 4.30V, with a cutoff current of 0.05C, and let it stand for 10 minutes;

[0100] 3. Discharge at a constant current of 1C to 2.8V, and record the discharged capacity as the recoverable capacity.

[0101] Capacity retention rate = recoverable capacity after storage / recoverable capacity of fresh battery * 100%, and the recorded data are shown in Table 1-3.

[0102] III. Volume expansion experiment: The batteries obtained in Examples 1 to 25 were charged to 4.30V at 1C and their volume was tested by the water displacement method. The initial volume and the volume after 7 days of storage at 85°C were recorded. The volume expansion rate was calculated as (volume after 7 days of storage at 85°C - initial volume) / initial volume * 100%. The storage termination condition was 80% SOC. The results are shown in Tables 1-3.

[0103] Table 1. Composition of the electrolyte and test results of the batteries obtained in Examples 1-17

[0104]

[0105] Table 2 shows the composition of the electrolyte and the test results of the batteries obtained in Examples 18-25.

[0106]

[0107] Note: In Formula I, compounds 1-7 refer to compounds 1 to 7 mentioned above, and in Formula II, compounds 8-13 refer to compounds 8 to 13 mentioned above.

[0108] Table 3. High-temperature storage of electrolytes in Examples 1-17 and their DCR inhibition effect after 30 days.

[0109]

[0110] Comparative Examples 1-5

[0111] The batteries in Comparative Examples 1-5 were prepared according to the following method:

[0112] Electrolyte: In an argon-atmospheric glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), weigh the organic solvent (ethylene carbonate, diethyl carbonate, methyl ethyl carbonate (mass ratio 3:2:5)) into a sample bottle. Add 12.5% ​​LiPF6 and 1% vinylene carbonate (VC) of the total mass to the sample bottle and mix thoroughly to obtain the prepared electrolyte. The composition (mass fraction) of the electrolyte and the test results of the battery performance are shown in Table 4.

[0113] Positive electrode sheet: Same as in Example 1.

[0114] Negative electrode sheet: Same as in Example 1.

[0115] Diaphragm: Same as in Example 1.

[0116] Table 4 shows the composition of the electrolytes in Comparative Examples 1-5 and the test results of the resulting batteries.

[0117]

[0118]

[0119] Examples 26-31

[0120] The batteries in Examples 26 / 28 / 30 were prepared according to the following method:

[0121] Electrolyte: In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), weigh the organic solvent (ethylene carbonate, diethyl carbonate, methyl ethyl carbonate (mass ratio 3:2:5)) into the sample bottle. Add 12.5% ​​LiPF6 and 1% vinylene carbonate (VC) of the total mass into the sample bottle and mix well to obtain the prepared electrolyte.

[0122] Positive electrode sheet: The positive electrode active material LiMn 0.6 Fe 0.4 PO4 and conductive agent acetylene black (Super P) are mixed evenly in a mixing tank. Then, N-methylpyrrolidone (NMP), binder polyvinylidene fluoride adhesive (PVDF), and compound of formula I are added in a certain mass ratio and stirred evenly to obtain a black slurry. This slurry is coated on aluminum foil, baked, rolled, and cut to obtain a positive electrode sheet. The mass ratio of conductive agent to binder is 1.5% and 2%, respectively.

[0123] Negative electrode sheet: Same as in Example 1.

[0124] Diaphragm: Same as in Example 1.

[0125] The batteries in Examples 27 / 29 / 31 were prepared according to the following method:

[0126] Electrolyte: Same as in Example 26.

[0127] Positive electrode sheet: Same as in Example 1.

[0128] Negative electrode sheet: Same as in Example 1.

[0129] Diaphragm: Compound I is sprayed onto the diaphragm surface of Example 1.

[0130] The only difference from Comparative Example 3 is that the compound of Formula I was mixed into the positive electrode or the membrane material instead of the electrolyte solution, and the results are shown in Table 5.

[0131] Table 5 shows the composition of the positive electrode or separator in Examples 26-31 and the test results of the resulting batteries.

[0132]

[0133]

[0134] Note: In Examples 26 / 28 / 30, the amount of Compound I added is 1% / 2% / 6% of the active material content of the positive electrode, respectively; in Examples 27 / 29 / 31, the amount of Compound I added is 1% / 2% / 6% of the membrane mass, respectively, and a solution containing a certain concentration of Compound I (NMP solution containing >10% PVDF binder) is added to the formulation as a slurry and adhered to one or both sides of the membrane by spraying / rolling.

[0135] Combining the data from Examples 1 to 31 and Comparative Examples 1 to 5 Figure 1-4 It can be seen that the compounds shown in Formula I and Formula II can effectively solve a series of problems caused by the Jahn-Teller effect accompanying the positive electrode containing lithium iron manganese phosphate during the charging and discharging process of high-voltage 4.3V manganese-based lithium-ion batteries. The polarization factors such as the large current brought about by charging and discharging cause manganese ions to easily undergo disproportionation and dissolution effects on the surface of the positive electrode particles, which easily destroys the particle stability. This easily damages the SEI film of the negative electrode, triggering more side reactions, leading to accelerated loss of active lithium. With the aggravation of side reactions at the negative electrode interface, the negative electrode potential continuously increases, thus deteriorating the cell performance.

[0136] Comparative analysis of the experimental results of Examples 1-5 and 6-10 leads to the conclusion that: when the amount of compound I added is <0.05%, the low content of the additive is insufficient to form an effective dense and uniform passivation film with a sufficient number of functional groups, and cannot effectively reduce the amount of manganese ion dissolution during charge-discharge cycles, thus deteriorating cycle life; when the content of compound I is >6%, the manganese-based lithium-ion battery does not experience a further linear decrease in the dissolution of manganese ions with the increase of the additive content.

[0137] Based on the experimental data from Examples 1-11 and 12-25, it can be concluded that when the amount of Compound II added is low, it cannot effectively improve the high interfacial impedance and other problems caused by the film formation of Compound I. Increasing the amount of Compound II added can greatly improve the defects such as high interfacial impedance caused by Compound I. With the content of Compound II >6%, the improvement of high-temperature storage DCR of manganese-based lithium batteries reaches the upper limit and will not continue to decrease the high-temperature storage DCR as the content increases.

[0138] The performance data from Examples 2, 3, 4, 6 and Examples 26-31 show that compounds of Formula I and Formula II participate in the formation of the interface stabilizing film of manganese-based lithium-ion batteries as electrolyte additives, positive electrode additives, and separator spraying agents, and both have the effect of improving the cycle life at room temperature / high temperature.

[0139] Examples 32-35

[0140] The only difference from Example 1 is that the structures and amounts of ingredients in Formula I and Formula II are different.

[0141]

[0142] The structures of compounds 14 and 15 in the table above are as follows.

[0143]

[0144] Compounds 14 and 15 have significant structural differences compared to compounds 1-7. This difference in the spatial distance between the two carbon groups results in poor complexation with manganese ions, poor improvement in high-temperature cycling, high dissolution of manganese ions, and minimal improvement. The high-temperature storage capacity retention rate is at the same level as the benchmark.

[0145] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A manganese-based additive for secondary batteries, characterized in that, Including compounds of formula I, the structures of which are as follows; In Equation I, X and Y are independently selected from one of C, P, S, and Se, n1 is 1 or 2, and n2 is 1 or 2; where, R1 and R2 are independently selected from one of hydrogen, halogen, C1-C10 straight-chain alkyl, C1-C10 cyclic alkyl, C1-C10 haloalkyl, C1-C10 straight-chain alkenyl, C1-C10 cyclic alkenyl, C1-C10 straight-chain alkynyl, C1-C10 cyclic alkynyl, phenyl, substituted phenyl, benzyl, and substituted benzyl. R3 and R4 are independently selected from one of the following: halogen, C1-C10 alkyl, C1-C10 substituted alkyl, C1-C10 alkenyl, C1-C10 substituted alkenyl, C1-C10 alkynyl, C1-C10 substituted alkynyl, phenyl, substituted phenyl, benzyl or substituted benzyl.

2. The manganese-based secondary battery additive according to claim 1, characterized in that, It also includes compounds of formula II, the structures of which are as follows; In Formula II, R' is independently selected from one of the following: halogen, alkane-containing amine, unsaturated hydrocarbon-containing amine, C1-C10 alkyl, C1-C10 substituted alkyl, C1-C10 alkenyl, C1-C10 substituted alkenyl, C1-C10 alkynyl, C1-C10 substituted alkynyl, phenyl, substituted phenyl, benzyl or substituted benzyl.

3. The manganese-based secondary battery additive according to claim 1, characterized in that, The compound of formula I includes at least one of compound 1 to compound 7, and the structures of compound 1 to compound 7 are as follows: 。 4. The manganese-based secondary battery additive according to claim 2, characterized in that, The compound of formula II includes at least one of compounds 8 to 13, the structures of which are as follows: 。 5. The manganese-based secondary battery additive according to claim 2, characterized in that, The molar ratio of the compound of formula I to the compound of formula II is 1:0.8 to 1:1.

2.

6. A manganese-based secondary battery, characterized in that, The battery comprises a negative electrode, a positive electrode, a separator, and a non-aqueous electrolyte, wherein at least one of the positive electrode, separator, or non-aqueous electrolyte includes the manganese-based secondary battery additive as described in any one of claims 1-5.

7. The manganese-based secondary battery according to claim 6, characterized in that, The content of compound I in the non-aqueous electrolyte is 0.05 wt% to 15 wt%. And / or, the content of compound of formula I in the positive electrode sheet is 0.05 wt% to 15 wt%; And / or, the content of compound I in the diaphragm is 0.05 wt% to 15 wt%.

8. The manganese-based secondary battery according to claim 7, characterized in that, The content of compound I in the non-aqueous electrolyte is 0.05 wt% to 6 wt%.

9. The manganese-based secondary battery according to claim 7, characterized in that, The content of compound of formula I in the positive electrode sheet is 0.05 wt% to 6 wt%.

10. The manganese-based secondary battery according to claim 7, characterized in that, The content of compound I in the diaphragm is 0.05 wt% to 6 wt%.

11. The manganese-based secondary battery according to claim 6, characterized in that, The positive electrode sheet includes a positive electrode active material, which includes at least one of lithium manganese iron phosphate or nickel cobalt manganese ternary materials.

12. The manganese-based secondary battery according to claim 11, characterized in that, The lithium manganese iron phosphate has the general formula LiMn. m Fe 1-m PO4, where 0.95 ≥ m ≥ 0.

05.

13. The manganese-based secondary battery according to claim 11, characterized in that, The nickel-cobalt-manganese ternary material has the general formula Li a Ni x Co y Mn z M w O2, where 0.9≤a≤1.1, y≤0.2, z>0, x+y+z+w=1, and M includes Al.

14. The manganese-based secondary battery according to claim 6, characterized in that, The non-aqueous electrolyte includes organic solvents, lithium salts, and additives.

15. The manganese-based secondary battery according to claim 14, characterized in that, The additives include at least one of the following: vinyl sulfate, fluoroethylene carbonate, difluoroethylene carbonate, vinylene carbonate, 1,3-propanesulfonate lactone, 1-propylene-1,3-sulfonate lactone, methanedisulfonate, tris(trimethylsilyl) phosphate and tris(trimethylsilyl) phosphite, tris(trimethylsilyl) borate, lithium difluorodioxolane phosphate, lithium difluorophosphate, lithium difluorooxolane borate, and fluorobenzene.

16. The manganese-based secondary battery according to claim 15, characterized in that, The concentration of the additive in the non-aqueous electrolyte is 0.1 wt% to 3 wt%.

17. The manganese-based secondary battery according to claim 14, characterized in that, The lithium salt includes LiFSI and C4BLi3O. 11 LiPF 6-n (CF3) n , LiN[(FSO2C6F4)(CF3SO2)], LiSO3CF3, LiTFSI, LiCH(SO2CF3)2, LiTFSM, LiPF6, LiBF4, LiBOB, LiDFOB, LiAsF6, LiPO2F2, LiN(CF3SO2)2, LiCF3SO3, LiClO4 and LiN(C b F 2b+1 SO2)(C c F 2c+1 At least one of SO2, where n is an integer from 0 to 6, and b and c are both natural numbers.

18. The manganese-based secondary battery according to claim 17, characterized in that, The lithium ion molar concentration in the non-aqueous electrolyte is 0.1~3 mol / L.

19. The manganese-based secondary battery according to claim 14, characterized in that, The organic solvent is at least one of carbonates, carboxylic esters, sulfates, phosphates, amides, nitriles, and ethers.

20. The manganese-based secondary battery according to claim 19, characterized in that, The organic solvent is at least one selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, ethyl acetate, acid anhydride, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, acetonitrile, sulfolane, dimethyl sulfoxide, ethylene sulfite, propylene sulfite, triethyl phosphate, methyl ethyl phosphite, dimethyl sulfide, diethyl sulfite, dimethyl sulfite, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, fluorinated cyclic organic esters, and sulfur-containing cyclic organic esters.

21. The manganese-based secondary battery according to claim 19, characterized in that, The organic solvent content in the non-aqueous electrolyte is 60 wt% to 80 wt%.

22. The manganese-based secondary battery according to claim 14, characterized in that, The non-aqueous electrolyte also includes lithium difluorosulfonylimide.

23. The manganese-based secondary battery according to claim 22, characterized in that, The concentration of lithium difluorosulfonyl imide in the non-aqueous electrolyte is 0.02 wt% to 25 wt%.

24. The manganese-based secondary battery according to claim 23, characterized in that, The concentration of lithium difluorosulfonylimide in the non-aqueous electrolyte is 0.2 wt% to 19 wt%.

25. An electrical appliance, characterized in that, Includes the manganese-based secondary battery according to any one of claims 6-24.

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