CN110890516A

CN110890516A - Method for prefabricating SEI film of lithium ion battery

Info

Publication number: CN110890516A
Application number: CN201811046427.XA
Authority: CN
Inventors: 李义; 李国敏; 李露; 黄小; 王敏
Original assignee: Jiangxi Greende Energy Co Ltd
Current assignee: Jiangxi Greende Energy Co Ltd
Priority date: 2018-09-08
Filing date: 2018-09-08
Publication date: 2020-03-17

Abstract

A method for prefabricating SEI film of lithium ion battery includes adding organic film forming additive with conductivity, inorganic film forming additive and diluent into negative electrode slurry of lithium ion battery while stirring, uniformly stirring the slurry, coating and drying, coating organic and inorganic film forming additives on the surface of material to automatically form a layer of SEI film, rolling and cutting pole piece according to normal process to obtain lithium ion battery. The consumption of lithium and electrolyte of the anode of the lithium ion battery can be reduced by prefabricating the SEI film, the capacity and the service life of the battery are greatly improved, and the safety and the reliability of the battery are improved.

Description

Method for prefabricating SEI film of lithium ion battery

Technical Field

The invention belongs to the technical field of lithium ion battery manufacturing, and particularly relates to a method for prefabricating an SEI film of a lithium ion battery.

Background

In the first charge-discharge process of the lithium ion battery, the electrode material and the electrolyte react on a solid-liquid interface to form a passivation layer covering the surface of the electrode material. The formed passivation film can effectively prevent solvent molecules from passing through, but Li < + > can be freely inserted into and taken out of the passivation film through the passivation film, and the passivation film has the characteristics of a Solid electrolyte, so the passivation film is called a Solid electrolyte interface film (SEI film) for short.

The SEI film has organic solvent insolubility, can exist stably in an organic electrolyte solution, and organic solvent molecules can not pass through the passivation film, so that the co-intercalation of the organic solvent molecules is effectively prevented, the damage of the co-intercalation of the organic solvent to a battery material is avoided, the cycle performance and the service life of an electrode are greatly improved, and the safety performance, the cycle performance and the like of the battery are improved.

However, the SEI film consumes a large amount of lithium ions during the formation process, so that the first charge-discharge irreversible capacity is increased, and the charge-discharge efficiency of the electrode material is reduced. During the circulation process, the SEI film continuously increases, consumes the electrolyte and causes the accelerated capacity decay. The SEI film increases the lithium ion transmission impedance of the interface and reduces the kinetics of the whole system. Moreover, the formation of the SEI film generates a large amount of gas, and in the case of a battery such as a closed-cell battery, a large pressure is applied to the inside of the battery when the battery is not used, which may cause a safety hazard.

Then, if the SEI film can be preformed, it is possible to reduce consumption of lithium ions and improve the capacity of the battery. The first efficiency of most batteries is between 80% and 90%, and if an SEI film can be prefabricated, the capacity of the battery can be improved by 20% at most, and the capacity space is considerable.

Disclosure of Invention

The invention provides a method for prefabricating an SEI film of a lithium ion battery. Conductive organic polymers such as poly (3, 4-ethylenedioxythiophene) -styrene sulfonic acid, polypyrrole and doped polyaniline (PAn-SSA, PAn-SA, PAn-ASA, PANI and the like) are coated on the surface of the battery electrode material, so that organic solvents in electrolyte can be effectively prevented from invading into the negative electrode material and causing side reaction with metal lithium. In addition, the main film components of the conventional lithium ion battery SEI are lithium fluoride, lithium carbonate, lithium hydroxide, and a part of organic compounds. Lithium fluoride, lithium carbonate, lithium hydroxide and the like can be completely doped when the battery is mixed and stirred, and after the pole piece is dried, the compounds are deposited on the surface of the electrode material to form an SEI-like film. Therefore, the method for prefabricating the SEI mainly comprises the steps of adding an organic film-forming additive with conductive performance and the like when battery materials are mixed and stirred, uniformly stirring the materials, coating and drying the materials, and coating the organic film-forming additive and the inorganic film-forming additive on the surfaces of the materials to automatically form a layer of SEI film.

The technical scheme of the invention is as follows:

a method for prefabricating SEI film of lithium ion battery includes adding organic film forming additive with conductivity, inorganic film forming additive and diluent into negative electrode slurry of lithium ion battery while stirring, uniformly stirring the slurry, coating and drying, coating organic and inorganic film forming additives on the surface of material to automatically form a layer of SEI film, rolling and cutting pole piece according to normal process to obtain lithium ion battery.

The organic film-forming additive is one or more of poly (3, 4-ethylenedioxythiophene) -polystyrene sulfonic acid, polypyrrole and doped polyaniline (PAn-SSA, PAn-SA, PAn-ASA, PANI and the like).

The inorganic film-forming additive is one or more of lithium carbonate, lithium fluoride and lithium hydroxide.

The diluent is N-methyl pyrrolidone (NMP), Dimethylformamide (DMF) and water.

The method comprises the steps of weighing a negative active substance, a conductive additive, an adhesive, an organic film forming additive or an inorganic film forming additive according to a proportion, adding the negative active substance, the conductive additive, the adhesive, the organic film forming additive or the inorganic film forming additive into a stirring kettle, stirring for a period of time, adding one diluent of NMP, DMF or water, stirring for a period of time, coating, automatically forming a layer of SEI film on the surface of a negative material after drying a pole piece, and finally rolling, cutting, winding, welding, packaging, baking, injecting liquid, forming, grading and the like the pole piece to prepare the lithium ion battery.

The invention has the advantages that the consumption of the lithium and the electrolyte of the anode of the lithium ion battery can be reduced by prefabricating the SEI film, the capacity and the service life of the battery are greatly improved, and the safety and the reliability of the battery are improved.

Detailed Description

The following description is intended as an additional illustration of the invention and not as a limitation thereof.

Example 1:

prefabricated SEI film of 50Ah flexible package ternary battery

100 kg of artificial graphite is taken and added into a stirring cylinder, 2 kg of conductive agent is added, and then 0.5 kg of lithium fluoride, 1.5 kg of lithium carbonate, 0.5 kg of lithium hydroxide and 1.0 kg of CMC are added and stirred for 30 minutes. Then 100 kg of 3% aqueous poly (3, 4-ethylenedioxythiophene) -styrenesulfonic acid solution, 2 kg of SBR solution, 25 g of deionized water were added. Then, the mixture was stirred slowly for 30 minutes and then stirred at a high speed for 5 hours. Taking the ternary material, the conductive agent, the adhesive, the diluent and the like, and stirring into slurry. Then, slurry is discharged, coating, rolling, cutting, welding, shell punching, packaging, baking, liquid injection, immersion, formation and the like to manufacture the lithium ion battery with the prefabricated SEI film.

Example 2:

prefabricated SEI film of 5Ah 21700 ternary battery

20 kg of silicon-carbon composite is taken and added into a stirring cylinder, 0.4 kg of conductive agent is added, and then 0.1 kg of lithium fluoride, 0.3 kg of lithium carbonate, 0.1 kg of lithium hydroxide, 0.2 kg of PVDF and 0.6 kg of polypyrrole are added and stirred for 30 minutes. Then 20 kg of NMP were added. Then, the mixture was stirred slowly for 30 minutes and then stirred at a high speed for 5 hours. Taking the ternary material, the conductive agent, the adhesive, the diluent and the like, and stirring into slurry. Then, producing the lithium ion battery with the prefabricated SEI film by slurry discharging, coating, rolling, cutting, welding, entering a shell, rolling a groove, baking, injecting liquid, sealing, dipping, forming and the like.

Example 3:

prefabricated SEI film of 10Ah square aluminum shell lithium iron battery

60 kg of artificial graphite is taken and added into a stirring cylinder, 1.2 kg of conductive agent is added, and then 0.3 kg of lithium fluoride, 0.9 kg of lithium titanate, 0.3 kg of lithium hydroxide, 0.6 kg of PVDF and 1.8 kg of polypyrrole are added and stirred for 30 minutes. Then 60 kg of NMP were added. Then, the mixture was stirred slowly for 30 minutes and then stirred at a high speed for 5 hours. Taking a lithium iron material, a conductive agent, an adhesive, a diluent and the like, and stirring into slurry. Then, producing slurry, coating, rolling, cutting, welding, entering a shell, welding a cover cap, baking, injecting liquid, sealing, dipping, forming and the like to manufacture the lithium ion battery with the prefabricated SEI film.

Claims

1. A method for prefabricating SEI film of lithium ion battery is characterized in that organic film forming additive, inorganic film forming additive and diluent with conductive performance are added when negative electrode slurry of the lithium ion battery is stirred, the slurry is uniformly stirred and then coated and dried, the organic film forming additive and the inorganic film forming additive are coated on the surface of the material to automatically form a layer of SEI film, and then the SEI film is rolled and cut according to normal process to manufacture the lithium ion battery by pole pieces.

2. The method for prefabricating the SEI film of the lithium ion battery as set forth in claim 1, wherein the organic film-forming additive is one or more of poly (3, 4-ethylenedioxythiophene) -polystyrene sulfonic acid, polypyrrole, doped polyaniline (PAn-SSA, PAn-SA, PAn-ASA, PANI, etc.).

3. The method for prefabricating the SEI film of the lithium ion battery as set forth in claim 1, wherein the inorganic film-forming additive is one or more of lithium carbonate, lithium fluoride and lithium hydroxide.

4. The method for prefabricating the SEI film of the lithium ion battery as set forth in claim 1, wherein the diluent is N-methyl pyrrolidone (NMP), Dimethylformamide (DMF), water.

5. The method for prefabricating the SEI film of the lithium ion battery according to claim 1, wherein the prefabrication process of the SEI film comprises the steps of weighing a negative electrode active material, a conductive additive, an adhesive, an organic film forming additive or an inorganic film forming additive according to a proportion, adding the negative electrode active material, the conductive additive, the adhesive, the organic film forming additive or the inorganic film forming additive into a stirring kettle, stirring for a period of time, adding one diluent of NMP, DMF or water, stirring for a period of time, coating, automatically forming a layer of SEI film on the surface of a negative electrode material after the electrode piece is dried, and finally rolling, cutting, winding, welding, packaging, baking, injecting liquid, forming, grading and the like to.