Lithium battery electrolyte and secondary lithium battery
By adding pyridine heterocyclic additives and other functional additives to the lithium battery electrolyte, the problem of poor circulation performance of lithium batteries at high voltage is solved, and the effect of reducing gas production and improving circulation performance is achieved.
Patent Information
- Application Number
- CN202310989617.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-08-08
- Publication Date
- 2025-02-18
AI Technical Summary
At high voltage, the cycling performance of lithium batteries is affected by problems such as gas production, self-discharge and SEI film damage, resulting in a degradation of battery performance.
Using electrolyte containing pyridine heterocyclic additives, combined with other functional additives, such as ethylene carbonate, succinitrile and ethylene sulfate, optimize the composition of the electrolyte to reduce gas production at high voltages and improve circulation performance. .
It significantly reduces the gas production of lithium batteries at high voltages, improves the discharge capacity retention rate, and enhances the long-term high-voltage charge and discharge cycle performance of the battery.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of lithium ion batteries, and in particular relates to a lithium battery electrolyte and a secondary lithium battery. Background Art
[0002] Spinel lithium nickel manganese oxide (LNMO) battery material is a high-performance cathode powder suitable for next-generation lithium-ion battery manufacturers and energy storage technology developers. LNMO cathode material is cost-effective, cobalt-free and low in nickel content. Due to its three-dimensional spinel structure and electrochemical properties, it can provide excellent energy density and high voltage platform. LNMO is developed based on lithium manganese oxide (LMO). LNMO formed when the Ni and Mn content is 1:1 has a 4.7V high voltage platform and a specific capacity similar to LCO, making the theoretical energy density exceed 500Wh / kg. At the same time, because the voltage platform is higher than the redox potential of Mn ions, there is no problem of LMFP structural changes, and the material cycle stability is good. But at the same time, due to the increase in the battery voltage platform, higher requirements are also placed on the electrolyte. Compared with conventional electrolytes, electrolytes matching high voltages not only need to have a higher decomposition potential, but also need to be able to better protect electrode materials. Although people have made many efforts on this basis, there are still many problems that affect the high-voltage cycle performance of batteries during the research process, such as transition metal dissolution, large self-discharge of fully charged batteries, serious gas production during the cycle, and damage to the SEI film leading to reduced battery performance. It is very important to overcome the above problems and obtain an electrolyte that can be cycled for a long time at high voltage. Summary of the invention
[0003] The technical problem to be solved by the present invention is to provide an electrolyte that can suppress the gas generation problem of a high-voltage lithium battery during cycling and improve the cycling performance.
[0004] In order to achieve the above object, the technical solution adopted by the present invention is:
[0005] A lithium battery electrolyte, comprising an organic solvent, an electrolyte lithium salt and an additive, wherein the additive comprises a structural formula Pyridine heterocyclic additives.
[0006] Preferably, the feeding mass of the pyridine heterocyclic additive is 0.5-2% of the total mass of the lithium battery electrolyte, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%.
[0007] Preferably, the additives further include other additives, and the other additives are one or more of ethylene carbonate, succinic anhydride, succinonitrile, lithium difluorophosphate, lithium dioxalatoborate, lithium difluorooxalatoborate, and ethylene sulfate.
[0008] Preferably, the mass of the other additives is 0.5-5% of the total mass of the lithium battery electrolyte, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%.
[0009] Preferably, the other additive is a combination of ethylene carbonate, succinonitrile, lithium difluorooxalatoborate and ethylene sulfate.
[0010] More preferably, the feed mass ratio of ethylene carbonate, succinonitrile, lithium difluorooxalatoborate and ethylene sulfate is (0.8-1.2):(0.8-1.2):(0.8-1.2):1.
[0011] More preferably, the feed weights of ethylene carbonate, succinonitrile, lithium difluorooxalatoborate and ethylene sulfate are 0.5-2% respectively.
[0012] Preferably, the electrolyte lithium salt is one or more of LiPF6, LiTFSI, LiBF4, LiClO4, LiCH3SO3, LiSCN, LiNO3, LiO3SCF2CF3, LiAsF6, and LiAlCl4.
[0013] Preferably, the concentration of the electrolyte lithium salt in the lithium battery electrolyte is 0.5-2 mol / L, for example, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2 mol / L.
[0014] Preferably, the organic solvent is one or more of carbonates, fluorocarbonates, carboxylates, fluorocarboxylates, ethers, fluoroethers, and sulfones.
[0015] More preferably, the carbonate is a cyclic carbonate and / or a chain carbonate.
[0016] More preferably, the carbonate is one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and propylene carbonate.
[0017] Further pre-selected, the fluorinated carbonate is a cyclic fluorinated carbonate and / or a chain fluorinated carbonate.
[0018] More preferably, the fluorocarbonate is one or more of fluoroethylene carbonate, fluorodimethyl carbonate, difluorodimethyl carbonate, and fluoroethyl methyl carbonate.
[0019] Further preferably, the carboxylate is a cyclic carboxylate and / or a chain carboxylate. When the cyclic carboxylate and the chain carboxylate are used simultaneously, the feed mass ratio of the cyclic carboxylate to the chain carboxylate is 1:(0.5-2.5).
[0020] More preferably, the carboxylic acid ester is one or more of methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, ethyl propionate, methyl butyrate, and ethyl butyrate.
[0021] More preferably, the fluorocarboxylate is a cyclic fluorocarboxylate and / or a chain fluorocarboxylate.
[0022] More preferably, the ether is one or more of dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, and 1,3-dioxolane.
[0023] More preferably, the sulfone is one or more of dimethyl sulfoxide, sulfolane, and dimethyl sulfone.
[0024] More preferably, the organic solvent is a mixture of carbonate and fluorocarbonate.
[0025] Still more preferably, the organic solvent is a combination of ethylene carbonate, fluoroethyl methyl carbonate, fluorodimethyl carbonate and ethyl methyl carbonate.
[0026] More preferably, the feed mass ratio of ethylene carbonate, fluoroethyl methyl carbonate, dimethyl fluorocarbonate and ethyl methyl carbonate is (2-6):(5-11):(1-2):1, more preferably (2-3):(5-7):(1-1.5):1.
[0027] A second aspect of the present invention provides a secondary lithium battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the electrolyte is the above-mentioned lithium battery electrolyte.
[0028] Preferably, the active material of the positive electrode is spinel nickel lithium manganese oxide.
[0029] Preferably, the negative electrode is selected from metallic lithium, graphite, natural graphite, artificial graphite, hard carbon, soft carbon, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, tin-based composite materials, spinel-structured lithiated TiO2, Li4Ti5O 12, Li-Al alloy, silicon, Li-Si alloy, Li-Si-O alloy, silicon-based composite materials, and one or more of tin-silicon composite materials.
[0030] Preferably, the diaphragm comprises a substrate and a coating, the substrate is made of polyethylene and / or polypropylene, and the coating is organic matter and / or metal oxide.
[0031] Preferably, the voltage of the secondary lithium battery is 3-4.9V.
[0032] Due to the adoption of the above technical solution, the present invention has the following advantages compared with other processes:
[0033] The electrolyte of the present invention reduces gas generation during high-voltage charge-discharge cycles at room temperature by adding specific pyridine heterocyclic additives, improves the discharge capacity retention rate under long-term cycles, and can further improve the long-term high-voltage charge-discharge cycle performance of lithium batteries by using other functional additives. DETAILED DESCRIPTION
[0034] The technical scheme of the present invention and its implementation process will be further explained below in conjunction with the embodiments and comparative examples. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to the different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in each embodiment of the present invention can be combined with each other as long as they do not conflict with each other.
[0035] In the present invention, unless otherwise specified, the raw materials and components in the following examples and comparative examples are all commercially available products.
[0036] The preparation method of the pyridine heterocyclic additive (Compound C) used in the following examples is as follows:
[0037] Dissolve 0.24 mol of compound A in 300 mL of acetone, and stir the resulting solution at 2-5 ° C. Then dissolve 0.16 mol of potassium permanganate and 0.08 mol of anhydrous manganese sulfate in 500 mL of water, and add the above aqueous solution dropwise to the previously configured acetone solution with a dropping funnel, and the dropping time needs to be greater than 20 minutes. Continue mechanical stirring for 10 minutes, and raise the reaction temperature to room temperature. After adding a small amount of hydroquinone, filter to obtain a mixture, remove solid matter, and distill the obtained filtrate under reduced pressure and nitrogen atmosphere, with a bath temperature of 50 ° C. When concentrated to 50 mL, add 200 mL of ethanol to precipitate potassium sulfate, and the mixture is placed in a refrigerator at 4 ° C for one night. The mixture obtained after filtration is distilled to obtain compound B.
[0038] Dissolve 1 mol of compound B and 1.2 mol of triethylamine in 500 mL of tetrahydrofuran, cool to -20°C, and add 1.2 mol of sulfonyl chloride dropwise for more than 20 minutes. After the addition is complete, heat to room temperature and react for 1 hour. Stop the reaction, filter with suction, wash the filtrate with water, concentrate it, and distill it to obtain compound C.
[0039] Compound A is: Compound B is: Compound C:
[0040] The preparation methods of the electrolytes of Examples 1 to 11 and Comparative Examples 1 to 8 are as follows:
[0041] The lithium salt LiPF6 was dissolved in a mixed solvent of ethylene carbonate / ethyl methyl fluorocarbonate / dimethyl fluorocarbonate / ethyl methyl carbonate (mass ratio 25 / 50 / 15 / 10) to obtain a basic electrolyte, wherein the LiPF6 concentration was 1 mol / L, and additives were added to the basic electrolyte according to Table 1.
[0042] Table 1
[0043] 25℃ VC SA SN LiDFP LiBOB LiDFOB DTD Compound C Comparative Example 1 - - - - - - - - Comparative Example 2 1％ - - - - - - - Comparative Example 3 - 1％ - - - - - Comparative Example 4 - - 1％ - - - - - Comparative Example 5 - - - 1％ - - - - Comparative Example 6 - - - - 1％ - - - Comparative Example 7 - - - - - 1％ - - Comparative Example 8 - - - - - - 1％ - Example 1 - - - - - - - 1％ Example 2 1％ - - - - - - 1％ Example 3 - 1％ - - - - - 1％ Example 4 - - 1％ - - - - 1％ Example 5 - - - 1％ - - - 1％ Example 6 - - - - 1％ - - 1％ Example 7 - - - - - 1％ - 1％ Example 8 - - - - - - 1％ 1％ Example 9 1％ - 1％ - - 1％ 1％ 1％ Example 10 - - - - - - - 1.5％ Embodiment 11 - - - - - - - 2％
[0044] Note: "-" in the table means no addition; "%" means mass percentage, and the table shows the percentage of the corresponding additive in the total mass of the electrolyte.
[0045] The preparation method of high voltage lithium ion battery is as follows:
[0046] LiNi 0.5 Mn 1.5 O4 (LNMO): conductive additive: binder are mixed in NMP at a mass ratio of 90:5:5 and coated on the aluminum foil current collector with a coating surface density of 360g / m 2 , a positive electrode was prepared, polyethylene (PE) was used as a base film (12 μm) and an aluminum oxide coating (2 μm) was coated on both sides of the base film as a separator, artificial graphite was used as a negative electrode, a high-voltage nickel manganese oxide soft-pack battery was assembled, an electrolyte was injected therein, the electrolyte was the electrolyte of Examples 1 to 11 and Comparative Examples 1 to 8, a Neware test cabinet was used to test the discharge capacity retention rate of the battery after 200 cycles at room temperature 25°C 1C at 3-4.9V, a thickness gauge was used to test the thickness of the battery before and after the cycle test, and the thickness change rate was calculated. The specific results are shown in Table 2:
[0047] Table 2
[0048] 1C 25℃ 200 cycles discharge capacity retention rate % Thickness change rate % Comparative Example 1 72.3 36.2 Comparative Example 2 73.9 35.3 Comparative Example 3 79.6 30.6 Comparative Example 4 78.3 36.1 Comparative Example 5 79.4 31.9 Comparative Example 6 83.6 37.5 Comparative Example 7 82.1 38.3 Comparative Example 8 76.5 29.3 Example 1 85.2 9.3 Example 2 87.6 10.2 Example 3 92.2 6.2 Example 4 90.3 9.6 Example 5 90.5 10.6 Example 6 92.6 15.6 Example 7 93.1 16 Example 8 83.9 8.2 Example 9 95.4 3.9 Example 10 86.0 9.2 Embodiment 11 85.6 9.35
[0049] Table 2 shows that the charge and discharge cycle performance of the high-voltage lithium nickel manganese oxide battery prepared by the electrolyte of each embodiment is significantly better than that of the high-voltage lithium nickel manganese oxide battery prepared by the electrolyte of each comparative example. The addition of compound C can significantly improve the battery high voltage cycle capacity retention rate, greatly reduce the solvent decomposition during the battery cycle, and thus reduce the battery gas production.
[0050] The above detailed description of the present invention is intended to enable persons familiar with the art to understand the contents of the present invention and implement them. It does not limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.
Claims
1. A lithium battery electrolyte, characterized in that: The invention comprises an organic solvent, an electrolyte lithium salt and an additive, wherein the additive comprises a structural formula Pyridine heterocyclic additives.
2. The lithium battery electrolyte according to claim 1, characterized in that: The mass of the pyridine heterocyclic additive is 0.5-2% of the total mass of the lithium battery electrolyte.
3. The lithium battery electrolyte according to claim 1, characterized in that: The additives also include other additives, which are one or more of ethylene carbonate, succinic anhydride, succinonitrile, lithium difluorophosphate, lithium dioxalatoborate, lithium difluorooxalatoborate, and ethylene sulfate; the mass of the other additives is 0.5 to 5% of the total mass of the lithium battery electrolyte.
4. The lithium battery electrolyte according to claim 3, characterized in that: The other additives are a combination of ethylene carbonate, succinonitrile, lithium difluorooxalatoborate and ethylene sulfate.
5. The lithium battery electrolyte according to claim 1, characterized in that: The electrolyte lithium salt is one or more of LiPF6, LiTFSI, LiBF4, LiClO4, LiCH3SO3, LiSCN, LiNO3, LiO3SCF2CF3, LiAsF6, and LiAlCl4, and the concentration of the electrolyte lithium salt in the lithium battery electrolyte is 0.5 to 2 mol / L.
6. The lithium battery electrolyte according to claim 1, characterized in that: The organic solvent is one or more of carbonates, fluorocarbonates, carboxylates, fluorocarboxylates, ethers, fluoroethers and sulfones.
7. The lithium battery electrolyte according to claim 6, characterized in that: The carbonate is a cyclic carbonate and / or a chain carbonate, the fluorinated carbonate is a cyclic fluorinated carbonate and / or a chain fluorinated carbonate, the carboxylate is a cyclic carboxylate and / or a chain carboxylate, and the fluorinated carboxylate is a cyclic fluorinated carboxylate and / or a chain fluorinated carboxylate.
8. A lithium battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, characterized in that: The electrolyte is the lithium battery electrolyte according to any one of claims 1 to 7.
9. The lithium battery according to claim 8, characterized in that: The active material of the positive electrode is spinel nickel lithium manganese oxide; And / or, the negative electrode is selected from metallic lithium, graphite, natural graphite, artificial graphite, hard carbon, soft carbon, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, tin-based composite materials, spinel-structured lithiated TiO2, Li4Ti5O 12 , one or more of Li-Al alloy, silicon, Li-Si alloy, Li-Si-O alloy, silicon-based composite material, tin-silicon composite material; And / or, the diaphragm comprises a substrate and a coating, the substrate is made of polyethylene and / or polypropylene, and the coating is organic matter and / or metal oxide.
10. The lithium battery according to claim 8, characterized in that: The voltage of the lithium battery is 3-4.9V.