Electrolyte additive and preparation method thereof, electrolyte and application thereof

Abstract

The invention discloses an electrolyte additive, a preparation method of the electrolyte additive, an electrolyte and application of the electrolyte, and relates to the technical field of electrolyte additives. The electrolyte additive disclosed by the invention is prepared from the following raw materials: DL-valine and isopropanol alkali metal salt; the molar ratio of the DL-valine to the isopropanol alkali metal salt is 1: (0.5-3). The electrolyte additive can be mutually soluble with a lithium ion battery electrolyte, reversibly absorb heat when being heated, and slowly release the heat at room temperature, so that thermal runaway of the battery is effectively prevented, and the safety is improved. In addition, the molecular conversion process of the electrolyte additive is reversible, no redundant product is generated or the electrolyte is consumed, the production cost is low, and the electrolyte additive is suitable for preparing the electrolyte for the secondary battery.

Description

Technical Field

[0001] This invention relates to the field of electrolyte additives, and particularly to an electrolyte additive, its preparation method, an electrolyte, and its application. Background Technology

[0002] With the development of science and technology, people have increasingly higher requirements for energy storage devices. Lithium-ion batteries, due to their high volumetric energy density, high gravimetric energy density, high single-cell voltage, good voltage stability, high charge-discharge cycle life, environmental friendliness, and recyclability, have gained market favor and are widely used in the energy storage field. However, the use and development of lithium-ion batteries still face challenges related to safety. For example, during the charging and discharging process, an increase in polarization voltage (especially during high-current charging and discharging) can lead to a significant increase in Joule heating and electrochemical polarization exothermics, posing a risk of thermal runaway. Alternatively, thermal runaway may also occur when the internal temperature rises due to overcharging, short circuits, or physical damage, affecting safety. Furthermore, lithium-ion batteries are sensitive to the environment, and their performance is affected by extreme temperatures. For instance, in low-temperature environments, their capacity decreases significantly, and they may even fail to function properly, limiting their application in extremely cold regions or special scenarios.

[0003] Currently, measures to reduce the risk of spontaneous combustion in lithium-ion batteries mainly include the development of solid-state electrolytes, aqueous electrolytes, and physical phase change cooling methods. However, existing technologies for addressing lithium-ion thermal runaway, such as solid-state and aqueous electrolytes, are not only difficult to develop but also face high synthesis costs; while physical phase change methods cannot fundamentally solve the thermal runaway problem. Therefore, there is an urgent need to develop a low-cost method to improve the thermal runaway of lithium-ion batteries. Summary of the Invention

[0004] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, the object of the present invention is to provide an electrolyte additive prepared using DL-valine and isopropanol alkali metal salts as raw materials. The resulting electrolyte additive has the characteristic of reversible high and low energy states, thereby reducing the risk of battery thermal runaway and improving battery safety.

[0005] A second aspect of the present invention is to provide an electrolyte additive.

[0006] A third aspect of the present invention is to provide an electrolyte.

[0007] A fourth aspect of the present invention is to provide a secondary battery.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides an electrolyte additive, wherein the raw materials for preparing the electrolyte include DL-valine and isopropanol alkali metal salt; the molar ratio of DL-valine to isopropanol alkali metal salt is 1:(0.5~3).

[0009] According to embodiments of the present invention, the first aspect of the present invention has at least the following beneficial effects: This invention uses DL-valine and isopropanol alkali metal salts as raw materials to prepare an electrolyte additive that is miscible with the electrolyte and does not react. Simultaneously, this electrolyte additive can reversibly transform its molecules from a low-energy state to a high-energy state upon heating, thereby absorbing heat. At room temperature, it can slowly and spontaneously transform from a high-energy state to a low-energy state and release energy. Therefore, the electrolyte additive of this invention can regulate environmental temperature changes by absorbing and releasing heat, preventing abnormal temperature rises and abnormal increases in polarization voltage under charging, discharging, overcharging, or short-circuiting conditions, thus avoiding thermal runaway and improving battery safety. Furthermore, this molecular transformation process of the electrolyte additive of this invention is reversible and does not produce excess products or consume electrolyte.

[0010] In some embodiments, the molar ratio of DL-valine to the isopropanol alkali metal salt is 1:(1~3).

[0011] In some embodiments, the molar ratio of DL-valine to the isopropanol alkali metal salt is 1:(1~2).

[0012] In some embodiments, the isopropoxide alkali metal salt includes at least one of lithium isopropoxide, sodium isopropoxide, and potassium isopropoxide.

[0013] A second aspect of the present invention provides a method for preparing an electrolyte additive, comprising the following steps: DL-valine and isopropanol alkali metal salt are dissolved separately in organic solvents and then mixed. The resulting electrolyte additive is obtained after the reaction.

[0014] In some embodiments, the reaction temperature is 10~50°C.

[0015] In some specific embodiments, the reaction temperature is 20~40°C.

[0016] In some other embodiments, the reaction temperature is 25~35°C.

[0017] In some embodiments, the reaction time is 2 to 4 hours.

[0018] In some embodiments, the molar ratio of DL-valine to the isopropanol alkali metal salt is 1:(1~3).

[0019] In some embodiments, the isopropoxide alkali metal salt includes at least one of lithium isopropoxide, sodium isopropoxide, and potassium isopropoxide.

[0020] In some embodiments, the reaction is carried out in an oxygen-free or low-oxygen atmosphere. For example, the reaction is carried out in a glove box.

[0021] In some embodiments, the organic solvent includes at least one of carbon tetrachloride, cyclohexane, and petroleum ether.

[0022] A third aspect of the present invention provides an electrolyte containing an electrolyte solution and an additive; the additive includes the electrolyte additive described in the first aspect of the present invention, or the electrolyte additive prepared by the preparation method described in the second aspect of the present invention.

[0023] In some embodiments, the mass ratio of the electrolyte additive to the electrolyte solution is 1:(20~500).

[0024] In some specific embodiments, the mass ratio of the electrolyte additive to the electrolyte solution is 1:(90~110).

[0025] Specifically, the electrolyte solution is obtained by dissolving an electrolyte in a solvent. In some embodiments, the electrolyte includes at least one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), and lithium nitrate (LiNO3). In some embodiments, the solvent includes dimethyl ethylene glycol (DME), 1,3-dioxolane (DOL), ethylene carbonate (EC), ethyl methyl carbonate (EMC), or dimethyl carbonate (DMC).

[0026] A fourth aspect of the present invention provides a secondary battery containing the electrolyte described in the third aspect of the present invention.

[0027] In some embodiments, the secondary battery is a lithium-ion battery.

[0028] Compared with the prior art, the beneficial effects of the present invention are: This invention uses DL-valine and isopropanol alkali metal salts as raw materials to prepare an electrolyte additive that is miscible with the electrolyte and does not react. Simultaneously, this electrolyte additive can rapidly convert its molecules from a low-energy state to a high-energy state by utilizing heat when the temperature rises, thereby absorbing heat. At room temperature, it can slowly and spontaneously convert from a high-energy state to a low-energy state and release energy. Therefore, under charging, discharging, overcharging, or short-circuiting conditions, the electrolyte additive of this invention can avoid abnormal temperature rise, increased polarization voltage, and thermal runaway caused by absorbing heat, thus improving battery safety. Furthermore, the molecular conversion process of this electrolyte additive is reversible, without generating excess products or consuming electrolyte. In addition, this electrolyte additive uses low-cost DL-valine as a raw material, reducing production costs. Therefore, the electrolyte additive of this invention is suitable for preparing electrolytes for secondary batteries, especially lithium-ion batteries. Attached Figure Description

[0029] Figure 1 The image shows the XRD pattern of the electrolyte additive in Example 1 of this invention.

[0030] Figure 2 This is a SEM image of the electrolyte additive in Example 1 of the present invention.

[0031] Figure 3 This is the 1H NMR spectrum of the electrolyte additive in Example 1 of the present invention.

[0032] Figure 4 The graph shows the polarization voltage changes during the cycling process of the lithium-ion pouch battery in Application Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0033] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0034] An embodiment of the first aspect of the present invention provides an electrolyte additive, wherein the raw materials for preparing the electrolyte include DL-valine and isopropanol alkali metal salt; the molar ratio of DL-valine to isopropanol alkali metal salt is 1:(0.5~3).

[0035] In the raw materials for preparing this electrolyte additive, the molar ratio of DL-valine to the isopropanol alkali metal salt can be 1:1, 1:2, or 1:3, or any range of two molar ratios, such as 1:(1~3) or 1:(2~3). By designing a reasonable molar ratio, the smooth reaction of DL-valine with the isopropanol alkali metal salt can be ensured, resulting in an electrolyte additive with ideal performance.

[0036] In some embodiments, the isopropoxide alkali metal salt includes at least one of lithium isopropoxide, sodium isopropoxide, and potassium isopropoxide. Lithium isopropoxide, sodium isopropoxide, and potassium isopropoxide have strong basicity and nucleophilicity, and can replace the hydrogen on the carboxyl group of DL-valine to obtain the electrolyte additive of the present invention.

[0037] A second aspect of the present invention provides a method for preparing an electrolyte additive, comprising the following steps: DL-valine is mixed with an alkali metal salt of isopropanol in an organic solvent, and the resulting electrolyte additive is obtained after the reaction.

[0038] In some embodiments, the reaction temperature is 10–50°C. For example, the reaction temperature is 10°C, 20°C, 30°C, 40°C, or 50°C. In some specific embodiments, the reaction temperature is 20–40°C. Further, the reaction temperature is 25–35°C.

[0039] Specifically, the reaction is carried out at a specific temperature for a certain period of time, which is 2 to 4 hours. More specifically, the reaction time can be 2 hours, 3 hours, or 4 hours, or other ranges within the 2 to 4 hour range, such as 2 to 3 hours.

[0040] Regarding the atmospheric conditions of the reaction, in some embodiments, the reaction is carried out in an oxygen-free or low-oxygen atmosphere. For example, the reaction is carried out in a glove box. It should be understood that when the reaction is carried out in a glove box, it is considered that the conditions of oxygen-free or low-oxygen are met.

[0041] In addition, carbon tetrachloride can be used as the organic solvent to stop the reaction of raw materials during the preparation of electrolyte additives.

[0042] An embodiment of the third aspect of the present invention provides an electrolyte containing an electrolyte, a solvent, and an additive; the additive includes the electrolyte additive described in the first aspect of the present invention, or the electrolyte additive prepared by the preparation method described in the second aspect of the present invention.

[0043] In some embodiments, the mass ratio of the electrolyte additive to the total amount of the electrolyte and solvent is 1:(20~500). Specifically, this mass ratio can be 1:20, 1:50, 1:80, 1:90, 1:100, 1:120, 1:150, 1:200, 1:300, 1:400, or 1:500, and adjusting the mass ratio affects the gain effect of the electrolyte additive. In some specific embodiments, the mass ratio of the electrolyte additive to the total amount of the electrolyte and solvent is 1:(90~110).

[0044] In some embodiments, the electrolyte includes at least one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), and lithium nitrate (LiNO3).

[0045] In some embodiments, the solvent includes dimethyl glycol ether (DME), 1,3-dioxolane (DOL), ethylene carbonate (EC), ethyl methyl carbonate (EMC), or dimethyl carbonate (DMC). Specifically, in the electrolyte, the solvent can be one of the different solvents mentioned above, or a combination of at least two, for example, the solvent is DME and DOL, or EC, EMC, and DMC.

[0046] The specific preparation process of the electrolyte of the present invention can be referred to the following steps: The electrolyte is obtained by mixing electrolyte additives, electrolytes and solvents.

[0047] The mixing temperature is 30~40℃, and the mixing time is 2~4h.

[0048] An embodiment of the fourth aspect of the present invention provides a secondary battery containing the electrolyte described in the third aspect of the present invention. Specifically, the secondary battery is a lithium-ion battery.

[0049] The following detailed description is provided in conjunction with embodiments and comparative examples.

[0050] Example 1 This embodiment provides an electrolyte additive. The raw materials for preparing the electrolyte include DL-valine and lithium isopropoxide; the molar ratio of DL-valine to lithium isopropoxide is 1:1. The specific preparation method of this electrolyte additive is as follows: Weigh 117.146 g of DL-valine and lithium isopropoxide according to a molar ratio of 1:1 between DL-valine and lithium isopropoxide. Dissolve and mix them in 500 mL of carbon tetrachloride solvent. Stir at 100 r / min in a glove box at a reaction temperature of 30 °C for 3 h. Then remove the carbon tetrachloride by distillation at 75 °C to obtain the electrolyte additive.

[0051] See Figure 1 The XRD pattern in the figure shows that the electrolyte additive obtained in this embodiment is DL-valine lithium salt, and its structural formula is shown in formula (1): Equation (1). Its SEM image is as follows: Figure 2 As shown, the surface of the electrolyte additive exhibits a wrinkled appearance. The proton NMR spectrum is shown below. Figure 3 As shown.

[0052] The electrolyte for lithium-ion batteries was prepared using the electrolyte additive described in this example. The electrolyte was LiPF6, and the solvent was a mixture of EC (ethylene carbonate), EMC (ethyl methyl carbonate), and DMC (dimethyl carbonate), with a volume ratio of 1:1:1. The electrolyte dissolved in the solvent to form a 1 mol / L electrolyte solution. The electrolyte additive was added to the solvent at a mass ratio of 1:100 (additive:electrolyte solution). The specific preparation method of this electrolyte is as follows: EC, EMC, and DMC were measured in a volume ratio of 1:1:1 and mixed to obtain a mixed solvent. LiPF6 was added to the mixed solvent to prepare a LiPF6 solution with a concentration of 1 mol / L, which is the electrolyte solution. Electrolyte additive and LiPF6 solution were weighed in a mass ratio of 1:100 and mixed. The mixture was stirred at 30°C for 18 hours until the electrolyte additive was completely dissolved and mixed evenly to obtain the electrolyte for lithium-ion batteries.

[0053] Example 2 This embodiment provides an electrolyte additive. The raw materials for preparing the electrolyte include DL-valine and lithium isopropoxide; the molar ratio of DL-valine to lithium isopropoxide is 1:1. The specific preparation method of this electrolyte additive is as follows: Weigh 117.146 g of DL-valine and lithium isopropoxide according to a molar ratio of 1:1 between DL-valine and lithium isopropoxide. Dissolve and mix them in 500 mL of carbon tetrachloride solvent. Stir at 100 r / min in a glove box at a reaction temperature of 60 °C for 3 h. Then remove carbon tetrachloride by distillation at 75 °C to obtain the electrolyte additive.

[0054] The electrolyte for lithium-ion batteries was prepared using the electrolyte additive described in this example. The electrolyte was LiPF6, and the solvent was a mixture of EC (ethylene carbonate), EMC (ethyl methyl carbonate), and DMC (dimethyl carbonate), with a volume ratio of 1:1:1. The electrolyte dissolved in the solvent to form a 1 mol / L electrolyte solution. The electrolyte additive was added to the solvent at a mass ratio of 1:100 (additive:electrolyte solution). The specific preparation method of this electrolyte is as follows: EC, EMC, and DMC were measured in a volume ratio of 1:1:1 and mixed to obtain a mixed solvent. LiPF6 was added to the mixed solvent to prepare a LiPF6 solution with a concentration of 1 mol / L, which is the electrolyte solution. Electrolyte additive and LiPF6 solution were weighed in a mass ratio of 1:100 and mixed. The mixture was stirred at 30°C for 18 hours until the electrolyte additive was completely dissolved and mixed evenly to obtain the electrolyte for lithium-ion batteries.

[0055] Example 3 This embodiment provides an electrolyte additive. The raw materials for preparing the electrolyte include DL-valine and lithium isopropoxide; the molar ratio of DL-valine to lithium isopropoxide is 1:2. The specific preparation method of this electrolyte additive is as follows: Weigh 117.146 g of DL-valine and lithium isopropoxide according to a molar ratio of DL-valine to lithium isopropoxide of 1:2. Dissolve and mix them in 500 mL of carbon tetrachloride solvent. Stir at 100 r / min in a glove box at a reaction temperature of 60 °C for 3 h. Then remove carbon tetrachloride by distillation at 75 °C to obtain the electrolyte additive.

[0056] The electrolyte for lithium-ion batteries was prepared using the electrolyte additive described in this example. The electrolyte was LiPF6, and the solvent was a mixture of EC (ethylene carbonate), EMC (ethyl methyl carbonate), and DMC (dimethyl carbonate), with a volume ratio of 1:1:1. The electrolyte dissolved in the solvent to form a 1 mol / L electrolyte solution. The electrolyte additive was added to the solvent at a mass ratio of 1:100 (additive:electrolyte solution). The specific preparation method of this electrolyte is as follows: EC, EMC, and DMC were measured in a volume ratio of 1:1:1 and mixed to obtain a mixed solvent. LiPF6 was added to the mixed solvent to prepare a LiPF6 solution with a concentration of 1 mol / L, which is the electrolyte solution. Electrolyte additive and LiPF6 solution were weighed in a mass ratio of 1:100 and mixed. The mixture was stirred at 30°C for 18 hours until the electrolyte additive was completely dissolved and mixed evenly to obtain the electrolyte for lithium-ion batteries.

[0057] Example 4 This embodiment provides an electrolyte additive. The raw materials for preparing the electrolyte include DL-valine and lithium isopropoxide; the molar ratio of DL-valine to lithium isopropoxide is 1:0.5. The specific preparation method of this electrolyte additive is as follows: Weigh 117.146 g of DL-valine and lithium isopropoxide according to a molar ratio of 1:1 between DL-valine and lithium isopropoxide. Dissolve and mix them in 500 mL of carbon tetrachloride solvent. Stir at 100 r / min in a glove box at a reaction temperature of 60 °C for 3 h. Then remove carbon tetrachloride by distillation at 75 °C to obtain the electrolyte additive.

[0058] The electrolyte for lithium-ion batteries was prepared using the electrolyte additive described in this example. The electrolyte was LiPF6, and the solvent was a mixture of EC (ethylene carbonate), EMC (ethyl methyl carbonate), and DMC (dimethyl carbonate), with a volume ratio of 1:1:1. The electrolyte dissolved in the solvent to form a 1 mol / L electrolyte solution. The electrolyte additive was added to the solvent at a mass ratio of 1:100 (additive:electrolyte solution). The specific preparation method of this electrolyte is as follows: EC, EMC, and DMC were measured in a volume ratio of 1:1:1 and mixed to obtain a mixed solvent. LiPF6 was added to the mixed solvent to prepare a LiPF6 solution with a concentration of 1 mol / L, which is the electrolyte solution. Electrolyte additive and LiPF6 solution were weighed in a mass ratio of 1:100 and mixed. The mixture was stirred at 30°C for 18 hours until the electrolyte additive was completely dissolved and mixed evenly to obtain the electrolyte for lithium-ion batteries.

[0059] Example 5 This embodiment provides a lithium-ion pouch battery, which is prepared by adding 10 mL of the electrolyte used in Example 1 for lithium-ion batteries to a lithium iron phosphate battery containing 10 layers of positive electrode sheets and 11 layers of negative electrode sheets. The pouch battery is then sealed to obtain the lithium-ion pouch battery described in this example. The prepared lithium-ion pouch battery is left to stand for a period of time before being used for charge-discharge testing.

[0060] Example 6 This embodiment provides a lithium-ion pouch battery, which is prepared by adding 10 mL of the electrolyte used in Example 2 for lithium-ion batteries to a lithium iron phosphate battery containing 10 layers of positive electrode sheets and 11 layers of negative electrode sheets. The pouch battery is then sealed to obtain the lithium-ion pouch battery described in this example. The prepared lithium-ion pouch battery is left to stand for a period of time before being used for charge-discharge testing.

[0061] Example 7 This embodiment provides a lithium-ion pouch battery, which is prepared by adding 10 mL of the electrolyte used in Example 3 for lithium-ion batteries to a lithium iron phosphate battery containing 10 layers of positive electrode sheets and 11 layers of negative electrode sheets. The pouch battery is then sealed to obtain the lithium-ion pouch battery described in this example. The prepared lithium-ion pouch battery is left to stand for a period of time before being used for charge-discharge testing.

[0062] Example 8 This embodiment provides a lithium-ion pouch battery, which is prepared by adding 10 mL of the electrolyte used in Example 4 for lithium-ion batteries to a lithium iron phosphate battery containing 10 layers of positive electrode sheets and 11 layers of negative electrode sheets. The pouch battery is then sealed to obtain the lithium-ion pouch battery described in this example. The prepared lithium-ion pouch battery is left to stand for a period of time before being used for charge-discharge testing.

[0063] Comparative Example 1 The electrolyte for lithium-ion batteries in this example is prepared using the following method, specifically including the following steps: the electrolyte is LiPF6, and the solvent is a mixed solvent of EC (ethylene carbonate), EMC (ethyl methyl carbonate), and DMC (dimethyl carbonate), with a volume ratio of EC, EMC, and DMC of 1:1:1. The electrolyte is dissolved in the solvent to form an electrolyte solution with a concentration of 1 mol / L. The specific preparation method of this electrolyte is as follows: EC, EMC, and DMC were measured in a volume ratio of 1:1:1 and mixed to obtain a mixed solvent. LiPF6 was added to the mixed solvent to prepare a LiPF6 solution with a concentration of 1 mol / L, i.e., an electrolyte solution. The solution was stirred at 30°C for 18 hours until the electrolyte additives were completely dissolved and mixed evenly to obtain an electrolyte for lithium-ion batteries.

[0064] The preparation method of the lithium-ion pouch battery in this example is as follows: 10 mL of the electrolyte used in this example for lithium-ion batteries is added to a lithium iron phosphate battery containing 10 layers of positive electrode plates and 11 layers of negative electrode plates. Then, the pouch battery is finally sealed to obtain the lithium-ion pouch battery in this example. After the prepared lithium-ion pouch battery is left to stand for a period of time, it is used for charge-discharge testing.

[0065] Result detection The polarization voltage of the lithium-ion pouch batteries obtained in Examples 5, 6, 7, 8, and Comparative Example 1 was tested during cyclic charge-discharge. A battery cycle testing system was used to perform isothermal cyclic charge-discharge tests on the lithium-ion pouch batteries at 25°C, with a voltage range of 2.5~3.65V and a charge-discharge rate of 0.5C. The polarization voltage value (i.e., the difference between the charging plateau voltage and the discharging plateau voltage) was recorded every 50 cycles, and its rate of change with the number of cycles was compared.

[0066] Polarization voltage is the voltage difference between charge and discharge platforms during the cyclic charge and discharge process of a pouch battery test system. It is data read from charge and discharge curves of different cycle numbers after the battery cycle test is completed. An increase in polarization voltage generates heat, and an increase in temperature will cause the polarization voltage to increase further, leading to thermal runaway. Therefore, by testing the magnitude and changes in polarization voltage during the cycle, the risk of thermal runaway can be reflected to a certain extent. The results of the polarization voltage of the lithium-ion pouch batteries in Example 5 and Comparative Example 1 as a function of cycle number are as follows: Figure 4 As shown. By Figure 4 As can be seen, compared with Comparative Example 1, the lithium-ion pouch battery in Example 5 of this invention introduces the electrolyte additive of this invention. Under 0.2C charge-discharge conditions, it has a smaller initial polarization voltage. Furthermore, as the number of charge-discharge cycles increases, the polarization voltage of the lithium-ion pouch battery in Example 5 increases more slowly. This indicates that the addition of the electrolyte additive of this invention can effectively alleviate the polarization of the electrode-electrolyte interface during the cycling process of the lithium-ion pouch battery, thereby improving the battery's cycle stability and safety. It further illustrates that by introducing an electrolyte additive with a specific energy potential well into the electrolyte, and through the reversible transformation of this electrolyte additive at different energy states, the invention can effectively eliminate the accumulation of uneven heat in the battery, improve the electrode reaction interface, ensure interface uniformity, and enhance battery safety and cycle stability.

[0067] In the tests, the polarization voltage of Examples 6, 7, 8 and Comparative Example 1 increased at a greater rate than that of Example 5.

[0068] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An electrolyte additive, characterized in that, The electrolyte is prepared from DL-valine and isopropanol alkali metal salt; the molar ratio of DL-valine to isopropanol alkali metal salt is 1:(0.5~3).

2. The electrolyte additive according to claim 1, characterized in that, The isopropoxide alkali metal salt includes at least one of lithium isopropoxide, sodium isopropoxide, and potassium isopropoxide.

3. A method for preparing an electrolyte additive, characterized in that, Includes the following steps: DL-valine and isopropanol alkali metal salt are dissolved separately in organic solvents and then mixed. The resulting electrolyte additive is obtained after the reaction.

4. The preparation method according to claim 3, characterized in that, The reaction temperature is 10~50℃; And / or, the reaction time is 2-4 hours.

5. The preparation method according to claim 3, characterized in that, The reaction is carried out in an oxygen-free or low-oxygen atmosphere.

6. The preparation method according to claim 3, characterized in that, The organic solvent includes at least one of carbon tetrachloride, cyclohexane, and petroleum ether.

7. An electrolyte, characterized in that, The electrolyte contains an electrolyte solution and an additive; the additive includes the electrolyte additive according to claim 1 or 2, or the electrolyte additive prepared by the preparation method according to any one of claims 3 to 6.

8. The electrolyte according to claim 7, characterized in that, The mass ratio of the electrolyte additive to the electrolyte solution is 1:(20~500).

9. A secondary battery, characterized in that, The secondary battery contains the electrolyte as described in claim 7 or 8.

10. The secondary battery according to claim 9, characterized in that, The secondary battery is a lithium-ion battery.

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