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|Design and testing of a reusable high temperature compatible electrochemical cell|
|Keywords: lithium, battery, electrochemistry|
|There is significant interest in improved high-temperature compatible energy storage. Desired attributes include a wider operating temperature range, higher power capability, and even the ability to recharge. There are many prospective electrochemical energy storage systems to consider. Researchers need to be able to test materials on a small scale in a laboratory environment before scale up, development, and deployment can occur. Lithium-ion electrode and electrolyte materials research is typically performed using coin cells (which are very similar to wristwatch batteries). Coin cells consist of a stack of components including a test electrode, a separator soaked in electrolyte, and a reference electrode in a hermetically sealed can. Cell sealing is achieved using a deformable, electrically insulating gasket. Coin cells are designed for room temperature lithium- and lithium-ion development, not high temperature applications, as the separator, gasket, and many electrolytes fail below 100 °C. A simple, accurate, and low cost high temperature compatible design is needed. Cell sealing is a significant challenge, as welding and the glass-to-metal seals used in full size (manufactured) cells are not feasible for most labs. High temperature compatible plastics (e.g. polytetrafluoroethylene, polyphenylsulfone) can be used up to ~250 °C, provided they do not contact the electrolyte and allow for electrical isolation, but may be too stiff at room temperature or too compliant at high temperature to maintain a consistent seal. Electrolyte salts and solvents common in lithium-ion cells cannot withstand high temperature exposure – LiPF6 degrades at 190 °C, and many standard solvents boil below 150 °C. High(er) temperature compatible electrolyte components like propylene carbonate (boiling point 240 °C) are also known to degrade graphite-based electrodes. We have designed and built a system for high temperature compatible energy storage research. Each test cell is operated in a separate temperature-controlled chamber; chamber and cell temperature can be maintained at 30 – 200+°C within 0.5 °C for weeks on end. We will present results from our reusable cell design using a variety of test electrodes and electrolytes at a wide range of temperatures.|
|Michael D. Fleischauer,
National Institute for Nanotechnology