Electrolyte taking amino carboxylic acid chelating agent as additive and application of electrolyte

Abstract

The invention belongs to the technical field of lithium metal batteries, and particularly relates to an electrolyte taking an aminocarboxylic acid chelating agent as an additive and application of the electrolyte. The specific scheme of the invention is as follows: the electrolyte taking an aminocarboxylic acid chelating agent as an additive is characterized in that the aminocarboxylic acid chelating agent is one or more of glutamic acid tetralithium diacetate (GLDA.Li4), methyl glycine trilithium diacetate (MGDA.Li3) and aspartic acid tetralithium diacetate (ASDA.Li4); the electrolyte is prepared from an electrolyte lithium salt, an organic solvent and the additive according to a certain proportion. The mass ratio of the electrolyte lithium salt to the organic solvent to the additive is 10: (80-100): (0.5-1). Compared with an organic phosphine chelating agent / organic acid polymer chelating agent, the electrolyte additive used in the invention has stronger electrochemical stability, and can better prolong the cycle service life of the battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium metal batteries, and in particular relates to an electrolyte containing an aminocarboxylic acid chelating agent as an additive and application thereof. Background Art

[0002] As a new type of secondary battery, lithium-ion batteries have been widely used in new energy vehicles, electronic products and other fields. During the use of lithium-ion batteries, it was found that as lithium ions precipitate and deposit, lithium dendrites will grow at the negative electrode of the battery. This lithium dendrite problem will accelerate the side reactions and produce a large amount of dead lithium, which will lead to serious polarization and volume expansion problems. In severe cases, it will cause the battery to short-circuit. Therefore, the lithium dendrite problem will cause the lithium-ion battery to have a lower coulombic efficiency, reduce the cycle life, and bring serious safety hazards. It is an important issue that limits the commercial application of lithium-ion batteries.

[0003] The current method for inhibiting the growth of lithium dendrites during the cycle mainly uses electrolyte additives. The purpose of adding electrolyte additives is to adjust the morphology of Li deposits and reduce the corrosion of Li metal. The types of electrolyte additives are mainly organic phosphonic acid scale inhibitors and organic acid / nitrogen-containing chemical group polymers. For example, patent CN107528086B proposes using molecular ion traps / polymers functionalized with alkali metal salts of organic acids / polymers functionalized with nitrogen-containing functional groups as chelating additives, which act on the battery in the form of dissolving in the electrolyte solution / coating on the surface of the diaphragm / coating on the surface of the negative electrode to achieve the purpose of inhibiting the production of lithium dendrites. Patent CN112103562A proposes introducing organic phosphonic acid scale inhibitors and corrosion inhibitors into the lithium battery electrolyte, forming stable complexes with iron, copper, zinc and other ions to achieve uniform deposition of lithium ions and thus improve the cycle life of lithium metal batteries.

[0004] The aforementioned electrolyte additives can effectively inhibit the formation of lithium dendrites at the negative electrode during charge and discharge, but as the battery cycle increases, they slowly undergo electrochemical oxidative decomposition, thus losing their effectiveness. Therefore, finding an electrolyte additive that can effectively inhibit the formation of lithium dendrites at the negative electrode and remain stable during battery use can effectively enhance the commercial application value of lithium-ion batteries. Summary of the Invention

[0005] To solve the above problems, the present invention provides an electrolyte containing an aminocarboxylic acid chelating agent as an additive and its application, which can effectively inhibit the formation of negative electrode lithium dendrites in lithium batteries and can stably exist without invariance.

[0006] To achieve the above object, the specific scheme of the present invention is as follows: An electrolyte containing an aminocarboxylic acid chelating agent as an additive, wherein the aminocarboxylic acid chelating agent is one or more of glutamic acid diacetate tetralithium (GLDA.Li4), methylglycine diacetate trilithium (MGDA.Li3), and aspartic acid diacetate tetralithium (ASDA.Li4); The electrolyte lithium salt, organic solvent and the above additives are prepared into an electrolyte according to a certain proportion.

[0007] According to the electrolyte containing the aminocarboxylic acid chelating agent as an additive, the mass ratio of the electrolyte lithium salt, the organic solvent and the additive is 10:(80-100):(0.5-1).

[0008] According to the electrolyte containing the aminocarboxylic acid chelating agent as an additive, the electrolyte lithium salt is at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium fluoroalkylphosphonate.

[0009] According to the electrolyte containing the aminocarboxylic acid chelating agent as an additive, the organic solvent is a mixture of organic carbonate and vinylene carbonate in a mass ratio of 100:(1-5).

[0010] According to the electrolyte containing the aminocarboxylic acid chelating agent as an additive, the organic carbonate includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0011] The application of the electrolyte of the present invention in a lithium battery is characterized in that the electrolyte, a lithium-containing positive electrode, a hard carbon negative electrode and a battery separator are combined to form a lithium-ion battery.

[0012] Beneficial effects of the present invention: The present invention uses aminocarboxylic acid chelating agents GLDA.Li4, MGDA.Li3 and ASDA.Li4 as electrolyte additives. Such electrolyte additives chelate metal ions such as manganese and titanium in the system, slowing the rate at which lithium ions form dead lithium in the two stages, protecting the SEI film and maintaining the capacity of cyclic charge and discharge; Compared with organic phosphine chelating agents / organic acid polymer chelating agents, the electrolyte additive used in the present invention has stronger electrochemical stability and can better extend the cycle life of the battery. DETAILED DESCRIPTION

[0013] The specific content of the present invention will be further described below: The electrolyte of the present invention comprises an electrolyte lithium salt, an organic solvent and an electrolyte additive, wherein the mass ratio of the electrolyte lithium salt, the organic solvent and the electrolyte additive is 10:(80-100):(0.5-1).

[0014] The electrolyte additive is an aminocarboxylic acid chelating agent, and the specific aminocarboxylic acid chelating agent is one or more of glutamic acid diacetate tetralithium (GLDA.Li4), methylglycine diacetate trilithium (MGDA.Li3), and aspartic acid diacetate tetralithium (ASDA.Li4).

[0015] The electrolyte lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium fluoroalkylphosphonate; The organic solvent is a mixture of organic carbonate and vinylene carbonate in a mass ratio of 100: (1-5); The organic carbonate is selected from at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

[0016] The prepared electrolyte, metal lithium positive electrode, hard carbon negative electrode and battery separator are combined into a lithium ion battery.

[0017] The present invention is further described below with specific parameters: Example 1

[0018] Under nitrogen atmosphere, 100 g of ethylene carbonate and 1 g of vinylene carbonate were mixed evenly, 10 g of lithium hexafluorophosphate was slowly added dropwise, and after the lithium hexafluorophosphate was completely dissolved, 0.5 g of GLDA.Li4 was added and stirred evenly to obtain an electrolyte. Example 2

[0019] Under a nitrogen atmosphere, 80 g of ethylene carbonate and 4 g of vinylene carbonate were mixed evenly, and 10 g of lithium hexafluorophosphate was slowly added dropwise. After the lithium hexafluorophosphate was completely dissolved, 1 g of GLDA.Li4 was added and stirred evenly to obtain an electrolyte. Example 3

[0020] Under nitrogen atmosphere, 100 g of dimethyl carbonate and 1 g of vinylene carbonate were mixed evenly, 10 g of lithium hexafluorophosphate was slowly added dropwise, and after complete dissolution, 0.5 g of MGDA.Li3 was added and stirred evenly to obtain an electrolyte. Example 4

[0021] Under nitrogen atmosphere, 100 g of diethyl carbonate and 1 g of vinylene carbonate were mixed evenly, 10 g of lithium hexafluorophosphate was slowly added dropwise, and after the lithium hexafluorophosphate was completely dissolved, 0.5 g of ASDA.Li4 was added and stirred evenly to obtain an electrolyte. Comparative Example 1

[0022] In this embodiment, the amount of LDA.Li4 added is 0, and the rest is the same as in Example 1.

[0023] Under a nitrogen atmosphere, 100 g of ethylene carbonate and 1 g of vinylene carbonate were evenly mixed, and 10 g of lithium hexafluorophosphate was slowly added dropwise. After the lithium hexafluorophosphate was completely dissolved, an electrolyte was obtained. Comparative Example 2

[0024] In this example, aminotri(methylenephosphonic acid) was used to replace GLDA.Li4, and the rest was the same as in Example 1.

[0025] Under a nitrogen atmosphere, 100 g of ethylene carbonate and 1 g of vinylene carbonate were mixed evenly, and 10 g of lithium hexafluorophosphate was slowly added dropwise. After the lithium hexafluorophosphate was completely dissolved, 0.5 g of aminotrimethylenephosphonic acid was added and stirred evenly to obtain an electrolyte. Comparative Example 3

[0026] In this embodiment, polyacrylic acid is used to replace GLDA.Li4, and the rest is the same as in Example 1.

[0027] Under a nitrogen atmosphere, 100 g of ethylene carbonate and 1 g of vinylene carbonate were mixed evenly, and 10 g of lithium hexafluorophosphate was slowly added dropwise. After the lithium hexafluorophosphate was completely dissolved, 0.5 g of polyacrylic acid was added and stirred evenly to obtain an electrolyte.

[0028] Battery assembly and performance testing: Assemble lithium-ion batteries according to the method provided in the national standard GB / T 42260-2022 (Lithium Iron Phosphate Electrochemical Performance Test Cycle Life Test Method) and perform cycle performance tests: The cycle performance test conditions are as follows: the prepared lithium-ion battery is charged to 4.2V at 1C constant current at 25°C and 55°C, then charged at constant voltage until the current drops to 0.05C, and then discharged to 2.5V at 1C constant current. The discharge capacity of the first cycle, 100 cycles, 200 cycles and 500 cycles is recorded in this cycle test, and the capacity retention rate of the battery in the first cycle and the Nth cycle is tested, where the capacity retention rate of the lithium ion Nth cycle (%) = discharge capacity of the Nth cycle / discharge capacity of the first cycle × 100% The battery cycle life performance test results are shown in Table 1:

[0029] From the comparison of the test results of the embodiment and the comparative example, it can be seen that when the aminocarboxylic acid chelating agent provided by the present invention is used as an electrolyte additive to prepare a lithium ion battery, the battery cycle capacity retention rate is significantly improved by more than 10% compared with the lithium ion battery without the addition of the aminocarboxylic acid chelating agent; compared with the lithium ion battery to which the organophosphorus chelating agent and the organic acid polymer chelating agent are added, the retention rate is significantly improved with the increase in the number of cycles, especially at high temperatures, the improvement in the retention rate is particularly obvious.

[0030] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. An electrolyte containing an aminocarboxylic acid chelating agent as an additive, wherein the aminocarboxylic acid chelating agent is an additive, wherein the amino The carboxylic acid chelating agent is one or more of glutamic acid diacetate tetralithium (GLDA.Li4), methylglycine diacetate trilithium (MGDA.Li3), and aspartic acid diacetate tetralithium (ASDA.Li4); The electrolyte lithium salt, organic solvent and the above additives are prepared into an electrolyte according to a certain proportion.

2. The electrolyte containing the aminocarboxylic acid chelating agent as an additive according to claim 1, characterized in that: The mass ratio of the electrolyte lithium salt, the organic solvent and the additive is 10: (80-100): (0.5-1).

3. The electrolyte containing the aminocarboxylic acid chelating agent as an additive according to claim 2, characterized in that: The electrolyte lithium salt is at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium fluoroalkylphosphonate.

4. The electrolyte containing the aminocarboxylic acid chelating agent as an additive according to claim 2 or 3, characterized in that: The organic solvent is a mixture of organic carbonate and vinylene carbonate in a mass ratio of 100: (1-5).

5. The electrolyte containing the aminocarboxylic acid chelating agent as an additive according to claim 4, characterized in that: The organic carbonate includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

6. The electrolyte containing the aminocarboxylic acid chelating agent as an additive according to claim 5, characterized in that: The additive is 0.5g of tetralithium glutamate diacetate (GLDA.Li4), the organic carbonate is a mixture of 100g of ethylene carbonate and 1g of vinylene carbonate, and the electrolyte lithium salt is 10g of lithium hexafluorophosphate. First, 100g of ethylene carbonate and 1g of vinylene carbonate are evenly mixed, and 10g of lithium hexafluorophosphate is slowly added dropwise. After the lithium hexafluorophosphate is completely dissolved, 0.5g of GLDA.Li4 is added and stirred evenly to obtain an electrolyte.

7. Use of the electrolyte according to claim 1 in a lithium battery, characterized in that: The electrolyte, a lithium-containing positive electrode, a hard carbon negative electrode and a battery separator are combined to form a lithium-ion battery.

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