Lithium battery electrolyte and preparation method

Abstract

The application relates to the technical field of lithium ion batteries, and discloses a lithium battery electrolyte and a preparation method. According to the application, each component is calculated by weight fraction, and the lithium battery electrolyte comprises 10-20 parts of lithium salt, 3-10 parts of flame-retardant material, 2-8 parts of additive and 60-90 parts of organic solvent; the flame-retardant material is a silane-modified flame-retardant carrier; and the flame-retardant carrier is a core of inorganic flame-retardant material and a shell of PAN. The inorganic flame-retardant material is coated by PAN, the inorganic flame-retardant material is isolated from the electrolyte through the coating effect, and thus the side reaction caused by directly adding the flame retardant is avoided.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to a lithium battery electrolyte and its preparation method. Background Technology

[0002] Lithium-ion batteries have become the mainstream power source due to their high energy density and excellent cycle stability. A lithium-ion battery mainly consists of a positive electrode, a negative electrode, an electrolyte, and a separator. Because the electrolyte is flammable, when thermal runaway occurs, the internal temperature of the battery rises, and the sustained thermal process can lead to combustion and explosion. The main factor causing this is the flammable electrolyte. Therefore, improving the safety of the electrolyte is a pressing technical problem that needs to be solved.

[0003] One effective method currently is to add flame retardants to the electrolyte to inhibit its combustion. However, existing common flame retardant additives have low flame retardant efficiency, thus requiring the addition of excessive amounts. In large quantities, this can lead to side reactions in the battery, resulting in a decrease in its electrochemical performance. Summary of the Invention

[0004] <Technical Problem Solved by the Invention>

[0005] This is intended to address the problem of decreased electrochemical performance of batteries due to excessive flame retardant additives in existing technologies.

[0006] <Technical Solution Adopted in This Invention>

[0007] To address the aforementioned technical problems, the present invention aims to provide a lithium battery electrolyte and its preparation method.

[0008] The details are as follows:

[0009] First, the present invention provides a lithium battery electrolyte, wherein each component, by weight, includes 10 to 20 parts of lithium salt, 3 to 10 parts of flame retardant, 2 to 8 parts of additive, and 60 to 90 parts of organic solvent.

[0010] The flame retardant is a silane-modified flame retardant support; the flame retardant support is an inorganic flame retardant core with PAN as the shell.

[0011] Second, the present invention provides a method for preparing the aforementioned lithium battery electrolyte, comprising the following steps:

[0012] The lithium salt, organic solvent, additives, and flame retardant are blended together to obtain the final product.

[0013] <Beneficial effects achieved by the present invention>

[0014] This invention encapsulates an inorganic flame retardant using a PAN (Polydioxanone) shell. This encapsulation isolates the inorganic flame retardant from the electrolyte, preventing side reactions caused by directly adding the flame retardant. Simultaneously, using the PAN shell, along with the flame-retardant elements from the inorganic flame retardant, increases the loading of these elements, thus reducing the amount of flame-retardant additives required. In the event of thermal runaway, the PAN shell decomposes, releasing the inorganic flame retardant and reducing the flame retardancy of the electrolyte. Furthermore, silane modification of the flame retardant ensures its stability before heating and allows silanes to form Si-O-Si bonds on the electrode surface, inhibiting additive embedding into the electrode. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0016] <Technical Solution>

[0017] First, the present invention provides a lithium battery electrolyte, wherein each component, by weight, includes 10 to 20 parts of lithium salt, 3 to 10 parts of flame retardant, 2 to 8 parts of additive, and 60 to 90 parts of organic solvent.

[0018] Specifically, the flame retardant is a silane-modified flame retardant support; the flame retardant support is an inorganic flame retardant core with PAN as the shell.

[0019] In this invention, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, and lithium trifluoromethanesulfonate.

[0020] In this invention, the additives include at least one of fluoroethylene carbonate and lithium nitrate.

[0021] In this invention, the organic solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and methyl propyl carbonate.

[0022] In this invention, the method for preparing the flame-retardant support is as follows:

[0023] The inorganic flame retardant was modified with a vinylsilane coupling agent to obtain the first modified body;

[0024] The first modifier, acrylonitrile, and initiator are polymerized to obtain a flame-retardant support.

[0025] The first modified material was ultrasonically dispersed to obtain a pretreated solution. Acrylonitrile and an emulsifier (LAS) were added to the pretreated solution and heated. Then, potassium persulfate, an initiator, was added to react. After the reaction was completed, the mixture was washed and dried to obtain the final product. The reaction temperature was 60–70 °C, and the reaction time was 4 hours. The potassium persulfate accounted for 3% of the acrylonitrile.

[0026] In this invention, the inorganic flame retardant includes at least one of ammonium polyphosphate, ammonium phosphate, and ammonium sulfate.

[0027] In this invention, the vinyl coupling agent is A151, A171, or A172.

[0028] In this invention, the mass ratio of inorganic flame retardant, vinyl silane coupling agent, and acrylonitrile is 1:0.2-0.6:1-3.

[0029] In this invention, after the polymerization reaction, NaOH is added for further reaction, followed by centrifugation, washing, and drying to obtain the final product. Specifically, the concentration of NaOH is 1 mol / L, and the reaction parameters are 75℃ for 1 hour. After NaOH treatment, the nitrile groups in the polyacrylonitrile are converted into carboxyl groups and amide bonds, thereby complexing flame-retardant elements and further enhancing the flame-retardant effect.

[0030] In this invention, the method for preparing the silane-modified flame-retardant support is to react APTES or APS with the flame-retardant support.

[0031] In this invention, the mass ratio of APTES or APS to the flame-retardant support is 1:3 to 10; the reaction temperature is 85 to 100°C; and the reaction time is 10 to 30 hours.

[0032] In this invention, the diameter of the flame-retardant support is 0.1μm-5μm, and the thickness of the PAN shell is 0.01μm-1.5μm.

[0033] Second, the present invention provides a method for preparing the aforementioned lithium battery electrolyte, comprising the following steps:

[0034] The lithium salt, organic solvent, additives, and flame retardant are blended together to obtain the final product.

[0035] <Example>

[0036] Example 1

[0037] The preparation method of lithium battery electrolyte includes the following steps:

[0038] (1) A151 and an aqueous ethanol solution were mixed at a mass ratio of 1:1 and ultrasonically dispersed to obtain the first treatment solution; ammonium polyphosphate and ethanol were mixed at a mass ratio of 1:20 and ultrasonically dispersed to obtain the second treatment solution; the first and second treatment solutions were mixed and reacted at 80°C for 5 hours. After the reaction, the mixture was centrifuged, filtered, and dried to obtain the first modified body. The first modified body was mixed with pure water and dispersed to obtain the third treatment solution. Acrylonitrile and LAS were added to the third treatment solution and reacted at 60-70°C for 4 hours. Potassium persulfate was added at the reaction temperature, and the reaction was finally completed to obtain the intermediate. The mass ratio of A151:ammonium polyphosphate:acrylonitrile was 1:0.5:1.5, and the amount of potassium persulfate added accounted for 3% of the mass of acrylonitrile. The intermediate was added to a 1 mol / L NaOH solution and reacted at 75°C for 1 hour. After centrifugation, washing, and drying, the flame-retardant support was obtained.

[0039] (2) The flame retardant support obtained in (1) is blended with APTES at a mass ratio of 5:1, and then reacted at 85-100℃ for 20-24h to obtain the silane-modified flame retardant support.

[0040] (3) 15 parts of lithium hexafluorophosphate, 8 parts of the silane-modified flame retardant support obtained in (2), 5 parts of fluoroethylene carbonate, and 72 parts of organic solvent (ethylene carbonate, propylene carbonate, diethyl carbonate = 3:1:6, mass ratio) were blended together.

[0041] Example 2

[0042] The difference between this embodiment and embodiment 1 is that, in (3), 10 parts of lithium trifluoromethanesulfonate, 3 parts of silane-modified support, 5 parts of fluoroethylene carbonate, and 82 parts of organic solvent (ethylene carbonate, propylene carbonate, diethyl carbonate = 3:1:6, mass ratio) are blended to obtain the lithium battery electrolyte.

[0043] Example 3

[0044] The difference between this embodiment and Embodiment 1 is that the mass ratio of A151:ammonium polyphosphate:acrylonitrile is 1:0.2:1.

[0045] <Comparative Example>

[0046] Comparative Example 1

[0047] The method for preparing lithium battery electrolyte involves blending 15 parts lithium hexafluorophosphate, 8 parts ammonium polyphosphate, 5 parts fluoroethylene carbonate, and 72 parts organic solvent (ethylene carbonate, propylene carbonate, and diethyl carbonate in a mass ratio of 3:1:6).

[0048] Comparative Example 2

[0049] The difference between this comparative example and Example 1 is that the intermediate was not treated with NaOH.

[0050] Comparative Example 3

[0051] The difference between this comparative example and Example 1 is that step (2) is omitted.

[0052] <Experimental Example>

[0053] The flame retardant effect of the electrolyte was tested using the SET test method.

[0054] The electrochemical performance indicators of the electrolyte include capacity retention (%) (after 300 cycles). The results are shown in Table 1.

[0055] Table 1 Performance Test Results

[0056]

[0057]

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lithium battery electrolyte, characterized in that, The components, by weight, include 10-20 parts lithium salt, 3-10 parts flame retardant, 2-8 parts additives, and 60-90 parts organic solvent; The flame retardant is a silane-modified flame retardant support. The preparation method of silane-modified flame retardant support is as follows: APTES or APS is reacted with the flame retardant support; the mass ratio of APTES or APS to the flame retardant support is 1:3~10; the reaction temperature is 85~100℃ and the reaction time is 10~30h. The flame-retardant load body is an inorganic flame-retardant material as the core and PAN as the shell; The preparation method of the flame-retardant support is as follows: The inorganic flame retardant was modified with a vinylsilane coupling agent to obtain the first modified body; The first modifier, acrylonitrile, and initiator are polymerized to obtain a flame-retardant support. Specifically, the first modifier is ultrasonically dispersed to obtain a pretreatment liquid. Acrylonitrile and emulsifier are added to the pretreatment liquid and heated. Then, potassium persulfate initiator is added to react. The reaction temperature is 60~70℃ and the reaction time is 4h. The mass ratio of inorganic flame retardant, vinyl silane coupling agent, and acrylonitrile is 1:0.2~0.6:1~3; After polymerization, NaOH is added to react, followed by centrifugation, washing, and drying to obtain the product; The concentration of NaOH was 1 mol / L, and the reaction parameters were 75℃ and 1 h.

2. The lithium battery electrolyte according to claim 1, characterized in that, Lithium salts include at least one of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, and lithium trifluoromethanesulfonate.

3. The lithium battery electrolyte according to claim 1, characterized in that, The additives include at least one of fluoroethylene carbonate and lithium nitrate.

4. The lithium battery electrolyte according to claim 1, characterized in that, Organic solvents include at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and methyl propyl carbonate.

5. A method for preparing a lithium battery electrolyte as described in any one of claims 1 to 4, characterized in that, Includes the following steps: The lithium salt, organic solvent, additives, and flame retardant are blended together to obtain the final product.

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