Realizing Multivalent Batteries: Recent Developments and Challenges

Electrical energy storage is a central concern for a society based on fossil-free and sustainable energy sources. The quest is on to find newer and smarter ways to efficiently store higher amounts of energy in comparison to the current state-of-the-art: the Lithium-ion battery. Specifically, the electrification of transportation (and eventual grid-scale storage) requires significant improvement in terms of energy density and costs that are beyond the capabilities of commercial Li-ion batteries.

Intercalation architectures reliant on multivalent (MV) chemistries, such as Mg²⁺, Ca²⁺, Zn²⁺, Al³⁺, etc. are attractive contenders in the development of higher energy density storage systems. Notably, the potential use of a safe and energy-dense metal anode, which results in a significant increase in volumetric capacity (∼3833 mAh/cm³ for Mg in contrast to ∼2046 mAh/cm³ for Li metal) and eventual energy density of the cell, represents a crucial advantage for this technology.

The development of commercial MV batteries, beyond laboratory prototypes, still faces several challenges, requiring rapid advancements ranging from fundamental discoveries to engineering progress.

In terms of fundamental discoveries, we welcome new scientific work in MV systems that would ultimately contribute toward the realization of competitive MV batteries. Topics of interest include but are not limited to:

 i) strategies to mitigate poor diffusion of MV ions and/or demonstration of facile MV mobility in potential cathode materials, protective coatings or MV solid electrolytes;
 ii) discovery of materials that could deliver high voltages comparable to Li-ion technology;
 iii) rationalization of the complex intercalation mechanisms of MV ions in materials at both the experimental and theoretical level;
 iv) development of novel liquid electrolyte chemistries, that are simultaneously compatible with both the cathode and the (metal) anode;
 v) strategies and/or proposed mechanisms to facilitate metal deposition and stripping at the metal anode;
 vi) design of protective materials (i.e. coatings) to facilitate use of facile electrolytes with incompatible electrodes.

In parallel, a number of cell design improvements and engineering advancements are required to build practical MV batteries. As such, we also welcome contributions on the following topics, including but not limited to:

 i) setting rigorous protocols toward data reproducibility and standardization of measurements;
 ii) developing and/or applying novel electrochemical, experimental, and/or theoretical tools suitable for MV chemistries;
 iii) providing definitive proof of MV intercalation via cross-validation using multiple and/or in-situ characterization techniques.