Tailoring the Kinetics of Sn Anodes for High Power Energy Storage Devices

Abstract

Alkali ion batteries, such as Li-ion batteries (LIBs) and Na-ion batteries (NIBs), have recently drawn much attention due to their high energy densities, high Coulombic efficiencies and low self-discharge rates, making them useful in electronics, electric vehicles and grid-scale energy storage. One of the major obstacles to widespread applications of these rechargeable batteries, however, is their poor electrochemical performance under high power densities. The obstacle is attributed to the sluggish electrochemical kinetics, including slow diffusion rate of alkali ions in solid electrodes, low electrical conductivity and undesired phase transformation. Sn-based anodes having both high gravimetric and volumetric capacities are considered a promising candidate for next-generation LIBs and NIBs, but they also face the same challenge. Herein, we demonstrate that the electrochemical kinetics of Sn-based anodes, such as SnO2 and SnS2, can be largely enhanced by amorphization, doping of heteroatoms and facilitating the pseudocapacitive charge storage. The mechanistic insight of the enhanced kinetics is revealed by combining the electrochemical measurements with in situ TEM characterization and the first-principles calculations. Thanks to the new findings, we successfully fabricate Sb-doped SnO2/graphene-CNT aerogel anodes which deliver a high areal capacity of 2.6 mAh cm-2 at a high current density of 8 mA cm-2 in LIBs. The Na hybrid capacitor consisting of an activated carbon cathode and a SnS2/graphene-CNT aerogel anode is further developed for applications requiring high power densities and low costs. The as-assembled hybrid capacitor delivers an exceptional energy density of 26.9 Wh kg−1 at an ultrahigh power density of 6053 W kg−1. The implications of these discoveries for both fundamental understanding and practical applications are discussed.