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鋰離子電池負極材料ZnSnO3/C復合物的制備與性能

Synthesis and performance of ZnSnO3/C composites as anode for lithium-ion battery

  • 摘要: 錫基雙金屬氧化物作為鋰離子電池負極材料因具有高的理論比容量、嵌脫鋰電位適中、儲量豐富、價格低廉、安全性高以及環保等優點,已經受到了廣泛的關注. 本研究采用一步原位水熱法制備了碳包覆的ZnSnO3復合材料(ZnSnO3/C). 利用掃描電子顯微鏡、透射電子顯微鏡、X射線衍射、拉曼光譜、X射線光電子能譜分析和恒流充放電測試等一系列表征測試方法對材料的微觀形貌、物相組成、結構和電化學性能進行分析. 電化學測試結果表明:當作為鋰離子電池負極材料時,ZnSnO3/C復合電極的儲鋰性能優于純ZnSnO3電極. 在200 mA·g–1電流密度下,ZnSnO3/C復合電極經200次循環后可逆容量可達1274.9 mA·h·g–1,即使在大電流5000 mA·g–1下經500次循環仍然提供663.2 mA·h·g–1的放電比容量,同時也表現出卓越的倍率性能. 優異的儲量性能歸因于ZnSnO3/C復合材料中具有高電導率的C不僅提高了整個電極的導電性,有利于電子的傳輸,而且增大了電解液與活性材料之間的接觸面積,縮短了鋰離子的擴散距離;同時碳包覆層可有效緩沖ZnSnO3在嵌脫鋰過程中由于體積變化產生的應力,也能在一定程度上抑制ZnSnO3在循環過程中的團聚.

     

    Abstract: Being one of the ternary metal oxides, different zinc stannate (ZnSnO3) nanostructures, including nanoparticles, nanowires, nanocubes, and nanosheets, have been synthesized and investigated for various applications, such as catalysts, phonics, sensors, piezoelectric, pyroelectric, and lithium-ion batteries (LIBs). The ZnSnO3 has received immense attention as potential anode materials for LIBs due to their high theoretical specific capacity, moderate intercalation and delithiation potential, abundant reserves, low cost, high safety, and environmental protection. In this study, a carbon-coated ZnSnO3 composite (ZnSnO3/C) was prepared using a one-step in situ hydrothermal method with glucose as a carbon source. The microscopic morphology of the as-prepared materials was observed using scanning electron microscopy and transmission electron microscopy. X-ray diffraction, Raman spectra, and X-ray photoelectron spectroscopy were used to analyze the phase composition and structure of the composite. The electrochemical properties were investigated through constant charge–discharge tests, cyclic voltammetry, and electrochemical impedance spectroscopy. When used as anode materials of LIBs, the prepared ZnSnO3/C composite electrode exhibited excellent lithium storage performance with an improved cycling performance and high capacities. A specific capacity value of 1274.9 mA·h·g?1 for ZnSnO3/C composite is much higher than that of pure ZnSnO3 electrode (491 mA·h·g?1) after 200 cycles at a current density of 200 mA·g?1. The ZnSnO3/C electrode retained a discharge capacity of 663.2 mA·h·g?1 even after 500 cycles at a high current density of 5000 mA·g?1, exhibiting excellent rate capability. Such remarkable electrochemical properties of the ZnSnO3/C composite are preferable to those of complex and costly ZnSnO3-based composites reported previously. The superior lithium storage performance of the ZnSnO3/C composite is attributed to the synergistic effect between the carbon coating on the surface and ZnSnO3 nanoparticles. Moreover, the composite exhibits the following attributes: (1) High conductivity of the carbon in the ZnSnO3/C composite can considerably enhance the conductivity of the electrode for facilitating electron transmissions. (2) The structure of nanoparticles can reduce the diffusion distance of Li+ and provide a large electrode-electrolyte contact area for high Li+ flux across the interface, leading to a high reversible specific capacity. (3) The ZnSnO3 nanoparticles and flexible carbon layer can generate a double buffering structure to retard the huge volume expansion of active materials during repeated charge–discharge cycles. (4) More importantly, the carbon coating layer can avoid side reactions by preventing direct contact between the ZnSnO3 hollow cubes and electrolytes and inhibiting the agglomeration of ZnSnO3 during the cycling process. Thus, this research may provide a new avenue for synthesizing bimetal oxide with a core–shell structure for high-performance energy storage materials, considering the simple principles involved in its preparation.

     

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