Garnet-structured solid electrolytes have been extensively studied for a solid-state lithium rechargeable battery. Previous works have been mostly focused on the materials' development and basic electrochemical properties but not the cathode/electrolyte interface. Understanding the cathode interface is critical to enhance chemical stability and electrochemical performance of a solid-state battery cell. In this work, we studied thoroughly the cathode/electrolyte interface between LiCoO 2 and Li 7 La 3 Zr 2 O 12 (LLZO). It was found that the high-temperature process to fuse LiCoO 2 and LLZO induced cross-diffusion of elements and formation of the tetragonal LLZO phase at the interface. These degradations affected electrochemical performance, especially the initial Coulombic efficiency and cycle life. In a clean cathode interface without the thermal process, an irreversible electrochemical decomposition at > ∼ 3.0 V vs Li + /Li was identified. The decomposition was able to be avoided by a surface modification of LLZO (e.g., Co-diffused surface layer and/or presence of an interlayer, Li 3 BO 3 ), and the surface modification was equally important to suppress a reaction during air storage. In a LiCoO 2 / LLZO interface, it is important to separate direct contacts between LiCoO 2 and pure LLZO.

A comprehensive review of the recent development of electrospun nanofibers as platform materials for advanced secondary batteries is presented.

To achieve a high reversibility and long cycle life for lithium-oxygen (Li-O) batteries, the irreversible formation of LiO, inevitable side reactions, and poor charge transport at the cathode interfaces should be overcome. Here, we report a rational design of air cathode using a cobalt nitride (CoN) functionalized carbon nanofiber (CNF) membrane as current collector-catalyst integrated air cathode. Brush-like CoN nanorods are uniformly anchored on conductive electrospun CNF papers via hydrothermal growth of Co(OH)F nanorods followed by nitridation step. CoN-decorated CNF (CoN/CNF) cathode exhibited excellent electrochemical performance with outstanding stability for over 177 cycles in Li-O cells. During cycling, metallic CoN nanorods provide sufficient accessible reaction sites as well as facile electron transport pathway throughout the continuously networked CNF. Furthermore, thin oxide layer (<10 nm) formed on the surface of CoN nanorods promote reversible formation/decomposition of film-type LiO, leading to significant reduction in overpotential gap (∼1.23 V at 700 mAh g). Moreover, pouch-type Li-air cells using CoN/CNF cathode stably operated in real air atmosphere even under 180° bending. The results demonstrate that the favorable formation/decomposition of reaction products and mediation of side reactions are hugely governed by the suitable surface chemistry and tailored structure of cathode materials, which are essential for real Li-air battery applications.