CN102800889A - Lithium-ion battery and preparation method for same - Google Patents

Abstract

A lithium ion battery, comprising a shell, a pole core housed in the shell, the pole core includes a positive pole, a negative pole, a diaphragm between the positive pole and the negative pole, wherein: a liquid electrolyte is contained in the pole core, and the pole core Gel is filled between the core and the shell. The present invention also provides a preparation method for the above-mentioned lithium ion battery, comprising the following steps: step 1, covering the pole core with adhesive tape to form a sealed space in the pole core; step 2, injecting liquid electrolyte into the sealed space of the pole core , carry out pre-charge formation, then inject the second solution between the shell and the pole core, heat to initiate a polymerization reaction, and form a gel between the pole core and the shell; or first inject the second solution into the shell and the pole core In between, heating initiates a polymerization reaction, and a gel is formed between the pole core and the shell, and then the liquid electrolyte is injected into the sealed space of the pole core for pre-charge formation. The invention not only overcomes the problem of electrolyte leakage, but also does not affect the SEI film of the negative electrode.

Description

A kind of lithium ion battery and preparation method thereof

technical field

The invention relates to the technical field of batteries, and more specifically, to a lithium ion battery and a preparation method thereof. the

Background technique

As a high-energy chemical power source, lithium-ion batteries have been widely used in mobile communications, notebook computers, video cameras, cameras, portable instruments and other fields. . According to the different electrolyte materials used in lithium-ion batteries, lithium-ion batteries can be divided into two categories: liquid lithium ion battery (LIB for short) and polymer lithium ion battery (PLIB for short). The positive and negative electrode materials used in polymer lithium-ion batteries are the same as those in liquid lithium ions, and the working principles of the batteries are basically the same. Their main difference lies in the different electrolytes. Traditional lithium-ion batteries use liquid electrolytes, which have safety problems such as liquid electrolyte leakage, combustion and explosion, while polymer lithium-ion batteries use solid polymer electrolytes or gel polymer electrolytes. Compared with liquid lithium-ion batteries, it has the advantages of thinner shape and arbitrary shape, and there will be no safety problems such as electrolyte leakage.

Among them, the gel polymer electrolyte not only has the characteristics of non-flowability of solid polymer electrolytes, but also has high ionic conductivity close to that of liquid electrolytes, and is widely used in current polymer lithium-ion batteries. The use of gel-state electrolyte in lithium-ion batteries overcomes the inherent safety hazards of liquid lithium-ion batteries such as leakage and corrosion. There are two main methods of preparing gel state electrolytes currently used: one is the Bellcore technology based on the principle of physical swelling; the other is the in-situ polymerization process based on chemical cross-linking polymerization.

Bellcore Technology of the United States pioneered the development of physical gel/solution technology. Their process is to use polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) as the skeleton matrix material, and prepare a porous film by extraction method. Through the physical adsorption process , the electrolyte enters the pores of the PVDF-HFP membrane. Throughout the process, the production of polymer electrolytes does not involve reaction processes such as chemical polymerization. However, the polymer electrolyte prepared by the Bellcore technology is a solid-liquid two-phase system. There is no chemical bond between the copolymer and the electrolyte, and the liquid phase in the two phases may flow out under a certain pressure or temperature, which poses a safety hazard. the

The in-situ polymerization process is to initiate chemical polymerization of monomers by heating or light radiation in a system containing unsaturated monomers, initiators, and electrolytes to form gels. Using this method to prepare electrolytes overcomes the shortcomings of the Bellcore process. In addition, the process is relatively simple and has attracted widespread attention.

For example: Application No. CN200410026814.9 discloses a polymer electrolyte lithium ion battery, which mainly consists of positive and negative electrode composite elements, a diaphragm composite element between the positive and negative electrode composite elements and an outer packaging composite element. Composition; wherein the diaphragm element is a mixture composed of a mesh-like fiber structure diaphragm as the skeleton of the composite element and a colloidal polymer electrolyte, which is characterized in that the polymer electrolyte alternately exists on the surface of the diaphragm in a continuous state and in the micropores; the continuous-state alternating electrolyte polymer is formed by a monomer and an initiator undergoing a thermal polymer chemical reaction to grow a two-dimensional and three-dimensional polymer network and react with the electrolyte.

The in-situ polymerization process injects the electrolyte solution containing the polymerizable monomer and the initiator together into the battery case, and initiates the polymerization to form a gel in one step. Those skilled in the art know that in the existing lithium battery manufacturing process, carbon materials are used as the negative electrode, and there is a process of formation and pre-charging, the purpose of which is to form a stable solid electrolyte interface (solid electrolyte interface) on the surface of the carbon negative electrode. Commonly known as SEI film). The quality of the SEI film determines the electrochemical performance of lithium batteries, especially the cycle performance. However, whether the in-situ polymerization process is polymerized before or after the formation, the existence (or residue) of unsaturated monomers and initiators will inevitably deteriorate the SEI film formed on the surface of the negative electrode during the formation, significantly It can seriously affect the electrochemical performance of the battery, especially the cycle performance.

Contents of the invention

The present invention aims to solve the problem of electrolyte leakage and poor safety performance in liquid lithium-ion batteries in the prior art, while gel-state lithium-ion batteries have unsaturated monomers and initiators that deteriorate the SEI film of the negative electrode and affect the electrochemical performance of the battery. technical problem.

For this reason, the present invention provides a kind of lithium-ion battery, comprises housing, the pole core that is housed in the housing, and described pole core comprises positive pole, negative pole, is positioned at the diaphragm between positive and negative pole, wherein: described pole core houses There is a liquid electrolyte, and a gel is filled between the core and the case.

In the lithium-ion battery of the present invention, the pole core is wound by a positive electrode, a negative pole, and a separator located between the positive and negative poles, and the wound pole core is covered with adhesive tape so that the inside of the pole core is formed for storage. A sealed space for the liquid electrolyte, and a first liquid injection port for injecting the liquid electrolyte is left on the pole core.

In the lithium ion battery of the present invention, the first liquid injection port is arranged on the top of the pole core, and the first liquid injection port passes through the adhesive tape; the adhesive tape is wrapped on the winding end of the wound pole core, the pole The bottom of the core and the top of the pole core except for the first liquid injection port.

In the lithium ion battery of the present invention, the casing is provided with a second liquid injection port for injecting the second gel-forming solution, and the second liquid injection port is far away from the first liquid injection port.

In the lithium ion battery of the present invention, the gel is a polymer formed by polymerization of acrylate monomers with one or more unsaturated double bonds.

At the same time, a preparation method of the above-mentioned lithium ion battery is also provided, the preparation method includes the following steps: Step 1, covering the pole core with adhesive tape, so that a sealed space is formed in the pole core;

Step 2. First inject the liquid electrolyte into the sealed space of the pole core for pre-charge formation, then inject the second solution between the shell and the pole core, heat to initiate a polymerization reaction, and form a gel between the pole core and the shell ; Or first inject the second solution between the shell and the pole core, heat to initiate a polymerization reaction, form a gel between the pole core and the shell, and then inject the liquid electrolyte into the sealed space of the pole core for pre-charge formation.

In the preparation method of the lithium-ion battery of the present invention, the temperature for the heating to initiate the polymerization reaction is 60-100° C., and the time is 10-120 min.

In the preparation method of the lithium ion battery of the present invention, the liquid electrolyte contains a lithium salt and a first solvent, and the concentration of the lithium salt is 0.5-1.5mol/L, wherein the lithium salt is selected from lithium hexafluorophosphate, lithium perchlorate , lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonamide, and lithium bisoxalate borate; the first solvent is linear or cyclic carbonate solvents.

In the preparation method of the lithium ion battery of the present invention, the second solution includes an unsaturated monomer, an initiator and a second solvent, and the unsaturated monomer is an acrylate containing one or more unsaturated double bonds monomer, the thermal initiator is selected from one or more of dibenzoyl peroxide, azobisisobutyronitrile, N-dimethylaniline, and the second solvent contains carbonate solvents or / and halogenated carbonate solvents; based on the total weight of the second solution, the content of the unsaturated monomer is 3wt-30wt%, the content of the initiator is 0.5wt-3wt%, the second solvent The content is 67wt-96.5wt%.

In the preparation method of the lithium ion battery of the present invention, the second solvent also includes an organic phosphide, and the organic phosphide is selected from trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, One or more of tributyl phosphate, tris(2-chloroethyl) phosphate, dimethyl methyl phosphate, vinyl ethyl phosphate, and hexamethylphosphoramide.

In the preparation method of the lithium-ion battery of the present invention, the positive pole, the negative pole, the diaphragm between the positive pole and the negative pole are wound to form a pole core, and the tape is coated on the wound pole core so that a sealed space is formed in the pole core, Moreover, a first liquid injection port for injecting liquid electrolyte is reserved on the pole core, and the liquid electrolyte is injected into the pole core through the first liquid injection port.

In the preparation method of the lithium-ion battery of the present invention, a second liquid injection port is provided on the casing, and the second liquid injection port is far away from the first liquid injection port, and flows into the casing through the second liquid injection port. Inject the second solution.

The preparation method of the present invention is divided into two injections, and the two processes of battery formation and monomer polymerization are separated. In the step of pre-charging formation, the first solution is injected into the pole core, and the first solution (that is, liquid electrolyte) is used. Carry out chemical conversion, form a stable SEI film on the surface of the carbon negative electrode according to the known chemical conversion process in the art, to ensure the electrochemical performance of the battery; in the step of monomer polymerization, inject the second solution between the pole core and the casing, Polymerization is initiated by heating to prepare a polymer gel. Compared with the existing in-situ polymerization technology, the lithium battery prepared by the present invention avoids the influence of monomers and initiators on the negative electrode SEI film, and can ensure excellent electrochemical performance, especially cycle performance, and because the battery pole core Surrounded by gel, the gel can absorb the liquid electrolyte that may flow out of the pole core, greatly reducing the risks of battery leakage, corrosion, burning, etc.; The liquid lithium-ion battery has the problems of electrolyte leakage and poor safety performance, and it will not affect the negative electrode SEI film, ensuring the electrochemical performance of the lithium-ion battery.

Description of drawings

Fig. 1 is a schematic diagram of the pole core of the lithium ion battery of the present invention.

FIG. 2 is a comparison chart of the cycle performance of lithium-ion batteries prepared in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

Those skilled in the art know that liquid lithium ion batteries using liquid electrolytes have safety problems such as liquid electrolyte leakage, combustion and explosion. At the same time, the inventors have found through repeated experiments that if the existing in-situ polymerization process is used to make the gel polymer electrolyte, the presence of the added monomer and initiator or the residue after polymerization will obviously affect the surface of the negative electrode. The performance of the SEI film will directly lead to the reduction of the electrochemical performance of the battery, such as the reduction of the cycle performance of the battery.

The inventors of the present invention conducted further research and separated the two processes of battery formation and monomer polymerization. In the step of pre-charging formation, the first solution was injected into the pole core, and the first solution (ie, liquid electrolyte) was used. Carry out chemical conversion, form a stable SEI film on the surface of the carbon negative electrode according to the known chemical conversion process in the art, to ensure the electrochemical performance of the battery; in the step of monomer polymerization, inject the second solution between the pole core and the casing, Polymerization is initiated by heating to prepare a polymer gel. Compared with the existing in-situ polymerization technology, the lithium battery prepared by the present invention avoids the influence of the monomer and the initiator on the SEI film of the negative electrode, and can ensure that the lithium ion battery obtains excellent electrochemical performance, especially cycle performance; at the same time, Because the battery pole core is surrounded by gel, the gel can absorb the liquid electrolyte that may flow out of the pole core, greatly reducing the risks of battery leakage, corrosion, burning, etc., and the safety performance is significantly improved.

Accordingly, the present invention provides a lithium ion battery and a preparation method thereof, which can better avoid the influence of monomers and initiators on the negative electrode SEI film, and have better safety performance. The lithium ion battery provided by the present invention includes: a casing, a pole core accommodated in the casing, the pole core includes a positive pole, a negative pole, and a diaphragm between the positive pole and the negative pole, and a liquid electrolyte is contained in the pole core. Gel is filled between the pole core and the shell.

The pole core structure of the lithium ion battery of the present invention can be similar to that of the existing liquid lithium ion battery, and the liquid electrolyte is accommodated in the diaphragm.

The gel contains or does not contain conductive lithium ions, preferably, the gel does not contain conductive lithium ions, so the gel is not used as a gel-state electrolyte, and its main function is to absorb the polar core The liquid electrolyte that may flow out of the battery improves the safety performance of lithium-ion batteries.

The present invention provides two methods for preparing the above-mentioned lithium ion battery. The two preparation methods separate the two steps of battery formation and monomer polymerization, and the order of the two steps can be reversed. The first preparation method includes the following steps: 1. First, inject the first solution, that is, the liquid electrolyte, into the sealed space of the pole core for pre-charge formation; 2. Then inject the second solution between the shell and the pole core, Heating initiates a polymerization reaction, and a gel is formed between the pole core and the case to obtain the lithium ion battery of the present invention. The second preparation method includes the following steps: 1. First, inject the second solution between the shell and the pole core, heat to initiate a polymerization reaction, and form a gel between the pole core and the shell; 2. Then inject the first solution , that is, the liquid electrolyte is injected into the sealed space of the pole core, and pre-charged and formed to obtain the lithium ion battery of the present invention. In the present invention, it is preferable to adopt the second preparation method to prepare the lithium-ion battery, so that the safety performance of the lithium-ion battery is better during the pre-charge formation process. It is worth mentioning that before the above steps, it also includes the step of covering the pole core with adhesive tape to form a sealed space in the pole core. The sealed space of the pole core prevents the second solution from entering the pole core, and at the same time makes The first solution will not leak from the pole core under normal conditions.

In the preparation method of above-mentioned two kinds of lithium-ion batteries, described first solution is the electrolytic solution containing lithium salt, comprises lithium salt and first solvent, and lithium salt is dissolved in the first solvent, and the concentration of lithium salt is 0.5- 1.5mol/L. Wherein, the lithium salt is well known in the technical field, and may be lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiBF ₄ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium bistrifluoromethanesulfonamide (LiN(CF ₃ SO ₂ ) ₂ ), lithium bisoxalate borate (LiBOB), or a mixture of two or more. The first solvent is a linear or cyclic carbonate solvent, preferably, the first solvent is selected from ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), Dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), dimethoxycarbonate (DME), vinylene carbonate (VC), fluoroethylene carbonate (FEC), chloroethylene carbonate (ClEC) ) of one or more of them.

Described second solution comprises second solvent, unsaturated monomer and initiator, and described unsaturated monomer and initiator are dissolved in the second solvent, and the effect of described second solution is to form gel, when heating , The initiator initiates the polymerization of unsaturated monomers to form a gel. The second solution contains or does not contain lithium salts, preferably, the second solution does not contain lithium salts, and does not participate in electrochemical processes and ion conduction; the main function of the second solution is to form a gel, different The gel-state electrolyte in the existing gel-state lithium-ion battery does not need to have the role of electrolyte.

Wherein, the second solvent and the first solvent of the first solution may or may not be the same, preferably, the second solvent is different from the first solvent, based on the weight of the second solution, the weight of the second solvent The content is 67wt-96.5wt%. Specifically, the second solvent contains carbonate solvents or/and halogenated carbonate solvents, specifically, the second solvent is selected from ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate ( DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), dimethoxycarbonate (DME), vinylene carbonate (VC), fluoroethylene carbonate (FEC), chloroethylene carbonate One or more of esters (ClEC). Further, the second solvent also contains an organic phosphorous compound, specifically, the organic phosphorous compound is selected from trimethyl phosphate (TMP), triethyl phosphate (TEP), tributyl phosphate (TBP), tributyl phosphate Phenyl ester (TPP), tributyl phosphate (TBP), tris(2-chloroethyl) phosphate (TCEP), dimethyl methyl phosphate (DMMP), vinyl ethyl phosphate (EEP), hexamethyl One or two or more of the base phosphoramides (TMPA), the organic phosphides contained in the second solvent are flame-retardant or flame-retardant phosphides, and when heating triggers the polymerization reaction of the second solution to form a gel, the The gel contains flame-retardant or flame-retardant phosphides, which significantly improves the safety performance of lithium-ion batteries.

The unsaturated monomer is an acrylate monomer containing one or more unsaturated double bonds. Preferably, the unsaturated monomer is selected from methyl methacrylate, methyl acrylate, butyl acrylate, One or more of butyl methacrylate, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, ethylene glycol diacrylate, polyethylene glycol dimethacrylate; Based on the weight of the second solution, the monomer content is 3wt-30wt%.

The thermal initiator is selected from one or more of dibenzoyl peroxide, azobisisobutyronitrile, N-dimethylaniline; based on the weight of the second solution, the content of the initiator is 0.5wt-3wt%.

By heating, the thermal initiator initiates the polymerization reaction of the unsaturated monomer, the temperature of the heating initiation polymerization reaction is 60-100°C, and the time is 10-120min, so that the second solution forms a gel, and the temperature is too low, The rate of initiating polymerization is slow or even unable to initiate the polymerization reaction; if the temperature is too high, it will easily cause the volatilization of the solvent and affect the performance of the battery.

The first preparation method of the above-mentioned lithium ion battery specifically comprises the following steps:

Step 1. Cover the wound pole core with adhesive tape, form a sealed space in the pole core, and reserve the first liquid injection port on the top; those skilled in the art know that the pole core is usually composed of positive pole, negative pole, The separator located between the positive and negative poles is wound; in this step, preferably, the winding end of the wound pole core and the bottom of the pole core are covered with adhesive tape, and a certain amount of space is reserved on the top of the pole core. After the liquid injection port area (the first liquid injection port), the remaining positions are covered with adhesive tape; it can be understood that the first liquid injection port is the liquid injection port reserved for the first solution on the top of the pole core A certain area, so that the electrolyte penetrates into the pole core through the first liquid injection port, and wets the pole piece and the diaphragm.

Step 2. Inject the first solution into the sealed space of the pole core from the first liquid injection port, and perform pre-charge formation on the battery containing the first solution; in this step, the pre-charge formation can be realized by existing technology .

Step 3. A second liquid injection port for injecting the second solution is provided on the casing of the battery, and the second solution is injected from the second liquid injection port into the casing of the battery after pre-charging and formation; in this step Among them, it is worth mentioning that the second liquid injection port is located on the housing at a position away from the first liquid injection port, that is, it is located at any position on the housing that is not opposite to the first liquid injection port, In order to prevent the second solution from entering the pole core through the first liquid injection port. According to specific circumstances, the position of the second liquid injection port can be any position except the first liquid injection port.

Step 4, heating the battery to 60° C. to 100° C. to initiate a polymerization reaction, so that the second solution in the casing forms a gel. In this step, the heating temperature is 60-100°C; if the temperature is too low, the rate of initiating polymerization is slow or even unable to initiate the polymerization reaction; if the temperature is too high, it will easily cause the volatilization of the solvent and affect the performance of the battery. , the heating temperature is 75-90°C; the heating time is 10-120min, and the heating method can be various heating methods known to those skilled in the art.

The second preparation method of the above-mentioned lithium-ion battery specifically comprises the following steps:

Step 1. Cover the wound pole core with adhesive tape, form a sealed space in the pole core, and reserve the first liquid injection port on the top; those skilled in the art know that the pole core is usually composed of positive pole, negative pole, The separator located between the positive and negative poles is wound; in this step, preferably, the winding end of the wound pole core and the bottom of the pole core are covered with adhesive tape, and a certain amount of space is reserved on the top of the pole core. After the liquid injection port area (the first liquid injection port), the remaining positions are covered with adhesive tape; it can be understood that the first liquid injection port is the liquid injection port reserved for the first solution on the top of the pole core A certain area, so that the electrolyte penetrates into the pole core through the first liquid injection port, and wets the pole piece and the diaphragm.

Step 2. A second liquid injection port for injecting the second solution is provided on the casing of the battery, and the second solution is injected from the second liquid injection port into the casing of the battery that has not been pre-charged and formed; In the step, it is worth mentioning that the second liquid injection port is located on the housing at a position away from the first liquid injection port, that is, it can be located at any position on the housing that is not opposite to the first liquid injection port to prevent the second solution from entering the pole core through the first liquid injection port. According to specific circumstances, the position of the second liquid injection port can be any position except the first liquid injection port.

Step 3, heating the battery to 60° C. to 100° C. to initiate a polymerization reaction, so that the second solution in the casing forms a gel. In this step, the heating temperature is 60-100°C; if the temperature is too low, the rate of initiating polymerization is slow or even unable to initiate the polymerization reaction; if the temperature is too high, it will easily cause the volatilization of the solvent and affect the performance of the battery. , the heating temperature is 75-90°C; the heating time is 10-120min.

Step 4. Inject the first solution into the sealed space of the pole core of the battery from the first liquid injection port, and perform pre-charge formation on the battery containing the first solution; in this step, the pre-charge formation can use this The common pre-charge formation process in the field forms a stable SEI film on the surface of the negative electrode through pre-charge formation.

In the lithium-ion battery prepared by the above two preparation methods, the pole core is wound by a positive electrode, a negative pole, and a separator between the positive and negative poles, and the wound pole core is covered with adhesive tape so that A sealed space for accommodating liquid electrolyte is formed in the pole core, and a first liquid injection port for injecting liquid electrolyte is left on the pole core; a second liquid injection port for injecting a second solution forming a gel is provided on the shell A liquid injection port, the second liquid injection port is far away from the first liquid injection port. As shown in Figure 1, preferably, the first liquid injection port 11 is arranged on the top of the pole core 1, and the first liquid injection port 11 passes through the adhesive plaster 2; the adhesive plaster 2 is wrapped on the wound pole core 1 The winding end of the pole core 1, the bottom of the pole core 1, and the top of the pole core 1 except for the first liquid injection port 11 form a sealed space for accommodating liquid electrolyte in the pole core.

The inventors of the present invention have further conducted research. By injecting liquid twice, the two processes of battery formation and monomer polymerization are separated. In the step of pre-charge formation, inject the first solution (i.e. liquid electrolyte ), form a stable SEI film on the surface of the carbon negative electrode according to the well-known chemical conversion process in the art to ensure the electrochemical performance of the battery; in the step of monomer polymerization, inject the second solution between the pole core and the casing, heat A polymerization reaction is initiated to prepare a polymer gel. At the same time, in the process of injecting the second solution, by controlling the position of the second liquid injection port, the second solution is prevented from entering the inside of the pole core, so that it adheres more to the inner wall of the battery case and the outside of the battery pole core, It is located between the battery casing and the pole core. After heating and polymerization, a gel is formed between the outside of the pole core and the inside of the casing to enclose the pole core in the casing.

Compared with the existing in-situ polymerization technology, the lithium battery prepared by the present invention avoids the influence of monomers and initiators on the SEI film of the negative electrode, and can ensure superior electrochemical performance, especially cycle performance. The core is surrounded by gel, which can absorb the liquid electrolyte that may flow out of the pole core. For example, when the battery is turned upside down, the liquid electrolyte may flow out from the first liquid injection port. The setting of the gel greatly reduces battery leakage. Risks such as liquid, corrosion, and burning; further, the gel contains flame-retardant or flame-retardant phosphides, and the safety performance is significantly improved.

The present invention is not particularly limited to the composition of positive pole, negative pole and diaphragm of lithium ion battery, can be any positive pole, negative pole and diaphragm known in the art, for example, the current collector of positive pole can be aluminum foil, the positive pole coated on the aluminum foil The active material can be positive electrode active materials such as LiCoO _{2 ,} LiMn ₂ O _{4 ,} LiFePO _{4 ,} LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , and the negative electrode can be copper foil containing graphite.

In addition, it should be noted that, in the present invention, both "above" and "below" include the original number.

The present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, and are not intended to limit the present invention.

Example 1

Wind the separator and positive and negative electrode materials (LiCoO ₂ positive electrode/diaphragm/graphite negative electrode) into a battery pole core; paste the bottom of the pole core and the winding end with tape, and reserve the top of the pole core behind the first liquid injection port , stick adhesive tape on the remaining positions; inject the first solution containing LiPF ₆ and EC-EMC-DEC-VC organic solvent from the first liquid injection port, wherein the concentration of LiPF ₆ is 1mol/L, EC: EMC: DEC: VC The weight ratio is 4:3:2.5:0.5. After aging, pre-charge the battery; A second solution of ethylene glycol dimethacrylate, 1wt% dibenzoyl peroxide and 90wt% EC-EMC-DEC-VC mixed solvent, wherein the weight ratio of EC:EMC:DEC:VC is 4 : 3: 2.5: 0.5; heating at 80°C for 60 min, the heating triggers the polymerization of the second solution to form a gel, and the lithium-ion battery A1 is obtained.

Comparative example 1

Comparative example 1 is used to illustrate the lithium-ion battery that adopts post-formation polymerization in the prior art;

Based on the weight of the total electrolyte, a mixture of 9 wt% tetraethylene glycol dimethacrylate, 1 wt% dibenzoyl peroxide and 90 wt% 1M LiPF6/EC-EMC-DEC-VC was prepared An electrolyte solution of a solvent, wherein the weight ratio of EC:EMC:DEC:VC is 4:3:2.5:0.5. Wind the separator and positive and negative electrode materials (for example: LiCoO ₂ positive electrode/diaphragm/graphite negative electrode) to form a battery pole core, paste the bottom of the pole core and the winding end with adhesive tape, and reserve the first liquid injection port on the top of the pole core After that, tape the rest of the position. Inject the electrolyte solution prepared above from the first liquid injection port, and after formation, heat at 80° C. for 60 minutes to induce polymerization of the electrolyte solution to form a gel, and obtain lithium-ion battery B1.

Comparative example 2

Comparative example 2 is used to illustrate the lithium-ion battery formed after polymerization in the prior art;

Based on the weight of the total solution, a mixture of 9 wt% tetraethylene glycol dimethacrylate, 1 wt% dibenzoyl peroxide and 90 wt% 1M LiPF6/EC-EMC-DEC-VC was prepared An electrolyte solution of a solvent, wherein the weight ratio of EC:EMC:DEC:VC is 4:3:2.5:0.5. The separator and positive and negative electrode materials (for example: LiCoO ₂ positive electrode/diaphragm/graphite negative electrode) are wound into a battery core. Stick the tape on the bottom of the pole core and the end of the winding. After the first liquid injection port area is reserved on the top of the pole core, stick tape on the rest of the position. Inject the electrolyte solution prepared above from the first liquid injection port, heat at 80° C. for 60 minutes, induce the electrolyte solution to polymerize to form a gel, and then carry out the chemical conversion process to obtain the lithium ion battery B2.

Performance Testing

Fig. 2 is a comparison chart of the cycle performance of the lithium-ion batteries made in Example 1 of the present invention, Comparative Example 1, and Comparative Example 2. From Fig. 2, it can be known that the cycle performance of the lithium-ion batteries made in Example 1 of the present invention is better .

Example 2

Wind the separator and positive and negative electrode materials (for example: LiCoO ₂ positive electrode/diaphragm/graphite negative electrode) to form a battery pole core; paste the bottom of the pole core and the winding end with transparent tape, and reserve the first injection liquid on the top of the pole core After the mouth area, stick transparent tape on the rest of the position. Inject a 1M first solution containing LiPF ₆ and EC-EMC-VC from the first liquid injection port, wherein the concentration of LiPF ₆ is 0.6 mol/L, the weight ratio of EC:EMC:VC is 3:6.5:0.5, Chen After thawing, the battery is pre-charged; then from the second liquid injection port, that is, the position on the shell relative to the pole core covered by the adhesive tape is injected containing 20 wt% methyl methacrylate monomer, 0.5 wt% supercharged A second solution of dibenzoyl oxide and 79.5wt% of a mixed solvent of EC and DMC, wherein the weight ratio of EC:DMC is =1:1; heating at 60°C for 180min, heating causes the second solution to polymerize to form a gel, and obtains Li-ion battery A2.

Example 3

Wind the separator and positive and negative electrode materials (for example: LiMn ₂ O ₄ positive electrode/diaphragm/graphite negative electrode) to form a battery pole core; paste the bottom of the pole core and the winding end with transparent tape, and reserve the top of the pole core for the second After the first liquid injection port, tape the remaining positions; inject the first solution containing LiBF ₄ and EC-EMC-DEC-VC organic solvent from the first liquid injection port, wherein the concentration of LiBF ₄ is 1mol/L, EC: EMC :DEC:VC with a weight ratio of 4:3:2.5:0.5. After aging, precharge the battery; The second solution of the tetraethylene glycol dimethacrylate of wt%, the dibenzoyl peroxide of 1wt% and the mixed solvent of 90wt% EC-EMC-DEC, wherein, the weight ratio of EC:EMC:DEC is 4 :3:3; heating at 75° C. for 60 min, heating causes the second solution to polymerize to form a gel, and obtains a lithium-ion battery A3.

Example 4

Wind the separator and positive and negative electrode materials (for example: LiCoO ₂ positive electrode/diaphragm/graphite negative electrode) to form a battery pole core; paste the bottom of the pole core and the winding end with transparent tape, and reserve the first injection liquid on the top of the pole core After the mouth area, stick adhesive tape on the remaining positions; inject the first solution containing LiPF ₆ -LiBF ₄ /EC-EMC-DEC-VC from the first liquid injection port, wherein the concentration of the mixed lithium salt LiPF ₆ -LiBF ₄ is 1mol /L, EC: EMC: DEC: VC with a weight ratio of 4:3:2.5:0.5. After aging, precharge the battery; The wrapped position is injected with a second solution containing 5 wt% polyethylene glycol dimethacrylate, 1 wt% azobisisobutyronitrile and 94 wt% DEC and TBP mixed solvent, wherein the weight ratio of DEC:TMP The ratio is 3:1; heating at 80°C for 45 minutes, the heating triggers the polymerization of the second solution to form a gel, and the lithium-ion battery A4 is obtained.

Example 5

Wind the separator and positive and negative electrode materials (for example: LiCoO ₂ positive electrode/diaphragm/graphite negative electrode) to form a battery pole core; paste the bottom of the pole core and the winding end with transparent tape, and reserve the first note on the top of the pole core. After the liquid port, stick a transparent adhesive tape on the rest of the position; inject polyethylene glycol dimethacrylate containing 5 wt% polyethylene glycol dimethacrylate, 2 wt% polyethylene glycol dimethacrylate, 2 wt% Azobisisobutyronitrile and a second solution of 94wt% DEC and TMP mixed solvent, wherein the weight ratio of DEC:TMP is 1:1; heating at 85°C for 30min, heating causes the second solution to polymerize to form a gel; then Inject the first solution that contains LiPF ₆ and EC-EMC-DEC-VC-FEC organic solvent from the first liquid injection port, wherein, LiPF ₆ Concentration is 1mol/L, EC: EMC: DEC: VC: The weight ratio of FEC is 4:2:2.5:0.5:1, after aging, the battery is precharged to complete the formation process, and the lithium-ion battery A5 is obtained.

Example 6

Wind the separator and positive and negative electrode materials (LiCoO ₂ positive electrode/diaphragm/graphite negative electrode) into a battery pole core; paste the bottom of the pole core and the winding end with transparent tape, and reserve the first liquid injection port on the top of the pole core Afterwards, paste transparent tape on the rest of the position; from the second liquid injection port, that is, inject 8wt% diol dimethacrylate, 2wt% azobisiso The second solution of DEC and TBP mixed solvent of butyronitrile and 90wt%, wherein DEC: The weight ratio of TBP is 2:3; Heating 20min at 90 ℃, heating causes the second solution to polymerize and form gel; Then from the first injection The liquid port is injected with the first solution containing LiPF ₆ - LiBOB and EC-EMC-DEC-VC-FEC, wherein the concentration of the mixed lithium salt LiPF ₆ - LiBF ₄ is 1.5mol/L, EC: EMC: DEC: VC: FEC The weight ratio of the battery is 3:2:3.5:0.5:1. After aging, the battery is precharged, and the formation process is completed to obtain the lithium ion battery A5.

Performance Testing

Cycle test: The prepared lithium-ion battery was used to conduct a charge-discharge performance test at 1C current at room temperature. Record the remaining rate of battery capacity after 400 cycles. Among them, the capacity retention rate = (the discharge capacity of the battery after 400 cycles - the discharge capacity of the battery before the cycle) / the discharge capacity of the battery before the cycle. The test results are shown in Table 1.

Table 1

Sample serial number A1 A2 A3 A4 A5 A6 B1 B2 Battery capacity remaining rate after 400 cycles (%) 83% 85% 84% 87% 87% 90% 27% 71.6%

As can be seen from Table 1, the lithium ion battery prepared by the preparation method of Example 1-6 of the present invention has better cycle performance than the lithium ion battery prepared in Comparative Example 1-2, and, due to the implementation of The gel between the casing and the pole core of the lithium-ion battery prepared by the preparation method of Examples 1-6 can absorb the leaked liquid electrolyte, therefore, it has good safety performance at the same time.

It is easy for those skilled in the art to know that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention are all Should be included within the protection scope of the present invention.

Claims (12)

1. A lithium-ion battery, comprising: a housing, a pole core accommodated in the housing, the pole core comprising a positive pole, a negative pole, a diaphragm positioned between the positive pole and the negative pole, characterized in that: liquid state is contained in the pole core Electrolyte, gel is filled between the pole core and the casing. 2. The lithium-ion battery according to claim 1, wherein the pole core is wound by a positive pole, a negative pole, and a diaphragm between the positive pole and the negative pole, and the wound pole core is covered with adhesive tape A sealed space for accommodating liquid electrolyte is formed in the pole core, and a first liquid injection port for injecting liquid electrolyte is left on the pole core. 3. The lithium-ion battery according to claim 2, characterized in that: the first liquid injection port is arranged on the top of the pole core, and the first liquid injection port passes through the adhesive tape; The winding end of the pole core, the bottom of the pole core, and the top of the pole core except for the first liquid injection port. 4. The lithium-ion battery according to claim 2 or 3, characterized in that: the casing is provided with a second liquid injection port for injecting the second solution forming a gel, and the second liquid injection port is far away from the The first liquid injection port. 5 . The lithium ion battery according to claim 1 , wherein the gel is a polymer formed by polymerization of acrylate monomers with one or more unsaturated double bonds. 6. A preparation method of lithium ion battery, characterized in that: said preparation method comprises the steps of: Step 1. Cover the pole core with adhesive tape to form a sealed space in the pole core; Step 2. First inject the liquid electrolyte into the sealed space of the pole core for pre-charge formation, then inject the second solution between the shell and the pole core, heat to initiate a polymerization reaction, and form a gel between the pole core and the shell ; Or first inject the second solution between the shell and the pole core, heat to initiate a polymerization reaction, form a gel between the pole core and the shell, and then inject the liquid electrolyte into the sealed space of the pole core for pre-charge formation. 7 . The method for preparing a lithium-ion battery according to claim 6 , characterized in that: the temperature of the heating-initiated polymerization reaction is 60-100° C., and the time is 10-120 minutes. 8. The preparation method of lithium ion battery according to claim 6, characterized in that: said liquid electrolyte contains lithium salt and a first solvent, the concentration of lithium salt is 0.5-1.5mol/L, wherein said lithium salt One or more selected from lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethanesulfonate, lithium bistrifluoromethylsulfonamide, and lithium bisoxalate borate; A solvent is a linear or cyclic carbonate solvent. 9. The preparation method of lithium-ion battery according to claim 6, characterized in that: the second solution comprises an unsaturated monomer, an initiator and a second solvent, and the unsaturated monomer contains one or more Acrylic ester monomers with unsaturated double bonds, the thermal initiator is selected from one or more of dibenzoyl peroxide, azobisisobutyronitrile, and N-dimethylaniline, and the second The second solvent comprises a carbonate solvent or/and a halogenated carbonate solvent; based on the total weight of the second solution, the content of the unsaturated monomer is 3wt-30wt%, and the content of the initiator is 0.5wt -3wt%, the content of the second solvent is 67wt-96.5wt%. 10. The preparation method of lithium-ion battery according to claim 9, characterized in that: the second solvent also includes an organic phosphide, and the organic phosphide is selected from trimethyl phosphate, triethyl phosphate, and trimethyl phosphate. One or two of butyl ester, triphenyl phosphate, tributyl phosphate, tris(2-chloroethyl) phosphate, dimethyl methyl phosphate, vinyl ethyl phosphate, hexamethylphosphoramide above. 11. The preparation method of lithium-ion battery according to claim 6, characterized in that: the positive pole, the negative pole, the diaphragm between the positive pole and the negative pole are wound to form a pole core, and the wound pole core is covered with adhesive tape A sealed space is formed in the pole core, and a first liquid injection port for injecting liquid electrolyte is reserved on the pole core, and the liquid electrolyte is injected into the pole core through the first liquid injection port. 12. The method for preparing a lithium-ion battery according to claim 11, characterized in that: a second liquid injection port is provided on the casing, the second liquid injection port is far away from the first liquid injection port, and through the The second liquid injection port injects the second solution into the casing.

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