A lithium iron manganese phosphate battery electrolyte, a lithium iron manganese phosphate battery and application thereof

Abstract

In order to solve the problem that the performance of the lithium iron manganese phosphate battery is poor under high temperature and high rate conditions, the application provides a lithium iron manganese phosphate battery electrolyte, a lithium iron manganese phosphate battery and application thereof.The electrolyte comprises an organic solvent, a lithium salt and an additive, and the additive is 4-bromo-3-nitroanisole.By adding the additive 4-bromo-3-nitroanisole to the electrolyte, the thermal stability and the electrochemical stability of the electrolyte under high temperature and low temperature conditions can be improved, so that the high-temperature cycle performance, the high-temperature storage performance and the high-low temperature charge-discharge performance of the battery are improved.

Description

Technical Field

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

[0002] Lithium manganese iron phosphate (LMFP), as a novel cathode material, has gradually attracted widespread attention in the industry due to its advantages such as low cost, high safety, and long cycle life. However, the performance of LMFP batteries under high temperature and high rate conditions still needs further improvement, especially the thermal stability, electrochemical stability, and low-temperature performance of the electrolyte. Although some additives have been added to existing electrolyte formulations to improve performance, the effects are still not ideal.

[0003] Therefore, there is an urgent need for a new type of additive that can significantly improve the overall performance of electrolytes, especially in high-temperature cycling, high-temperature storage, high and low temperature charge and discharge, and DCR performance. Summary of the Invention

[0004] The first objective of this invention is to provide a lithium manganese iron phosphate battery electrolyte that, by adding 4-bromo-3-nitroanisole, can significantly improve the battery's high-temperature cycle performance, high-temperature storage performance, high and low temperature charge-discharge performance, and DCR performance.

[0005] The second objective of this invention is to provide a lithium manganese iron phosphate battery.

[0006] A third objective of this invention is to provide an application of lithium manganese iron phosphate batteries.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a lithium iron phosphate battery electrolyte, comprising an organic solvent, a lithium salt, and an additive, wherein the additive is 4-bromo-3-nitrobenzene ether.

[0009] 4-Bromo-3-nitrobenzene ether, as a novel additive, exhibits significant advantages in the application of lithium manganese iron phosphate battery electrolytes. Firstly, regarding electrolyte stability, 4-bromo-3-nitrobenzene ether effectively inhibits side reactions in the electrolyte, reduces electrolyte decomposition under high voltage, and its unique chemical structure forms a stable passivation film on the electrode surface, thereby reducing adverse reactions between the electrolyte and electrode materials, extending electrolyte lifespan, and improving the overall cycle stability of the battery. Secondly, 4-bromo-3-nitrobenzene ether significantly enhances the electrochemical performance of the battery. It exhibits excellent electrochemical stability under high temperature and high voltage conditions, effectively improving the high-temperature performance of lithium manganese iron phosphate batteries, reducing capacity decay at high temperatures, thus improving capacity retention and enhancing charge-discharge performance. It also effectively reduces the battery's internal resistance, increasing energy density and power density. Furthermore, 4-bromo-3-nitrobenzene ether also exhibits positive effects in terms of safety. By inhibiting electrolyte decomposition and reducing gas generation, it can effectively reduce the safety risks of batteries under high-temperature conditions and decrease the possibility of thermal runaway. Therefore, as an additive for lithium manganese iron phosphate battery electrolytes, 4-bromo-3-nitrobenzene ether can not only significantly improve the cycle life and electrochemical performance of batteries but also enhance battery safety, showing broad application prospects.

[0010] Preferably, the additive accounts for 0.1% to 5% of the total mass of the electrolyte.

[0011] More preferably, the additive accounts for 0.5% to 2% of the total mass of the electrolyte, for example, 0.5%, 1%, 1.5%, or 2%.

[0012] Preferably, the organic solvent comprises at least one cyclic carbonate and at least one chain carbonate. Optimization of the organic solvent can further improve battery performance.

[0013] In some embodiments, the cyclic carbonate includes ethylene carbonate and propylene carbonate.

[0014] In some embodiments, the chain carbonate includes dimethyl carbonate and ethyl methyl carbonate.

[0015] Preferably, the volume ratio of cyclic carbonates to chain carbonates in the organic solvent is 1:(1.5-3), more preferably 1:(2-2.5).

[0016] In some specific embodiments, the organic solvent is ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0017] Furthermore, the volume ratio of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate is 1:(1-1.5):(1-1.5).

[0018] In some specific embodiments, the organic solvent is dimethyl carbonate, ethyl methyl carbonate, and propylene carbonate.

[0019] Furthermore, the dimethyl carbonate, ethyl methyl carbonate, and propylene carbonate are in a ratio of (1-1.5):(1-1.5):1.

[0020] Preferably, the lithium salt is selected from one or more of lithium hexafluorophosphate and / or lithium bis(trifluoromethanesulfonyl)imide.

[0021] Preferably, the molar concentration of the lithium salt is 0.1 to 2 mol / L.

[0022] More preferably, the molar concentration of the lithium salt is 0.5 to 1.5 mol / L, for example, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, or 1.5 mol / L.

[0023] A second aspect of the present invention provides a lithium manganese iron phosphate battery, comprising the electrolyte as described above. This lithium manganese iron phosphate battery exhibits superior high-temperature cycling performance, high-temperature storage performance, high and low temperature charge-discharge performance, and DCR performance.

[0024] Preferably, the positive electrode material of the lithium manganese iron phosphate battery is lithium manganese iron phosphate, and the negative electrode material is graphite.

[0025] A third aspect of the present invention provides an application of the lithium manganese iron phosphate battery as described above, including using the lithium manganese iron phosphate battery in an electric vehicle or an energy storage system.

[0026] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0027] This invention improves the thermal and electrochemical stability of the electrolyte under high and low temperature conditions by adding the additive 4-bromo-3-nitroanisole to the electrolyte, thereby improving the battery's high-temperature cycle performance, high-temperature storage performance, and high and low temperature charge and discharge performance. Detailed Implementation

[0028] Lithium manganese iron phosphate (LFP) batteries, as an emerging lithium-ion battery system, possess high safety, long cycle life, and relatively low cost, making them an ideal choice for future energy storage and electric vehicle applications. However, existing LFP batteries exhibit poor performance under extreme conditions such as high temperature, high rate, and low temperature, primarily due to insufficient electrolyte stability and electrochemical performance. Therefore, developing an electrolyte system that can significantly improve the performance of LFP batteries is of great importance.

[0029] Experimental research has shown that 4-bromo-3-nitroanisole, compared to other ether additives, can significantly improve the high-temperature cycle performance, high-temperature storage performance, high and low temperature charge-discharge performance, and DCR (DC internal resistance) performance of lithium manganese iron phosphate batteries. This additive can reduce the loss of electrode materials during high-temperature charge-discharge cycles, thereby extending the cycle life of the battery and improving its overall performance.

[0030] 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.

[0031] 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.

[0032] Electrolyte preparation:

[0033] In a glove box filled with inert gas and with a humidity of less than 1%, the required organic solvents are thoroughly mixed in proportion. Electrolyte salts with a total volume of 1 mol / L are added to the mixed solution in portions. After the electrolyte salts are completely dissolved, the basic electrolyte is obtained. Then, different proportions or different types of additives are added to the basic electrolyte to prepare the desired electrolyte.

[0034] The additives in the electrolytes of the examples and comparative examples are 4-bromo-3-nitrosoanisole, fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinylene sulfate (PES), anisole, or o-methoxyanisole; the solvent system consists of one or more of EC (ethylene carbonate), DMC (dimethyl carbonate), EMC (ethyl methyl carbonate), and PC (propylene carbonate); the lithium salt is lithium hexafluorophosphate (LiPF6) or lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The electrolyte formulations of each example and comparative example are shown in Tables 1 and 2 below.

[0035] Table 1

[0036]

[0037]

[0038] Table 2

[0039]

[0040] The electrolytes prepared in the above embodiments and comparative examples were assembled into lithium manganese iron phosphate graphite batteries. The batteries underwent the following performance tests, and the specific data are listed in Table 3.

[0041] 1. High-Temperature Cycling Test: The lithium manganese iron phosphate graphite battery was first placed in a constant temperature chamber at 55°C for a certain period of time to ensure that the battery reached the target temperature. Then, it was subjected to 100 charge-discharge cycles at a rate of 0.1C. Both charging and discharging were performed within the standard voltage range (e.g., 2.5V to 4.2V), and the battery charge-discharge cycle data were recorded. The test results show that the battery capacity gradually decreases during high-temperature cycling, but the battery of this embodiment still maintains a high capacity retention rate after 100 cycles, demonstrating good high-temperature cycling performance.

[0042] 2. High-Temperature Storage Test: The lithium manganese iron phosphate graphite battery was stored at 70°C for 30 days without charging or discharging. After storage, the battery's capacity was tested at room temperature. The results showed that after high-temperature storage, the battery capacity decreased to some extent, and the battery performance slightly degraded. However, the battery in this example still maintained a capacity retention rate of over 90%, and the battery did not show significant swelling. This indicates that under extreme high-temperature conditions, the internal materials of the battery underwent some aging, but the overall performance remained relatively stable, making it suitable for use in high-temperature environments.

[0043] 3. High and Low Temperature Charge-Discharge Test: First, the battery was stabilized at -20℃ and 60℃ for a certain period of time to reach the set temperature. Then, 50 charge-discharge cycles were performed at each of these two extreme temperatures, with the charge-discharge rate remaining at 0.1C. The results show that the battery of this embodiment exhibits strong adaptability and can operate over a wide temperature range.

[0044] Table 3

[0045]

[0046] Compared to conventional additives (such as fluoroethylene carbonate, vinylene carbonate, or vinylene sulfate), or ether additives such as anisole / o-methoxyanisole, 4-bromo-3-nitroanisole can significantly improve battery performance, especially in high-temperature cycling, high-temperature storage, high and low temperature charge and discharge, and DCR tests. 4-bromo-3-nitroanisole as an electrolyte additive for lithium manganese iron phosphate batteries has shown higher capacity retention and relatively lower internal resistance.

[0047] As the proportion of 4-bromo-3-nitroanisole in the electrolyte increases, the high-temperature cycle performance, high-temperature storage performance, and high and low temperature charge and discharge performance of the battery all show a trend of first increasing and then decreasing. Preferably, 4-bromo-3-nitroanisole accounts for 0.1% to 5% of the total mass of the electrolyte, more preferably 0.5% to 2.0%, and best at 1%.

[0048] The solvent system has a certain impact on battery performance. Compared to a mixture of dimethyl carbonate, methyl ethyl carbonate, and propylene carbonate, a mixture of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate is more helpful in improving battery performance. Optimizing the ratio of each solvent can further enhance battery performance.

[0049] Lithium salts also have some impact on battery performance, but the impact is not significant. Using lithium trifluoromethanesulfonylimide or lithium hexafluorophosphate can achieve better results.

[0050] 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 lithium iron phosphate battery electrolyte, comprising an organic solvent, a lithium salt, and additives, characterized in that: The additive is 4-bromo-3-nitrobenzene ether.

2. The lithium iron phosphate battery electrolyte according to claim 1, characterized in that: The additive accounts for 0.1% to 5% of the total mass of the electrolyte.

3. The lithium iron phosphate battery electrolyte according to claim 2, characterized in that: The additive accounts for 0.5% to 2% of the total mass of the electrolyte.

4. The lithium iron phosphate battery electrolyte according to claim 1, characterized in that: The organic solvent includes at least one cyclic carbonate and at least one chain carbonate.

5. The lithium iron phosphate battery electrolyte according to claim 4, characterized in that: The cyclic carbonates include ethylene carbonate and propylene carbonate; and / or, The chain carbonates include dimethyl carbonate and ethyl methyl carbonate.

6. The lithium iron phosphate battery electrolyte according to claim 4 or 5, characterized in that: The volume ratio of cyclic carbonates to chain carbonates in the organic solvent is 1:(1.5-3).

7. The lithium iron phosphate battery electrolyte according to claim 1, characterized in that: The lithium salt is selected from lithium hexafluorophosphate and / or lithium bis(trifluoromethanesulfonyl)imide.

8. The lithium iron phosphate battery electrolyte according to claim 1, characterized in that: The molar concentration of the lithium salt is 0.1–2 mol / L.

9. A lithium manganese iron phosphate battery, characterized in that: Includes the electrolyte as described in any one of claims 1 to 8.

10. The application of the lithium manganese iron phosphate battery as described in claim 9, characterized in that: The lithium manganese iron phosphate battery is used in electric vehicles or energy storage systems.

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