Lithium iron silicate (Li2FeSiO4) is capable of affording a much higher capacity than conventional cathodes, and thus, it shows great promise for high-energy battery applications. However, its capacity has often bee...Lithium iron silicate (Li2FeSiO4) is capable of affording a much higher capacity than conventional cathodes, and thus, it shows great promise for high-energy battery applications. However, its capacity has often been adversely affected by poor reaction activity due to the extremely low electronic and ionic conductivity of silicates. Here, we for the first time report on a rational engineering strategy towards a highly active Li2FeSiO4 by designing a carbon nanotube (CNT) directed three-dimensional (3D) porous Li2FeSiO4 composite. As the CNT framework enables rapid electron transport, and the rich pores allow efficient electrolyte penetration, this unique 3D Li2FeSiO4-CNT composite exhibits a high capacity of 214 mAh·g^-1 and retains 96% of this value over 40 cycles, thus, outstripping many previously reported Li2FeSiO4-based materials. Kinetic analysis reveals a high Li+ diffusivity due to coupling of the migration of electrons and ions. This research highlights the potential for engineering 3D porous structure to construct highly efficient electrodes for battery applications.展开更多
基金Acknowledgements We acknowledge the financial support of the National Natural Science Foundation of China (Nos. 51302181, 51372159, 51422206, and 51672182), the Thousand Youth Talents Plan, the Jiangsu Shuangchuang Plan, the Natural Science Foundation of Jiangsu Province (Nos. BK20151219 and BK20140009), the Jiangsu Undergraduate Student Innovation and Entrepreneurship Project, the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), and Russian Scientific Fund (No. 14-43-00072).
文摘Lithium iron silicate (Li2FeSiO4) is capable of affording a much higher capacity than conventional cathodes, and thus, it shows great promise for high-energy battery applications. However, its capacity has often been adversely affected by poor reaction activity due to the extremely low electronic and ionic conductivity of silicates. Here, we for the first time report on a rational engineering strategy towards a highly active Li2FeSiO4 by designing a carbon nanotube (CNT) directed three-dimensional (3D) porous Li2FeSiO4 composite. As the CNT framework enables rapid electron transport, and the rich pores allow efficient electrolyte penetration, this unique 3D Li2FeSiO4-CNT composite exhibits a high capacity of 214 mAh·g^-1 and retains 96% of this value over 40 cycles, thus, outstripping many previously reported Li2FeSiO4-based materials. Kinetic analysis reveals a high Li+ diffusivity due to coupling of the migration of electrons and ions. This research highlights the potential for engineering 3D porous structure to construct highly efficient electrodes for battery applications.
文摘采用溶胶-凝胶法,以抗坏血酸作为碳源并添加表面活性剂聚乙二醇(PEG)合成纳米复合材料Li2FeSiO4/C。研究了PEG对Li2FeSiO4/C结构及电化学性能的影响。结果表明:添加PEG后合成的纳米Li2FeSiO4/C颗粒细小(约50 nm),表面均匀包覆一层碳。因此,纳米复合粉体Li2FeSiO4/C在充放电过程中具有更小的扩散阻力和更高的电导率,而均匀的碳层能够减少活性物质与电解液之间副反应的发生。室温下以C/16倍率充放电,首次放电比容量为138.2mA h/g,并且在不同倍率下循环40次后仍保持在130.4 mA h/g。