阅读说明：本技术 一种适用于钢壳的电解液的筛选方法及筛选确定的电解液 (Screening method of electrolyte suitable for steel shell and screened and determined electrolyte ) 是由 王自霞 朱红庆 郭可可 吴志隆 王理 刘金成 刘建华 于 2020-12-24 设计创作，主要内容包括：本发明提供了一种适用于钢壳的电解液的筛选方法及筛选确定的电解液,所述的筛选方法包括：将待筛选的电解液注入钢壳内制成锂电池,测试锂电池的K值,K值≤0.08mv/h时,表明相应的电解液通过筛选,适用于钢壳。本发明通过测试不同种类的电解液制成的锂电池的K值,利用K值的大小判断待筛选的电解液是否适用于钢壳,从而将可以量化的K值作为了判断电解液是否适用于钢壳的指标。(The invention provides a screening method of electrolyte suitable for a steel shell and the electrolyte determined by screening, wherein the screening method comprises the following steps: and injecting the electrolyte to be screened into the steel shell to prepare the lithium battery, testing the K value of the lithium battery, and when the K value is less than or equal to 0.08mv/h, showing that the corresponding electrolyte passes screening and is suitable for the steel shell. According to the invention, the K values of lithium batteries made of different types of electrolytes are tested, and whether the electrolyte to be screened is suitable for the steel shell is judged by utilizing the K values, so that the quantifiable K value is used as an index for judging whether the electrolyte is suitable for the steel shell.)

1. A screening method of electrolyte suitable for a steel shell is characterized by comprising the following steps: and injecting the electrolyte to be screened into the steel shell to prepare the lithium battery, testing the K value of the lithium battery, and when the K is less than or equal to 0.08mv/h, showing that the corresponding electrolyte passes screening and is suitable for the steel shell.

2. The screening method according to claim 1, wherein the screening method specifically comprises:

(I) preparing one part of each electrolyte to be screened, injecting the electrolyte into a steel shell for primary screening, and testing K of all lithium batteries₁Value, K₁When the concentration is less than or equal to 0.08mv/h, the corresponding electrolyte passes through the primary screen;

(II) equally dividing the electrolyte passing through the primary screening into at least 10 parts, respectively injecting the 10 parts into the steel shell to prepare at least 10 groups of completely same lithium batteries, randomly performing random inspection on the lithium batteries, and testing K of the lithium batteries in the random inspection₂Value, K₂When the concentration is less than or equal to 0.08mv/h, the electrolyte passing through the primary screen passes through the final screen, and the method is suitable for steel shells.

3. The screening method according to claim 2, wherein the step (I) specifically comprises:

preparing one part of each electrolyte to be screened, injecting the electrolyte into a steel shell to prepare a lithium battery, storing the lithium battery for 1-7 days under a specific temperature condition, testing open-circuit voltages of all the lithium batteries, and recording the open-circuit voltages as OCV₁(ii) a Under the condition of specific temperature, D is continuously stored₁In the day, the open-circuit voltage of all lithium batteries is tested again and recorded as OCV₂(ii) a Calculating K of lithium battery₁Value, K₁When the concentration of the electrolyte is less than or equal to 0.08mv/h, marking the corresponding electrolyte as qualified by primary screening, and K₁When the concentration is more than 0.08mv/h, marking the corresponding electrolyte as unqualified primary screen; k₁The calculation formula of (a) is as follows:

K₁＝(OCV₁-OCV₂)/D₁/24。

4. the screening method of claim 3, wherein the OCV is tested₁Before, all lithium batteries are stored for 1-7 days at 20-30 ℃;

preferably, OCV is tested₁Before, all lithium batteries are stored for 1-7 days at 45-60 ℃;

preferably, OCV is tested₁Before, all lithium batteries are stored for 1-2 days at 20-30 ℃, and then the storage temperature is adjusted to 45-60 ℃ for continuous storage for 1-6 days.

5. The screening method according to claim 3 or 4, wherein OCV is tested₂Previously, all lithium batteries were stored at 20-30 ℃ D₁Day;

preferably, OCV is tested₂Previously, all lithium batteries were stored at 45-60 ℃ D₁Day;

preferably, OCV is tested₂Previously, all lithium batteries were stored at 20-30 ℃ d₁After a day, the storage temperature is adjusted to 45-60 ℃ for further storage (D)₁-d₁) Day, wherein d₁1-2 days;

preferably, D₁The day is 2-20 days.

6. The screening method according to any one of claims 2 to 5, wherein the step (II) specifically comprises:

equally dividing qualified electrolyte for primary screening into at least 10 parts, respectively injecting the 10 parts into a steel shell to prepare at least 10 identical lithium batteries, randomly performing random sampling inspection, storing the sampled lithium batteries at a specific temperature for 2-5 days, and recording open-circuit voltage of the tested lithium batteries as OCV₃Continue to store D₂In days, the open circuit voltage of the lithium battery was again measured and recorded as OCV₄Calculating K of lithium battery₂Value, K₂When the concentration of the electrolyte is less than or equal to 0.08mv/h, the electrolyte passing through the primary screen passes through the final screen, and the method is suitable for steel shells, K₂The calculation formula of (a) is as follows:

K₂＝(OCV₃-OCV₄)/D₂/24。

7. the screening method of claim 6, wherein the OCV is tested₃Storing the selected lithium battery at 20-30 ℃ for 2-5 days;

preferably, OCV is tested₃Storing the selected lithium battery at 45-60 ℃ for 2-5 days;

preferably, OCV is tested₃The selected lithium battery is stored for 1-2 days at 20-30 ℃ and then stored for 1-4 days at 45-60 ℃.

8. The screening method according to claim 6 or 7, wherein OCV is tested₄Previously, selected lithium batteries were stored at 20-60 ℃ D₂Day, D₂The day is 10-365 days.

9. The screening method according to any one of claims 6 to 8, wherein OCV is tested₄Previously, the selected lithium battery was stored at 20 ± 5 ℃ for 365 days;

preferably, OCV is tested₄Previously, selected lithium batteries were stored at 25 ± 5 ℃ for 183 days;

preferably, OCV is tested₄Previously, the selected lithium batteries were stored at 25 ± 5 ℃ for 28 days;

preferably, OCV is tested₄Previously, the selected lithium battery is stored for 90 days at the temperature of 45 +/-5 ℃;

preferably, OCV is tested₄Previously, selected lithium batteries were stored at 60 ± 5 ℃ for 30 days.

10. An electrolyte suitable for steel shells, which is determined by screening according to the screening method of any one of claims 1 to 9;

the electrolyte to be screened comprises any one of LiFeSi, LiTFSi, SN or ADN;

electrolytes identified as suitable for use in steel shells screened using the screening method of any one of claims 1 to 9 include SN and ADN.

Technical Field

The invention belongs to the technical field of electrolyte screening, and relates to a screening method of electrolyte suitable for a steel shell and the screened and determined electrolyte.

Background

The lithium ion battery plays a significant role in promoting the intelligent, portable and diversified progress of social development, and the quality of life of human beings is greatly improved. The electrolyte is one of four key materials (positive electrode, negative electrode, diaphragm and electrolyte) of the lithium ion battery, is called as 'blood' of the lithium ion battery, plays a role in conducting electrons between the positive electrode and the negative electrode in the battery, and is a guarantee for the lithium ion battery to obtain the advantages of high voltage, high specific energy and the like. The electrolyte generally comprises a high-purity organic solvent, and an electrolyte lithium salt (lithium hexafluorophosphate, LiPF)₆) And necessary additives and other raw materials are prepared according to a certain proportion under certain conditions.

The electrolyte is a very complex system not only because it contains several solvents, several salts, several additives, but also more complicated are the interactions between them and the interactions between potential by-products, which are so complex and variable that it is difficult to obtain specific chemical compositions by using the existing chemical characterization methods, and the complexity greatly restricts the rapid development of the lithium ion battery electrolyte. The oxidative decomposition of the common lithium ion battery electrolyte at high voltage limits the development of high voltage potassium ion batteries, and in order to solve the problem, a novel high voltage resistant electrolyte needs to be designed and synthesized or a proper electrolyte additive needs to be found. However, from the economic point of view, the development of suitable electrolyte additives to stabilize the electrode/electrolyte interface is much more favored by researchers. Common electrolyte additives include boron-containing additives, organic phosphorus additives, carbonate additives, sulfur-containing additives, ionic liquid additives, and other types of additives.

In the application process, the capacity of a steel shell adopted by a lithium ion battery is greatly limited due to the limitation of the structure size, the high-rate and long-cycle battery is produced in order to improve the applicability of the product, and in order to improve the high-rate and long-cycle of the battery, many manufacturers adopt a universal method to reduce the surface density and improve the rate, adopt artificial graphite to improve the cyclicity, and add an ionic liquid additive TFSi/FSi into the electrolyte.

CN106920910A discloses a lithium battery, which comprises a cellulose non-woven fabric diaphragm and an electrolyte, wherein the electrolyte contains an ionic liquid solvent. The cellulose non-woven fabric battery diaphragm is used as a battery diaphragm and is selected from one or more of polypropylene fiber, polyacrylonitrile fiber, polyvinyl formal fiber, poly (ethylene glycol terephthalate), polyethylene glycol terephthalate, polyamide fiber and poly (p-phenylene terephthalamide). The ionic liquid solvent is preferably aliphatic quaternary ammonium salt, quaternary phosphonium salt, pyrrole salt, pyrrolidone salt, imidazole salt and piperidine salt, and the general formula is C⁺[A]^-Said C is⁺The cation has the following structural formula: wherein R1, R2, R3 and R4 are any one of C1-C3 alkyl, allyl and ether, and [ A ] in the general formula]^-The anion being CF₃SO₃ ^-，TFSi^-、FSi^-、BOB^-Or ODFB^-Any one of them.

CN101087035B discloses an electrolyte for a secondary lithium battery, which contains lithium salt, ionic liquid and an organic solvent, wherein the ionic liquid comprises two ionic liquids, the first ionic liquid is piperidine ionic liquid, the second ionic liquid comprises pyrazole ionic liquid and imidazole ionic liquid, and the weight ratio of the pyrazole ionic liquid to the imidazole ionic liquid is 1: 3 to 3: 1.

CN112086619A discloses an all-solid-state lithium battery positive plate, which includes a positive current collector and a functional layer coated on the positive current collector, wherein the raw materials of the functional layer include a lithium-containing active material, a conductive agent, a solid electrolyte and a polyion liquid. The solid electrolyte is a halide-based solid electrolyte, and the halide-based solid electrolyte is Li_aMX_bY_cWherein M is selected from B, Al, Ga, In, Ta, Si, Ge, Sn, Pb, Sb, Bi, Sc, Y, Ti, Zr, V, Cr, Cu, Zn, Mg, Ca, X is selected from F^-、Cl^-、Br^-、I^-Y is selected from OH^-、BF₄ ^-、PF₆ ^-、BOB^-、TFSi^-、FSi^-Wherein a is more than or equal to 1 and less than or equal to 4, b is not equal to 0, c is more than or equal to 0 and less than 6, and b + c is more than 0 and less than or equal to 6.

However, some components in the electrolyte react with Ni in the steel shell, which causes a sudden increase in voltage drop of the lithium battery when the lithium battery is manufactured, and thus, the electrolyte suitable for the steel shell needs to be judged and screened.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a screening method of electrolyte suitable for a steel shell and the electrolyte determined by screening.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a screening method for an electrolyte suitable for a steel shell, the screening method comprising: and injecting the electrolyte to be screened into the steel shell to prepare the lithium battery, testing the K value of the lithium battery, and when the K is less than or equal to 0.08mv/h, showing that the corresponding electrolyte passes screening and is suitable for the steel shell.

Some components in the electrolyte react with Ni in the steel shell, and the voltage drop of the lithium battery is increased rapidly when the lithium battery is manufactured, so that the electrolyte suitable for the steel shell needs to be judged and screened. According to the invention, the K values of lithium batteries made of different types of electrolytes are tested, and whether the electrolyte to be screened is suitable for the steel shell is judged by utilizing the K values, so that the quantifiable K value is used as an index for judging whether the electrolyte is suitable for the steel shell. It should be noted that the K value referred to in the present invention refers to the voltage drop of the battery in unit time, usually expressed in mV/h, which is an index for measuring the self-discharge rate of the lithium battery, and the applicant found that 0.08mV/h is the voltage drop limit of the reaction of the electrolyte and the steel shell, and when the K value is greater than 0.08mV/h, the voltage drop exceeds the conventional voltage drop loss generated by the lithium battery, which indicates that some components in the electrolyte and the steel shell have reacted, and thus a higher voltage drop is caused, further indicating that the electrolyte containing the components is not suitable for the steel shell.

As a preferred technical solution of the present invention, the screening method specifically comprises:

(I) preparing one part of each electrolyte to be screened, injecting the electrolyte into a steel shell for primary screening, and testing K of all lithium batteries₁Value, K₁When the concentration is less than or equal to 0.08mv/h, the corresponding electrolyte passes through the primary screen;

(II) equally dividing the electrolyte passing through the primary screening into at least 10 parts, respectively injecting the 10 parts into the steel shell to prepare at least 10 groups of completely same lithium batteries, randomly performing random inspection on the lithium batteries, and testing K of the lithium batteries in the random inspection₂Value, K₂When the concentration is less than or equal to 0.08mv/h, the electrolyte passing through the primary screen passes through the final screen, and the method is suitable for steel shells.

The screening method provided by the invention comprises two screening processes, namely primary screening and final screening, wherein the primary screening aims at quickly detecting and quickly screening the electrolyte which reaches the standard under conventional storage conditions and use conditions in a short time. The screening conditions of the final screening are more strict than those of the primary screening, on one hand, whether the electrolyte qualified by the primary screening can still keep lower voltage drop at high temperature needs to be screened and determined, and on the other hand, whether the electrolyte qualified by the primary screening can keep lower voltage drop after being stored for a long time needs to be screened and determined; therefore, more extreme use conditions and storage conditions are simulated, and if the K value can still be kept to be less than or equal to 0.08mv/h after the final screening, the electrolyte is suitable for the steel shell under both conventional conditions and extreme conditions.

As a preferred technical scheme of the invention, the step (I) specifically comprises the following steps:

preparing one part of each electrolyte to be screened, injecting the electrolyte into a steel shell to prepare a lithium battery, storing the lithium battery for 1-7 days under a specific temperature condition, testing open-circuit voltages of all the lithium batteries, and recording the open-circuit voltages as OCV₁(ii) a Under the condition of specific temperature, D is continuously stored₁In the day, the open-circuit voltage of all lithium batteries is tested again and recorded as OCV₂(ii) a Calculating K of lithium battery₁Value, K₁When the concentration of the electrolyte is less than or equal to 0.08mv/h, marking the corresponding electrolyte as qualified by primary screening, and K₁When the concentration is more than 0.08mv/h, marking the corresponding electrolyte as unqualified primary screen; k₁The calculation formula of (a) is as follows:

K₁＝(OCV₁-OCV₂)/D₁/24。

as a preferred technical scheme of the invention, the OCV is tested₁All lithium batteries have been stored at 20 to 30 ℃ for 1 to 7 days, for example, at 20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃, 25 ℃, 26 ℃, 27 ℃, 28 ℃, 29 ℃ or 30 ℃, for example, for 1, 2, 3, 4, 5, 6 or 7 days, but are not limited to the recited values, and other values not recited in the range of values are also applicable.

Preferably, OCV is tested₁All lithium batteries have been stored at 45 to 60 ℃ for 1 to 7 days, and may be stored at 45 ℃, 46 ℃, 47 ℃, 48 ℃, 49 ℃, 50 ℃, 51 ℃, 52 ℃, 53 ℃, 54 ℃, 55 ℃, 56 ℃, 57 ℃, 58 ℃, 59 ℃ or 60 ℃ for 1 day, 2 days, 3 days, 4 days, 5 days, 6 days or 7 days, but are not limited to the values listed, and other values not listed within the range of values are also applicable.

Preferably, OCV is tested₁Before, all lithium batteries are stored at 20 to 30 ℃ for 1 to 2 days, the storage temperature is adjusted to 45 to 60 ℃ and then stored for 1 to 6 days, for example, after the lithium batteries are stored at 20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃, 25 ℃, 26 ℃, 27 ℃, 28 ℃, 29 ℃ or 30 ℃ for 1 to 2 days, the storage temperature is adjusted to 45 ℃, 46 ℃, 47 ℃, 48 ℃, 49 ℃, 50 ℃, 51 ℃, 52 ℃, 53 ℃, 54 ℃, 55 ℃, 56 ℃, 57 ℃, 58 ℃, 59 ℃ or 60 ℃ and then stored for 1 day, 2 days, 3 days, 4 days, 5 days or 6 days, but not limited to the values mentioned above, and other values not mentioned in the range of the values are also applicable.

As a preferred technical scheme of the invention, the OCV is tested₂Previously, all lithium batteries were stored at 20-30 ℃ D₁For example, the temperature may be 20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃, 25 ℃, 26 ℃, 27 ℃, 28 ℃, 29 ℃ or 30 ℃, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, OCV is tested₂Before, allThe lithium battery of (1) is stored at 45 to 60 ℃ for D1 days, and may be, for example, 45 ℃, 46 ℃, 47 ℃, 48 ℃, 49 ℃, 50 ℃, 51 ℃, 52 ℃, 53 ℃, 54 ℃, 55 ℃, 56 ℃, 57 ℃, 58 ℃, 59 ℃ or 60 ℃, but is not limited to the values listed, and other values not listed in the range of the values are also applicable.

Preferably, OCV is tested₂Previously, all lithium batteries were stored at 20-30 ℃ d₁After a day, the storage temperature is adjusted to 45-60 ℃ for further storage (D)₁-d₁) Day, wherein d₁For example, the storage temperature may be adjusted to 45 ℃, 46 ℃, 47 ℃, 48 ℃, 49 ℃, 50 ℃, 51 ℃, 52 ℃, 53 ℃, 54 ℃, 55 ℃, 56 ℃, 57 ℃, 58 ℃, 59 ℃, or 60 ℃ after storage at 20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃, 25 ℃, 26 ℃, 27 ℃, 28 ℃, 29 ℃, or 30 ℃ for 1 or 2 days, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, D₁For example, the number of days is 2 to 20, and the number of days may be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20, but the number is not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable.

As a preferred technical solution of the present invention, the step (ii) specifically comprises:

equally dividing qualified electrolyte for primary screening into at least 10 parts, respectively injecting the 10 parts into a steel shell to prepare at least 10 identical lithium batteries, randomly performing random sampling inspection, storing the sampled lithium batteries at a specific temperature for 2-5 days, and recording open-circuit voltage of the tested lithium batteries as OCV₃Continue to store D₂In days, the open circuit voltage of the lithium battery was again measured and recorded as OCV₄Calculating K of lithium battery₂Value, K₂When the concentration of the electrolyte is less than or equal to 0.08mv/h, the electrolyte passing through the primary screen passes through the final screen, and the method is suitable for steel shells, K₂The calculation formula of (a) is as follows:

K₂＝(OCV₃-OCV₄)/D₂/24。

is one kind of the inventionThe selected technical scheme is that the OCV is tested₃The selected lithium battery is stored at 20-30 ℃ for 2-5 days, such as at 20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃, 25 ℃, 26 ℃, 27 ℃, 28 ℃, 29 ℃ or 30 ℃ for 2 days, 3 days, 4 days or 5 days, but is not limited to the recited values, and other non-recited values within the range of values are also applicable.

Preferably, OCV is tested₃Previously, the selected lithium battery is stored at 45-60 ℃ for 2-5 days, for example, at 45 ℃, 46 ℃, 47 ℃, 48 ℃, 49 ℃, 50 ℃, 51 ℃, 52 ℃, 53 ℃, 54 ℃, 55 ℃, 56 ℃, 57 ℃, 58 ℃, 59 ℃ or 60 ℃ for 2 days, 3 days, 4 days or 5 days, but not limited to the recited values, and other non-recited values within the range of values are also applicable.

Preferably, OCV is tested₃Previously, the selected lithium battery is stored at 20 to 30 ℃ for 1 to 2 days, and then at 45 to 60 ℃ for 1 to 4 days, for example, at 20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃, 25 ℃, 26 ℃, 27 ℃, 28 ℃, 29 ℃ or 30 ℃ for 1 day or 2 days, and at any time, at 45 ℃, 46 ℃, 47 ℃, 48 ℃, 49 ℃, 50 ℃, 51 ℃, 52 ℃, 53 ℃, 54 ℃, 55 ℃, 56 ℃, 57 ℃, 58 ℃, 59 ℃ or 60 ℃ for 1 day, 2 days, 3 days or 4 days, but not limited to the enumerated values, and other non-enumerated values within the range of values are also applicable.

As a preferred technical scheme of the invention, the OCV is tested₄Previously, selected lithium batteries were stored at 20-60 ℃ D₂Day, D₂For example, the storage may be carried out for 10 to 365 days, for 10 days, 14 days, 28 days, 30 days, 45 days, 60 days, 80 days, 100 days, 120 days, 140 days, 160 days, 180 days, 200 days, 220 days, 240 days, 260 days, 300 days, 320 days, 340 days, 360 days or 365 days at 20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃ or 60 ℃,

as a preferred technical scheme of the invention, the OCV is tested₄Previously, selected lithium cells were stored at 20. + -. 5 ℃ for 365 days.

Preferably, OCV is tested₄Previously, selected lithiumThe cells were stored at 25. + -. 5 ℃ for 183 days.

Preferably, OCV is tested₄Previously, selected lithium batteries were stored at 25. + -. 5 ℃ for 28 days.

Preferably, OCV is tested₄Previously, selected lithium batteries were stored at 45. + -. 5 ℃ for 90 days.

Preferably, OCV is tested₄Previously, selected lithium batteries were stored at 60 ± 5 ℃ for 30 days.

In a second aspect, the invention provides an electrolyte suitable for steel shells, and the electrolyte is screened and determined by the screening method of the first aspect.

The electrolyte to be screened comprises any one of LiFeSi, LiTFSi, SN or ADN.

The electrolyte which is screened and determined to be suitable for the steel shell by adopting the screening method of the first aspect comprises SN and ADN.

Compared with the prior art, the invention has the beneficial effects that:

some components in the electrolyte react with Ni in the steel shell, and the voltage drop of the lithium battery is increased rapidly when the lithium battery is manufactured, so that the electrolyte suitable for the steel shell needs to be judged and screened. According to the invention, the K values of lithium batteries made of different types of electrolytes are tested, and whether the electrolyte to be screened is suitable for the steel shell is judged by utilizing the K values, so that the quantifiable K value is used as an index for judging whether the electrolyte is suitable for the steel shell. It should be noted that the K value referred to in the present invention refers to the voltage drop of the battery in unit time, usually expressed in mV/h, which is an index for measuring the self-discharge rate of the lithium battery, and the applicant found that 0.08mV/h is the voltage drop limit of the reaction of the electrolyte and the steel shell, and when the K value is greater than 0.08mV/h, the voltage drop exceeds the conventional voltage drop loss generated by the lithium battery, which indicates that some components in the electrolyte and the steel shell have reacted, and thus a higher voltage drop is caused, further indicating that the electrolyte containing the components is not suitable for the steel shell.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments.

In one embodiment, the invention provides a screening method of an electrolyte suitable for a steel shell, the screening method comprising:

(1) preparing one part of each electrolyte to be screened, injecting the electrolyte into a steel shell to prepare a lithium battery, storing the lithium battery for 1-7 days under a specific temperature condition, testing open-circuit voltages of all the lithium batteries, and recording the open-circuit voltages as OCV₁(ii) a Under the condition of specific temperature, D is continuously stored₁In the day, the open-circuit voltage of all lithium batteries is tested again and recorded as OCV₂(ii) a Calculating K of lithium battery₁Value, K₁When the concentration of the electrolyte is less than or equal to 0.08mv/h, marking the corresponding electrolyte as qualified by primary screening, and K₁When the concentration is more than 0.08mv/h, marking the corresponding electrolyte as unqualified primary screen; k₁The calculation formula of (a) is as follows:

K₁＝(OCV₁-OCV₂)/D₁/24。

(2) equally dividing qualified electrolyte for primary screening into at least 10 parts, respectively injecting the 10 parts into a steel shell to prepare at least 10 identical lithium batteries, randomly performing random sampling inspection, storing the sampled lithium batteries at a specific temperature for 2-5 days, and recording open-circuit voltage of the tested lithium batteries as OCV₃Continue to store D₂In days, the open circuit voltage of the lithium battery was again measured and recorded as OCV₄Calculating K of lithium battery₂Value, K₂When the concentration of the electrolyte is less than or equal to 0.08mv/h, the electrolyte passing through the primary screen passes through the final screen, and the method is suitable for steel shells, K₂The calculation formula of (a) is as follows:

K₂＝(OCV₃-OCV₄)/D₂/24。

example 1

This example provides a screening method of electrolyte suitable for steel shell, which takes 4 electrolyte samples to be screened, and records them as A₁、A₂、A₃And A₄The 4 electrolyte samples to be screened are the same in components and content except for different additives, and A₁The additive in (1) is lithium bis (fluorosulfonyl) imide (LiFSSi); a. the₂The additive in (1) is lithium bistrifluoromethylsulfonyl imide (LiTFS)i is abbreviated as TFSi); a. the₃The additive in (1) is Succinonitrile (SN), A₄The additive in (1) is Adiponitrile (ADN).

And screening the four electrolyte samples to be screened, wherein the screening method comprises the following steps:

(1) preparing one part of each electrolyte to be screened, injecting the electrolyte into a steel shell to prepare a lithium battery, storing the lithium battery at 20 ℃ for 5 days, testing the open-circuit voltage of all the lithium batteries, and recording the open-circuit voltage as OCV₁(ii) a After further storage at 20 ℃ for 5 days, the open-circuit voltages of all lithium batteries were again measured and recorded as OCV₂(ii) a Calculating K of lithium battery₁Value, K₁When the concentration of the electrolyte is less than or equal to 0.08mv/h, marking the corresponding electrolyte as qualified by primary screening, and K₁When the concentration is more than 0.08mv/h, marking the corresponding electrolyte as unqualified primary screen; k₁The calculation formula of (a) is as follows:

K₁＝(OCV₁-OCV₂)/5/24；

calculated, A₁K of₁Is 0.23, A₂K of₁Is 0.18, A₃K of₁Is 0.03, A₄K of₁The value was 0.02, from which A was determined₁And A₂Not suitable for steel shells, pair A₃And A₄Carrying out final screening;

(2) qualified by primary screening A₃And A₄Respectively equally dividing into 15 parts, respectively injecting into a steel shell to obtain 15 identical lithium batteries, randomly sampling, storing at 20 deg.C for 5 days, and recording open circuit voltage as OCV₃And stored at 20 ℃ for 28 days, and the open-circuit voltage of the lithium battery was again measured and recorded as OCV₄Calculating K of lithium battery₂Value, K₂When the concentration of the electrolyte is less than or equal to 0.08mv/h, the electrolyte passing through the primary screen passes through the final screen, and the method is suitable for steel shells, K₂The calculation formula of (a) is as follows:

K₂＝(OCV₃-OCV₄)/28/24；

calculated, A₃K of₂Is 0.028, A₄K of₂Was 0.017.

Through the above screening steps, it was determined that the electrolyte containing SN and ADN was suitable for steel shells, whereas LiFSi and LiTFSi were not.

Example 2

This example provides a screening method of electrolyte suitable for steel shell, which takes 4 electrolyte samples to be screened, and records them as A₁、A₂、A₃And A₄The 4 electrolyte samples to be screened are the same in components and content except for different additives, and A₁The additive in (1) is lithium bis (fluorosulfonyl) imide (LiFSI); a. the₂The additive in (1) is lithium bistrifluoromethylsulfonimide (LiTFSi); a. the₃The additive in (1) is Succinonitrile (SN), A₄The additive in (1) is Adiponitrile (ADN).

And screening the four electrolyte samples to be screened, wherein the screening method comprises the following steps:

(1) preparing one part of each electrolyte to be screened, injecting the electrolyte into a steel shell to prepare a lithium battery, storing the lithium battery for 3 days at 25 ℃, testing the open-circuit voltage of all the lithium batteries, and recording the open-circuit voltage as OCV₁(ii) a After further storage at 25 ℃ for 3 days, the open-circuit voltages of all lithium batteries were again measured and recorded as OCV₂(ii) a Calculating K of lithium battery₁Value, K₁When the concentration of the electrolyte is less than or equal to 0.08mv/h, marking the corresponding electrolyte as qualified by primary screening, and K₁When the concentration is more than 0.08mv/h, marking the corresponding electrolyte as unqualified primary screen; k₁The calculation formula of (a) is as follows:

K₁＝(OCV₁-OCV₂)/3/24；

calculated, A₁K of₁Is 0.28, A₂K of₁Is 0.17, A₃K of₁Is 0.04, A₄K of₁The value was 0.03, whereby A was determined₁And A₂Not suitable for steel shells, pair A₃And A₄Carrying out final screening;

(2) qualified by primary screening A₃And A₄Respectively equally dividing into 15 parts, respectively injecting into a steel shell to obtain 15 identical lithium batteries, randomly sampling, storing at 25 deg.C for 3 days, and recording open circuit voltage as OCV₃And storing at 25 ℃ for 183 days, and testing the open-circuit voltage of the lithium battery again to recordOCV₄Calculating K of lithium battery₂Value, K₂When the concentration of the electrolyte is less than or equal to 0.08mv/h, the electrolyte passing through the primary screen passes through the final screen, and the method is applicable to steel shells, wherein K is₂The calculation formula of (a) is as follows:

K₂＝(OCV₃-OCV₄)/183/24；

calculated, A₃K of₂Is 0.015, A₄K of₂Is 0.01.

Through the above screening steps, it was determined that the electrolyte containing SN and ADN was suitable for steel shells, whereas LiFSi and LiTFSi were not.

Example 3

This example provides a screening method of electrolyte suitable for steel shell, which takes 4 electrolyte samples to be screened, and records them as A₁、A₂、A₃And A₄The 4 electrolyte samples to be screened are the same in components and content except for different additives, and A₁The additive in (1) is lithium bis (fluorosulfonyl) imide (LiFSI); a. the₂The additive in (1) is lithium bistrifluoromethylsulfonimide (LiTFSi); a. the₃The additive in (1) is Succinonitrile (SN), A₄The additive in (1) is Adiponitrile (ADN).

And screening the four electrolyte samples to be screened, wherein the screening method comprises the following steps:

(1) preparing one part of each electrolyte to be screened, injecting the electrolyte into a steel shell to prepare a lithium battery, storing the lithium battery at 30 ℃ for 2 days, testing the open-circuit voltage of all the lithium batteries, and recording the open-circuit voltage as OCV₁(ii) a After further storage at 30 ℃ for 2 days, the open-circuit voltages of all lithium batteries were again measured and recorded as OCV₂(ii) a Calculating K of lithium battery₁Value, K₁When the concentration of the electrolyte is less than or equal to 0.08mv/h, marking the corresponding electrolyte as qualified by primary screening, and K₁When the value is more than 0.08mv/h, marking the corresponding electrolyte as unqualified primary screening; said K₁The calculation of the values is as follows:

K₁＝(OCV₁-OCV₂)/2/24；

calculated, A₁K of₁Is 0.32, A₂K of₁Is 0.21, A₃K of₁Is 0.042, A₄K of₁Value 0.035, whereby A was determined₁And A₂Not suitable for steel shells, pair A₃And A₄Carrying out final screening;

(2) qualified by primary screening A₃And A₄Respectively equally dividing into 15 parts, respectively injecting into a steel shell to obtain 15 identical lithium batteries, randomly sampling, storing at 30 deg.C for 2 days, and recording open circuit voltage as OCV₃And stored at 45 ℃ for 90 days, and the open-circuit voltage of the lithium battery is tested again and recorded as OCV₄Calculating K of lithium battery₂Value, K₂When the concentration of the electrolyte is less than or equal to 0.08mv/h, the electrolyte passing through the primary screen passes through the final screen, and the method is suitable for steel shells, K₂The calculation formula of (a) is as follows:

K₂＝(OCV₃-OCV₄)/90/24；

calculated, A₃K of₂Is 0.075, A₄K of₂Was 0.068.

Through the above screening steps, it was determined that the electrolyte containing SN and ADN was suitable for steel shells, whereas LiFSi and LiTFSi were not.

Example 4

This example provides a screening method of electrolyte suitable for steel shell, which takes 4 electrolyte samples to be screened, and records them as A₁、A₂、A₃And A₄The 4 electrolyte samples to be screened are the same in components and content except for different additives, and A₁The additive in (1) is lithium bis (fluorosulfonyl) imide (LiFSI); a. the₂The additive in (1) is lithium bistrifluoromethylsulfonimide (LiTFSi); a. the₃The additive in (1) is Succinonitrile (SN), A₄The additive in (1) is Adiponitrile (ADN).

And screening the four electrolyte samples to be screened, wherein the screening method comprises the following steps:

(1) preparing one part of each electrolyte to be screened, injecting the electrolyte into a steel shell to prepare a lithium battery, storing the lithium battery at 45 ℃ for 5 days, testing the open-circuit voltage of all the lithium batteries, and recording the open-circuit voltage as OCV₁(ii) a After further storage at 45 ℃ for 5 days, the open-circuit voltages of all lithium batteries were again measured and recorded as OCV₂(ii) a Calculating K of lithium battery₁Value, K₁When the concentration of the electrolyte is less than or equal to 0.08mv/h, marking the corresponding electrolyte as qualified by primary screening, and K₁When the concentration is more than 0.08mv/h, marking the corresponding electrolyte as unqualified primary screen; said K₁The calculation of the values is as follows:

K＝(OCV₁-OCV₂)/5/24；

calculated, A₁K of₁Is 0.45, A₂K of₁Is 0.38, A₃K of₁Is 0.079, A₄K of₁Value 0.078, from which A is determined₁And A₂Not suitable for steel shells, pair A₃And A₄Carrying out final screening;

(2) qualified by primary screening A₃And A₄Respectively equally dividing into 20 parts, respectively injecting into a steel shell to obtain 20 identical lithium batteries, randomly sampling, storing at 45 deg.C for 5 days, and recording open circuit voltage as OCV₃And storing at 60 ℃ for 30 days, and testing the open-circuit voltage of the lithium battery again to record the open-circuit voltage as OCV₄Calculating K of lithium battery₂Value, K₂When the concentration of the electrolyte is less than or equal to 0.08mv/h, the electrolyte passing through the primary screen passes through the final screen, and the method is suitable for steel shells, K₂The calculation formula of (a) is as follows:

K₂＝(OCV₃-OCV₄)/30/24；

calculated, A₃K of₂Is 0.078, A₄K of₂Is 0.076.

Through the above screening steps, it was determined that the electrolyte containing SN and ADN was suitable for steel shells, whereas LiFSi and LiTFSi were not.

Example 5

This example provides a screening method of electrolyte suitable for steel shell, which takes 4 electrolyte samples to be screened, and records them as A₁、A₂、A₃And A₄The 4 electrolyte samples to be screened are the same in components and content except for different additives, and A₁In (1)The additive is lithium bis (fluorosulfonyl) imide (LiFSI); a. the₂The additive in (1) is lithium bistrifluoromethylsulfonimide (LiTFSi); a. the₃The additive in (1) is Succinonitrile (SN), A₄The additive in (1) is Adiponitrile (ADN).

And screening the four electrolyte samples to be screened, wherein the screening method comprises the following steps:

(1) preparing one part of each electrolyte to be screened, injecting the electrolyte into a steel shell to prepare a lithium battery, storing the lithium battery at 50 ℃ for 3 days, testing the open-circuit voltage of all the lithium batteries, and recording the open-circuit voltage as OCV₁(ii) a After further storage at 50 ℃ for 3 days, the open-circuit voltages of all lithium batteries were again measured and recorded as OCV₂(ii) a Calculating K of lithium battery₁Value, K₁When the concentration is less than or equal to 0.08mv/h, marking the corresponding electrolyte as qualified by primary screening; k₁When the concentration is more than 0.08mv/h, marking the corresponding electrolyte as unqualified primary screen; k₁The calculation formula of (a) is as follows:

K₁＝(OCV₁-OCV₂)/3/24；

calculated, A₁K of₁Is 0.48, A₂K of₁Is 0.42, A₃K of₁Is 0.079, A₄K of₁Value 0.078, from which A is determined₁And A₂Not suitable for steel shells, pair A₃And A₄Carrying out final screening;

(2) qualified by primary screening A₃And A₄Respectively equally dividing into 20 parts, respectively injecting into a steel shell to obtain 20 identical lithium batteries, randomly sampling, storing at 50 deg.C for 3 days, and recording open circuit voltage as OCV₃And storing at 20 ℃ for 365 days, and testing the open-circuit voltage of the lithium battery again to record the open-circuit voltage as OCV₄Calculating K of lithium battery₂Value, K₂When the concentration of the electrolyte is less than or equal to 0.08mv/h, the electrolyte passing through the primary screen passes through the final screen, and the method is suitable for steel shells, K₂The calculation formula of (a) is as follows:

K₂＝(OCV₃-OCV₄)/365/24；

calculated, A₃K of₂Is 0.013, A₄K of₂And was 0.012.

Through the above screening steps, it was determined that the electrolyte containing SN and ADN was suitable for steel shells, whereas LiFSi and LiTFSi were not.

Example 6

This example provides a screening method of electrolyte suitable for steel shell, which takes 4 electrolyte samples to be screened, and records them as A₁、A₂、A₃And A₄The 4 electrolyte samples to be screened are the same in components and content except for different additives, and A₁The additive in (1) is lithium bis (fluorosulfonyl) imide (LiFSI); a. the₂The additive in (1) is lithium bistrifluoromethylsulfonimide (LiTFSi); a. the₃The additive in (1) is Succinonitrile (SN), A₄The additive in (1) is Adiponitrile (ADN).

And screening the four electrolyte samples to be screened, wherein the screening method comprises the following steps:

(1) preparing one part of each electrolyte to be screened, injecting the electrolyte into a steel shell to prepare a lithium battery, storing the lithium battery at 60 ℃ for 2 days, testing the open-circuit voltage of all the lithium batteries, and recording the open-circuit voltage as OCV₁(ii) a After further storage at 60 ℃ for 2 days, the open-circuit voltages of all lithium batteries were again measured and recorded as OCV₂(ii) a Calculating K of lithium battery₁Value, K₁When the concentration of the electrolyte is less than or equal to 0.08mv/h, marking the corresponding electrolyte as qualified by primary screening, and K₁When the concentration is more than 0.08mv/h, marking the corresponding electrolyte as unqualified primary screen; k₁The calculation formula of (a) is as follows:

K₁＝(OCV₁-OCV₂)/2/24；

calculated, A₁K of₁Is 0.51, A₂K of₁Is 0.48, A₃K of₁Is 0.08, A₄K of₁Value 0.079, from which A is determined₁And A₂Not suitable for steel shells, pair A₃And A₄Carrying out final screening;

(2) qualified by primary screening A₃And A₄Respectively equally dividing into 20 parts, respectively injecting into a steel shell to obtain 20 identical lithium batteries, randomly sampling, storing at 60 deg.C for 2 days, and testingOpen circuit voltage is noted OCV₃And stored at 45 ℃ for 183 days, and the open-circuit voltage of the lithium battery was again measured and recorded as OCV₄Calculating K of lithium battery₂Value, K₂When the concentration of the electrolyte is less than or equal to 0.08mv/h, the electrolyte passing through the primary screen passes through the final screen, and the method is suitable for steel shells, K₂The calculation formula of (a) is as follows:

K₂＝(OCV₃-OCV₄)/183/24；

calculated, A₃K of₂Is 0.078, A₄K of₂Is 0.076.

Through the above screening steps, it was determined that the electrolyte containing SN and ADN was suitable for steel shells, whereas LiFSi and LiTFSi were not.

Example 7

This example provides a screening method of electrolyte suitable for steel shell, which takes 4 electrolyte samples to be screened, and records them as A₁、A₂、A₃And A₄The 4 electrolyte samples to be screened are the same in components and content except for different additives, and A₁The additive in (1) is lithium bis (fluorosulfonyl) imide (LiFSI); a. the₂The additive in (1) is lithium bistrifluoromethylsulfonimide (LiTFSi); a. the₃The additive in (1) is Succinonitrile (SN), A₄The additive in (1) is Adiponitrile (ADN).

And screening the four electrolyte samples to be screened, wherein the screening method comprises the following steps:

(1) preparing one part of each electrolyte to be screened, injecting the electrolyte into a steel shell to prepare a lithium battery, storing the lithium battery at 20 ℃ for 2 days, adjusting the storage temperature to 45 ℃, continuously storing the lithium battery for 1 day, testing the open-circuit voltage of all the lithium batteries, and recording the open-circuit voltage as OCV₁(ii) a After further storage at 45 ℃ for 3 days, the open-circuit voltages of all lithium batteries were again measured and recorded as OCV₂(ii) a Calculating K of lithium battery₁Value, K₁When the concentration of the electrolyte is less than or equal to 0.08mv/h, marking the corresponding electrolyte as qualified by primary screening, and K₁When the concentration is more than 0.08mv/h, marking the corresponding electrolyte as unqualified primary screen; k₁The calculation formula of (a) is as follows:

K₁＝(OCV₁-OCV₂)/3/24；

calculated, A₁K of₁Is 0.47, A₂K of₁Is 0.42, A₃K of₁Is 0.067, A₄K of₁The value was 0.065, whereby A was determined₁And A₂Not suitable for steel shells, pair A₃And A₄Carrying out final screening;

(2) qualified by primary screening A₃And A₄Respectively and equally dividing into 10 parts, respectively injecting into a steel shell to obtain 10 identical lithium batteries, randomly sampling, storing at 20 deg.C for 2 days, adjusting storage temperature to 45 deg.C, storing for 1 day, and recording open circuit voltage as OCV₃And stored at 45 ℃ for 180 days, and the open-circuit voltage of the lithium battery is tested again and recorded as OCV₄Calculating K of lithium battery₂Value, K₂When the concentration of the electrolyte is less than or equal to 0.08mv/h, the electrolyte passing through the primary screen passes through the final screen, and the method is suitable for steel shells, K₂The calculation formula of (a) is as follows:

K₂＝(OCV₃-OCV₄)/180/24；

calculated, A₃K of₂Is 0.076, A₄K of₂Is 0.072.

Through the above screening steps, it was determined that the electrolyte containing SN and ADN was suitable for steel shells, whereas LiFSi and LiTFSi were not.

Example 8

This example provides a screening method of electrolyte suitable for steel shell, which takes 4 electrolyte samples to be screened, and records them as A₁、A₂、A₃And A₄The 4 electrolyte samples to be screened are the same in components and content except for different additives, and A₁The additive in (1) is lithium bis (fluorosulfonyl) imide (LiFSI); a. the₂The additive in (1) is lithium bistrifluoromethylsulfonimide (LiTFSi); a. the₃The additive in (1) is Succinonitrile (SN), A₄The additive in (1) is Adiponitrile (ADN).

And screening the four electrolyte samples to be screened, wherein the screening method comprises the following steps:

(1) preparing one part of each electrolyte to be screened, injecting the electrolyte into a steel shell to prepare a lithium battery, storing the lithium battery at 25 ℃ for 1 day, adjusting the storage temperature to 50 ℃, continuously storing the lithium battery for 2 days, testing the open-circuit voltage of all the lithium batteries, and recording the open-circuit voltage as OCV₁(ii) a After further storage at 50 ℃ for 3 days, the open-circuit voltages of all lithium batteries were again measured and recorded as OCV₂(ii) a Calculating K of lithium battery₁Value, K₁When the concentration of the electrolyte is less than or equal to 0.08mv/h, marking the corresponding electrolyte as qualified by primary screening, and K₁When the concentration is more than 0.08mv/h, marking the corresponding electrolyte as unqualified primary screen; k₁The calculation formula of (a) is as follows:

K₁＝(OCV₁-OCV₂)/3/24；

calculated, A₁K of₁Is 0.52, A₂K of₁Is 0.47, A₃K of₁Is 0.078, A₄K of₁Value 0.077, from which A was determined₁And A₂Not suitable for steel shells, pair A₃And A₄Carrying out final screening;

(2) qualified by primary screening A₃And A₄Respectively and equally dividing into 10 parts, respectively injecting into a steel shell to obtain 10 identical lithium batteries, randomly sampling, storing at 25 deg.C for 1 day, adjusting storage temperature to 50 deg.C, storing for 2 days, and recording open circuit voltage as OCV₃And stored at 50 ℃ for 30 days, and the open-circuit voltage of the lithium battery is tested again and recorded as OCV₄Calculating K of lithium battery₂Value, K₂When the concentration of the electrolyte is less than or equal to 0.08mv/h, the electrolyte passing through the primary screen passes through the final screen, and the method is suitable for steel shells, K₂The calculation formula of (a) is as follows:

K₂＝(OCV₃-OCV₄)/30/24；

calculated, A₃K of₂Is 0.079, A₄K of₂Was 0.077.

Through the above screening steps, it was determined that the electrolyte containing SN and ADN was suitable for steel shells, whereas LiFSi and LiTFSi were not.

Example 9

This example provides a screening method of electrolyte suitable for steel shell, which takes 4 electrolyte samples to be screened, and records them as A₁、A₂、A₃And A₄The 4 electrolyte samples to be screened are the same in components and content except for different additives, and A₁The additive in (1) is lithium bis (fluorosulfonyl) imide (LiFSI); a. the₂The additive in (1) is lithium bistrifluoromethylsulfonimide (LiTFSi); a. the₃The additive in (1) is Succinonitrile (SN), A₄The additive in (1) is Adiponitrile (ADN).

And screening the four electrolyte samples to be screened, wherein the screening method comprises the following steps:

(1) preparing one part of each electrolyte to be screened, injecting the electrolyte into a steel shell to prepare a lithium battery, storing the lithium battery at 30 ℃ for 1 day, adjusting the storage temperature to 60 ℃, continuously storing the lithium battery for 3 days, testing the open-circuit voltage of all the lithium batteries, and recording the open-circuit voltage as OCV₁(ii) a After further storage at 60 ℃ for 4 days, the open-circuit voltages of all lithium batteries were again measured and recorded as OCV₂(ii) a Calculating K of lithium battery₁Value, K₁When the concentration of the electrolyte is less than or equal to 0.08mv/h, marking the corresponding electrolyte as qualified by primary screening, and K₁When the concentration is more than 0.08mv/h, marking the corresponding electrolyte as unqualified primary screen; k₁The calculation formula of (a) is as follows:

K₁＝(OCV₁-OCV₂)/4/24；

calculated, A₁K of₁Is 0.58, A₂K of₁Is 0.52, A₃K of₁Is 0.079, A₄K of₁Value 0.077, from which A was determined₁And A₂Not suitable for steel shells, pair A₃And A₄Carrying out final screening;

(2) qualified by primary screening A₃And A₄Respectively equally dividing into 10 parts, respectively injecting into a steel shell to obtain 10 identical lithium batteries, randomly sampling, storing at 30 deg.C for 1 day, adjusting storage temperature to 60 deg.C, storing for 3 days, and recording open circuit voltage as OCV₃And storing at 60 ℃ for 365 days, and testing the open-circuit voltage of the lithium battery again to record the open-circuit voltage as OCV₄Counting of lithium batteriesK₂，K₂When the K value is less than or equal to 0.08mv/h, the electrolyte passing through the primary screen passes through the final screen, and the method is applicable to the steel shell, and the calculation formula of the K value is as follows:

K₂＝(OCV₃-OCV₄)/365/24；

calculated, A₃K of₂Is 0.075, A₄K of₂Is 0.072.

Through the above screening steps, it was determined that the electrolyte containing SN and ADN was suitable for steel shells, whereas LiFSi and LiTFSi were not.

The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.