Lithium battery assembly process for heating in-situ solidified electrolyte

文档序号：140374 发布日期：2021-10-22 浏览：7次中文

阅读说明：本技术 一种加热原位固化电解液的锂电池组装工艺 (Lithium battery assembly process for heating in-situ solidified electrolyte ) 是由李明涛田晓录于 2021-06-24 设计创作，主要内容包括：一种加热原位固化电解液的锂电池组装工艺,向电解液中加入聚合物单体和热引发剂,并搅拌均匀,得到可加热固化的电解液；正极片、负极片和隔膜装配在一起,卷绕成芯后得到电芯；将电芯装入壳体内完成顶封、侧封,形成未注液的软包电池；将可加热固化的电解液注入软包电池内,然后密封,加热电解质固化,得到锂电池。本发明中电解液在锂电池封装之后由加热引发原位固化,保证了固态电解质与电极之间的良好接触,能够减少锂枝晶的形成,改善电池寿命。由本发明组装得到的锂离子电池中表现出较好的循环性能以及倍率性能。以NCM523/石墨电池为例,在循环100次后的容量保持率在98％-99.8％,表现出较好的循环稳定性。(A lithium battery assembly process for heating in-situ curing electrolyte is characterized in that a polymer monomer and a thermal initiator are added into the electrolyte and uniformly stirred to obtain the electrolyte capable of being heated and cured; assembling the positive plate, the negative plate and the diaphragm together, and winding into a core to obtain a battery core; the battery core is arranged in the shell to complete top sealing and side sealing, so that a soft package battery without liquid injection is formed; and injecting the electrolyte capable of being cured by heating into the soft package battery, sealing, and heating the electrolyte to cure to obtain the lithium battery. The electrolyte is heated to initiate in-situ solidification after the lithium battery is packaged, so that good contact between the solid electrolyte and the electrode is ensured, the formation of lithium dendrites can be reduced, and the service life of the battery is prolonged. The lithium ion battery assembled by the invention has better cycle performance and rate capability. Taking the NCM 523/graphite battery as an example, the capacity retention rate after 100 cycles is 98-99.8%, and the better cycle stability is shown.)

1. A lithium battery assembly process for heating in-situ solidified electrolyte is characterized by comprising the following steps:

s1, adding a polymer monomer and a thermal initiator into the electrolyte, and uniformly stirring to obtain the electrolyte capable of being cured by heating;

assembling the positive plate, the negative plate and the diaphragm together, and winding into a core to obtain a battery core;

s2, the battery cell is arranged in the shell to complete top sealing and side sealing, and a soft package battery without liquid injection is formed;

and S3, injecting the electrolyte capable of being cured by heating into a soft package battery, sealing, and heating the electrolyte to cure to obtain the lithium battery.

2. A lithium battery assembly process with heating of in-situ solidified electrolyte according to claim 1, the polymer is characterized in that the polymer monomer is one or two of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, dimethylaminoethyl methacrylate, hydroxyethyl methacrylate, polyethylene glycol dimethacrylate, itaconic acid, maleic anhydride, acrylamide glycolic acid methyl ether, 2-methacryloyl ethyl isocyanate, 2- (1-ethyleneimine) ethyl methacrylate, N' -bisacryloyl cystamine, N-methylenebisacrylamide, triallyl isocyanurate and ethylene glycol dimethacrylate.

3. The process of claim 1, wherein the thermal initiator is one of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptonitrile, azobisisobutyronitrile, azobisdicyclohexyl formamide, azobiscyclohexyl carbonitrile, dimethyl azobisisobutyrate, azobisisobutyramidine hydrochloride, azobisisopropylimidazoline hydrochloride, and azobiscyanovaleric acid.

4. The process of claim 1, wherein in step S1, the concentration of the polymer monomer in the electrolyte solution is 10-25% by mass.

5. The process of claim 1 or 4, wherein in step S1, the thermal initiator in the heat-curable electrolyte has a mass concentration of 0.1-0.25%.

6. The process of claim 1, wherein in step S1, the stirring time is 0.5-6 h; the stirring temperature is 25-45 ℃.

7. The process of claim 1, wherein in step S3, the heating temperature is 50-110 ℃ and the heating time is 3-24 h.

8. A lithium battery produced by the assembly process according to any one of claims 1 to 7.

Technical Field

The invention relates to a lithium battery assembly process for heating in-situ solidified electrolyte, and belongs to the field of lithium battery assembly.

Background

With the increasing demand of energy in the current market and the high attention of the current situation on clean energy, the field of lithium ion batteries has become a hot point of research. At present, the most widely used lithium battery electrolyte is an organic liquid electrolyte, but there are many potential safety hazards in the practical application process, mainly because the organic electrolyte components are easy to volatilize and leak under extreme conditions, and are easy to cause safety accidents such as fire and explosion.

Compared with organic electrolyte, the solid electrolyte has the advantages of higher safety, better thermal stability, good machining performance and the like. However, in practical application, the application of the solid electrolyte is still limited due to the complexity of the preparation process and the disadvantage of low ionic conductivity at room temperature. The method for upgrading the commercial liquid electrolyte into the solid electrolyte is a simpler and easier method for improving the safety of the commercial electrolyte, and the solid state upgrading of the electrolyte is realized by adding a small amount of polymer into the commercial electrolyte, so that the raw material cost for preparing the electrolyte is greatly saved. However, the processing steps of diaphragm modification, liquid absorption, ultraviolet light-initiated polymerization, positive and negative electrode modification and the like can not be separated in the conventional method, so that the processing flow of the lithium battery is greatly complicated, and the process cost is increased.

Therefore, a new electrolyte solidification upgrading idea is needed to be provided, and the processing flow of the lithium battery is simplified, so that conditions are provided for the safe popularization of the lithium ion battery.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a lithium battery assembling process for heating in-situ solidified electrolyte. The lithium battery can be assembled by only adding two steps of preparation of the curable electrolyte and heating and curing after the lithium battery is packaged, the process is simple and feasible, the operation is convenient, and the method can be applied to large-scale production.

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

a lithium battery assembly process for heating in-situ solidified electrolyte comprises the following steps:

s1, adding a polymer monomer and a thermal initiator into the electrolyte, and uniformly stirring to obtain the electrolyte capable of being cured by heating;

assembling the positive plate, the negative plate and the diaphragm together, and winding into a core to obtain a battery core;

s2, the battery cell is arranged in the shell to complete top sealing and side sealing, and a soft package battery without liquid injection is formed;

and S3, injecting the electrolyte capable of being cured by heating into a soft package battery, sealing, and heating the electrolyte to cure to obtain the lithium battery.

The invention further improves that the polymer monomer is one or two of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, dimethylaminoethyl methacrylate, hydroxyethyl methacrylate, polyethylene glycol dimethacrylate, itaconic acid, maleic anhydride, methyl acrylamide glycolate, 2-methacryloyloxyethyl isocyanate, 2- (1-ethyleneimine) ethyl methacrylate, N' -bisacryloyl cystamine, N-methylenebisacrylamide, triallyl isocyanurate and ethylene glycol dimethacrylate.

In a further improvement of the present invention, the thermal initiator is one of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptonitrile, azobisisobutyronitrile formamide, azobisdicyclohexylcarbonitrile, dimethyl azobisisobutyrate, azobisisobutyramidine hydrochloride, azobisisopropylimidazoline hydrochloride, and azobiscyanovaleric acid.

In a further development of the invention, in step S1, the concentration by mass of the polymer monomer in the heat-curable electrolyte is 10 to 25%.

In a further development of the invention, in step S1, the thermal initiator is present in the heat-curable electrolyte in a mass concentration of 0.1 to 0.25%.

The invention is further improved in that in the step S1, the stirring time is 0.5-6 h; the stirring temperature is 25-45 ℃.

The invention further improves the method that in the step S3, the heating temperature is 50-110 ℃, and the heating time is 3-24 h.

A lithium battery made according to the assembly process described above.

Compared with the prior art, the invention has the beneficial effects that: on the basis of the mature lithium battery assembly process, the invention only adds two steps of preparation of the curable electrolyte and heating and curing after the lithium battery is packaged, has simple and feasible process and convenient operation, and can be applied to large-scale production. The electrolyte is heated to initiate in-situ solidification after the lithium battery is packaged, so that good contact between the solid electrolyte and the electrode is ensured, the formation of lithium dendrites can be reduced, and the service life of the battery is prolonged. The lithium ion battery assembled by the invention has better cycle performance and rate capability. Taking the NCM 523/graphite battery as an example, the capacity retention rate after 100 cycles is 98-99.8%, and the better cycle stability is shown.

Furthermore, the proportion of the polymer monomer in the prepared curable electrolyte is low, so that the high ionic conductivity of the cured solid electrolyte is ensured.

Furthermore, the polymer formed by heating the electrolyte contains functional groups such as carboxyl, hydroxyl, ester, amide and the like, so that the thermal stability, electrochemical window, hydrophilicity, ionic conductivity and other characteristics of the electrolyte can be improved, and the electrolyte is matched with a high-voltage positive electrode material, namely ternary NCM811, lithium cobaltate and lithium nickel manganese oxide, so that the energy density of the battery is improved.

Drawings

Fig. 1 is a graph showing discharge capacity and coulombic efficiency of a lithium battery prepared according to example 1 of the present invention.

Fig. 2 is a graph showing the discharge capacity and the coulombic efficiency of the lithium battery prepared in example 2 according to the present invention.

Fig. 3 is a graph showing the discharge capacity and coulombic efficiency of a lithium battery prepared according to example 3 of the present invention.

Detailed Description

The invention is further described in the following description with reference to the figures and specific preferred embodiments, but without thereby limiting the scope of protection of the invention. The examples are preferred in the experimental process and are only used for more complete illustration of the present invention, but are not to be construed as limiting the scope of the present invention.

The instruments and drug materials used in the present invention are commercially available.

First, the electrolyte solution of the present invention which can be cured by heating will be described.

In the present invention, an electrolyte is provided which can be cured by heating, the electrolyte comprising: commercial electrolyte, polymer monomer and initiator.

The conductive lithium salt in the commercial electrolyte is lithium hexafluorophosphate (LiPF)₆) Lithium perchlorate (LiCiO)₄) Lithium tetrafluoroborate (LiBF)₄) And lithium trifluoromethanesulfonate (LiFSI), wherein the solvent is one or more of Ethylene Carbonate (EC), Propylene Carbonate (PC), dimethyl carbonate (DEC), diethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC).

Preferably, the concentration of the conductive lithium salt in the electrolyte is 1 mol/L. The solute in the commercial electrolyte is conductive lithium salt LiPF₆The solvent is ethylene carbonate, dimethyl carbonate and diethyl carbonate (volume ratio is 1:1: 1).

The polymer monomer is one or two of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, dimethylaminoethyl methacrylate, hydroxyethyl methacrylate, polyethylene glycol dimethacrylate, itaconic acid, maleic anhydride, acrylamide glycolic acid methyl ether, 2-methacryloyl isocyanate oxyethyl ester, 2- (1-ethyleneimine) ethyl methacrylate, N' -bisacrylamide, N-methylenebisacrylamide, triallyl isocyanurate and ethylene glycol dimethacrylate.

The thermal initiator is one of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptonitrile, azobisisobutyronitrile formamide, azobiscyclohexylcarbonitrile, dimethyl azobisisobutyrate, azobisisobutyramidine hydrochloride, azobisisopropylimidazoline hydrochloride and azobiscyanovaleric acid.

Next, a lithium battery assembly process based on a curable electrolyte is described.

The invention provides a lithium battery assembly process for heating in-situ solidified electrolyte, which specifically comprises the following steps:

s1, preparing electrolyte: adding a polymer monomer and a thermal initiator into the electrolyte, and uniformly stirring to obtain a heat-curable electrolyte;

the total concentration of the modifier monomer in the mixed solution is 10-25 wt%, and the concentration of the thermal initiator in the mixed solution is 0.1-0.25 wt%.

The mixed solution containing the polymer monomer and the thermal initiator is stirred for sufficient mixing. The stirring method is not particularly required, and may be selected according to the actual conditions. For example, in embodiments of the present invention, mechanical agitation is used. The stirring time and temperature are not particularly required, and in the embodiment of the present invention, the preferable stirring time is 0.5 to 6 hours; stirring is carried out at 25-45 ℃.

S2, preparing a battery cell: assembling the positive and negative pole pieces and the diaphragm together, and winding the positive and negative pole pieces and the diaphragm into a core to obtain a battery core;

the positive plate comprises a positive current collector, a positive active material coated on the positive current collector, a positive conductive agent and a binder. The positive current collector can be selected from aluminum foil, nickel foil, carbon foil or stainless steel sheet; the positive electrode active material may be selected according to the actual LiCoO₂、LiFePO₄、NCM523、NCM811、LiNi_0.5Mn_1.5O₄And the like cathode materials; the positive electrode conductive agent can be acetylene black, graphite, Super P or conductive fiber according to actual selection.

The anode material to be applied according to the present invention may be selected according to the actual. For example, the anode is a lithium metal-based anode material or a carbon-based anode material.

S3, assembling the soft package battery: the battery core is arranged in the shell to complete top sealing and side sealing, so that a soft package battery without liquid injection is formed;

s4, liquid injection and solidification: and injecting the electrolyte into the soft package battery, sealing, and heating the lithium battery at a certain temperature to solidify the electrolyte in the lithium battery to obtain the solid-state upgraded lithium battery.

The heating temperature has no special requirement and can be adjusted according to the actual requirement. For example, in embodiments of the present invention, the heating temperature is 50-110 ℃.

The heating time has no special requirements and can be adjusted according to actual requirements. For example, in the examples of the present invention, the heating time is 3 to 24 hours.

The present invention will be described in more detail with reference to examples.

Example 1

A lithium battery assembly process for heating in-situ solidified electrolyte comprises the following steps:

firstly, dissolving polymer monomers of methyl methacrylate, polyethylene glycol dimethacrylate and thermal initiator of azodiisoheptonitrile into electrolyte respectively in mass fractions of 5 wt%, 10 wt% and 0.15 wt%, wherein the electrolyte is 1mol/L LiPF₆Ethylene Carbonate (EC)/diethyl carbonate (DEC)/dimethyl carbonate (DMC) (volume ratio 1:1: 1). Mechanically stirred at 25 ℃ for 1h to obtain the electrolyte with thermocuring capability.

Mixing NCM523, Super P, PVDF (polyvinylidene fluoride) and NMP in a mass ratio of 8:1:1 to obtain positive slurry, and coating the positive slurry on an aluminum foil; the negative electrode slurry was obtained by mixing graphite, Super P, PVDF, 8:1:1 in NMP in a mass ratio, and the slurry was coated on a copper foil. Drying, rolling and cutting to obtain the positive and negative pole pieces.

And then, placing the diaphragm between the positive and negative pole pieces according to a conventional lithium battery assembly process, welding the lugs, and winding into a core to obtain the battery core.