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

Abstract

A porous carbon spherical shell (PCS) with an ordered pore structure is a promising electrode material for electrocatalysis and energy storage applications. However, the preparation of high-performance PCS on a large scale is complex and energy-consuming. We report a gram-scale synthesis of a hierarchical meso/macroporous carbon spherical shell (C–FN) through a facile spray-drying carbonization strategy. Systematic characterizations, including Raman and BET analysis, reveal that C–FN has a high degree of graphitization and a large specific surface area of 893.3 m² g⁻¹. In addition, a certain amount of doped N atoms in C–FN are beneficial in enhancing its electrocatalytic activity. When used as the cathode material in Li–O₂ batteries, 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 shells, which results in an ultrahigh discharge capacity of 11 038 mA h g⁻¹ or 7.85 mA h cm⁻². Moreover, when assembling Li–S/Li–Se battery with S and Se infiltrated into C–FN, the nanocomposites obtained show favorable electrochemical performances in terms of specific capacity (Li–S: 1336.8 mA h g⁻¹; Li–Se: 829.3 mA h g⁻¹), cycling stability (after 270 cycle capacity retention of 661.5 mA h g⁻¹ for Li–S; after 1000 cycle capacity retention of 150.1 mA h g⁻¹ for Li–Se), and high-rate capability. Through rational and delicate design, the C–FN holds great promise for the development of Li–X (O₂, S, Se) batteries with high power and energy densities.