No abstract

As a high‐capacity layered cathode material, Li[Ni0.8Co0.1Mn0.1]O2 (NCM811) has been one of the most felicitous candidates for utilization in the next generation of high‐energy lithium ion batteries (LIBs). Notwithstanding its superiority, there are some issues concerning its cyclability, rate capability, and thermal stability that need to be settled prior to its further practical application. It is believed that upon cycling, chemical, mechanical, and electrochemical stability of the cathode–electrolyte interface plays a key role in resolving these issues. Therefore, all the extensive efforts directed so far toward the optimization of NCM811 electrochemical performance are by some means in connection with the cathode–electrolyte interface. Herein, unique structural and electrochemical characteristics of NCM811 together with in‐depth understanding of its underlying bulk/surface degradation mechanism through cycling are reviewed. More importantly, for the first time, all compatible approaches thus far adopted to perfect the performance of NCM811 are exclusively and scrupulously addressed. Lastly, the most reasonable resolutions to accomplish a robust cathode–electrolyte interface, and consequently impeccable NCM811, along with proposed future research directions are presented.

Heterostructure construction is an efficient method for reinforcing K+ storage of transition metal selenides. The spontaneously developed internal electric fields give a strong boost to charge transport and significantly reduce the activation energy. Nevertheless, perfection of the interfacial region based on the energy level gradient and lattice matching degree is still a great challenge. Herein, rich vacancies and ultrafine CoSe2–FeSe2 heterojunctions with semicoherent phase boundary are simultaneously obtained, which possess unique electronic structures and abundant active sites. When employed as anodes for potassium‐ion batteries (PIBs), CoSe2–FeSe2@C composites display a reversible potassium storage of 401.1 mAh g−1 at 100 mA g−1 and even 275 mAh g−1 at 2 A g−1. Theoretical calculation also reveals that the potassium‐ion diffusion can be dramatically promoted by the controllable CoSe2–FeSe2 heterojunction.