球形高电压LiNi_(0.5)Mn_(1.5)O_4的制备及其电化学性能

Synthesis and electrochemical performance of spherical high-voltage LiNi_(0.5)Mn_(1.5)O_4

以化学共沉淀法制备的球形Ni0.25Mn0.75CO3为前驱体合成高电压正极材料LiNi0.5Mn1.5O4,探讨用前驱体与Li2CO3直接反应和用前驱体分解后的氧化物与Li2CO3反应两种工艺路线对LiNi0.5Mn1.5O4形貌和电化学性能的影响。用扫描电镜（SEM）和X射线衍射（XRD）对Ni0.25Mn0.75CO3前驱体和LiNi0.5Mn1.5O4样品进行表征,用充放电测试和循环伏安法对LiNi0.5Mn1.5O4样品进行电化学性能研究。结果表明：两种方法合成的LiNi0.5Mn1.5O4均具有尖晶石型结构。但以前驱体Ni0.25Mn0.75CO3直接与Li2CO3反应合成的LiNi0.5Mn1.5O4的一次粒子颗粒较大,形貌较差,性能也较差;而以前驱体分解后的氧化物与Li2CO3反应合成的LiNi0.5Mn1.5O4的形貌及性能均较好。在3.0~4.9 V的电压范围内,1C倍率下电池的放电比容量达到136.3 mA.h/g,循环100次仍有126.5 mA.h/g,且材料具有较好的倍率性能;5C倍率下的首次放电比容量高达120.7 mA.h/g。

Spherical LiNi0.5Mn1.5O4 powder was synthesized from the coprecipitated Ni0.25Mn0.75CO3 precursor.The effects of two synthesis routes,Ni0.25Mn0.75CO3 precursor directly mixed with Li2CO3 and（Ni0.25Mn0.75）2O3 mixed with Li2CO3,on the morphology and electrochemical performance of LiNi0.5Mn1.5O4 cathode material were investigated.XRD,SEM,charge-discharge tests and cyclic voltammetry were utilized to characterize the properties of samples.The XRD results indicate that the LiNi0.5Mn1.5O4 samples synthesized from both methods exhibit spinel structure.The morphologies of the samples prepared from two routes are spherical.However,the LiNi0.5Mn1.5O4 sample synthesized directly from mixture of Ni0.25Mn0.75CO3 and Li2CO3 possesses larger primary particle size compared with the LiNi0.5Mn1.5O4 synthesized from the（Ni0.25Mn0.75）2O3 and Li2CO3.Besides,the latter LiNi0.5Mn1.5O4 shows more excellent electrochemical properties,delivers an initial discharge capacity 136.3 mA.h/g at the rate of 1C in the voltage range of 3.0？4.9 V.Particularly,its capacity is still 126.5 mA.h/g after 100 cycles.Furthermore,the sample performs excellent rate capability,even at 5C,the discharge capacity still keeps 120.7 mA.h/g.