Synthesis\nand Electrochemical Reaction of Tin Oxalate-Reduced\nGraphene Oxide Composite Anode for Rechargeable Lithium Batteries

Abstract

Unlike for SnO₂, few studies\nhave reported on the use\nof SnC₂O₄ as an anode material for rechargeable\nlithium batteries. Here, we first introduce a SnC₂O₄-reduced graphene oxide composite produced via hydrothermal\nreactions followed by a layer-by-layer self-assembly process. The\naddition of rGO increased the electric conductivity up to ∼10^–3 S cm^–1. As a result, the SnC₂O₄-reduced graphene oxide electrode exhibited a\nhigh charge (oxidation) capacity of ∼1166 mAh g^–1 at a current of 100 mA g^–1 (0.1 C-rate) with a\ngood retention delivering approximately 620 mAh g^–1 at the 200th cycle. Even at a rate of 10 C (10 A g^–1), the composite electrode was able to obtain a charge capacity of\n467 mAh g^–1. In contrast, the bare SnC₂O₄ had inferior electrochemical properties relative to\nthose of the SnC₂O₄-reduced graphene oxide composite:\n∼643 mAh g^–1 at the first charge, retaining\n192 mAh g^–1 at the 200th cycle and 289 mAh g^–1 at 10 C. This improvement in electrochemical properties\nis most likely due to the improvement in electric conductivity, which\nenables facile electron transfer via simultaneous conversion above\n0.75 V and de/alloy reactions below 0.75 V: SnC₂O₄ + 2Li⁺ + 2e^– → Sn + Li₂C₂O₄ + <i>x</i>Li⁺ + <i>x</i>e^– → Li_<i>x</i>Sn on discharge (reduction) and vice versa on charge. This\nwas confirmed by systematic studies of ex situ X-ray diffraction,\ntransmission electron microscopy, and time-of-flight secondary-ion\nmass spectroscopy.