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2024年11月11日星期一

Lithium-ion Full Cell Manufacturing Process Training--Cathode Electrode Materials Section

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Lithium-ion Full Cell Manufacturing Process Training--Cathode Electrode Materials Section

1.Principle of Lithium-ion Batteries

 

Note: EC and DEC are electrolyte solvents.In the diagram, the cathode is lithium cobalt oxide,

and the anode is graphite.

 

With Li+ as the ion conduction medium, the reaction of lithium ion insertion and extraction occurs between the anode and cathode, also known as a "rocking chair battery".

 
  1. 2.

    The Composition of Lithium-ion Battery

     

Materials

2.1.Positive electrode materials refer to materials that can provide a source of lithium ions during the charging process.
For example: lithium compounds LiCoO2, LiNiO2, LiMnO2, LiNiCoMnO2, and LiFePO4.

2.2.Negative electrode materials are materials that provide a receiving site for lithium ions during the charging process.
For example: graphite (synthetic or natural), silicon alloys, tin alloys,etc.

2.3.Electrolyte is a material that provides a conduction medium for lithium ions.For example: organic solutions dissolved with lithium salts such as LiPF6, LiAsF6, etc.

2.4.Separator is a porous material that blocks the conduction of electrons between the positive and negative electrodes while allowing the conduction of ions.For example: PP, PE, non-woven fabric etc.

2.5.The current collector refers to a material carrier that provides a path for material coverage and a bundle of conductors for current.
For examples: copper foil (negative electrode), aluminum foil (for the positive electrode) etc.

2.6.The packaging shell refers to the composite material used to package and protect the battery cell.
Examples: aluminum-plastic film, stainless steel shell, and aluminum shell.

2.7.The conductive agent refers to a material that can enhance the electronic conductivity between active materials and between active materials and the current collector.Examples: conductive carbon black, carbon nanotube,etc.

2.8.The binder refers to a material that enhances the adhesion between materials and between materials and the current collector.
Examples: SBR and PVDF,etc.

2.9.Additives refer to special substances that enhance the safety and stability of the battery.Examples: film-forming additives and flame retardant additives,etc

 

3.Role and Selection Criteria of Cathode Electrode Materials

3.1.Requirements for the Selection of Cathode Electrode Materials

As an ideal cathode electrode material for lithium-ion batteries, lithium-ion insertion compounds must meet the following requirements:

3.1.1.Have a high redox potential to ensure the high voltage characteristics of lithium-ion batteries;

 
 
 
 

3.1.2.Allow a large amount of lithium ions to be inserted and extracted,

ensuring the high capacity characteristics of lithium-ion batteries;

Calculation of theoretical capacity: C0 = 26.8n m/M

Co---- theoretical capacity; n---- number of electrons gained or lost in the redox reaction;
m ----  mass of the active material completely reacting; M----molar mass of the active material
Using LiCoO2 as an example:
Co = 96500/M = 96500*1000/3600*98 = 273 mAh/g
LiNiO2has a capacity of 274 mAh/g;  
LiMn2O4has a capacity of 148 mAh/g;  
LiFePO4 has a capacity of 170 mAh/g.

 

3.1.3.Good reversibility during the insertion and extraction process, with minimal changes in material structure during charging and discharging;

3.1.4.Rapid insertion and extraction of lithium ions, with high electronic and ionic conductivity;

3.1.5.Good chemical stability in the electrolyte;

3.1.6.Low cost, easy to prepare, and environmentally friendly.

 

Currently, there are various cathode materials for lithium-ion batteries that are under extensive research, including LiCoO2, nickel-cobalt binary systems, nickel-cobalt-manganese, manganese compounds, and LiFePO4.

4.Classification of Cathode Materials

 

After process optimization and improvement, the gram capacity of lithium cobalt oxide and ternary materials has been significantly increased.