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

Introduction

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 their promise, thermal batteries are not yet suitable for practical application as they have only been demonstrated with liquid electrolytes. This severely restricts the operational temperature range to ΔT < 50 K and limits the electrochemical stability window to pair with thermodynamically efficient electrodes.

Project Goal

The goal is to develop a completely new paradigm towards all-solid-state thermal batteries (thermal cells). This new approach is based on reversible changes in the materials’ electrochemical properties and H+ transport, operating on recovered waste heat over an unusually wide range of temperatures from ambient to 300°C.

Charging Mechanism

We envision the solid thermal battery to charge at defined low and high constant temperatures due to phase changes and H+ intercalation taking place at the electrodes.

Contributions

Fundamentally, we contribute to a new thermal battery concept by:

1. Suggesting materials to translate the proposed chemistry-at-work.
2. Providing a proof-of-concept to gain initial electrochemical performance insights.
3. Defining thin film device architectures.

Bridging Gaps

Collectively, the proposed solid thermal battery closes the existing gap between thermoelectric and liquid-based thermal batteries. This is achieved by widening the thermal operation window to capture waste heat and defining a new set of H+ solid conductors and interfaces suited for energy storage.

Design Fundamentals

The fundamentals derived on electrochemical interfaces and H+ conductor films, such as:

• Ceria-based materials
• Metal hydrides
• Binary oxides
• Possibly high entropy alloys for electrolytes and electrodes

These contributions are essential for the design and careful discussion of electro-thermo-chemistry, thermodynamics, and kinetics. They inform the engineering design principles of the proposed fully solid thermal batteries for energy harvesting, putting waste heat to work with a perspective for industry translation.