Novel Tin (IV) Oxide-Carbon Composite Anode Material for High-Capacity Li-ion Batteries
Authors: Weeks Jason A. , Mullins Charles Buddie , Heller Adam 
Published: February 2020

Increasingly modern society relies on the use of electrical energy for a large portion of their everyday tasks. Many of these tasks require the use of portable energy sources. Currently, lithium ion batteries (LIBsdominate the portable energy storage market.1 Almost exclusively, these LIBs utilize a graphite anode, due to graphite’s long lifetime and high capacity retention.2 This project aims to develop a cheap, high capacity alternative to graphite via a SnO2-C based anode material. Tin oxide is an effective candidate for an anode due to its low price and tin’s high abundance.

Tin oxide anodes have been studied previously, motivated by its high theoretical capacity (1494 mAh/g).2 However, tin oxide is not currently used in commercial cells because of the large volumetric expansion during lithiation (up to 300%) leading to fracturing of the particle.3 In turn, the fracturing can cause the particle to electrically disconnect from the current collector and lose effectiveness. We believe these issues can be counteracted through the employment of a carbon backbone. The presence of semi-crystalline carbon could act as a flexible component to resist the expansion of the tin atoms, preventing the degradation and fracturing of the particle caused by expansion.4 Previous studies have utilized SnO2-C composites to form anodic materials with high capacities and high columbic efficiencies, but tend to display sub-par cycling lifetimes.4,5 However, these studies did not examine how the effects of doping and extent of crystallinity can influence the overall electrochemical performance. The analysis of these factors could lead to the production of a higher capacity and more economically viable alternative to graphitic anodes.

The goal of this research is to develop SnO2-C anodes and investigate the storage and transport of Li within the electrodes to improve the efficiency and cost of LIBs. Due to their higher tap densities and industrial viability, micron-sized anode materials were generated for this study. Ditin citrate was chosen as a tin containing pyrolysis precursor because of its novelty and inexpensive synthesis.6 Precursors such as sucrose and citric acid were added to pyrolysis mixture to form a semi-graphitized framework around the tin-oxide particles. XRD, Raman, XPS, and SEM/EDX data suggest the uniform coating of a semi-graphitized coating around the SnO2 particles. Preliminary data suggest this process has led to the formation of a high specific capacity (750 mA/g) anode material with satisfactory cycling performance. The future pursuits of this study is to optimize the cycling performance and determine the effects of using dopants such as nitrogen and sulfur.

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