Impact-resistant electrolyte for lithium battery and preparation method of impact-resistant electrolyte

Abstract

The invention discloses an anti-impact electrolyte for a lithium battery and a preparation method of the anti-impact electrolyte, and belongs to the technical field of chemical power sources, the preparation method comprises the following steps: S1, adding 1, 3-dioxopentane (DOL) into an ether solvent, and fully stirring to obtain a mixed solution A; s2, dissolving LiFSI in the solution A, and stirring to obtain a mixed solution B; s3, adding a fluorinated diluent into the mixed solution B, and stirring to obtain a mixed solution C; s4, adding fluoroethylene carbonate into the mixed solution C, and stirring to obtain a mixed solution D; and S5, adding LiPF6 into the mixed solution D, and stirring to obtain the anti-impact electrolyte for the lithium battery in a gel state. According to the invention, the lewis acid is introduced to form the impact-resistant electrolyte in situ in the battery, so that the defect that the liquid electrolyte is easy to volatilize and leak is effectively overcome, good interface contact and high ionic conductivity are achieved, and the impact resistance of the chromium-based metal oxide battery is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical power sources, and in particular relates to an impact-resistant electrolyte for a lithium battery and a preparation method thereof. Background Art

[0002] Lithium primary batteries play a key role in the application of energy storage devices due to their high energy density and low self-discharge rate. They have been widely used in special fields, implantable devices and various equipment. Chromium-based metal oxides have a high theoretical energy density (1210Wh kg -1 ), higher theoretical specific capacity (642mAh g -1 ) and higher operating voltage (3.0Vvs.Li + / Li) and has attracted much attention.

[0003] Great efforts have been made in the preparation of chromium-based metal oxide positive electrodes, including cation doping and high-temperature sintering strategies. The room temperature discharge capacity can be effectively improved by synthesizing new cathode materials through cation doping. In addition, high-temperature sintering can further purify the raw materials, thereby improving the high-temperature performance of the battery. However, the above strategies all need to consider additional costs, complex experimental operations and adverse effects on the environment. In addition, most of the electrolytes currently used in chromium-based metal oxide batteries are liquid electrolytes. Under the action of impact, the battery is easily destroyed, causing leakage and safety problems. Therefore, it is of great significance to study low-cost, high-safety, and easy-to-operate impact-resistant electrolytes. As an important part of transferring ions in the battery, the impact-resistant electrolyte has a significant effect on improving the safety performance of lithium primary batteries. Summary of the invention

[0004] The problem to be solved by the present invention is an impact-resistant electrolyte for lithium batteries and a preparation method thereof, which effectively solves the problem that batteries prepared with liquid electrolytes in the prior art are easily destroyed under impact, causing leakage and safety problems.

[0005] In order to solve the above technical problems, the technical solution provided by the present invention is: a method for preparing an impact-resistant electrolyte for a lithium battery, comprising the following steps:

[0006] S1: adding 1,3-dioxolane (DOL) to an ether solvent, wherein the volume ratio of the ether solvent to DOL is 1:6-6:1, and stirring thoroughly to obtain a mixed solution A;

[0007] S2: dissolving LiFSI in solution A with a lithium salt concentration of 2-6 M, and stirring to obtain a mixed solution B;

[0008] S3: adding a fluorinated diluent to the mixed solution B, wherein the volume ratio of the diluent to the solution B is 1:1-1:10, and stirring to obtain a mixed solution C;

[0009] S4: adding fluoroethylene carbonate to the mixed solution C, wherein the volume ratio of fluoroethylene carbonate to the mixed solution C is 1:1-1:10, and stirring to obtain a mixed solution D;

[0010] S5: Add LiPF6 to the mixed solution D, the lithium salt concentration is 0.05-0.6M, and after stirring, obtain a gel-state impact-resistant electrolyte for lithium batteries.

[0011] The ether solvent is one of ethylene glycol dimethyl ether (DME), ethylene glycol diethyl ether (DEE), ethylene glycol dibutyl ether (DBE), triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether, or a combination of more than one of the above.

[0012] The fluorinated diluent is one or a combination of 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), bis(2,2,2-trifluoroethyl) ether (BTFE), 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane (TFEE), 2,2,2-trifluorobutyric acid ethyl ester (TFEB), and 3,3,3-trifluoropropionic acid methyl ester (MTFP).

[0013] The LiFSI is of ultra-dry grade, the ether solvent is of ultra-dry grade, the DOL is of ultra-dry grade, and the fluoroethylene carbonate is of ultra-dry grade; steps S1-S5 are all performed in a glove box with an oxygen concentration and a water concentration both less than 0.1 ppm.

[0014] In step S1, stirring is performed at a rotation speed of 100-400 r / min for 0.1 h-1 h.

[0015] In step S2, stirring is performed at a rotation speed of 100-500 r / min for 0.2 h-0.6 h.

[0016] In step S3, stirring is performed at a rotation speed of 100-300 r / min for 0.15 h-2 h.

[0017] In step S4, stirring is performed at a rotation speed of 100-300 r / min for 0.1 h-1 h.

[0018] In step S5, stirring is performed at a rotation speed of 100-400 r / min for 0.1 h-0.6 h.

[0019] The impact-resistant electrolyte for lithium batteries prepared by the above preparation method.

[0020] Compared with the prior art, the present invention has the following advantages and positive effects:

[0021] 1. Use organic solvents with low viscosity and high dielectric constant, such as ether solvents and small cyclic ether molecules (DOL), as the main solvent of the electrolyte, which ensures high solubility of lithium salts and high ionic conductivity;

[0022] 2. The use of fluorinated diluents can improve the overall oxidation stability of the electrolyte and reduce the self-discharge and side reactions of the battery under high voltage;

[0023] 3. Fluoroethylene carbonate is beneficial to the formation of a protective layer at the lithium anode interface, promotes the transmission and diffusion of lithium ions, and improves the electrochemical performance of the battery; LiPF6, as a Lewis acid, triggers the ring-opening polymerization of DOL to form an impact-resistant electrolyte, which solves the problems of battery leakage and safety caused by the electrolyte's difficulty in resisting impact. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the electrochemical impedance curve (EIS) of the impact-resistant electrolyte prepared in Example 1 of the present invention.

[0025] Figure 2 This is the linear sweep voltammetry (LSV) curve of the impact-resistant electrolyte prepared in Example 1 of the present invention.

[0026] Figure 3 This is the impedance diagram of the impact-resistant electrolyte prepared in Example 1 of the present invention in a chromium-based metal oxide battery.

[0027] Figure 4 This is the discharge curve of the impact-resistant electrolyte prepared in Example 1 of the present invention in a chromium-based metal oxide battery at room temperature (25° C.). DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation methods described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] The present invention will be further described below in conjunction with embodiments:

[0030] Example 1

[0031] A shock-resistant electrolyte for lithium batteries, wherein a chromium-based metal oxide positive electrode, a shock-resistant electrolyte and a metal lithium negative electrode are assembled into a button-type lithium metal battery. The specific preparation process is as follows:

[0032] S1: adding 1,3-dioxolane (DOL) to ethylene glycol dimethyl ether (DME) with a solvent volume ratio of 1:1, and stirring the mixture with a magnetic stirrer at a speed of 200 r / min for 0.5 h to fully mix the mixture, thereby obtaining solution A;

[0033] S2: Dissolve bis(fluorosulfonyl)imide lithium salt (LiFSI) in solution A, and stir with a magnetic bar at a speed of 300-500 r / min for 0.3 h to fully dissolve it. The solution is clear and transparent, and the lithium salt concentration is 4 M, to obtain a mixed solution B;

[0034] S3: adding 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) to the mixed solution B in a volume ratio of 1:1, and stirring the mixture at a speed of 200 r / min for 0.8 h with a magnetic stirrer to fully mix the mixture, thereby obtaining a mixed solution C;

[0035] S4: adding fluoroethylene carbonate to the mixed solution C in a volume ratio of 1:10, and stirring the mixture at a speed of 200 r / min for 0.1 h using a magnetic stirrer to obtain a mixed solution D;

[0036] S5: Add LiPF6 to the mixed solution D, the lithium salt concentration is 0.3M, and stir with a magnet at a speed of 200-300 r / min for 0.6 h to obtain a shock-resistant electrolyte for lithium batteries;

[0037] S6: In a glove box filled with argon atmosphere, the chromium-based metal oxide positive electrode, the impact-resistant electrolyte and a φ20 metal lithium sheet are assembled into a button-type lithium-ion battery, and the electrochemical performance of the battery is tested in a battery testing system with a voltage range of 1.5V to 4V and a test temperature of 25°C.

[0038] Figure 1 is the impedance diagram of a stainless steel symmetrical battery assembled with a shock-resistant electrolyte. According to the formula

[0039] The ionic conductivity (σ) of the impact-resistant electrolyte can be calculated, where L represents the thickness between the two stainless steel gaskets, R represents the measured impedance value, and S represents the facing area between the two stainless steel gaskets. The specific parameters and conductivity results are shown in Table 1. After calculation, the ionic conductivity of the impact-resistant electrolyte is as high as 5×10 -3 S / cm, which is conducive to the rapid transport of lithium ions and improves the electrochemical performance.

[0040] Table 1 Ionic conductivity of shock-resistant electrolytes

[0041] Thickness(cm) Impedance(Ω) <![CDATA[Frontal area (cm 2 )]]> Conductivity (S / cm) 1.958 1.40 2.83385 <![CDATA[5×10 -3 ]]>

[0042] Figure 2 The linear sweep voltammetry (LSV) curve measured by an electrochemical workstation shows that the voltage at which the impact-resistant electrolyte can work normally is within 4.5V, which meets the requirements of lithium batteries. Figure 3This is the impedance diagram of a chromium-based metal oxide battery assembled using a shock-resistant electrolyte. The resistance is about 100Ω, which meets the normal use of the battery. Figure 4 It is the discharge curve of the impact-resistant electrolyte in the chromium-based metal oxide battery at room temperature (25°C), and the discharge specific capacity is as high as 400.3mAh / g.

[0043] Example 2

[0044] S1: 1,3-dioxolane (DOL) was added to ethylene glycol dimethyl ether (DME) in a solvent volume ratio of 2:1, and the mixture was stirred at a speed of 200 r / min for 0.5 h using a magnetic stirrer to fully mix the mixture, thereby obtaining solution A;

[0045] Steps S2-S6 are the same as those in Example 1.

[0046] Implementation Case 3

[0047] S1: 1,3-dioxolane (DOL) was added to ethylene glycol dimethyl ether (DME) in a solvent volume ratio of 1:2, and the mixture was stirred at a speed of 200 r / min for 0.5 h using a magnetic stirrer to fully mix the mixture, thereby obtaining solution A;

[0048] Steps S2-S6 are the same as those in Example 1.

[0049] Implementation Case 4

[0050] Steps S1-S4 are the same as in Example 1

[0051] S5: Add LiPF6 to the mixed solution D, the lithium salt concentration is 0.1M, and stir with a magnet at a speed of 200r / min for 0.3h to obtain a shock-resistant electrolyte for lithium batteries;

[0052] Implementation Case 5

[0053] Steps S1-S4 are the same as in Example 1

[0054] S5: Add LiPF6 to the mixed solution D, the lithium salt concentration is 0.5M, and stir with a magnet at a speed of 200 r / min for 0.3 h to obtain a shock-resistant electrolyte for lithium batteries;

[0055] Table 2 is a summary of ionic conductivity, gelation time, and electrochemical window size for implementation cases 1 to 5.

[0056]

[0057]

[0058] The above describes in detail the multiple embodiments of the present invention, but the contents are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for preparing an impact-resistant electrolyte for a lithium battery, characterized in that: The following steps are involved: S1: adding 1,3-dioxolane (DOL) to an ether solvent, wherein the volume ratio of the ether solvent to DOL is 1:6-6:1, and stirring thoroughly to obtain a mixed solution A; S2: dissolving LiFSI in solution A with a lithium salt concentration of 2-6 M, and stirring to obtain a mixed solution B; S3: adding a fluorinated diluent to the mixed solution B, wherein the volume ratio of the diluent to the solution B is 1:1-1:10, and stirring to obtain a mixed solution C; S4: adding fluoroethylene carbonate to the mixed solution C, wherein the volume ratio of fluoroethylene carbonate to the mixed solution C is 1:1-1:10, and stirring to obtain a mixed solution D; S5: Add LiPF6 to the mixed solution D, the lithium salt concentration is 0.05-0.6M, and after stirring, obtain a gel-state impact-resistant electrolyte for lithium batteries.

2. The method for preparing the impact-resistant electrolyte for lithium battery according to claim 1, characterized in that: The ether solvent is one of ethylene glycol dimethyl ether (DME), ethylene glycol diethyl ether (DEE), ethylene glycol dibutyl ether (DBE), triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether, or a combination of more than one of the above.

3. The method for preparing the impact-resistant electrolyte for lithium battery according to claim 1, characterized in that: The fluorinated diluent is one or a combination of 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), bis(2,2,2-trifluoroethyl) ether (BTFE), 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane (TFEE), 2,2,2-trifluorobutyric acid ethyl ester (TFEB), and 3,3,3-trifluoropropionic acid methyl ester (MTFP).

4. The method for preparing the impact-resistant electrolyte for lithium battery according to claim 1, characterized in that: The LiFSI is of ultra-dry grade, the ether solvent is of ultra-dry grade, the DOL is of ultra-dry grade, and the fluoroethylene carbonate is of ultra-dry grade; steps S1-S5 are all performed in a glove box with an oxygen concentration and a water concentration both less than 0.1 ppm.

5. The method for preparing the impact-resistant electrolyte for lithium battery according to claim 1, characterized in that: In step S1, stirring is performed at a rotation speed of 100-400 r / min for 0.1 h-1 h.

6. The method for preparing the impact-resistant electrolyte for lithium battery according to claim 1, characterized in that: In step S2, stirring is performed at a rotation speed of 100-500 r / min for 0.2 h-0.6 h.

7. The method for preparing the impact-resistant electrolyte for lithium battery according to claim 1, characterized in that: In step S3, stirring is performed at a rotation speed of 100-300 r / min for 0.15 h-2 h.

8. The method for preparing the impact-resistant electrolyte for lithium battery according to claim 1, characterized in that: In step S4, stirring is performed at a rotation speed of 100-300 r / min for 0.1 h-1 h.

9. The method for preparing the impact-resistant electrolyte for lithium battery according to claim 1, characterized in that: In step S5, stirring is performed at a rotation speed of 100-400 r / min for 0.1 h-0.6 h.

10. The impact-resistant electrolyte for lithium battery prepared by the preparation method according to any one of claims 1 to 9.

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