锂离子电池正极材料磷酸钒锂制备及改性.pdf

钝离子电池止极材料磷酸钒钝的制桥及改性摘要本文采用固相法合成了纯Li3V2(P04)3,然后对纯Li3V2(P04)3进行了碳包覆;采用溶胶一凝胶法合成了Li3V2(P04)3,然后对样品进行不同金属元素的掺杂。采用XRD、 SEM对产物进行了微观结构和形貌的分析,采用恒电流充放电、循环伏安法和电化学阻抗谱对产物进行了电化学性能的研究。考察了不同合成方法、不同温度、掺杂不同元素及掺杂量的不同对材料的结构、形貌和电化学性能的影响。以LiOH·H20、NH4V03、NI-14H2P04、草酸等为原料,采用固相反应法合成了锂离子电池正极材料Li3V2(P04)3,其中草酸作为还原剂,然后对合成的Li3V2(P04)3进行碳包覆。研究表明,Li3V2(P04)3和碳包覆Li3V2(P04)3均具有空间群为P21/n的单斜结构, 碳包覆Li3V2(P04)3的电化学性能优于Li3V2(P04)3纯样品。 V电压范围内,以 ,碳包覆Li3V2(P04)3具有较高的充放电比容量,·g-·g-1,并且其循环性能稳定,经过20次循环后放电比容量仍保持为105mAh·g-1。以LiOH·H20、NH4V03、NH4H2P04、柠檬酸等为原料,采用溶胶一凝胶法合成 Li3V2(P04)3,并对合成的样品进行了一元及二元掺杂,研究了不同温度、掺杂不同元素及掺杂量的不同对材料的结构、形貌及电化学性能的影响。研究表明,在700。(2煅烧8h 得到的样品电化学性能最好,,,·g-1。以溶胶—凝胶法合成掺杂C一的U3v2晴Cr,(P04)3(z=O、、、)样品,电化学测试结果表明,,掺杂Cr3+后样品的初始充放电比容量均低于未掺杂样品的初始充放电比容量,但是在较高倍率下(如1C或2C),当掺杂量x= 时,样品的倍率性能和循环性能均有所改善,这可以归功于CP掺杂使得样品的颗粒粒径减小,提高了结构稳定性;掺杂7_a2+时,当x=1/12时,Li3+xV2《Znx(P04)3(x=O、1/12、 1/6、1/3)的循环性能最好,说明适量掺杂zn2+元素可以改善样品的电化学性能;掺杂 Ti4+、M92+时,在较高倍率下(如1C或2C),掺杂量x=,样品的倍率性能和循环性能均有所改善;而掺杂Ti“、Mn2+并未改善样品的电化学性能。关键词:Li3V2(P04)3;固相法;溶胶一凝胶法;包覆;掺杂钾离子电池Jl:极材料磷酸钒锂的制备及改性 ABSTRACT Inthispaper,solid statereaction method and sol-gel method were employed toprepare Li3V2(P04)3 ascathode materials forlithiumion addition,Li3V2(P04)3 isdoped with different prepared samples were characterized byXRD,SEM,cyclic voltammetry,electrochemical charge-discharge cycling and SO structure and electrochemical properties ofthesamples prepared by different synthesis methods,different temperatures,doping and doping amount ofdifferentelements wereinvestigated. LiOH·H20,NH4V03,NH4H2P04 and oxalic acid were used as starting materials. Thereamong,oxalic acidWas used as areducing coating Was subsequently conducted toprepareLi3V2(P04)3/ prepared Li3V2(P04)3 andLi3V2(P04)3/Csamples were characterized by XRD,cyclic voltammetry andgalvanostatic charge·discharge cycling. The results indicated thatLi3V2