Li-free Cathode Materials for High Energy Density Lithium Batteries

Conversion-type cathode materials, such as transition metal halides, chalcogenides, and oxides, demonstrate high operational voltages and high specific capacities, offering high energy densities for rechargeable lithium-metal batteries. In this review, a series of low-cost, environmentally benign, and high energy density Li-free cathode materials are selected based on thermodynamic calculations. Coupled with Li/C anodes, these cathodes (e.g., S, FeF3, CuF2, FeS2, and MnO2) have the potential to offer energy densities of 1,000–1,600 Wh kg−1 and 1,500–2,200 Wh L−1 at the cell level. Their main challenges, including capacity fading, high voltage hysteresis, large volume change, and parasitic reactions with electrolytes, are discussed. Strategies to circumvent these issues based on the state-of-the-art technologies are summarized. It seems that all of these challenges are able to be solved. We believe that with the development of practical Li-metal-based anodes and solid-state electrolytes, conversion-type cathodes have a promising future for the next-generation high energy density energy storage devices.