CN113871706B

CN113871706B - Preparation method and application of gel electrolyte cell

Info

Publication number: CN113871706B
Application number: CN202111009885.8A
Authority: CN
Inventors: 闫鹏; 胡海波; 曾涛
Original assignee: Hunan Lifang New Energy Science and Technology Co Ltd
Current assignee: Hunan Lifang New Energy Science and Technology Co Ltd
Priority date: 2021-08-31
Filing date: 2021-08-31
Publication date: 2023-03-28
Anticipated expiration: 2041-08-31
Also published as: CN113871706A

Abstract

The invention provides a preparation method and application of a gel electrolyte battery cell, which comprises the following steps: s1, adding a liquid gel electrolyte with the temperature of less than or equal to 5 ℃ into a battery cell, and sealing; s2, placing the sealed battery cell in an environment with the temperature less than or equal to 5 ℃, and standing for more than or equal to 6 hours; s3, carrying out charging formation under the environment that the temperature is less than or equal to 10 ℃, wherein the formation pressure is 0.1-1.3 MPa, and the charging current is less than or equal to 0.2C; and S4, degassing and sealing after formation, standing for polymerization reaction, and converting the liquid gel electrolyte into a gel electrolyte to complete the preparation of the battery cell. Compared with the prior art, the method has the advantages that the rate of copolymerization is slowed down through low temperature, so that the pole piece and the diaphragm are fully soaked before liquid electrolyte is converted into gel, and the problems that the lithium ion transmission channel is blocked and the local lithium precipitation of the negative electrode is caused because the copolymer of the gel electrolyte cannot be fully dispersed into the battery cell before polymerization are solved.

Description

Preparation method and application of gel electrolyte cell

Technical Field

The invention relates to the field of lithium batteries, in particular to a preparation method and application of a gel electrolyte battery cell.

Background

Lithium ion batteries are currently broadly classified into liquid lithium ion batteries, gel electrolyte lithium batteries, and solid state batteries according to the type of electrolyte. The liquid lithium ion battery is widely used in daily life of people due to the advantages of high lithium ion migration rate, high voltage platform, high energy density, small self-discharge and the like. However, in recent years, due to the potential safety hazards of leakage and corrosion of the liquid electrolyte, safety accidents frequently occur under the influence of factors such as high temperature and high pressure, external force extrusion, overcharge and the like. Compared with a liquid lithium ion battery, the solid-state battery adopts the solid-state electrolyte to completely replace the liquid electrolyte, so that the risk of electrolyte leakage is completely avoided, the thermal stability is obviously improved, side reactions hardly exist in the charging and discharging process, and the cycle life is longer. However, the solid electrolyte has a conductivity much lower than that of the liquid electrolyte, and the application requirements of the liquid lithium ion battery cannot be met at present.

The gel electrolyte in the gel electrolyte lithium battery is not liquid or solid, but has the characteristics of liquid diffusion and ion transmission, and the mechanical strength and the adhesion of the solid, and is beneficial to relieving the defects of cell deformation, expansion and the like in the later period of circulation. Therefore, studies on gel electrolyte batteries have been increasing in recent years.

The gel electrolyte precursor mainly comprises liquid electrolyte mother liquor, at least 2 monomers and an initiator, and is disclosed in Chinese patent CN103872379B. The copolymer formed in the initial stage of the polymerization reaction can be dissolved in liquid electrolyte due to the difference of reactivity ratios of the two monomers; in the middle and later stages of the polymerization reaction, as the content and the concentration of the homopolymer of the insoluble nonaqueous organic solvent are gradually increased, the copolymer is gradually separated out to form gel small particles, and the function of transmitting lithium ion physical crosslinking points can be achieved. However, if the copolymer is not sufficiently dispersed in the cell before polymerization, the lithium ion transport channel will be blocked after polymerization, and local lithium dendrite precipitation may be induced in the negative electrode.

In view of the above, it is necessary to provide a technical solution to solve the above problems.

Disclosure of Invention

One of the objects of the present invention is: the preparation method of the gel electrolyte battery cell is provided to solve the problems that the copolymer of the gel electrolyte cannot be fully dispersed in the battery cell before polymerization, so that a lithium ion transmission channel is blocked, and local lithium precipitation of a negative electrode is caused.

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

a preparation method of a gel electrolyte cell comprises the following steps:

s1, adding a liquid gel electrolyte with the temperature of less than or equal to 5 ℃ into a battery cell, and sealing;

s2, placing the sealed battery cell in an environment with the temperature of less than or equal to 5 ℃, and standing for more than or equal to 6 hours;

s3, carrying out charging formation at the temperature of less than or equal to 10 ℃, wherein the formation pressure is 0.1-1.3 MPa, and the charging current is less than or equal to 0.2C;

and S4, degassing and sealing after formation, standing for polymerization reaction, and converting the liquid gel electrolyte into a gel electrolyte to complete the preparation of the battery cell.

Preferably, in step S1, before the liquid gel electrolyte is injected into the battery cell, the battery cell is placed at a temperature of not more than 5 ℃ and the standing time is not less than 1 hour.

Preferably, in step S1, before the electric core is allowed to stand still, the electric core is baked in vacuum, so that the water content test of the electric core is qualified.

Preferably, in step S1, before the liquid gel electrolyte is injected into the battery cell, the liquid gel electrolyte is placed at a temperature of-30 to 5 ℃, and the standing time is not less than 1 hour.

Preferably, in step S2, the temperature of the standing environment is-30 to 5 ℃.

Preferably, in step S3, the ambient temperature for the formation is-30 to 10 ℃.

Preferably, in step S4, the ambient temperature of the polymerization reaction is greater than the formation ambient temperature, and/or the ambient pressure of the polymerization reaction is greater than the formation pressure.

Preferably, in step S4, the ambient temperature of the polymerization reaction is 20-90 ℃, and the ambient pressure of the polymerization reaction is 0.15-1.5 MPa; the polymerization reaction time is 0.5-100 h.

Another object of the present invention is to provide a gel electrolyte battery including a battery cell prepared by the method for preparing a gel electrolyte battery cell according to any one of the above aspects.

It is a further object of the present invention to provide an electric device including the above gel electrolyte battery.

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

1) According to the preparation method provided by the invention, the low-temperature liquid gel electrolyte is added into the battery cell, then the battery cell is continuously placed at a low temperature for standing, and the rate of copolymerization reaction is slowed down through the low temperature, so that the pole piece and the diaphragm are fully soaked before the liquid electrolyte is converted into gel, and the purpose of dispersing the gel electrolyte is further achieved.

2) Meanwhile, the method is carried out at the same low temperature in the formation state, the speed of the copolymerization reaction is continuously delayed, and the electrolyte in the formation state is still in a liquid state, so that the aim of further fully dispersing the gel electrolyte is fulfilled. Meanwhile, the formation current is controlled to be below 0.2C, and the formation conditions of low temperature and small current can ensure that the migration rate of lithium ions is consistent with the movement rate of electrons on one hand, so that the phenomenon that the lithium ions are not embedded into the negative electrode when the lithium ions are separated from the positive electrode and are dissociated to the surface of the negative electrode through electrolyte due to the fact that the movement rate of the lithium ions is too low in a low-temperature state, and electrons are obtained on the surface of the negative electrode to cause lithium precipitation is avoided; on the other hand, the liquid electrolyte has a higher migration rate than that of lithium ions in the gel electrolyte, so that the migration rate of the lithium ions is further ensured to be consistent with that of electrons, the impedance is lower during ion diffusion during formation, the polarization is better improved, and a formed SEI film is more compact and uniform, so that the pole piece interface is obviously improved.

3) According to the preparation method, the liquid gel electrolyte is converted into the gel electrolyte after formation, so that the formed SEI film is more compact and uniform during formation, the chemical interface of a pole piece is better, the gel electrolyte can be dispersed more fully in the battery cell, the risk of local lithium precipitation of the battery cell is avoided, and the electrochemical performance and the safety performance of the battery cell are improved.

Drawings

FIG. 1 is a flow chart of the preparation method of the present invention.

FIG. 2 is a diagram of the gel low temperature verification experiment groups 1 to 9 according to the present invention.

Fig. 3 is a physical diagram of the battery cell obtained by the experimental group 6 in fig. 2.

Fig. 4 is a physical diagram of the battery cell obtained by the experimental group 7 in fig. 2.

Fig. 5 is a physical diagram of the battery cell obtained by the experimental group 8 in fig. 2.

Fig. 6 is a diagram of a battery cell obtained in the experimental group 9 in fig. 2.

Fig. 7 is a real object diagram of a negative electrode sheet formation interface of the battery cell obtained in example 1 of the present invention.

Fig. 8 is a physical diagram of a negative electrode sheet formation interface of the battery cell obtained in comparative example 1 of the present invention.

Detailed Description

In a first aspect, the present invention provides a method for preparing a gel electrolyte cell, as shown in fig. 1, including the following steps:

s2, placing the sealed battery cell in an environment with the temperature less than or equal to 5 ℃, and standing for more than or equal to 6 hours;

s3, carrying out charging formation under the environment that the temperature is less than or equal to 10 ℃, wherein the formation pressure is 0.1-1.3 MPa, and the charging current is less than or equal to 0.2C;

The liquid gel electrolyte comprises a liquid electrolyte mother solution, at least 2 monomers and an initiator. The liquid electrolyte mother solution is a conventional electrolyte for a lithium ion battery and consists of a non-aqueous organic solvent, lithium salt and an additive; the monomer is at least one of unsaturated hydrocarbon, lipid and amide, and the reactivity of the two monomers is greatly different, which can be seen in patent CN 103872379B; the initiator is organic or inorganic matter with strong oxidizing property.

The preparation method of the gel electrolyte battery cell provided by the invention solves the problems that the copolymer of the gel electrolyte can not be fully dispersed into the battery cell before polymerization, so that the lithium ion transmission channel is blocked, and the local lithium precipitation of the negative electrode is caused. The main reason is that the inventor finds that the copolymerization reaction rate has a great influence on the chemical interface and the dispersibility of the electrolyte in the research and development process, and designs a plurality of groups of DOE experiments to verify the electrolyte gel effect by fully considering the copolymerization reaction rate, and finds that the low temperature can effectively inhibit the rate of converting the liquid state into the gel state.

The gel low temperature verification experiment is as follows: 9 sets of comparative tests were designed in a fine bottle and placed at 20 ℃ and-17 ℃ for 24-36 h at the same time to see whether gels appeared. The contents of the fine vial and the results of the verification are shown in Table 1 and FIG. 2, wherein the results in FIG. 2 are the results of the experiments of groups 1 to 9 in the order from left to right.

TABLE 1

Serial number	Adding species	Temperature of	Whether or not to gel
				1	Monomer a + initiator =4.66:0.1	20℃	√
2	Monomer B + initiator =2.33:0.1	20℃	√
				3	Mother liquor + monomer a + initiator =93:4.66:0.1	20℃	√
4	Mother liquor + monomer B + initiator =93:2.33:0.1	20℃	√
				5	Monomer a + monomer B + initiator =4.66:2.33:0.1	20℃	√
6	Mother liquor + monomer a + monomer B + initiator =93	20℃	√
				7	Mother liquor + monomer a + monomer B + initiator =93	-17℃	×
8	Mother liquor + monomer a + monomer B + initiator =93	20℃	√
				9	Mother liquor + monomer a + monomer B + initiator =93	-17℃	×

As can be seen from the results in table 1 and fig. 2 above, gels appeared in the experimental groups 1 to 6, 8, while the experimental groups 7 and 9 were still in liquid form and no gels appeared. That is, the above-mentioned substances showed at least a part of gel state after a certain period of standing at 20 ℃ and remained in liquid form after standing at-17 ℃, wherein the above-mentioned results are only the results at-17 ℃ in the two groups attached, and the results at-17 ℃ in the experimental groups 1 to 5 were also liquid. It can be seen that the rate of liquid to gel transition can be effectively suppressed at low temperatures.

The electrolytes of the experimental groups 6 to 9 are applied to the battery cell to prepare a semi-finished product, and the gel effect of the electrolytes is continuously verified and is shown in fig. 3 to 6. As can be seen from fig. 3 and 5, the cell bodies made from experimental groups 6 and 8 are hard, and gels appear in the pole pieces, which is consistent with the test result of fig. 2; as can be seen from fig. 4 and 6, the cells prepared in experimental groups 7 and 9 were soft, and no gel appeared in the pole pieces, which is also consistent with the test results of fig. 2.

Further, in step S1, before the liquid gel electrolyte is injected into the battery cell, the battery cell is placed at a temperature of not more than 5 ℃ and the standing time is not less than 1 hour. The internal temperature of the battery core is synchronously reduced, the speed of the copolymerization reaction can be more favorably slowed down, and sufficient time is provided for the electrolyte to fully infiltrate the pole piece and the diaphragm.

Further, in step S1, before the battery cell is allowed to stand still, the battery cell is vacuum-baked, so that the water content test of the battery cell is qualified. The water content control of the battery core can be referred to the setting of a liquid lithium ion battery, and redundant description is omitted here.

Further, in step S1, before the liquid gel electrolyte is injected into the battery cell, the liquid gel electrolyte is placed at a temperature of-30 to 5 ℃, and the standing time is not less than 1 hour. Wherein, in the range, the lower the environmental temperature of the liquid gel electrolyte is, the shorter the standing time of the liquid gel electrolyte can be, so as to rapidly reduce the temperature; on the contrary, the higher the temperature of the environment for placing the electrolyte, the longer the standing time of the electrolyte is, and the temperature of the liquid gel electrolyte is ensured to be lower than 5 ℃. Further preferably, the standing temperature of the liquid gel electrolyte is-20 to 5 ℃. Specifically, the temperature of the liquid gel electrolyte can be-20 to-15 ℃, 15 to-10 ℃, 10 to-5 ℃, 5 to 0 ℃ and 0 to 5 ℃.

Further, in step S2, the ambient temperature of the still standing is-30 to 5 ℃. Similarly, in the above range, the lower the environmental temperature to which the liquid gel electrolyte is placed, the shorter the standing time of the liquid gel electrolyte can be, so as to rapidly reduce the temperature; on the contrary, the higher the temperature of the environment for placing the electrolyte, the longer the standing time of the electrolyte is, and the temperature of the liquid gel electrolyte is ensured to be lower than 5 ℃. Further preferably, the standing temperature of the liquid gel electrolyte is-20 to 5 ℃. Specifically, the temperature of the liquid gel electrolyte can be-20 to-15 ℃, 15 to-10 ℃, 10 to-5 ℃, 5 to 0 ℃ and 0 to 5 ℃.

Further, in step S3, the ambient temperature for formation is-30 to 10 ℃. During formation, the low temperature is continuously kept to be carried out so as to continuously delay the rate of copolymerization reaction and ensure that the electrolyte during formation is still in a liquid state, so that the soluble copolymer can be further ensured to be fully dispersed in the battery cell before being converted into gel electrolyte, the migration rate of lithium ions at the low temperature can be improved, the impedance during diffusion of the lithium ions can be reduced, and the polarization can be improved; meanwhile, the formed SEI film is more compact and uniform, and the pole piece interface is obviously improved.

Further, in step S4, the ambient temperature of the polymerization reaction is higher than the ambient temperature of the formation reaction, and/or the ambient pressure of the polymerization reaction is higher than the formation pressure. The reaction rate of the polymerization reaction can be increased by increasing the reaction temperature and pressure, the electrolyte in the battery cell is uniformly dispersed and a uniform and compact SEI film is formed after formation, and the polymerization reaction can be accelerated by increasing the temperature and/or pressure of the polymerization reaction, so that the purpose of converting the liquid electrolyte into the gel electrolyte is achieved. Preferably, in step S4, the ambient temperature of the polymerization reaction is 20-90 ℃, and the ambient pressure of the polymerization reaction is 0.15-1.5 MPa; the polymerization reaction time is 0.5-100 h.

In a second aspect, the invention provides a gel electrolyte battery, which comprises a battery cell prepared by the preparation method of the gel electrolyte battery cell.

In a third aspect, the present invention provides an electric device comprising the gel electrolyte battery described above. The electric device can be a vehicle, a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy, an electric tool and the like. The vehicle can be a fuel oil vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle or a range-extended vehicle and the like; spacecraft include aircraft, rockets, space shuttles, and spacecraft, among others; electric toys include stationary or mobile electric toys, such as game machines, electric car toys, electric ship toys, electric airplane toys, and the like; the electric power tools include metal cutting electric power tools, grinding electric power tools, assembly electric power tools, and electric power tools for railways, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, electric impact drills, concrete vibrators, and electric planers.

In order to make the technical solutions and advantages of the present invention clearer, the present invention and its advantageous effects will be described in further detail with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

Example 1

A preparation method of a gel electrolyte cell comprises the following steps:

s1, dehydrating the battery cell to enable the water content of the battery cell to be qualified in a test, and then respectively placing the battery cell and the liquid gel electrolyte in an environment with the temperature of-30-5 ℃ for standing time of more than or equal to 1h; then adding the liquid gel electrolyte into the battery cell, and sealing;

s2, after primary sealing, placing the battery cell in an environment with the temperature of-30-5 ℃, and standing for more than or equal to 6 hours;

s3, carrying out charging formation at the temperature of-30-10 ℃, wherein the formation pressure is 0.1-1.3 MPa, and the charging current is less than or equal to 0.2C;

and S4, degassing and sealing after formation, standing for carrying out polymerization reaction, wherein the environmental temperature of the polymerization reaction is 20-90 ℃, the pressure is 0.15-1.5 MPa, and the time is 0.5-100 h, so that the liquid gel electrolyte is converted into the gel electrolyte, and the preparation of the battery cell is completed.

Comparative example 1

A preparation method of a gel electrolyte cell comprises the following steps:

s3, carrying out charging formation at normal temperature, wherein the formation pressure is 0.1-1.3 MPa, and the charging current is 0.1-2C;

and S4, degassing after formation, sealing twice, and standing for polymerization reaction at the ambient temperature of 20-90 ℃, the pressure of 0.15-1.5 MPa for 0.5-100 h, so that the liquid gel electrolyte is converted into gel electrolyte, and the preparation of the battery cell is finished.

The negative electrode sheets of the cells obtained in example 1 and comparative example 1 described above were examined for formation of interfaces, as shown in fig. 7 to 8.

As can be seen from fig. 7, the preparation method of the present invention is performed at a low temperature before gelation, that is, the polymerization reaction rate can be effectively slowed down before gelation, the gelled negative electrode interface gel electrolyte is dispersed more uniformly, the gel particles are finer, and the physical crosslinking effect for lithium ion transport is better. As can be seen from fig. 8, the gel electrolyte at the negative electrode interface is dispersed unevenly only by changing the temperature during formation, and the gel particles are agglomerated visually, which is very likely to block the lithium ion transmission channel. In other words, before formation, namely, the processes of liquid injection and standing are kept to be carried out at normal temperature, the gel electrolyte at the negative electrode interface can not be uniformly dispersed, which is also a great influence factor causing that the current gel electrolyte battery can not be widely applied.

In conclusion, the preparation provided by the invention controls the formation process before the liquid injection of the battery cell to be carried out at low temperature, so that the gel electrolyte in the battery cell is uniformly dispersed, the local precipitation of lithium dendrites on a negative plate is avoided, the negative interface is effectively improved, and the electrochemical performance and the safety performance of the battery cell are further improved.

Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A preparation method of a gel electrolyte cell is characterized by comprising the following steps:

2. The method of claim 1, wherein in step S1, the cell is placed at a temperature of less than or equal to 5 ℃ for a time period of greater than or equal to 1 hour before the liquid gel electrolyte is injected into the cell.

3. The method of claim 2, wherein in step S1, the cell is vacuum baked before the cell is allowed to stand, so that the water content of the cell is qualified in the test.

4. The method of claim 2, wherein in step S1, the liquid gel electrolyte is first placed at a temperature of-30 to 5 ℃ for a time of at least 1h before being injected into the cell.

5. The method of preparing a gel electrolyte cell according to claim 1, wherein in step S2, the ambient temperature of standing is-30 to 5 ℃.

6. The method of manufacturing a gel electrolyte cell according to any of claims 1 to 5, wherein in step S3, the ambient temperature of formation is-30 to 10 ℃.

7. The method of preparing a gel electrolyte cell according to claim 6, wherein in step S4, the ambient temperature of the polymerization reaction is greater than the ambient temperature of the formation, and/or the ambient pressure of the polymerization reaction is greater than the formation pressure.

8. The method of preparing a gel electrolyte cell according to claim 7, wherein in step S4, the ambient temperature of the polymerization reaction is 20 to 90 ℃, and the ambient pressure of the polymerization reaction is 0.15 to 1.5MPa; the polymerization reaction time is 0.5-100 h.

9. A gel electrolyte battery comprising a cell produced by the method for producing a gel electrolyte cell according to any one of claims 1 to 8.

10. An electric device comprising the gel electrolyte battery according to claim 9.