High energy density lithium battery systems: from key cathode materials to pouch cell design

The ongoing energy revolution and technological development of energy storage require high-energy-density lithium battery systems beyond 500 Wh kg^-1. However, the commercialized lithium-ion batteries using graphite as the anode with a limited theoretical energy density of about 350 Wh kg^-1 are far from this goal. Promisingly, the lithium metal batteries (LMBs) matched with a variety of cathode materials have great potential to achieve ultra-high-energy-densities in practice. Nevertheless, the energy density of LMBs depends greatly on the energy density of different types of cathodes. Therefore, research on how to improve the output energy density and durability of various cathode materials under practical working conditions is essential for realizing the ultra-high-energy-density LMBs. In this review, we systematically explore the pathway to achieving high-energy and durable LMBs from the perspective of key cathode materials to pouch cell configuration design. We discuss the fundamental characteristics and key challenges of five promising cathode materials, including a lithium cobalt oxide cathode, a high-nickel oxide cathode, a Li-rich oxide cathode, a sulfur cathode, and an oxygen cathode, and also summarize the feasible solutions and recent progress in addressing the key bottlenecks. Furthermore, using pouch cell configurations as a typical pattern, we precisely summarize the impact of each component in pouch cells on energy density and provide detailed routes for acquiring the maximum practical energy density by using different cathode materials in pouch cells. This review offers guidelines for promoting the practical applications of high-energy-density LMBs.