锂离子电池负极材料ZnSnO3/C复合物的制备与性能

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

  • 摘要: 锡基双金属氧化物作为锂离子电池负极材料因具有高的理论比容量、嵌脱锂电位适中、储量丰富、价格低廉、安全性高以及环保等优点,已经受到了广泛的关注. 本研究采用一步原位水热法制备了碳包覆的ZnSnO3复合材料(ZnSnO3/C). 利用扫描电子显微镜、透射电子显微镜、X射线衍射、拉曼光谱、X射线光电子能谱分析和恒流充放电测试等一系列表征测试方法对材料的微观形貌、物相组成、结构和电化学性能进行分析. 电化学测试结果表明:当作为锂离子电池负极材料时,ZnSnO3/C复合电极的储锂性能优于纯ZnSnO3电极. 在200 mA·g–1电流密度下,ZnSnO3/C复合电极经200次循环后可逆容量可达1274.9 mA·h·g–1,即使在大电流5000 mA·g–1下经500次循环仍然提供663.2 mA·h·g–1的放电比容量,同时也表现出卓越的倍率性能. 优异的储量性能归因于ZnSnO3/C复合材料中具有高电导率的C不仅提高了整个电极的导电性,有利于电子的传输,而且增大了电解液与活性材料之间的接触面积,缩短了锂离子的扩散距离;同时碳包覆层可有效缓冲ZnSnO3在嵌脱锂过程中由于体积变化产生的应力,也能在一定程度上抑制ZnSnO3在循环过程中的团聚.

     

    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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