Multidimensional Characterizations for All-Solid-State Batteries

All-solid-state batteries (ASSBs) are regarded as one of the future energy storage technologies capable of competing with the state-of-the-art Li-ion batteries. Despite significant development, the room temperature long-cycle performance of lithium metal ASSBs still remains a challenge. The failure of a solid-state Li battery may be linked to two primary causes: interfacial resistance increase and Li dendrite growth. The former may be further attributed to electrolyte decomposition and interfacial void formation (<i>i.e.,</i> loss of physical contact). Electrolyte decomposition happens in two ways: oxidative decomposition at the cathode active material-electrolyte interface and reductive decomposition at the Li (including dendrites)-electrolyte interface. The complex origins of battery failure necessitate multidimensional characterizations using a combination of tools capable of quantifying the void and dendrites, identifying the chemical and mechanical natures of the Li dendrites and electrolyte decomposition products, and<i> </i>monitoring the processes in situ. The tools must also cover a sufficiently large scale, have a spatial resolution of a few nanometers, and be sensitive enough to detect subtle changes in chemical and mechanical properties. These considerations led us to a suite of methods for structural, chemical, and mechanical characterizations that include PFIB-SEM, ToF-SIMS, and nanoindentation-based stiffness mapping. We fabricated solid-state micro-cells with electrochemical performance comparable to their bulk-type cells. Electrochemical tests with temperature control and external pressure monitoring of solid-state cells were demonstrated in an air-free vessel with an integrated in-situ cell test platform. We investigate the function of an interlayer between lithium metal anode and solid electrolyte in preventing lithium dendrite formation and allowing reversible lithium plating and stripping over 1000 cycles. With these in-depth understandings, we will be able to predict and optimize the physical and chemical changes that occur in solid-state Li batteries during operation.<br/><br/>This work was supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Vehicle Technologies Program under Contract DE-EE0008864.