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Synthesis and Electrochemical Reaction of Tin Oxalate-Reduced Graphene Oxide Composite Anode for Rechargeable Lithium Batteries

Park, Jae-Sang, Jo, Jae-Hyeon, Yashiro, Hitoshi, Kim, Sung-Soo, Kim, Sun-Jae, Sun, Yang-Kook, Myung, Seung-Taek
ACS Applied Materials & Interfaces 2017 v.9 no.31 pp. 25941-25951
X-ray diffraction, alloys, anodes, electrical conductivity, electrochemistry, electron transfer, graphene oxide, lithium batteries, mass spectrometry, oxidation, tin, tin dioxide, transmission electron microscopy
Unlike for SnO₂, few studies have reported on the use of SnC₂O₄ as an anode material for rechargeable lithium batteries. Here, we first introduce a SnC₂O₄-reduced graphene oxide composite produced via hydrothermal reactions followed by a layer-by-layer self-assembly process. The addition of rGO increased the electric conductivity up to ∼10–³ S cm–¹. As a result, the SnC₂O₄-reduced graphene oxide electrode exhibited a high charge (oxidation) capacity of ∼1166 mAh g–¹ at a current of 100 mA g–¹ (0.1 C-rate) with a good 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 467 mAh g–¹. In contrast, the bare SnC₂O₄ had inferior electrochemical properties relative to those of the SnC₂O₄-reduced graphene oxide composite: ∼643 mAh g–¹ at the first charge, retaining 192 mAh g–¹ at the 200th cycle and 289 mAh g–¹ at 10 C. This improvement in electrochemical properties is most likely due to the improvement in electric conductivity, which enables facile electron transfer via simultaneous conversion above 0.75 V and de/alloy reactions below 0.75 V: SnC₂O₄ + 2Li⁺ + 2e– → Sn + Li₂C₂O₄ + xLi⁺ + xe– → LiₓSn on discharge (reduction) and vice versa on charge. This was confirmed by systematic studies of ex situ X-ray diffraction, transmission electron microscopy, and time-of-flight secondary-ion mass spectroscopy.