Large scale synthesis of N‒doped carbon spherical shells as high-performance cathode materials for Li‒X (X=O2, S, Se) batteries

Abstract

Porous carbon spherical shell (PCS) with ordered pore structure is a promising electrode material for electrocatalysis and energy storage applications. However, the manner of preparing high-performance PCS on a large scale is complex and high‒energy consuming. We report a gram‒scale synthesis of hierarchical meso/macro‒porous carbon spherical shell (C‒FN) through a facile spray drying‒carbonization strategy. Systematic characterizations including Raman and BET reveal that C‒FN has a high degree of graphitization and large specific surface area of 893.3 m2 g‒1. In addition, a certain amount of doped nitrogen atoms in C‒FN are benefit to enhance its electrocatalytic activity. When used as the cathode material for Li‒O2 battery, the optimized three‒dimensional channels within C‒FN not only can facilitate the transportation of oxygen, lithium ion and electrons, but also accommodate the discharge product on both the inner‒ and outer‒shell, which resulting in an ultrahigh discharge capacity of 11038 mAh g‒1 or 7.85 mAh cm‒2. Moreover, when assembling Li‒S/Li‒Se battery with S and Se infiltrated into C‒FN, the obtained nanocomposites show favorable electrochemical performances in terms of specific capacity (Li‒S:1336.8mAh g‒1; Li‒Se: 829.3 mAh g‒1), cycling stability (after 270 cycle capacity retention of 661.5 mAh g‒1 for Li‒S; after 1000 cycle capacity retention of 150.1 mAh g‒1 for Li‒Se), and high‒rate capability. Through rational and delicate design, C‒FN holds great promise for the development of Li‒X (O2, S, Se) batteries with high power and energy densities.