How to Improve the Initial Coulombic Efficiency of Lithium-ion Batteries?

Improving the initial coulombic efficiency of lithium-ion batteries is a complex and important topic, which is directly related to the energy utilization and overall performance of the battery. The following is an in-depth analysis of the factors affecting the first coulombic efficiency of lithium-ion batteries from multiple perspectives, and proposes corresponding solutions.

1.Factors affecting the first coulombic efficiency of lithium-ion batteries

（1）Anode material characteristics

①Specific surface area: The larger the specific surface area ofthe graphite anode electrode, the more lithium ions are required to form the solid electrolyte interface film (SEI film), thereby reducing the first coulombic efficiency.

②Material type: Although silicon-based anode electrode materials have high lithium storage capacity, their large volume changes can easily lead to SEI film instability, further reducing the first coulombic efficiency.

（2）Electrolyte composition

①Solvent type: The type of solvent in the electrolyte has a significant effect on the formation and stability of the SEI film. For example, an electrolyte with a high content of ethylene carbonate (EC) is conducive to the formation of a stable SEI film, but too high or too low a content may lead to a decrease in the first coulombic efficiency.

②Additives: Film-forming additives in the electrolyte, such as vinylene carbonate (VC), can promote the formation of the SEI film and improve its stability, thereby improving the first coulombic efficiency.

（3）Formation

①Charging voltage and current: The voltage and current settings during formation charging directly affect the formation quality and thickness of the SEI film. Excessive voltage and current may cause the SEI film to be too thick and uneven, thereby increasing the consumption of lithium ions and reducing the first coulombic efficiency.

②Formation capacity: The formation charge capacity is an important factor affecting the SEI film formation effect. The appropriate formation capacity can ensure the formation quality of the SEI film while avoiding excessive lithium ion consumption.

（4）Battery Manufacturing Process

①Coating and calendering: The coating thickness and compaction density of the cathode and anode have an important influence on the transport of lithium ions and the formation of the SEI film. Uneven coating and excessive compaction density may lead to a decrease in the first coulombic efficiency.

②Winding and assembly: Factors such as tension control and alignment during winding，cleanliness during assembly may affect the internal structure and performance of the battery, thereby affecting the first coulombic efficiency.

2. Ways to improve the first coulombic efficiency of lithium-ion batteries

（1）Optimize anode materials

①Reduce specific surface area: By optimizing the particle morphology and particle size distribution of the anode electrode material, its specific surface area can be reduced, thereby reducing the amount of lithium ions required for SEI film formation.

②Adding stabilizers: Introducing stabilizers such as carbon coating into the anode electrode material to improve its structural stability and the stability of the SEI film.

（2）Adjusting the electrolyte formulation

①Optimize solvent ratio: Adjust the ratio of each solvent in the electrolyte according to the characteristics of the anode electrode material to form a stable and dense SEI film.

②Adding film-forming additives: Add an appropriate amount of film-forming additives such as VC to the electrolyte to promote the formation of SEI film and improve its stability.

（3）Optimize the formation

①Precise control of voltage and current: Precisely control the voltage and current settings during formation charging according to the characteristics of the anode electrode material and battery design requirements.

②Optimize formation capacity: Determine the optimal formation charge capacity range through experiments to ensure the quality of SEI film formation and avoid excessive lithium ion consumption.

（4）Improving battery manufacturing processes

①Improve coating and compaction accuracy: Use advanced coating and calendering equipment and technology to improve the uniformity of coating thickness and compaction density of positive and anode electrodes.

②Strengthen cleanliness and quality control: Strengthen cleanliness control and quality inspection during the battery manufacturing process to ensure the integrity of the battery's internal structure and performance stability.

（5）Using pre-lithiation technology

Anode electrode pre-lithiation: A lithium layer is pre-deposited on the anode electrode surface through pre-lithiation technology to compensate for the lithium ions consumed when the SEI film is formed, thereby improving the first coulombic efficiency. Common pre-lithiation methods include early formation of the anode electrode and spraying lithium powder on the anode electrode.

3. Conclusion

Improving the first coulombic efficiency of lithium-ion batteries requires multiple approaches. Comprehensively consider factors such as anode material properties, electrolyte composition, formation and charging system, and battery manufacturing process. By optimizing these factors and adopting advanced pre-lithiation technology, the first coulombic efficiency of lithium-ion batteries can be effectively improved and their overall performance can be enhanced. It should be noted that the strategies for improving the first coulombic efficiency may be different under different material and process conditions, so experiments and optimization need to be carried out according to specific circumstances.