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 operation 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 an all-solid-state thermal battery (thermal cell), which is based on reversible changes in the materials’ electrochemical properties and on H+ transport operating on recovered waste heat over an unusually wide range of temperatures from ambient to 300°C.

Concept Overview

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 first electrochemical performance insights.
3. Defining thin film device architectures.

Collectively, the proposed solid thermal battery closes the existing gap between thermoelectric and liquid-based thermal batteries 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 Principles

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 to their design.

This careful discussion of electro-thermo-chemistry, thermodynamics, and kinetics informs 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.