Alloying -Type Anode Materials for Dual -Ion Batteries: An Inceptive Review

Abstract

Dual-ion batteries are an interesting class of high voltage batteries that incorporate an anion-intercalating cathode, usually graphite. The anodes in these cells operate via an electrochemical reaction of a metal cation with an appropriate anode material. Traditionally, dual-ion cells were based on graphitic anodes that intercalate lithium ions. However, recent developments in this field include an expansion of available anode chemistries from lithium (Li) cations only to other cations, such as sodium (Na) and potassium (K), and trials of high capacity anode candidates that can alloy with alkali metals. This field is emerging and needs an appropriate critical review. In this inceptive review, we analyse various anode materials capable of electrochemical alloying with Li, Na or K in the context of dual-ion battery cells. Starting from an overview of alloying reaction mechanisms in candidate materials (Al, Sn, Si, P, etc.), we progress to the discussion of anode material fabrication methods, the differences observable in cells with different cation chemistries, the nature of suitable electrolytes and appropriate cell designs for both more insightful experiments and performance optimisation. Finally, we identify gaps in the field and suggest possible areas to explore. We also comment on the energy density considerations when accessing the performance metrics of dual-ion batteries with alloying anodes. This inceptive review will stimulate the development of dual-ion battery anode materials and will assist the community of material scientists, chemists and electrochemical engineers working in the field.