Lithium manganese iron phosphate battery electrolyte and lithium manganese iron phosphate battery

Abstract

In order to improve the high-temperature durability and safety of the lithium manganese iron phosphate battery, the invention provides the lithium manganese iron phosphate battery electrolyte and the lithium manganese iron phosphate battery, the electrolyte comprises an organic solvent, a lithium salt and an additive, and the additive comprises N, N-dimethyl sulfonamide and diphenyl phosphate. N, N-dimethyl sulfonamide and diphenyl phosphite are added into the electrolyte, and the N, N-dimethyl sulfonamide and diphenyl phosphite cooperate to inhibit dissolution of manganese ions in the lithium manganese iron phosphate battery, relieve swelling of the battery at high temperature, improve the high-temperature capacity retention ratio of the battery and prolong the high-temperature cycle life of the battery, so that the market competitiveness of the lithium manganese iron phosphate battery is improved; and a more reliable and efficient energy solution is provided for electric automobiles, energy storage systems and consumer electronics.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a lithium manganese iron phosphate battery electrolyte and a lithium manganese iron phosphate battery. Background Technology

[0002] Lithium manganese iron phosphate (LMFP) batteries, as an emerging type of lithium-ion battery, are gradually gaining widespread application due to their advantages in energy density, operating voltage, and low-temperature performance.

[0003] In the electric vehicle sector, battery pack temperatures rise significantly during operation, especially at high speeds or during fast charging. Under these high-temperature conditions, the chemical stability and safety of the battery are crucial. If the battery cannot maintain stability at high temperatures, it will not only affect driving range but may also lead to safety accidents. In energy storage systems, large-scale systems are often exposed to high-temperature environments, particularly in outdoor applications such as solar power plants. High temperatures place higher demands on battery durability; rapid aging or failure at high temperatures significantly increases maintenance and replacement costs. In consumer electronics, devices such as mobile phones and laptops experience significant temperature increases during prolonged use or fast charging. Batteries must be able to operate safely and reliably at high temperatures to ensure device stability and user safety. All these fields require batteries with superior high-temperature performance. However, while lithium manganese iron phosphate batteries perform well at room temperature, their electrolyte and electrode materials are prone to chemical reactions at high temperatures, leading to capacity decay, increased internal resistance, and even the risk of thermal runaway. These problems not only affect battery life but also threaten device safety. Therefore, improving the high-temperature durability and safety of lithium manganese iron phosphate batteries is a key technological challenge that must be addressed.

[0004] Electrolyte is a crucial component of lithium-ion batteries, directly impacting their performance and stability. Optimizing electrolyte formulations is a key research direction for lithium manganese iron phosphate (LFP) batteries. By adjusting the proportions of solvents, salts, and additives in the electrolyte, the battery's ionic conductivity, interfacial stability, and electrode material compatibility can be controlled. For example, some studies have shown that using solvents with high dielectric constants, such as acrylonitrile and dimethyl carbonate, can improve the electrolyte's ionic conductivity, thereby enhancing the battery's discharge performance. Research on electrolyte additives is also critical, as they can improve the electrolyte's chemical stability, suppress battery polarization, and enhance cycle life. For instance, the use of surfactants and phosphate additives can form a protective film, reducing electrode material dissolution and electrolyte corrosion, thus extending battery life. Furthermore, addressing solvent degradation and oxidation in the electrolyte is currently a research hotspot. As the number of battery cycles increases, solvents in the electrolyte decompose and oxidize, leading to decreased battery performance and reduced safety. Therefore, researchers are searching for solvents and additives with better stability to improve electrolyte durability and cycle stability. Furthermore, research on lithium manganese iron phosphate (LFP) battery electrolytes must fully consider battery safety. The instability and flammability of the electrolyte can lead to serious safety accidents such as thermal runaway and explosions. Therefore, researchers are developing safer and more reliable electrolyte formulations and improving battery safety by controlling the proportions of electrolyte components and adding appropriate inhibitors. In general, research on LFP battery electrolytes is one of the important research directions in the field of lithium-ion batteries, involving multiple aspects such as electrolyte formulation optimization, additive research, and solvent stability. Through in-depth research and optimization of electrolytes, the performance and safety of LFP batteries can be further improved, promoting their widespread application in electric vehicles, energy storage systems, and other fields. Summary of the Invention

[0005] The purpose of this invention is to provide a lithium manganese iron phosphate battery electrolyte and a lithium manganese iron phosphate battery with good high-temperature cycling performance and good thermal stability.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A lithium iron phosphate battery electrolyte includes an organic solvent, a lithium salt, and additives, wherein the additives include N,N-dimethylsulfonamide and diphenyl phosphite.

[0008] By adding N,N-dimethylsulfonamide and diphenyl phosphite to the electrolyte, the synergistic effect of these two substances can inhibit the dissolution of manganese ions, effectively prevent electrolyte decomposition at high temperatures, reduce battery swelling at high temperatures, thereby lowering the risk of battery thermal runaway and improving battery safety performance in high-temperature environments. Furthermore, it can also improve the battery's high-temperature capacity retention rate and high-temperature cycle life.

[0009] Preferably, the sum of the mass of N,N-dimethylsulfonamide and diphenyl phosphite accounts for 10-20% of the total mass of the electrolyte, and the mass ratio of N,N-dimethylsulfonamide to diphenyl phosphite is (0.7-2.5):1.

[0010] More preferably, the mass ratio of the N,N-dimethylsulfonamide to the diphenyl phosphite is (0.75-2):1.

[0011] In some embodiments, the N,N-dimethylsulfonamide accounts for 5 to 10% of the total mass of the electrolyte, for example, 5%, 6%, 7%, 8%, 9% or 10%.

[0012] In some embodiments, the diphenyl phosphite accounts for 4 to 10% of the total mass of the electrolyte, for example, 4%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0013] Preferably, the additive further includes one or more of fluorinated cyclic carbonates, phosphate esters, sulfate esters, and lithium difluorophosphate (LiDFP). The addition of these additives helps improve the electrochemical stability of the electrolyte, reduces the wear on electrode materials during high-temperature charge-discharge cycles, thereby extending the battery's lifespan and improving its overall reliability.

[0014] Preferably, the fluorocyclic carbonate is fluoroethylene carbonate.

[0015] Preferably, the fluorocyclic carbonate accounts for 0.1% to 8% of the total mass of the electrolyte, more preferably 1% to 8%, for example 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8%.

[0016] Preferably, the phosphate ester is selected from triethyl phosphate and / or methyl methyl phosphate.

[0017] Preferably, the phosphate ester accounts for 1-9% of the total mass of the electrolyte, more preferably 2-6%, for example 2%, 3%, 4%, 5%, 6%.

[0018] Preferably, the sulfate ester is dimethyl sulfate.

[0019] Preferably, the sulfate ester accounts for 0.1% to 6% of the total mass of the electrolyte, more preferably 1% to 6%, for example 1%, 2%, 3%, 4%, 5%, or 6%.

[0020] Preferably, the lithium difluorophosphate accounts for 0.5% to 5% of the total mass of the electrolyte, more preferably 0.5% to 3%, for example 0.5%, 1%, 2%, or 3%.

[0021] In some embodiments, the additive further includes fluoroethylene carbonate, which accounts for 4 to 7% of the total mass of the electrolyte, for example 4%, 5%, 6%, or 7%.

[0022] In some embodiments, the additive further includes triethyl phosphate and / or methyl methyl phosphate, wherein the triethyl phosphate and methyl methyl phosphate each independently account for 2 to 4% of the total mass of the electrolyte, for example 2%, 2.5%, 3%, 3.5%, and 4%.

[0023] In some embodiments, the additive further includes fluoroethylene carbonate and lithium difluorophosphate or dimethyl sulfate or triethyl phosphate or methyl methyl phosphate, wherein the fluoroethylene carbonate accounts for 1 to 5% of the total mass of the electrolyte, for example 1%, 2%, 3%, 4%, or 5%; and the lithium difluorophosphate or dimethyl sulfate or triethyl phosphate or methyl methyl phosphate accounts for 0.5 to 5% of the total mass of the electrolyte, for example 0.5%, 1%, 2%, 3%, 4%, or 5%.

[0024] In some embodiments, the additive further includes dimethyl sulfate, which accounts for 2 to 5% of the total mass of the electrolyte, for example 2%, 3%, 4% or 5%.

[0025] In some embodiments, the additive further includes methyl methyl phosphate and lithium difluorophosphate, wherein the methyl methyl phosphate and lithium difluorophosphate each independently account for 1.5% to 3.5% of the total mass of the electrolyte, for example 1.5%, 2%, 2.5%, 3%, and 3.5%.

[0026] Preferably, the organic solvent is selected from one or more carbonate organic solvents.

[0027] More preferably, the carbonate organic solvent includes cyclic carbonates and / or chain carbonates.

[0028] More preferably, the cyclic carbonate includes ethylene carbonate and propylene carbonate.

[0029] More preferably, the chain carbonate includes methyl ethyl carbonate, dimethyl carbonate, and diethyl carbonate.

[0030] In some embodiments, the organic solvent is selected from one of cyclic carbonates and one of linear carbonates.

[0031] Furthermore, the mass ratio of the cyclic carbonate to the chain carbonate is 1:(1 to 2.5).

[0032] In some embodiments, the organic solvent is selected from any two cyclic carbonates.

[0033] Furthermore, the mass ratio of the two cyclic carbonates is (2-3):(2-3).

[0034] Preferably, the lithium salt is selected from one or more of lithium tetrafluoroborate, lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, and lithium difluorophosphate.

[0035] More preferably, the molar concentration of the lithium salt in the electrolyte is 0.1–1.5 M, and more preferably 0.5–1.5 M.

[0036] The present invention also provides a lithium manganese iron phosphate battery, wherein the lithium manganese iron phosphate battery includes the electrolyte as described above.

[0037] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0038] The present invention adds N,N-dimethylsulfonamide and diphenyl phosphite to the electrolyte. The two work synergistically to inhibit the dissolution of manganese ions in lithium iron phosphate batteries, reduce battery swelling at high temperatures, improve battery high-temperature capacity retention and high-temperature cycle life, which is conducive to enhancing the market competitiveness of lithium iron phosphate batteries and providing a more reliable and efficient energy solution for electric vehicles, energy storage systems and consumer electronics products. Detailed Implementation

[0039] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific applications, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0040] Unless otherwise specified, the reagents, instruments, etc. used in the following examples and comparative examples are all commercially available products commonly used in the art, or can be prepared by conventional preparation methods in the art.

[0041] Unless otherwise specified, the preparation method of the electrolyte includes: in a glove box filled with Ar and with H2O content not exceeding 10 ppm, the required organic solvent is thoroughly mixed in proportion, and the electrolyte salt LiPF6 with a total amount of 1 mol / L is added to the mixed solution in portions. After it is completely dissolved, a basic electrolyte is obtained. Then, different proportions or different types of additives or combinations of additives are added to the basic electrolyte to obtain the electrolyte.

[0042] Unless otherwise specified, "%" refers to a mass percentage. Taking Example 1 as an example, the base electrolyte EC 50% and DMC 50% means that EC and DMC are mixed in a mass ratio of 1:1; the additive FEC 5% means that FEC accounts for 5% of the total mass of the electrolyte.

[0043] Example 1

[0044] Basic electrolyte: 50% ethylene carbonate (EC), 50% dimethyl carbonate (DMC), 1 mol / L LiPF6;

[0045] Additives: 5% fluoroethylene carbonate (FEC), 10% N,N-dimethylsulfonamide, and 5% diphenyl phosphite.

[0046] Example 2

[0047] Basic electrolyte: 30% ethylene carbonate (EC), 70% dimethyl carbonate (DMC), 1 mol / L LiPF6;

[0048] Additives: 6% fluoroethylene carbonate (FEC), 8% N,N-dimethylsulfonamide, and 8% diphenyl phosphite.

[0049] Example 3

[0050] Basic electrolyte: 40% ethylene carbonate (EC), 60% diethyl carbonate (DEC), 1 mol / L LiPF6;

[0051] Additives: Triethyl phosphate (TEP) 3%, Methyl methyl phosphate 2%, N,N-dimethylsulfonamide 8%, Diphenyl phosphite 5%.

[0052] Example 4

[0053] Basic electrolyte: 60% propylene carbonate (PC), 40% ethylene carbonate (EC), 1 mol / L LiPF6;

[0054] Additives: Triethyl phosphate (TEP) 4%, N,N-dimethylsulfonamide 6%, diphenyl phosphite 5%.

[0055] Example 5

[0056] Basic electrolyte: 50% ethylene carbonate (EC), 50% dimethyl carbonate (DMC), 1 mol / L LiPF6;

[0057] Additives: 4% fluoroethylene carbonate (FEC), 1% lithium difluorophosphate (LiDFP), 10% N,N-dimethylsulfonamide, and 6% diphenyl phosphite.

[0058] Example 6

[0059] Basic electrolyte: 40% ethylene carbonate (EC), 60% diethyl carbonate (DEC), 1 mol / L LiPF6;

[0060] Additives: 2% fluoroethylene carbonate (FEC), 3% dimethyl sulfate (DMS), 8% N,N-dimethylsulfonamide, and 5% diphenyl phosphite.

[0061] Example 7

[0062] Basic electrolyte: 50% ethylene carbonate (EC), 50% propylene carbonate (PC), 1 mol / L LiPF6;

[0063] Additives: 2% fluoroethylene carbonate (FEC), 3% triethyl phosphate (TEP), 8% N,N-dimethylsulfonamide, and 7% diphenyl phosphite.

[0064] Example 8

[0065] Basic electrolyte: 60% ethylene carbonate (EC), 40% propylene carbonate (PC), 1 mol / L LiPF6;

[0066] Additives: Lithium difluorophosphate (LiDFP) 2%, methyl methyl phosphate 3%, N,N-dimethylsulfonamide 5%, diphenyl phosphite 5%.

[0067] Example 9

[0068] Basic electrolyte: 30% ethylene carbonate (EC), 70% dimethyl carbonate (DMC), 1 mol / L LiPF6;

[0069] Additives: 5% dimethyl sulfate (DMS), 9% N,N-dimethylsulfonamide, and 5% diphenyl phosphite.

[0070] Example 10

[0071] Basic electrolyte: ethylene carbonate (EC) 35%, diethyl carbonate (DEC) 65%, LiPF6 1mol / L;

[0072] Additives: Triethyl phosphate (TEP) 2%, Methyl methyl phosphate 3%, N,N-dimethylsulfonamide 6%, Diphenyl phosphite 8%.

[0073] Example 11

[0074] Basic electrolyte: 50% ethylene carbonate (EC), 50% dimethyl carbonate (DMC), 1 mol / L LiPF6;

[0075] Additives: 3% fluoroethylene carbonate (FEC), 2% dimethyl sulfate (DMS), 7% N,N-dimethylsulfonamide, and 7% diphenyl phosphite.

[0076] Example 12

[0077] Basic electrolyte: 40% ethylene carbonate (EC), 60% diethyl carbonate (DEC), 1 mol / L LiPF6;

[0078] Additives: 1% fluoroethylene carbonate (FEC), 4% triethyl phosphate (TEP), 9% N,N-dimethylsulfonamide, and 5% diphenyl phosphite.

[0079] Example 13

[0080] Basic electrolyte: 50% ethylene carbonate (EC), 50% dimethyl carbonate (DMC), 1 mol / L LiPF6;

[0081] Additives: 5% fluoroethylene carbonate (FEC), 5% N,N-dimethylsulfonamide, and 5% diphenyl phosphite.

[0082] Example 14

[0083] Basic electrolyte: 50% ethylene carbonate (EC), 50% dimethyl carbonate (DMC), 1 mol / L LiPF6;

[0084] Additives: 5% fluoroethylene carbonate (FEC), 10% N,N-dimethylsulfonamide, and 4% diphenyl phosphite.

[0085] Example 15

[0086] Basic electrolyte: 50% ethylene carbonate (EC), 50% dimethyl carbonate (DMC), 1 mol / L LiPF6;

[0087] Additives: 10% N,N-dimethylsulfonamide, 5% diphenyl phosphite.

[0088] Comparative Example 1

[0089] Basic electrolyte: 50% ethylene carbonate (EC), 50% dimethyl carbonate (DMC), 1 mol / L LiPF6;

[0090] Additive: 5% fluoroethylene carbonate (FEC).

[0091] Comparative Example 2

[0092] Basic electrolyte: 30% ethylene carbonate (EC), 70% dimethyl carbonate (DMC), 1 mol / L LiPF6;

[0093] Additive: 5% fluoroethylene carbonate (FEC).

[0094] Comparative Example 3

[0095] Basic electrolyte: 50% ethylene carbonate (EC), 50% diethyl carbonate (DEC), 1 mol / L LiPF6;

[0096] Additive: 4% fluoroethylene carbonate (FEC).

[0097] Comparative Example 4

[0098] Basic electrolyte: 60% propylene carbonate (PC), 40% ethylene carbonate (EC), 1 mol / L LiPF6;

[0099] Additive: 5% fluoroethylene carbonate (FEC).

[0100] Comparative Example 5

[0101] Basic electrolyte: 50% ethylene carbonate (EC), 50% propylene carbonate (PC), 1 mol / L LiPF6;

[0102] Additives: 3% fluoroethylene carbonate (FEC), 2% dimethyl sulfate (DMS).

[0103] Comparative Example 6

[0104] Basic electrolyte: 60% ethylene carbonate (EC), 40% dimethyl carbonate (DMC), 1 mol / L LiPF6;

[0105] Additives: 1% fluoroethylene carbonate (FEC), 4% triethyl phosphate (TEP).

[0106] Comparative Example 7

[0107] Basic electrolyte: 40% ethylene carbonate (EC), 60% diethyl carbonate (DEC), 1 mol / L LiPF6;

[0108] Additive: Triethyl phosphate (TEP) 4%.

[0109] Comparative Example 8

[0110] Basic electrolyte: 50% ethylene carbonate (EC), 50% dimethyl carbonate (DMC), 1 mol / L LiPF6;

[0111] Additive: 10% N,N-dimethylsulfonamide.

[0112] Comparative Example 9

[0113] Basic electrolyte: 50% ethylene carbonate (EC), 50% dimethyl carbonate (DMC), 1 mol / L LiPF6;

[0114] Additive: 5% diphenyl phosphite.

[0115] Comparative Example 10

[0116] Basic electrolyte: ethylene carbonate (EC) 35%, diethyl carbonate (DEC) 65%, LiPF6 1mol / L;

[0117] Additives: 2% triethyl phosphate (TEP), 3% methyl phosphate.

[0118] The electrolytes prepared in the above embodiments and comparative proportions were respectively assembled into lithium manganese iron phosphate graphite batteries, and the following performance tests were performed on the batteries.

[0119] 1. Thermal stability test:

[0120] Test conditions: The battery was charged to 4.2V at 0.33C under constant current / constant voltage (CC / CV) conditions at 25℃, then stored at 70℃ for 14 days. After storage, it was discharged to 2.5V at 0.33C, and then charged again to 4.2V at 0.33C. The capacity and battery thickness were tested after 14 days of storage at 70℃. The self-discharge and swelling of the battery were observed, and the capacity retention rate, battery swelling rate, and Mn ion content in the electrodes after storage were tested. The test data are shown in Table 1.

[0121] Results: The batteries in the examples maintained good shape after high-temperature storage without significant expansion, while the comparative batteries showed significant expansion.

[0122] 2. Cycle life test:

[0123] Test conditions: Charge-discharge cycle test at 1C / 1C rate under high temperature (45℃) and DCR test at 3C constant current discharge for 30s under 50% SOC state. The relevant experimental data are shown in Table 2.

[0124] Results: The cycle life of the battery in the example is significantly better than that of the comparative battery. Specifically, after 300 cycles, the capacity retention of the battery in the example is more than 90%, while the capacity retention of the comparative battery is less than 80%.

[0125] The capacity retention rate (C1 / C0) of the battery after storage at 70°C is equal to the capacity C1 at the end of storage at 70°C divided by the capacity C0 before storage; the battery swelling rate ((d2-d1) / d1) of the battery after storage at 70°C is equal to the difference between the battery thickness d2 after storage and the battery thickness d1 before storage divided by the battery thickness d1 before storage.

[0126] The capacity retention rate test method for the above-mentioned lithium manganese iron phosphate graphite battery after 300 cycles at 45℃ is as follows: under constant current / constant voltage (CC / CV) conditions at 45℃, the battery is charged to 4.2V at 0.5C and discharged to 2.5V at 1C. The ratio of the battery capacity after 300 cycles at 45℃ to the battery capacity after the first charge-discharge cycle is the capacity retention rate after 300 cycles at 45℃. The DCR test method at 50% SOC and 3C for 30s is as follows: the ratio of the voltage difference to the current during 3C constant current discharge for 30s at 50% SOC is ((V2-V1) / V2) / V2. I The test was conducted under the following conditions.

[0127] Table 1

[0128]

[0129]

[0130] Table 2

[0131]

[0132]

[0133] Comparative examples and comparative examples show that the simultaneous addition of N,N-dimethylsulfonamide and diphenyl phosphite to the electrolyte can effectively improve the thermal stability of the battery and enhance its high-temperature cycle life.

[0134] Furthermore, in addition to N,N-dimethylsulfonamide and diphenyl phosphite, the addition of one or more of fluoroethylene carbonate, phosphate ester additives, lithium difluorophosphate, and dimethyl sulfate can further optimize battery performance.

[0135] For organic solvents, this application uses carbonate organic solvents such as ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate. The effects of using two of these organic solvents in combination are similar.

[0136] The present invention has been described in detail above, with the aim of enabling those skilled in the art to understand and implement the invention. However, this description should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be included within the scope of protection of the invention.

Claims

1. A manganese iron lithium phosphate battery electrolyte comprising an organic solvent, a lithium salt and an additive, characterized in that: The additive comprises N,N-dimethyl sulfamide and diphenyl phosphite.

2. The lithium iron manganese phosphate battery electrolyte according to claim 1, characterized in that: The sum of the mass of the N,N-dimethyl sulfamide and the diphenyl phosphite accounts for 10-20% of the total mass of the electrolyte, and the mass ratio of the N,N-dimethyl sulfamide to the diphenyl phosphite is (0.7-2.5):

1.

3. The lithium iron manganese phosphate battery electrolyte of claim 1, wherein: The N,N-dimethyl sulfamide accounts for 5-10% of the total mass of the electrolyte; and / or, The diphenyl phosphite accounts for 4-10% of the total mass of the electrolyte.

4. The lithium iron manganese phosphate battery electrolyte of claim 1, wherein: The additive further comprises one or more of fluorinated cyclic carbonate, phosphate ester, sulfate ester, and lithium difluorophosphate.

5. The lithium iron manganese phosphate battery electrolyte of claim 4, wherein: The fluorinated cyclic carbonate is fluorinated ethylene carbonate; and / or, The phosphate ester is selected from triethyl phosphate and / or methyl methylphosphonate; and / or, The sulfate ester is dimethyl sulfate.

6. The lithium iron manganese phosphate battery electrolyte of claim 4, wherein: The fluorinated cyclic carbonate accounts for 0.1-8% of the total mass of the electrolyte; and / or, The phosphate ester accounts for 1-9% of the total mass of the electrolyte; and / or, The sulfate ester accounts for 0.1-6% of the total mass of the electrolyte; and / or, The lithium difluorophosphate accounts for 0.5-5% of the total mass of the electrolyte.

7. The lithium iron manganese phosphate battery electrolyte according to any one of claims 4 to 6, characterized in that: The additive further comprises fluorinated ethylene carbonate, which accounts for 4-7% of the total mass of the electrolyte; Alternatively, the additive further comprises triethyl phosphate and / or methyl methylphosphonate, which independently accounts for 2-4% of the total mass of the electrolyte; Alternatively, the additive further comprises fluorinated ethylene carbonate and lithium difluorophosphate or dimethyl sulfate or triethyl phosphate or methyl methylphosphonate, the fluorinated ethylene carbonate accounts for 1-5% of the total mass of the electrolyte, and the lithium difluorophosphate or dimethyl sulfate or triethyl phosphate or methyl methylphosphonate accounts for 0.5-5% of the total mass of the electrolyte; Alternatively, the additive further comprises dimethyl sulfate, which accounts for 2-5% of the total mass of the electrolyte; Alternatively, the additive further comprises methyl methylphosphonate and lithium difluorophosphate, which independently accounts for 1.5-3.5% of the total mass of the electrolyte.

8. The lithium iron manganese phosphate battery electrolyte of claim 1, wherein: The organic solvent is selected from one or more of carbonate-based organic solvents.

9. The lithium iron manganese phosphate battery electrolyte of claim 1, wherein: The lithium salt is selected from one or more of lithium tetrafluoroborate, lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, and lithium difluorophosphate; and / or, The molar concentration of the lithium salt in the electrolyte is 0.1-1.5 M.

10. A lithium iron manganese phosphate battery characterized by: The lithium iron manganese phosphate battery comprises the electrolyte according to any one of claims 1-9.

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