(423c) Anode Lithium Plating Detection and Charging Rate Optimization in Lithium-Ion Batteries

Lithium-ion batteries have played a crucial role in enabling the digital revolution. The technology has established itself as a reliable energy storage mechanism over the past decade. But the technology still suffers from problems such as safety issues, extended charging time, and degradation with cycling. One of the major concerns of safety is the lithium plating phenomenon encountered in lithium-ion batteries. Lithium plating is the reduction of lithium ions on the surface of the negative electrode while charging a lithium-ion battery. Lithium plating reaction can eventually lead to dendrite formation and shorting of the battery. The lithium plating phenomenon has been attributed to two major factors viz. increased charging voltage and charging at low temperatures. Charging a battery under these conditions leads to increased concentration of lithium-ions at the negative electrode than what can be intercalated into the electrode. This leads to the ions getting reduced on the surface of the electrode when the potential of the electrode falls below 0V.

In order to understand the degradation of the lithium-ion battery at different temperatures a first-principles based electro-thermal battery model was developed. The model incorporates two different parasitic side reactions viz. lithium plating reaction and the solid electrolyte interphase (SEI) layer formation reaction. These two reactions consume the lithium-ions present in the battery which in turn leads to degradation of the battery. In the first principles-based model the rate constants associated with the desired intercalation reaction as well as the undesired side reactions are coupled with the temperature of the cell. Hence, the model is able to detect changes in desired and undesired reactions at different temperatures. The model is also able to quantify the amount of lithium lost to the above-mentioned side reactions.

Charging rate is a user-controlled parameter which is gaining increased attention because of the requirement to fast charge the battery. However, fast charging by increasing the charging rate or charging voltage can also accelerate the degradation reactions inside the battery thereby reducing the life of the battery. This might also create safety hazards. The temperature of the battery plays a significant role in determining the extent of degradation at different charging rates and charging voltages since the rates of these reactions are dependent on temperature. There is a need to arrive at an optimal condition for charging taking into consideration all the above-mentioned parameters. Towards this end, a statistical optimization approach will be employed to identify optimal charging conditions at different ambient conditions of the battery. The objective of the optimization is to minimize the amount of lithium lost to plating and SEI layer formation. This approach which relies on understanding the degradation of the battery with the operating temperature will help in reducing the degradation of the battery while improving its safety.