Sonochemical synthesis of nanostructured VOPO4 · 2H2O/carbon nanotube composites with improved lithium ion battery performance
Sonochemical synthesis of nanostructured VOPO4 · 2H2O/carbon nanotube composites with improved lithium ion battery performance
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DOI：
10.1007/s11051-009-9626-x
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发表时间：
2010-02
影响因子：
2.5
通讯作者：
Yongfu Sun;Changzheng Wu;Yi Xie
中科院分区：
文献类型：
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作者：
Yongfu Sun;Changzheng Wu;Yi Xie
过渡金属磷酸盐作为锂离子电池的正极材料，由于其高电压、低成本和环境友好性而引起人们极大的兴趣。然而，它们的低本征电导率对实际实施提出了主要缺点。本文首次采用超声波辅助插层-裂解机理实现VOPO_4·2 H_2 O的纳米化，以增加其扩散系数和与电解质接触的表面积，从而提高其容量和循环性能;然后，通过吸附，成功地实现了上述分裂纳米晶体和酸官能化多壁碳纳米管的纳米复合，再嵌入机制，以增加它们的导电性，从而使它们能够以高速率高效率放电。纳米VOPO_4·2 H_2 O比微米VOPO_4·2 H_2 O具有更长的放电平台（平均放电电压为3.7V）、更高的容量（理论容量的93.4%）和更好的循环性能（50次循环后首次放电容量保持率为95.1%）。纳米复合材料的高倍率放电性能较VOPO_4·2 H_2 O微晶有明显提高，首次放电容量保持率为83%，而VOPO_4·2 H_2 O微晶的首次放电容量仅保持率为31.7%。总之，纳米晶化和纳米复合技术的应用使高电压、低成本、环境友好的VOPO 4·2 H2O在实际应用中显示出良好的前景。
Transition metal phosphates have become of great interest as cathode materials for lithium ion batteries because of their high voltage, low cost and environmental friendliness. However, their low-intrinsic conductivity presents a major drawback to practical implementation. Here, nanocrystallization of VOPO4· 2H2O was first realized by a sonication-assisted intercalation-split mechanism in order to increase its diffusion coefficient and surface area contacting with electrolyte thus improving its capacity and cyclability; then nanocompounding of the above split nanocrystals and acid-functionalized multiwalled carbon nanotubes to form the resulting nanocomposites was successfully achieved by an adsorption-reintercalation mechanism to increase their conductivity thus enabling them to discharge at high rate with high efficiency. As expected, nanosized VOPO4· 2H2O possesses longer discharge plateau (average discharge voltage: 3.7 V), higher capacity (93.4% of the theoretical capacity) and much better cyclability (retain 95.1% of the first discharge capacity after 50 cycles) than microsized VOPO4· 2H2O. Furthermore, the relatively high-rate capability of the nanocomposites, retaining 83% of the first discharge capacity, is remarkably improved compared with VOPO4· 2H2O microcrystals (retain only 31.7%). In brief, the use of nanocrystallization and nanocompounding techniques enables the high voltage, low cost, environmentally benign VOPO4· 2H2O to show the prospective signs for the future practical applications.