CN116072825A - A kind of preparation method of negative electrode protective film and battery - Google Patents

Abstract

The application provides a preparation method and a preparation device of a negative electrode protective film, which are applied to the technical field of batteries, wherein the method comprises the steps of obtaining a first solvent prepared from dimethyl carbonate, trifluoroethyl ether and lithium difluorosulfimide; soaking lithium metal in the first solvent; placing the lithium metal soaked in the first solvent in an argon glove box, and drying the lithium metal in an ultraviolet irradiation mode; adding pentafluorophenyl borane anions into the first solvent to obtain battery electrolyte; and placing the dried lithium metal in the battery electrolyte to generate a negative electrode protection film on the surface of the lithium metal. According to the method, the specially treated lithium metal is placed in the battery electrolyte containing the pentafluorophenyl borane anions, so that the negative electrode protective film is formed on the surface of the lithium metal, and the stability of the negative electrode protective film is improved.

Description

A kind of preparation method of negative electrode protective film and battery

technical field

The present application relates to the field of battery technology, in particular to a method for preparing a negative electrode protective film and a battery.

Background technique

Improving the energy density of the backup battery of the communication base station, arranging as many batteries as possible in a limited space, and prolonging the backup time of the communication base station are important ways to improve the efficiency of communication services. In order to improve the energy density of the battery, lithium metal is often used as the negative electrode material. However, the lithium metal negative electrode intercalation process is easily hindered by the non-uniform solid electrolyte film (Solid Electrolyte Interphase, SEI), resulting in uneven deposition of lithium ions. The phenomenon of lithium dendrites and dead lithium eventually leads to a rapid decline in battery capacity. In the prior art, the construction of uniform SEI is mainly through artificial ex-situ construction of specific nanostructures. However, the SEI prepared by this method lacks self-healing properties, and often cracks or detaches from the lithium surface, and then gradually loses protection. function, and its stability is low.

Contents of the invention

The embodiment of the present application provides a method for preparing a negative electrode protective film and a battery, so as to solve the problem of low stability of the negative electrode protective film prepared in the existing method for preparing the negative electrode protective film.

In order to solve the above-mentioned technical problems, the application is implemented as follows:

In the first aspect, the embodiment of the present application provides a method for preparing a negative electrode protective film. The method includes:

Obtaining a first solvent prepared from dimethyl carbonate, trifluoroethyl ether and lithium bisfluorosulfonyl imide;

Soaking lithium metal in the first solvent;

placing the lithium metal soaked in the first solvent in an argon glove box, and drying the lithium metal by ultraviolet irradiation;

adding pentafluorophenylborane anion to the first solvent to obtain a battery electrolyte;

The dried lithium metal is placed in the battery electrolyte to form a negative electrode protective film on the surface of the lithium metal.

Optionally, adding pentafluorophenylborane anion to the first solvent to obtain a battery electrolyte includes:

Add N times of pentafluorophenylborane anion to the first solvent, wherein, the interval time between every two additions of pentafluorophenylborane anion is in the range of 10 to 30 minutes, and the five The first solvent after the fluorophenylborane anion is stirred at the first temperature at the first rotation speed for the first time to obtain the battery electrolyte;

Wherein, the value range of the weight percentage of the pentafluorophenylborane anion is 0.1-0.5, the value range of the N is 3-5, and the value range of the first temperature is -10-0 Celsius, the first rotation speed is 500 revolutions per minute, and the value range of the first duration is 24 to 48 hours.

Optionally, the acquisition of the first solvent prepared from dimethyl carbonate, trifluoroethyl ether and lithium bisfluorosulfonimide includes:

obtaining a second solvent prepared from the dimethyl carbonate and the trifluoroethyl ether;

The lithium bisfluorosulfonyl imide is added to the second solvent to obtain a third solvent, and the concentration of the lithium bisfluorosulfonyl imide in the third solvent ranges from 0.1 to 0.5 mol/ Lift;

After stirring the third solvent at the second temperature for a second period of time, the lithium bisfluorosulfonyl imide is added, and the stirring temperature is increased to the third temperature to obtain the first solvent, wherein the The value range of the concentration of lithium bisfluorosulfonyl imide is 0.5-1 mol/liter, the value range of the second temperature is -10-0 degrees Celsius, and the value range of the second time length is 24-48 hour, the value range of the third temperature is 25-50 degrees Celsius.

Optionally, the acquisition of the second solvent prepared from the dimethyl carbonate and the trifluoroethyl ether includes:

Mix the dried dimethyl carbonate and trifluoroethyl ether in a reagent bottle according to a first molar ratio, and stir at a first rotational speed for a third time to obtain a second solvent. The value range is 1-24 hours, and the value range of the first molar ratio is 1:1-1:10.

Optionally, before the dried dimethyl carbonate and trifluoroethyl ether are mixed in the reagent bottle according to the first molar ratio, the method further includes:

The dimethyl carbonate and the trifluoroethyl ether are respectively placed in an argon glove box, and the dimethyl carbonate and the trifluoroethyl ether are respectively dried for a fourth period of time through molecular sieves in the argon glove box , and maintain the fourth temperature to stir the dimethyl carbonate and the trifluoroethyl ether respectively;

Wherein, the value range of the added amount of the molecular sieve is 0.1-10 g/ml, the value range of the fourth temperature is -10-0 degrees Celsius, and the value range of the fourth time length is 24-48 hours .

Optionally, the soaking of lithium metal in the first solvent includes:

At a fifth temperature, the lithium metal is soaked in the first solvent for a fifth time, wherein the mass ratio of the first solvent to the lithium metal ranges from 10:1 to 100:1, The value range of the fifth temperature is 30-50 degrees Celsius, and the value range of the fifth time length is 0.5-2 hours.

Optionally, the lithium metal soaked in the first solvent is placed in an argon glove box, and the lithium metal is dried by ultraviolet irradiation, including:

The lithium metal soaked in the first solvent is placed in an argon glove box, and the lithium metal is dried for a sixth time under ultraviolet irradiation, and the value of the sixth time ranges from 0.5 to 2 hours. The value range of the intensity of the ultraviolet rays is 100-2000 microwatts/square centimeter.

In the second aspect, the embodiment of the present application further provides a battery, the battery includes the negative electrode protective film prepared by using the above-mentioned method for preparing the negative electrode protective film.

The preparation method of the negative electrode protective film of the embodiment of the present application includes obtaining a first solvent prepared from dimethyl carbonate, trifluoroethyl ether and lithium bisfluorosulfonimide; soaking lithium metal in the first solvent; placing the lithium metal soaked in the first solvent in an argon glove box, and drying the lithium metal by ultraviolet irradiation; adding pentafluorophenylborane anion to the first solvent , to obtain a battery electrolyte; placing the dried lithium metal in the battery electrolyte to form a negative electrode protective film on the surface of the lithium metal. In the method, a negative electrode protection film is formed on the surface of the lithium metal by placing the specially treated lithium metal in a battery electrolyte containing pentafluorophenylborane anions, and the stability of the negative electrode protection film is improved.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that need to be used in the description of the embodiments of the present application will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those skilled in the art, other drawings can also be obtained based on these drawings without any creative effort.

Fig. 1 is the flow chart of the preparation method of the negative electrode protective film that the embodiment of the present application provides;

Fig. 2 is a negative electrode surface comparison diagram of the battery obtained based on the battery electrolyte provided in the embodiment of the present application and the battery obtained based on the comparative electrolyte;

Fig. 3 is the lithium deintercalation diagram of the battery obtained based on the battery electrolyte obtained in Example 1 of the present application and the battery obtained based on the comparative electrolyte;

4 is a battery cycle diagram of a battery obtained based on the battery electrolyte obtained in Example 2 of the present application and a battery obtained based on a comparative electrolyte;

Fig. 5 is a Coulombic efficiency diagram of a battery obtained based on the battery electrolyte obtained in Example 2 of the present application and a battery obtained based on a comparative electrolyte.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of them. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of this application.

The embodiment of the present application provides a method for preparing a negative electrode protective film. Referring to Fig. 1, Fig. 1 is a flow chart of the preparation method of the negative electrode protective film provided by the embodiment of the present application, as shown in Fig. 1, comprising the following steps:

Step 101, obtaining the first solvent prepared from dimethyl carbonate, trifluoroethyl ether and lithium bisfluorosulfonyl imide;

Step 102, soaking lithium metal in the first solvent;

Step 103, placing the lithium metal soaked in the first solvent in an argon glove box, and drying the lithium metal by ultraviolet irradiation;

Step 104, adding pentafluorophenylborane anion into the first solvent to obtain a battery electrolyte;

Step 105, placing the dried lithium metal in the battery electrolyte to form a negative electrode protective film on the surface of the lithium metal.

In the existing preparation method of the negative electrode protective film, the specific nanostructure is mainly constructed by artificial ex-situ, and the negative electrode protective film is pasted on the surface of the lithium metal negative electrode. Such a negative electrode protective film is very unstable and often occurs Cracking or detachment from the lithium metal surface gradually loses its protective function.

In the preparation method of the negative electrode protective film of the embodiment of the present application, the first solvent prepared by dimethyl carbonate, trifluoroethyl ether and lithium bisfluorosulfonimide is obtained, and the lithium metal is placed in the first solvent for soaking, The lithium metal soaked in the first solvent is placed in an argon glove box, and the lithium metal is dried by ultraviolet irradiation, which provides reaction sites for forming a negative electrode protective film on the surface of the lithium metal.

Pentafluorophenylborane anion is added to the first solvent to obtain a battery electrolyte, and then the dried lithium metal is placed in the battery electrolyte, and the pentafluorophenylborane anion can weaken the difluorosulfonyl The stability of lithium amide, thereby accelerating the separation of bisfluorosulfonyl imide anion and lithium ion in lithium bisfluorosulfonyl imide, so that lithium ion can combine with other polysulfides in the battery electrolyte to form on the surface of lithium metal A negative electrode protective film containing lithium sulfide. It should be noted that the negative electrode protective film is a composite that contains non-polar components and organic components. The dimethyl carbonate and trifluoroethyl ether in the electrolyte are conducive to promoting the formation of the negative electrode protective film . The preparation method of the negative electrode protective film of the embodiment of the present application places the specially treated lithium metal in the battery electrolyte containing pentafluorophenylborane anions, thereby forming a negative electrode protective film on the surface of the lithium metal, and improving the negative electrode protective film. stability.

Optionally, adding pentafluorophenylborane anion to the first solvent to obtain a battery electrolyte includes:

Add N times of pentafluorophenylborane anion to the first solvent, wherein, the interval time between every two additions of pentafluorophenylborane anion is in the range of 10 to 30 minutes, and the five The first solvent after the fluorophenylborane anion is stirred at the first temperature at the first rotation speed for the first time to obtain the battery electrolyte;

Wherein, the value range of the weight percentage of the pentafluorophenylborane anion is 0.1-0.5, the value range of the N is 3-5, and the value range of the first temperature is -10-0 Celsius, the first rotation speed is 500 revolutions per minute, and the value range of the first duration is 24 to 48 hours.

In the preparation method of the negative electrode protective film of the embodiment of the present application, N times of pentafluorophenylborane anion is added to the first solvent, wherein, the value range of the interval time between every two additions of pentafluorophenylborane anion 10 to 30 minutes, and the first solvent after adding the pentafluorophenylborane anion is stirred at the first temperature at the first rotation speed for the first time to obtain a battery electrolyte, wherein the pentafluorophenylborane anion The value range of the weight content percentage is 0.1-0.5, the value range of N is 3-5, the value range of the first temperature is -10-0 degrees Celsius, the first rotation speed is 500 revolutions per minute, and the value range of the first duration is The value range is 24~48h. The method can fully contact the pentafluorophenylborane anion with the lithium bisfluorosulfonimide, thereby accelerating the separation of the bifluorosulfonimide anion and the lithium ion, and promoting the formation of a negative electrode protective film containing lithium sulfide.

Exemplarily, in the first solvent, pentafluorophenylborane anion can be added 3 times, wherein, the interval time between every two additions of pentafluorophenylborane anion can be 15 minutes, and the pentafluorophenylborane anion will be added The first solvent after the alkane anion was stirred at a temperature of -9 degrees Celsius at a speed of 500 revolutions per minute for 25 hours to obtain a battery electrolyte.

Optionally, the acquisition of the first solvent prepared from dimethyl carbonate, trifluoroethyl ether and lithium bisfluorosulfonimide includes:

obtaining a second solvent prepared from the dimethyl carbonate and the trifluoroethyl ether;

The lithium bisfluorosulfonyl imide is added to the second solvent to obtain a third solvent, and the concentration of the lithium bisfluorosulfonyl imide in the third solvent ranges from 0.1 to 0.5 mol/ Lift;

After stirring the third solvent at the second temperature for a second period of time, the lithium bisfluorosulfonyl imide is added, and the stirring temperature is increased to the third temperature to obtain the first solvent, wherein the The value range of the concentration of lithium bisfluorosulfonyl imide is 0.5-1 mol/liter, the value range of the second temperature is -10-0 degrees Celsius, and the value range of the second time length is 24-48 hour, the value range of the third temperature is 25-50 degrees Celsius.

In the preparation method of the negative electrode protective film of the embodiment of the present application, the second solvent prepared from dimethyl carbonate and trifluoroethyl ether is obtained, and lithium bisfluorosulfonyl imide is added to the second solvent to obtain the third solvent, wherein The range of concentration of lithium bisfluorosulfonyl imide in the third solvent is 0.1-0.5 mol/liter;

After stirring the third solvent at the second temperature for a second period of time, lithium bisfluorosulfonyl imide is added, and the stirring temperature is increased to the third temperature to obtain the first solvent, wherein the lithium bisfluorosulfonyl imide in the first solvent is The value range of the concentration is 0.5-1 mol/liter, the value range of the second temperature is -10-0 degrees Celsius, the value range of the second time length is 24-48 hours, and the value range of the third temperature is 25 ~50 degrees Celsius. In the method, the lithium bisfluorosulfonyl imide is added in batches to the second solvent prepared from dimethyl carbonate and trifluoroethyl ether under different temperature conditions, which is beneficial to the full dissolution of the lithium bisfluorosulfonyl imide.

Exemplarily, the second solvent prepared by dimethyl carbonate and trifluoroethyl ether is obtained, and lithium bisfluorosulfonimide is added to the second solvent to obtain a third solvent, wherein bisfluorosulfonimide in the third solvent The concentration of lithium can be 0.4 mol/liter. After stirring the third solvent at a temperature of -9 degrees Celsius for 26 hours, add lithium bisfluorosulfonyl imide, and increase the stirring temperature to 26 degrees Celsius to obtain the first solvent. Wherein, the concentration of lithium bisfluorosulfonyl imide in the first solvent may be 0.8 mol/liter.

Optionally, the acquisition of the second solvent prepared from the dimethyl carbonate and the trifluoroethyl ether includes:

Mix the dried dimethyl carbonate and trifluoroethyl ether in a reagent bottle according to a first molar ratio, and stir at a first rotational speed for a third time to obtain a second solvent. The value range is 1-24 hours, and the value range of the first molar ratio is 1:1-1:10.

In the preparation method of the negative electrode protective film of the embodiment of the present application, the dried dimethyl carbonate and trifluoroethyl ether are mixed in the reagent bottle according to the first molar ratio, and stirred at the first rotation speed for the third time to obtain the second For the second solvent, the value range of the third time length is 1-24 hours, and the value range of the first molar ratio is 1:1-1:10. This method is conducive to the thorough mixing of dimethyl carbonate and trifluoroethyl ether.

Exemplarily, the dried dimethyl carbonate and trifluoroethyl ether were mixed in a reagent bottle at a molar ratio of 1:2, and stirred for 12 hours on a magnetic stirring table at a speed of 500 revolutions per minute to obtain the second solvent.

Optionally, before the dried dimethyl carbonate and trifluoroethyl ether are mixed in the reagent bottle according to the first molar ratio, the method further includes:

The dimethyl carbonate and the trifluoroethyl ether are respectively placed in an argon glove box, and the dimethyl carbonate and the trifluoroethyl ether are respectively dried for a fourth period of time through molecular sieves in the argon glove box , and maintain the fourth temperature to stir the dimethyl carbonate and the trifluoroethyl ether respectively;

Wherein, the value range of the added amount of the molecular sieve is 0.1-10 g/ml, the value range of the fourth temperature is -10-0 degrees Celsius, and the value range of the fourth time length is 24-48 hours .

In the preparation method of the negative electrode protective film of the embodiment of the present application, dimethyl carbonate and trifluoroethyl ether are respectively placed in an argon glove box, and the dimethyl carbonate and trifluoroethyl ether are respectively separated by molecular sieves in the argon glove box. Drying for a fourth time, and maintaining the fourth temperature to stir the dimethyl carbonate and trifluoroethyl ether respectively, the aforementioned molecular sieve may be 3A molecular sieve. Wherein, the value range of the added amount of molecular sieve is 0.1-10 g/ml, the value range of the fourth temperature is -10-0 degrees Celsius, and the value range of the fourth time length is 24-48 hours. This method removes moisture adsorbed on dimethyl carbonate and trifluoroethyl ether.

Exemplarily, dimethyl carbonate and trifluoroethyl ether were respectively placed in an argon glove box, and the dimethyl carbonate and trifluoroethyl ether were dried through molecular sieves in the argon glove box for 24 hours, respectively, at a temperature of -10 degrees Celsius. Stir the dimethyl carbonate and trifluoroethyl ether separately under certain conditions, wherein the amount of molecular sieve added can be 0.1 g/ml.

Optionally, the soaking of lithium metal in the first solvent includes:

At a fifth temperature, the lithium metal is soaked in the first solvent for a fifth time, wherein the mass ratio of the first solvent to the lithium metal ranges from 10:1 to 100:1, The value range of the fifth temperature is 30-50 degrees Celsius, and the value range of the fifth time length is 0.5-2 hours.

In the preparation method of the negative electrode protection film of the embodiment of the present application, at the fifth temperature, the lithium metal is placed in the first solvent and soaked for the fifth time, wherein the value range of the mass ratio of the first solvent to the lithium metal is 10:1 to 100:1, the value range of the fifth temperature is 30 to 50 degrees Celsius, and the value range of the fifth duration is 0.5 to 2 hours. In the method, the growth of the negative electrode protective film on the surface of the lithium metal can be promoted by soaking the lithium metal in the first solvent.

Exemplarily, the lithium metal may be soaked in the first solvent at a temperature of 35 degrees Celsius for 1 hour, wherein the mass ratio of the first solvent to the lithium metal may be 20:1.

Optionally, the lithium metal soaked in the first solvent is placed in the first argon glove box, and the lithium metal is dried by ultraviolet irradiation, including:

placing the lithium metal soaked in the first solvent in the first argon glove box, and drying the lithium metal under ultraviolet irradiation for a sixth time, and the sixth time ranges from 0.5 to 2 hours , the value range of the intensity of the ultraviolet rays is 100-2000 microwatts/square centimeter.

In the preparation method of the negative electrode protective film of the embodiment of the present application, the lithium metal soaked in the first solvent is placed in the first argon glove box, and the lithium metal is dried for the sixth time under ultraviolet irradiation. The value range is 0.5-2 hours, and the value range of the intensity of ultraviolet rays is 100-2000 microwatts/square centimeter. The method increases the reaction sites on the surface of the lithium metal by means of ultraviolet irradiation, and promotes the formation of a negative electrode protective film containing lithium sulfide on the surface of the lithium metal.

Exemplarily, the lithium metal soaked in the first solvent is placed in the first argon glove box, and the lithium metal is dried for 1 hour under ultraviolet irradiation with an intensity of 1000 microwatts/square centimeter.

In order to further illustrate the beneficial effect obtained by the preparation method of the negative electrode protective film of the embodiment of the present application, the battery electrolyte obtained in the embodiment 1 of the application and the embodiment 2 of the application and the comparative electrolyte are used for experiments. The aforementioned comparative electrolyte is Dissolve bisfluorosulfonimide lithium salt with a concentration of 0.5 mol/liter in a mixed solvent of dimethyl carbonate and trifluoroethyl ether with a volume ratio of 1:1, and then add lithium nitrate with a mass fraction of 2%. mixed solution.

分子筛分别对碳酸二甲酯和三氟乙醚进行干燥，干燥的时间控制在24小时，并在0摄氏度的温度下对碳酸二甲酯和三氟乙醚分别进行搅拌，其中

分子筛的添加量为0.5克/毫升。将纯化后的碳酸二甲酯和三氟乙醚按照1:3的摩尔比加入试剂瓶中进行混合，随后在磁力搅拌台上以每分钟500转的速度搅拌12小时，确保碳酸二甲酯和三氟乙醚充分混合，得到第二溶剂。在第二溶剂中加入双氟磺酰亚胺锂，得到双氟磺酰亚胺锂浓度为0.2摩尔/升的第三溶剂，随后，将第三溶剂在-10摄氏度的温度下搅拌24小时，确保双氟磺酰亚胺阴离子充分溶解，随后再补充一定量的双氟磺酰亚胺锂，并提高搅拌温度至30摄氏度，加速双氟磺酰亚胺阴离子的溶解，得到第一溶剂，其中，第一溶剂中双氟磺酰亚胺锂的浓度为0.7摩尔/升。在第一溶剂中加入3次五氟苯基硼烷阴离子，每次间隔20分钟，其中，五氟苯基硼烷阴离子在第一溶剂中的重量含量百分数为0.1，将加入五氟苯基硼烷阴离子后的第一溶剂在-10摄氏度的温度下以每分钟500转的速度搅拌24小时，得到电池电解液。In the preparation method of the negative electrode protective film in Example 1 of the present application, first use

Molecular sieves are used to dry dimethyl carbonate and trifluoroethyl ether respectively, and the drying time is controlled at 24 hours, and dimethyl carbonate and trifluoroethyl ether are stirred respectively at a temperature of 0 degrees Celsius, wherein

The amount of molecular sieve added is 0.5 g/ml. The purified dimethyl carbonate and trifluoroethyl ether were added into the reagent bottle according to the molar ratio of 1:3 and mixed, then stirred for 12 hours at a speed of 500 revolutions per minute on a magnetic stirring table to ensure that dimethyl carbonate and trifluoroethyl ether were mixed. Fluoroethyl ether is mixed well to obtain the second solvent. Add lithium bisfluorosulfonyl imide to the second solvent to obtain a third solvent with a lithium bisfluorosulfonyl imide concentration of 0.2 mol/liter, and then stir the third solvent at a temperature of -10 degrees Celsius for 24 hours, Ensure that the bisfluorosulfonimide anion is fully dissolved, then add a certain amount of lithium bisfluorosulfonimide, and increase the stirring temperature to 30 degrees Celsius to accelerate the dissolution of the bisfluorosulfonimide anion to obtain the first solvent, wherein , the concentration of lithium bisfluorosulfonyl imide in the first solvent is 0.7 mol/liter. Add pentafluorophenylborane anion 3 times in the first solvent, each interval is 20 minutes, wherein, the percentage by weight of pentafluorophenylborane anion in the first solvent is 0.1, will add pentafluorophenylborane The first solvent after the alkane anion was stirred at a temperature of -10 degrees Celsius at a speed of 500 revolutions per minute for 24 hours to obtain a battery electrolyte.

Before assembling the battery, some special treatment is required for the lithium metal: soak the lithium metal in the first solvent for 0.5 hours at a temperature of 50 degrees Celsius, where the mass ratio of the first solvent to lithium metal is 75:1. The lithium metal soaked in the first solvent was placed in an argon glove box, and dried for 2 hours under ultraviolet irradiation with an intensity of 2000 microwatts/square centimeter, so as to provide reaction sites for forming the negative electrode protective film.

Referring to Figure 2, Figure 2 is the negative electrode surface of the lithium battery prepared by using the comparative electrolyte and the battery electrolyte obtained in Example 1 of the present application after 50 cycles, as can be seen from the (a) diagram shown in Figure 2 Due to the lack of a stable negative electrode protective film in the lithium battery prepared by the comparison electrolyte, a large number of irregular lithium dendrites grow on the surface of the negative electrode. The growth of lithium dendrites will consume the comparison electrolyte and pierce the separator at the same time, causing serious damage Security risks. However, it can be seen from the (b) figure shown in Figure 2 that for the lithium battery prepared by the battery electrolyte obtained in Example 1 of the present application, due to the existence of a stable negative electrode protective film, the deposition of lithium ions requires Much uniform, after many cycles, the lithium metal surface is dominated by dense and regular hemispheres, less lithium metal and battery electrolyte are consumed, and no sharp lithium dendrite growth is observed, indicating that the negative electrode of Example 1 of the present application The preparation method of the protective film improves the stability of the negative electrode protective film.

Referring to Fig. 3, Fig. 3 is the diagram of deintercalation of lithium at a constant current of 1 milliampere/square centimeter using the battery electrolyte obtained in Example 1 of the present application and the comparative electrolyte respectively. 1 The lithium-copper battery made from the obtained battery electrolyte is the experimental group, and the lithium-copper battery made from the comparative electrolyte is the blank group. It can be seen from the figure that in the lithium copper battery made by using the battery electrolyte obtained in Example 1 of the present application, due to the good ion permeability and stable mechanical structure of the negative electrode protective film made by it, the battery is stable at 1 millisecond. Under the current density of amps/cm2, it can be cycled stably for more than 500 hours, and the Coulombic efficiency is maintained above 98%, which has obvious performance advantages compared with the 200-hour cycle of the lithium-copper battery made of the comparative electrolyte.

分子筛分别对碳酸二甲酯和三氟乙醚进行干燥，干燥的时间控制在48小时，并在-10摄氏度的温度下对碳酸二甲酯和三氟乙醚分别进行搅拌，其中

分子筛的添加量为0.1克/毫升。将纯化后的碳酸二甲酯和三氟乙醚按照1:5的摩尔比加入试剂瓶中进行混合，随后在磁力搅拌台上以每分钟500转的速度搅拌12小时，确保碳酸二甲酯和三氟乙醚充分混合，得到第二溶剂。在第二溶剂中加入双氟磺酰亚胺锂，得到双氟磺酰亚胺锂浓度为0.1摩尔/升的第三溶剂，随后，将第三溶剂在-10摄氏度的温度下搅拌48小时，确保双氟磺酰亚胺阴离子充分溶解，随后再补充一定量的双氟磺酰亚胺锂，并提高搅拌温度至25摄氏度，加速双氟磺酰亚胺阴离子的溶解，得到第一溶剂，其中，第一溶剂中双氟磺酰亚胺锂的浓度为0.5摩尔/升。在第一溶剂中加入5次五氟苯基硼烷阴离子，每次间隔30分钟，其中，五氟苯基硼烷阴离子在第一溶剂中的重量含量百分数为0.5，将加入五氟苯基硼烷阴离子后的第一溶剂在-10摄氏度的温度下以每分钟500转的速度搅拌48小时，得到电池电解液。In the preparation method of the negative electrode protective film in Example 2 of the present application, first use

Molecular sieves are used to dry dimethyl carbonate and trifluoroethyl ether respectively, and the drying time is controlled at 48 hours, and the dimethyl carbonate and trifluoroethyl ether are stirred respectively at a temperature of -10 degrees Celsius, wherein

The amount of molecular sieve added is 0.1 g/ml. The purified dimethyl carbonate and trifluoroethyl ether were added into the reagent bottle according to the molar ratio of 1:5 and mixed, then stirred for 12 hours at a speed of 500 revolutions per minute on a magnetic stirring table to ensure that the dimethyl carbonate and trifluoroethyl ether were mixed. Fluoroethyl ether is mixed well to obtain the second solvent. Add lithium bisfluorosulfonyl imide to the second solvent to obtain a third solvent with a lithium bisfluorosulfonyl imide concentration of 0.1 mol/liter, and then stir the third solvent at a temperature of -10 degrees Celsius for 48 hours, Ensure that the bisfluorosulfonimide anion is fully dissolved, then add a certain amount of lithium bisfluorosulfonimide, and increase the stirring temperature to 25 degrees Celsius to accelerate the dissolution of the bisfluorosulfonimide anion to obtain the first solvent, wherein , the concentration of lithium bisfluorosulfonyl imide in the first solvent is 0.5 mol/liter. Add pentafluorophenylborane anion 5 times in the first solvent, each interval is 30 minutes, wherein, the weight content percentage of pentafluorophenylborane anion in the first solvent is 0.5, will add pentafluorophenylborane The first solvent after the alkane anion was stirred at a temperature of -10 degrees Celsius at a speed of 500 revolutions per minute for 48 hours to obtain a battery electrolyte.

Before assembling the battery, some special treatment is required for the lithium metal: soak the lithium metal in the first solvent for 2 hours at a temperature of 30 degrees Celsius, where the mass ratio of the first solvent to lithium metal is 100:1. The lithium metal soaked in the first solvent was placed in an argon glove box, and dried for 0.5 hours under ultraviolet irradiation with an intensity of 500 microwatts/square centimeter, so as to provide reaction sites for forming a negative electrode protective film.

Referring to Fig. 4, Fig. 4 is the battery cycle diagram under 1 milliampere/square centimeter constant current charge and discharge of the lithium-lithium symmetrical battery that uses the battery electrolyte that the application embodiment two obtains and comparative electrolyte to make, can be seen from Fig. 4 It can be seen that the lithium-lithium battery prepared by using the battery electrolyte obtained in Example 2 of the present application can stably cycle for more than 600 cycles at a current density of 1 mA/cm2, with an overpotential of only 35 millivolts, and has a good lithium battery. Ion deposition ability.

Referring to Fig. 5, Fig. 5 is the coulombic efficiency performance diagram of the lithium-lithium symmetric battery prepared by using the battery electrolyte obtained in Example 2 of the present application and the comparative electrolyte under 1 milliampere/square centimeter constant current charge and discharge, from the figure It can be seen that the lithium-lithium battery prepared by using the battery electrolyte obtained in Example 2 of the present application can be cycled for about 225 cycles at a current density of 1 mA/cm2, showing good mechanical properties and stable performance of the negative electrode protective film. The ability to deintercalate lithium.

The embodiment of the present application also provides a battery, which includes the negative electrode protective film prepared by the above-mentioned method for preparing the negative electrode protective film.

It should be noted that, in this document, the term "comprising", "comprising" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article or apparatus comprising a set of elements includes not only those elements, It also includes other elements not expressly listed, or elements inherent in the process, method, article, or device. Without further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus comprising that element.

Through the description of the above embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus a necessary general-purpose hardware platform, and of course also by hardware, but in many cases the former is better implementation. Based on such an understanding, the technical solution of the present application can be embodied in the form of a software product in essence or the part that contributes to the prior art, and the computer software product is stored in a storage medium (such as ROM/RAM, disk, CD) contains several instructions to enable a terminal (which may be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) to execute the methods described in various embodiments of the present application.

The embodiments of the present application have been described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementations. The above-mentioned specific implementations are only illustrative and not restrictive. Those of ordinary skill in the art will Under the inspiration of this application, without departing from the purpose of this application and the scope of protection of the claims, many forms can also be made, all of which belong to the protection of this application.

Claims (8)

1. a preparation method of negative electrode protection film, is characterized in that, described method comprises: Obtaining a first solvent prepared from dimethyl carbonate, trifluoroethyl ether and lithium bisfluorosulfonyl imide; Soaking lithium metal in the first solvent; placing the lithium metal soaked in the first solvent in an argon glove box, and drying the lithium metal by ultraviolet irradiation; adding pentafluorophenylborane anion to the first solvent to obtain a battery electrolyte; The dried lithium metal is placed in the battery electrolyte to form a negative electrode protective film on the surface of the lithium metal. 2. the preparation method of negative electrode protection film according to claim 1 is characterized in that, described in described first solvent, adds pentafluorophenylborane anion, obtains battery electrolyte, comprises: Add N times of pentafluorophenylborane anion to the first solvent, wherein, the interval time between every two additions of pentafluorophenylborane anion is in the range of 10 to 30 minutes, and the five The first solvent after the fluorophenylborane anion is stirred at the first temperature at the first rotation speed for the first time to obtain the battery electrolyte; Wherein, the value range of the weight percentage of the pentafluorophenylborane anion is 0.1-0.5, the value range of the N is 3-5, and the value range of the first temperature is -10-0 Celsius, the first rotation speed is 500 revolutions per minute, and the value range of the first duration is 24 to 48 hours. 3. the preparation method of negative electrode protective film according to claim 1, is characterized in that, described acquisition is prepared by the first solvent of dimethyl carbonate, trifluoroethyl ether and bisfluorosulfonimide lithium, comprising: obtaining a second solvent prepared from the dimethyl carbonate and the trifluoroethyl ether; The lithium bisfluorosulfonyl imide is added to the second solvent to obtain a third solvent, and the concentration of the lithium bisfluorosulfonyl imide in the third solvent ranges from 0.1 to 0.5 mol/ Lift; After stirring the third solvent at the second temperature for a second period of time, add the lithium bisfluorosulfonyl imide, and increase the stirring temperature to the third temperature to obtain the first solvent, the first solvent said The value range of the concentration of lithium bisfluorosulfonyl imide is 0.5-1 mol/liter, the value range of the second temperature is -10-0 degrees Celsius, and the value range of the second time length is 24-48 hour, the value range of the third temperature is 25-50 degrees Celsius. 4. the preparation method of negative electrode protective film according to claim 3, is characterized in that, described acquisition is prepared by the second solvent of described dimethyl carbonate and described trifluoroethyl ether, comprises: Mix the dried dimethyl carbonate and trifluoroethyl ether in a reagent bottle according to a first molar ratio, and stir at a first rotation speed for a third time to obtain a second solvent. The value range is 1-24 hours, and the value range of the first molar ratio is 1:1-1:10. 5. the preparation method of negative electrode protection film according to claim 4 is characterized in that, before described described dimethyl carbonate after drying and described trifluoroethyl ether are mixed in reagent bottle according to first molar ratio , the method also includes: The dimethyl carbonate and the trifluoroethyl ether are respectively placed in an argon glove box, and the dimethyl carbonate and the trifluoroethyl ether are respectively dried for a fourth period of time through molecular sieves in the argon glove box , and maintain the fourth temperature to stir the dimethyl carbonate and the trifluoroethyl ether respectively; Wherein, the value range of the added amount of the molecular sieve is 0.1-10 g/ml, the value range of the fourth temperature is -10-0 degrees Celsius, and the value range of the fourth time length is 24-48 hours . 6. The preparation method of negative electrode protection film according to claim 1, is characterized in that, described lithium metal is placed in described first solvent soaking, comprises: At a fifth temperature, the lithium metal is soaked in the first solvent for a fifth time, wherein the mass ratio of the first solvent to the lithium metal ranges from 10:1 to 100:1, The value range of the fifth temperature is 30-50 degrees Celsius, and the value range of the fifth time length is 0.5-2 hours. 7. the preparation method of negative electrode protective film according to claim 1 is characterized in that, the lithium metal after soaking in the first solvent is placed in an argon glove box, and the lithium metal is irradiated by ultraviolet rays. Metals are dried, including: placing the lithium metal soaked in the first solvent in an argon glove box, and drying the lithium metal under ultraviolet irradiation for a sixth time period, the sixth time period ranges from 0.5 to 2 hours, The value range of the intensity of the ultraviolet rays is 100-2000 microwatts/square centimeter. 8. A battery, characterized in that the battery comprises a negative electrode protective film prepared by the method for preparing a negative electrode protective film according to any one of claims 1 to 7.

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