All in One: Harvesting of waste heat with solid thermal battery

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Thermal batteries are devices that convert thermal energy without the need for a spatial temperature gradient, giving them an enormous potential advantage over competing methods. Despite its promise, thermal batteries are yet not suitable for practical application as they were demonstrated only with liquid electrolytes, which severely restricts the operation temperature range to ΔT<50 K and an electrochemical stability window to pair with thermodynamically efficient electrodes. The goal is to develop a completely new paradigm towards all-solid-state thermal battery (thermal cell), which is based on reversible changes of the materials’ electrochemical properties and on H+ transport operating on recovered waste heat over an unusual wide range of temperatures of ambient to 300°C. We envision the solid thermal battery to charge at a defined low and high constant temperature due to phase changes and H+ intercalation taking place at the electrodes. Fundamentally, we contribute to a new thermal battery concept, suggest materials to translate the proposed chemistry-at-work and give a proof-of-concept to gain first electrochemical performance insights defining thin film device architectures. Collectively, the here proposed solid thermal battery closes the ever-existing gap between thermoelectric and liquid based thermal batteries through widening of the thermal operation window to capture waste heat and defining a new set of H+ solid conductors and interfaces suited for energy storage. The fundamentals derived on electrochemical interfaces and H+ conductor films such as ceria-based, metal hydride, binary oxide and possibly high entropy alloys for electrolytes and electrodes contribute in their design and careful discussion of electro-thermo-chemistry, thermodynamics and kinetics to engineering design principles of the here proposed fully solid thermal batteries for energy harvesting putting waste heat to work with perspective for industry translation.