Design of Surface-Modified Anode Materials with High Electrical Conductivity for High-Performance Lithium-Ion Batteries

Abstract

In the past decades, sustainable and clean energy have been demanded because of a serious exhaustion of resources and environmental problems. For this reason, many researchers have tried to develop more efficient and powerful energy devices. Among them, lithium ion batteries (LIBs) have been considered the most promising energy storage devices, because they can exhibit high power and high energy densities that meet the requirements for hybrid electric vehicles (HEVs) and electric vehicles (EVs) applications. However, although LIBs have been successfully commercialized, a considerable improvement of anode materials is still required for large scale energy storage applications and advanced future electronic devices. Natural graphite anode in LIBs shows very small volume change (~10 % at high temperature), a stable cycling life, a low reaction potential (vs. Li/Li+) and a low cost. These factors satisfy the requirements for commercialization as LIB anodes. However, limited specific capacity (372 mAh g-1) of graphite hinders its usage to high-energy density applications. For this reason, alternative anode materials which can exhibit a high specific capacity at a low reaction potential have been studied. Silicon (Si) is one of the most promising candidates for the next -generation anode material due to its high theoretical specific capacity (>3500 mAh g-1 at room temperature), low lithiation potential (<0.5 V vs. Li/Li+), low cost, and environmental safety. However, Si anode should solve two major problems to replace graphite anode in commercial LIBs. One is a large volume changes (>300%) upon insertion and extraction of lithium ions, leading to the pulverization and significant capacity fading. The other is a low intrinsic electrical conductivity. To overcome these critical obstacles, various strategies have been developed including design of novel structures, reduction of particle size, and combination of active materials and other materials having excellent electrical conductivity. In this study, we introduced nanomaterials with high electrical conductivity (e.g., silver, antimony-doped tin oxide, etc.) on the surface of Si and graphite. These newly-developed anode materials exhibited significantly improved electrochemical properties, compared to bare Si or graphite anode materials. These simple, but straightforward synthetic routes can be extended to make other advanced anode materials for high-performance LIBs.