Abstract

Silicon flakes of about 100 × 1000 × 1000 nm in sizes recycled from wastes of silicon wafer manufacturing processes were coated with combined silicon carbide (SiC) and graphitic (Resorcinol–Formaldehyde (RF)) carbon coatings to serve as active materials of the anode of lithium ion battery (LIB). Thermal carbonization of silicon at 1000 °C for 5 h forms 5-nm SiC encapsulating silicon flakes. SiC provides physical strength to help silicon flakes maintain physical integrity and isolating silicon from irreversible reactions with the electrolyte. Lithium diffuses through SiC before alloying with silicon. The SiC buffer layer results in uniform alloying reactions between lithium and silicon on the surface around a silicon flake. RF carbon coatings provide enhanced electrical conductivity of SiC encapsulated silicon flakes. We characterized the coatings and anode by SEM, TEM, FTIR, XRD, cyclic voltammetry (CV), electrochemical impedance spectra (EIS), and electrical resistance measurements. Coin half-cells with combined SiC and RF carbon coatings exhibit an initial Coulombic efficiency (ICE) of 76% and retains a specific capacity of 955 mAh/g at 100th cycle and 850 mAh/g at 150th cycle of repetitive discharge and charge operation. Pre-lithiation of the anode increases the ICE to 97%. The SiC buffer layer reduces local stresses caused by non-uniform volume changes and improves the capacity retention and the cycling life.

Highlights

  • We coated silicon flakes of about 100 × 1000 × 1000 nm in size, which were recycled from wastes of silicon wafer manufacturing processes with combined silicon carbide (SiC)

  • Silicon flakes served as the active materials of lithium ion battery (LIB) anode

  • SiC provides physical strength to help with maintaining integrity of silicon flakes and isolate silicon from irreversible reactions with electrolyte

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Summary

Introduction

High-Capacity Long-Cycling-Life Anode for Lithium Ion Battery. Lithium ion battery (LIB) is the most popular and ubiquitous rechargeable energy storage device in the modern society. The anticipated electric vehicles and large-scale renewable energy storage are two examples. Electric vehicles with a long drive range require LIBs with high energy density and capacity. Energy density, power density per weight and per volume of LIBs, and the discharge/charge cycling life require much improvement. Battery safety is at the highest priority especially for futuristic LIBs of very high energy and power densities [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19]. Graphite is the main active material for modern LIBs because graphite is abundant, inexpensive, and electrochemically stable in a LIB system

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