The active material studied with high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy. Source: Nature Communications

A new class of materials has been demonstrated to improve the storage capacity and cycling stability of rechargeable batteries. The stability of high-entropy oxides (HEO) results from a disordered distribution of the elements, making them suitable as conversion materials for reversible lithium storage.

Entropy-stabilized HEO are complex oxides exhibiting a single-phase crystal structure and containing five or more different metal cations in the same amounts. Although typical crystal structures of the elements differ considerably, they form a joint lattice and distribute to the positions in the crystal without any apparent order. This disorder, also known as high entropy, stabilizes the material, probably because it impairs migration of defects in the lattice.

The electrochemical properties of HEO can be customized by varying their compositions. Conversion batteries based on electrochemical material conversion allow for an increase of the stored amount of energy and a reduction in battery weight.

Researchers studied the structure of HEO based on transition metals, revealing that removal of one element only reduces entropy and adversely affects cycling stability. Each individual element influences the electrochemical behavior of the TM-HEO, such that the materials can be tailored to various applications. The result is a modular approach to the systematic development of electrode materials. These materials were used to produce conversion-based electrodes that survived more than 500 charging cycles without any significant degradation of capacity.

Scientists from Germany’s Karlsruhe Institute of Technology and the Indian Institute of Technology Madras contributed to this research, which is published in Nature Communications.