CN117673461A - Solid polymer electrolyte, preparation method thereof, and application in secondary batteries - Google Patents

Abstract

The invention provides a solid polymer electrolyte, a preparation method thereof, and application in secondary batteries. The solid polymer electrolyte includes a polymer matrix with a network structure, an oxidation product of an aromatic diamine, and graphene. Oxidation products of aromatic diamines and graphene fill the network structure. The polymer matrix is a copolymer of vinylene carbonate and polyethylene glycol diacrylate. The polymer matrix composed of the copolymer of vinylene carbonate and polyethylene glycol diacrylate has a network structure, which increases the conduction channel of the solid polymer electrolyte. Combined with the introduction of nitrogen atoms in the oxidation products of aromatic diamines, it can improve Rate performance of secondary batteries. Graphene can not only increase the conductivity of the solid polymer electrolyte and reduce the battery impedance, but filling it in the mesh structure can also give the solid polymer electrolyte a certain mechanical strength, preventing structural damage during the battery cycle and causing secondary batteries. The cycle performance and safety performance are reduced.

Description

Solid polymer electrolyte, preparation method thereof, and application in secondary batteries

Technical field

The present invention relates to the technical field of material preparation, and in particular to a solid polymer electrolyte, a preparation method thereof, and its application in secondary batteries.

Background technique

With the shortage of social energy and the promotion of low-carbon development, new energy vehicles have become one of the future development directions of the automobile industry. The core component of new energy vehicles is the power battery. As a power battery that has developed rapidly in recent years, lithium-ion batteries have the characteristics of large specific energy, no pollution, high working voltage and long cycle life. They have gained popularity in the new energy vehicle industry. extensive attention. However, problems such as slow charging speed and short cruising range of lithium-ion batteries used in automobiles still exist. In order to solve this problem, manufacturers use ternary materials as cathode materials. At present, the electrolyte corresponding to this type of material generally uses liquid electrolyte. In the ternary material system, the electrolyte is prone to violent combustion, which poses serious safety problems.

Based on the demand for lithium-ion batteries with high capacity and high safety performance, the industry has turned its attention to solid-state batteries. By using solid electrolytes instead of liquid electrolytes, it not only improves safety but also increases energy density. However, the current solid electrolyte used in lithium-ion batteries generally has the problem of high battery impedance, and battery-related properties such as internal resistance, rate and other properties are lower than those of liquid electrolyte.

Therefore, there is an urgent need for a new solid electrolyte or its preparation method that can not only meet the needs of high-capacity and high-safety lithium-ion batteries, but also further improve the rate, reduce impedance, etc.

Contents of the invention

The object of the present invention is to provide a solid polymer electrolyte, a preparation method thereof, and its application in secondary batteries. The solid polymer electrolyte has a network structure, has more ion conduction channels, and has high conductivity. Application in secondary batteries can improve the rate performance of secondary batteries and reduce impedance.

In order to achieve the above object, one aspect of the present invention provides a solid polymer electrolyte, including a polymer matrix with a network structure, an oxidation product of an aromatic diamine and graphene, the oxidation product of an aromatic diamine and the graphene. Ethylene is filled in the network structure, and the polymer matrix is a copolymer of vinylene carbonate and polyethylene glycol diacrylate.

In the technical solution adopted by the present invention, the polymer matrix composed of the copolymer of vinylene carbonate and polyethylene glycol diacrylate has a network structure, which increases the conduction channel of the solid polymer electrolyte, and combined with the oxidation of aromatic diamine The introduction of nitrogen atoms in the product can improve the rate performance of secondary batteries. Graphene can not only increase the conductivity of the solid polymer electrolyte and reduce the battery impedance, but filling the network structure can also give the solid polymer electrolyte a certain mechanical strength, preventing structural damage during the battery cycle and causing secondary batteries. The cycle performance and safety performance are reduced. Therefore, the solid polymer electrolyte of the present invention includes a polymer matrix with a network structure, oxidation products of aromatic diamines and graphene, which can not only improve the safety performance of secondary batteries but also further improve rate, cycle and other properties.

As a technical solution of the present invention, the aromatic diamine includes at least one of o-phenylenediamine, m-phenylenediamine and p-phenylenediamine.

As a technical solution of the present invention, the mass ratio of the polymer matrix, the oxidation product of the aromatic diamine and the graphene is 4 to 6:3 to 5:1.

A second aspect of the present invention provides a method for preparing a solid polymer electrolyte, which includes the steps of: mixing vinylene carbonate, aromatic diamine, polyethylene glycol diacrylate and graphene oxide, then adding an initiator at 45 to Polymerize at 60°C for 2 to 12 hours.

In the preparation method of the solid polymer electrolyte of the present invention, vinylene carbonate (VC) is used as a polymerization monomer and polyethylene glycol diacrylate is used as a long-chain cross-linking agent. After the vinylene carbonate is polymerized, it can form Elastic gel state and build a network structure. Using graphene oxide as a raw material to be reduced to produce graphene can avoid the problem of easy agglomeration and poor dispersion of graphene directly as a raw material. Aromatic diamines can not only assist the polymerization of vinylene carbonate to form an elastic gel state and build a porous network structure on a microscopic level, but can also reduce graphene oxide and enable it to participate in the porous network of solid electrolytes. Structure under construction.

As a technical solution of the present invention, the mass ratio of the vinylene carbonate, the aromatic diamine, the polyethylene glycol diacrylate and the graphene oxide is 0.5~2:3~5:3~ 5:0.5～2.

As a technical solution of the present invention, based on the sum of the masses of the vinylene carbonate, the aromatic diamine, the polyethylene glycol diacrylate and the graphene oxide being 100%, the initiator The quality is 0.1~1.0%.

As a technical solution of the present invention, the initiator includes at least one of azobisisobutyronitrile, azobisisoheptanitrile and dimethyl azobisisobutyrate.

A third aspect of the present invention provides a solid polymer electrolyte or the use of a solid polymer electrolyte prepared by the aforementioned solid polymer electrolyte preparation method in a secondary battery.

A fourth aspect of the present invention provides a method for preparing a secondary battery, including the steps:

(1) Preparation of battery core

(2) Electrolyte preparation

After mixing vinylene carbonate, aromatic diamine, polyethylene glycol diacrylate and graphene oxide, an initiator is added to mix to obtain a premix, and the premix and a liquid electrolyte are mixed to obtain an electrolyte;

(3) Pack the battery core in a package, inject the electrolyte, seal, and perform polymerization reaction at 45 to 60°C for 2 to 12 hours after activation, and then conduct formation.

The secondary battery of the present invention uses a mixture of solid polymer electrolyte and liquid electrolyte as the electrolyte, which not only has better safety and higher energy density, but also has better cycle and rate performance of the secondary battery.

As a technical solution of the present invention, the mass ratio of the premix and the liquid electrolyte is 1 to 9:1.

Description of drawings

Figure 1 is an EIS diagram obtained by impedance testing of the semi-solid batteries of Examples 1 to 3 and Comparative Examples 1 to 4.

Detailed ways

The solid polymer electrolyte of the present invention includes a polymer matrix with a network structure, an oxidation product of aromatic diamine and graphene. The oxidation products of aromatic diamines and graphene are filled in the network structure, and the polymer matrix is a copolymer of vinylene carbonate and polyethylene glycol diacrylate. Among them, the aromatic diamine includes at least one of o-phenylenediamine, m-phenylenediamine and p-phenylenediamine. The mass ratio of the polymer matrix, the oxidation product of the aromatic diamine and graphene is 4 to 6:3 to 5:1.

The solid polymer electrolyte of the present invention can be used in all-solid secondary batteries. For all-solid-state secondary batteries, an electrolyte salt and a solid polymer electrolyte can be added and mixed to form an all-solid electrolyte. The electrolyte salt can be, but is not limited to, LiPF ₆ , LiTFSI, LiClO ₄ , LiAsF ₄ , LiBF ₄ , etc. The preparation method of the all-solid-state secondary battery may include the following steps.

(1) Preparation of solid polymer electrolyte

After mixing vinylene carbonate, aromatic diamine, polyethylene glycol diacrylate and graphene oxide, add an initiator and polymerize at 45-60°C for 2-12 hours. Among them, the mass ratio of vinylene carbonate, aromatic diamine, polyethylene glycol diacrylate and graphene oxide is 0.5~2:3~5:3~5:0.5~2. Based on the sum of the mass of vinylene carbonate, aromatic diamine, polyethylene glycol diacrylate and graphene oxide being 100%, the mass of the initiator is 0.1 to 1.0%. The initiator includes at least one of azobisisobutyronitrile, azobisisoheptanitrile and dimethyl azobisisobutyrate.

(2) Preparing battery cells

The positive electrode sheet, all-solid electrolyte (electrolyte salt and solid polymer electrolyte mixed) and negative electrode sheet are stacked and wound in sequence to make a battery core, or the positive electrode sheet, all-solid electrolyte (electrolyte salt and solid polymer electrolyte are mixed) can be made into a battery core. The electrolyte mixture) and the negative electrode sheet are sequentially stacked to form a single stacked body, and then multiple stacked bodies are stacked to obtain an electric core.

(3) Pack the battery core in a package, seal it, and activate it before forming it.

The solid polymer electrolyte of the present invention can also be mixed with a liquid electrolyte as an electrolyte and used in semi-solid secondary batteries.

For semi-solid secondary batteries, a solid polymer electrolyte and a liquid electrolyte are mixed to form a semi-solid secondary battery, and the solid polymer electrolyte is the main component. The mass ratio of solid polymer electrolyte and liquid electrolyte can be 1 to 9:1. Liquid electrolytes usually include electrolyte salts and non-aqueous organic solvents. The electrolyte salt may be, but is not limited to, LiPF ₆ , LiTFSI, LiClO ₄ , LiAsF ₄ , LiBF ₄ , etc. The non-aqueous organic solvent is at least one of chain carbonate, cyclic carbonate and carboxylic acid ester. Further, the non-aqueous organic solvent is selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl propionate, ethyl propionate, ethyl butyrate, and difluoroacetate. At least one of ethyl ester and ethyl 2,2,2-trifluoroacetate.

The preparation method of the semi-solid secondary battery may include the following steps.

A method for preparing a secondary battery, characterized by comprising the steps:

(1) Preparation of battery core

The battery core can be made by laminating and winding the positive electrode sheet, the separator film and the negative electrode sheet in sequence, or stacking the positive electrode sheet, the separator film and the negative electrode sheet in sequence to form a single laminate, and then laminating multiple laminates. Batteries are available.

(2) Electrolyte preparation

After mixing vinylene carbonate, aromatic diamine, polyethylene glycol diacrylate and graphene oxide, an initiator is added to mix to obtain a premix, and the premix and liquid electrolyte are mixed to obtain an electrolyte. Among them, the mass ratio of vinylene carbonate, aromatic diamine, polyethylene glycol diacrylate and graphene oxide is 0.5~2:3~5:3~5:0.5~2. Based on the sum of the mass of vinylene carbonate, aromatic diamine, polyethylene glycol diacrylate and graphene oxide being 100%, the mass of the initiator is 0.1 to 1.0%. The initiator includes at least one of azobisisobutyronitrile, azobisisoheptanitrile and dimethyl azobisisobutyrate.

(3) Pack the battery core in a package, inject the electrolyte and seal it. After activation, perform polymerization reaction at 45-60°C for 2-12 hours, and then carry out the formation.

In order to better explain the purpose, technical solutions and beneficial effects of the present invention, the present invention will be further described below with reference to specific embodiments. It should be noted that the following implementation of the method is a further explanation of the present invention and should not be used as a limitation of the present invention.

Example 1

This embodiment is a solid polymer electrolyte. It includes a polymer matrix with a network structure, an oxidation product of o-phenylenediamine and graphene in a mass ratio of 5:4:1, and the oxidation product of o-phenylenediamine and graphene are filled in the network structure. The polymer matrix is a copolymer of vinylene carbonate and polyethylene glycol diacrylate.

The solid polymer electrolyte is used in a semi-solid secondary battery. The preparation method of the secondary battery includes the following steps.

(1) Preparation of battery core

The battery core can be made by laminating and winding the positive electrode sheet, the separator film and the negative electrode sheet in sequence.

(2) Electrolyte preparation

After mixing vinylene carbonate, o-phenylenediamine, polyethylene glycol diacrylate and graphene oxide with a mass ratio of 1:4:4:1, add azobisisobutyronitrile (accounting for the mass of the first four substances 0.5% of the total) to obtain a premix, and mix the premix and the liquid electrolyte to obtain an electrolyte. The mass ratio of the premix and the liquid electrolyte is 5:1.

(3) Pack the battery core in an aluminum plastic film, inject electrolyte and seal it. After activation, perform polymerization reaction at 50°C for 8 hours, and then proceed to formation.

Example 2

This embodiment is a solid polymer electrolyte. It includes a polymer matrix with a network structure, an oxidation product of m-phenylenediamine and graphene in a mass ratio of 5:4:1, and the oxidation product of m-phenylenediamine and graphene are filled in the network structure. The polymer matrix is a copolymer of vinylene carbonate and polyethylene glycol diacrylate.

The solid polymer electrolyte is used in a semi-solid secondary battery. The preparation method of the secondary battery includes the following steps.

(1) Preparation of battery core

The battery core can be made by laminating and winding the positive electrode sheet, the separator film and the negative electrode sheet in sequence.

(2) Electrolyte preparation

After mixing vinylene carbonate, m-phenylenediamine, polyethylene glycol diacrylate and graphene oxide with a mass ratio of 1:4:4:1, add azobisisobutyronitrile (accounting for the mass of the first four substances 0.5% of the total) to obtain a premix, and mix the premix and the liquid electrolyte to obtain an electrolyte. The mass ratio of the premix and the liquid electrolyte is 5:1.

(3) Pack the battery core in an aluminum plastic film, inject electrolyte and seal it. After activation, perform polymerization reaction at 50°C for 8 hours, and then proceed to formation.

Example 3

This embodiment is a solid polymer electrolyte. It includes a polymer matrix with a network structure, an oxidation product of o-phenylenediamine and graphene in a mass ratio of 6:3:1, and the oxidation product of o-phenylenediamine and graphene are filled in the network structure. The polymer matrix is a copolymer of vinylene carbonate and polyethylene glycol diacrylate.

The solid polymer electrolyte is used in a semi-solid secondary battery. The preparation method of the secondary battery includes the following steps.

(1) Preparation of battery core

The battery core can be made by laminating and winding the positive electrode sheet, the separator film and the negative electrode sheet in sequence.

(2) Electrolyte preparation

After mixing vinylene carbonate, o-phenylenediamine, polyethylene glycol diacrylate and graphene oxide with a mass ratio of 2:3:4:1, add azobisisobutyronitrile (accounting for the mass of the first four substances 0.3% of the total) to obtain a premix, and mix the premix and the liquid electrolyte to obtain an electrolyte. The mass ratio of the premix and the liquid electrolyte is 5:1.

(3) Pack the battery core in an aluminum plastic film, inject electrolyte and seal it. After activation, perform polymerization reaction at 55°C for 7 hours, and then proceed to formation.

Comparative example 1

This comparative example is a solid polymer electrolyte. It includes a polymer matrix with a network structure. The polymer matrix is a copolymer of vinylene carbonate and polyethylene glycol diacrylate.

The solid polymer electrolyte is used in a semi-solid secondary battery. The preparation method of the secondary battery includes the following steps.

(1) Preparation of battery core

The battery core can be made by laminating and winding the positive electrode sheet, isolation film and negative electrode sheet in sequence.

(2) Electrolyte preparation

After mixing vinylene carbonate and polyethylene glycol diacrylate with a mass ratio of 1:4, add azobisisobutyronitrile (accounting for 0.5% of the sum of the mass of vinylene carbonate and polyethylene glycol diacrylate). ) to obtain a premix, and mix the premix and the liquid electrolyte to obtain an electrolyte. The mass ratio of the premix and the liquid electrolyte is 5:1.

(3) Pack the battery core in an aluminum plastic film, inject electrolyte and seal it. After activation, perform polymerization reaction at 50°C for 8 hours, and then proceed to formation.

Comparative example 2

This comparative example is a solid polymer electrolyte. It includes a polymer matrix with a network structure and graphene in a mass ratio of 5:1, and the graphene is filled in the network structure. The polymer matrix is a copolymer of vinylene carbonate and polyethylene glycol diacrylate.

The solid polymer electrolyte is used in a semi-solid secondary battery. The preparation method of the secondary battery includes the following steps.

(1) Preparation of battery core

The battery core can be made by laminating and winding the positive electrode sheet, the separator film and the negative electrode sheet in sequence.

(2) Electrolyte preparation

After mixing vinylene carbonate, polyethylene glycol diacrylate and graphene with a mass ratio of 1:4:1, add azobisisobutyronitrile (accounting for 0.5% of the sum of the mass of the first three substances) and mix to obtain Premix, mix the premix and the liquid electrolyte to obtain an electrolyte, and the mass ratio of the premix and the liquid electrolyte is 5:1.

(3) Pack the battery core in an aluminum plastic film, inject electrolyte and seal it. After activation, perform polymerization reaction at 50°C for 8 hours, and then proceed to formation.

Comparative example 3

This comparative example is a solid polymer electrolyte. It includes a polymer matrix with a network structure and o-phenylenediamine in a mass ratio of 5:4, and the o-phenylenediamine is filled in the network structure. The polymer matrix is a copolymer of vinylene carbonate and polyethylene glycol diacrylate.

The solid polymer electrolyte is used in a semi-solid secondary battery. The preparation method of the secondary battery includes the following steps.

(1) Preparation of battery core

The battery core can be made by laminating and winding the positive electrode sheet, the separator film and the negative electrode sheet in sequence.

(2) Electrolyte preparation

After mixing vinylene carbonate, o-phenylenediamine and polyethylene glycol diacrylate with a mass ratio of 1:4:4, add azobisisobutyronitrile (accounting for 0.5% of the sum of the mass of the first three substances) Mix the premix to obtain an electrolyte, and mix the premix and the liquid electrolyte to obtain an electrolyte. The mass ratio of the premix to the liquid electrolyte is 5:1.

(3) Pack the battery core in an aluminum plastic film, inject electrolyte and seal it. After activation, perform polymerization reaction at 50°C for 8 hours, and then proceed to formation.

Comparative example 4

This embodiment is a solid polymer electrolyte. It includes a polymer matrix with a network structure, o-phenylenediamine and graphene in a mass ratio of 5:4:1, and the o-phenylenediamine and graphene are filled in the network structure. The polymer matrix is a copolymer of vinylene carbonate and polyethylene glycol diacrylate.

The solid polymer electrolyte is used in a semi-solid secondary battery. The preparation method of the secondary battery includes the following steps.

(1) Preparation of battery core

The battery core can be made by laminating and winding the positive electrode sheet, the separator film and the negative electrode sheet in sequence.

(2) Electrolyte preparation

After mixing vinylene carbonate, o-phenylenediamine, polyethylene glycol diacrylate and graphene with a mass ratio of 1:4:4:1, add azobisisobutyronitrile (accounting for the mass of the first four substances). and 0.5%) to obtain a premix, and mix the premix and the liquid electrolyte to obtain an electrolyte. The mass ratio of the premix and the liquid electrolyte is 5:1.

(3) Pack the battery core in an aluminum plastic film, inject electrolyte and seal it. After activation, perform polymerization reaction at 50°C for 8 hours, and then proceed to formation.

The semi-solid secondary batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were subjected to electrochemical performance tests. The test conditions were as follows, and the test results are shown in Table 1.

(1)Normal temperature cycle performance test

Place the semi-solid secondary battery in an environment of 25°C, charge it with a constant current of 1C to 4.2V, then charge it with a constant voltage to a current of 0.05C, and then discharge it with a constant current of 1C to 2.5V. This cycle is recorded. The discharge capacity of the first cycle and the discharge capacity of the last cycle are used to calculate the capacity retention rate of the normal temperature cycle according to the following formula.

Capacity retention rate = discharge capacity of the last cycle/discharge capacity of the first cycle × 100%

(2) High temperature cycle performance test

Place the semi-solid secondary battery in an environment of 45°C, charge it with a constant current of 1C to 4.2V, then charge it with a constant voltage to a current of 0.05C, and then discharge it with a constant current of 1C to 2.5V. This cycle is recorded. The discharge capacity of the first cycle and the discharge capacity of the last cycle are used to calculate the capacity retention rate of the high-temperature cycle according to the following formula.

Capacity retention rate = discharge capacity of the last cycle/discharge capacity of the first cycle × 100%

(3) Rate performance test

Charge the semi-solid secondary battery with a constant current of 0.5C to 4.2V, then charge with a constant voltage to a current of 0.05C, then discharge the battery with a constant current to 2.5V, record the discharge capacity as C0, and then charge the battery with the above method. Charge to 4.2V, then discharge the battery with a current of 3C, and record the discharge capacity as C1.

Capacity retention rate=C1/C0*100%

(4)Impedance test

The rigidized semi-solid secondary battery was discharged until the SOC was 50%, and the battery was placed on the electrochemical workstation for EIS testing. The results are shown in Figure 1.

Table 1 Cycle and rate test results of Examples 1 to 3 and Comparative Examples 1 to 4

It can be seen from the results in Table 1 that the semi-solid secondary batteries of Examples 1 to 3 have better cycle and rate performance. This is because the introduction of nitrogen atoms in the oxidation product of aromatic diamine can improve the rate performance of the secondary battery. Graphene filled in the network structure can give the solid polymer electrolyte a certain mechanical strength and prevent structural damage during battery cycling, so it can improve cycle performance.

Reference documents 1 to 3 lack oxidation products of aromatic diamines or graphene, so the overall performance of the semi-solid secondary battery is poor. Comparative Example 4 directly uses graphene, which is prone to agglomeration during the preparation process, thus leading to deterioration in performance.

Combining the results in Figure 1, it can be seen that the impedance value of the semi-solid secondary batteries of Examples 1 to 3 is low. Comparative Examples 1 and 3 do not contain graphene, so the impedance value is relatively high. In Comparative Example 4, the graphene is agglomerated. It is difficult to exert its conductive effect in a mesh structure, so the improvement in impedance is limited.

Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention and do not limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it is not limited to those listed in the examples. , Those of ordinary skill in the art should understand that the technical solution of the present invention can be modified or equivalently substituted without departing from the essence and scope of the technical solution of the present invention.

Claims (10)

1. A solid polymer electrolyte, characterized in that it includes a polymer matrix with a network structure, an oxidation product of an aromatic diamine and graphene, and the oxidation product of an aromatic diamine and the graphene are filled in the In the network structure, the polymer matrix is a copolymer of vinylene carbonate and polyethylene glycol diacrylate. 2. The solid polymer electrolyte according to claim 1, wherein the aromatic diamine includes at least one of o-phenylenediamine, m-phenylenediamine and p-phenylenediamine. 3. The solid polymer electrolyte according to claim 1, wherein the mass ratio of the polymer matrix, the oxidation product of the aromatic diamine and the graphene is 4 to 6:3 to 5:1. . 4. A method for preparing a solid polymer electrolyte, characterized by comprising the steps of: mixing vinylene carbonate, aromatic diamine, polyethylene glycol diacrylate and graphene oxide, then adding an initiator at 45 to 60 Polymerize at ℃ for 2 to 12 hours. 5. The preparation method of solid polymer electrolyte according to claim 4, characterized in that the vinylene carbonate, the aromatic diamine, the polyethylene glycol diacrylate and the graphene oxide are The mass ratio is 0.5~2:3~5:3~5:0.5~2. 6. The preparation method of solid polymer electrolyte according to claim 4, characterized in that, with the vinylene carbonate, the aromatic diamine, the polyethylene glycol diacrylate and the graphene oxide When the sum of the masses is 100%, the mass of the initiator is 0.1 to 1.0%. 7. The preparation method of solid polymer electrolyte according to claim 4, characterized in that the initiator includes azobisisobutyronitrile, azobisisoheptanitrile and dimethyl azobisisobutyrate. of at least one. 8. Use of the solid polymer electrolyte prepared by the solid polymer electrolyte according to any one of claims 1 to 3 or the solid polymer electrolyte preparation method according to any one of claims 4 to 7 in a secondary battery. application. 9. A method for preparing a secondary battery, characterized in that it includes the steps of: (1) Preparation of battery core (2) Electrolyte preparation After mixing vinylene carbonate, aromatic diamine, polyethylene glycol diacrylate and graphene oxide, an initiator is added to mix to obtain a premix, and the premix and a liquid electrolyte are mixed to obtain an electrolyte; (3) Pack the battery core in a package, inject the electrolyte, seal, and perform polymerization reaction at 45 to 60°C for 2 to 12 hours after activation, and then conduct formation. 10. The method for preparing a secondary battery according to claim 9, wherein the mass ratio of the premix and the liquid electrolyte is 1 to 9:1.