The next frontier in Li-ion batteries: Intergrown cathodes?

Cathode materials have been playing an important role in the development of high-energy, safe and low-cost lithium-ion batteries. However, the widely used single-phase cathode materials are facing great challenges in solving the mileage and safety problems related to electric vehicles due to their inherent structural defects. Intergrown design of bulk structure is believed to be one of the most fundamental ways to improve structural stability and capacity for cathode materials. Due to the diversity of structural configurations, the systematic understanding is still lack for the intergrown structures of different combinations. Therefore, it is very desirable, but also of great importance to summarize the current progress and challenges for intergrown cathodes. In this review, we comprehensively reviewed the design and synthesis methods of intergrown cathodes including layered-spinel intergrown structures, layered-rocksalt intergrown structures, and spinel-rocksalt intergrown structured cathode materials. The charge compensation mechanism of intergrown cathodes with different structural configurations was analyzed in depth, and a targeted optimization schematic diagram was also proposed. Finally, combined with advanced characterization techniques, the understanding of the structural changes has been deepened for the intergrown cathodes during the electrochemical process. It is hoped this review should shed light on the development of advanced cathode materials for the next-generation Li-ion batteries.