Topic Name: Research Areas Improved Models for Lithium-Battery Performance

Category: Electric Vehicle

Research persons:

Location: Berkeley, United States

Details

Goal: Develop experimental and computational methods for predicting lithium-battery performance If you can't measure something, how can you improve it? That's the question driving efforts to create better models of the way the electrochemical systems associated with thin-film polymer electrolytes used in battery applications behave. Polymer electrolytes have generated interest in recent years for transportation battery applications, but they have some drawbacks that prevent them from being widely implemented. If these concerns could be addressed effectively, these promising electrolytes might find greater use in high-power battery applications. Scope of Work Based at the University of California at Berkeley and Lawrence Berkeley National Laboratory, this project focuses on developing ways to simulate electrochemical processes that are difficult to demonstrate and measure experimentally. One of the simulation efforts involves modeling of the processes of heat generation that occur within batteries using polymer electrolytes. It is important to understand heat generation to (1) avoid overheating and (2) interpret results from calorimetry experiments that are designed to show how energy is absorbed or evolves. But to simulate heat generation effectively, the researchers need to know the behavioral properties of what is being heated. They also need to be able to measure how the chemical reactions for different electrode materials degrade under varying conditions. Another aspect of the research focuses on modeling electrode performance, specifically, alloy electrodes that are being considered as alternatives to carbon or lithium electrodes more typically paired with polymer electrolytes. Results and Future Plans So far, the research team has validated some of its behavioral data for various electrochemical solutions. The researchers next plan to modify their simulation program to test the nonaqueous liquid electrolytes used in lithium cells. In studying the degradation of reaction for the various electrode materials being considered, the researchers have succeeded in developing a simulation model that produces results similar to those measured experimentally for one type of lithium electrode tested. Lithium metal has the highest energy density of any electrode material. But lithium has one critical flaw, which is its tendency to form branch-like growths (dendrities) during charging that can short out a cell. To identify ways of countering this tendency, the researchers have created a preliminary model of the effects of surface energy on dendrite growth, which they will be working to refine. Future efforts will focus on further improving the various models that have been developed so far, and on developing new models that will contribute to the evolution of polymer electrolytes.