掺杂型尖晶石LiMn_(2-x)Mg_xO_(3.97)F_(0.03)(x=0.05,0.1)的合成与性能研究

采用"熔融浸渍法"合成了Mg和F共掺杂的不同温度下的锂离子电池正极材料Li Mn2-xMgxO3.97F0.03(x=0.05,0.1);煅烧温度为700,750和800°C。通过XRD对样品进行测试,样品为单一尖晶石结构的物相;并用SEM测试,对样品进行了形貌研究。用所制备的材料作为正极材料组装了模拟锂离子电池;在室温下进行恒电流充-放电性能测试,测试条件为3.3~4.3 V和0.2mA/cm2电流密度。随着材料制备温度的升高,电池的初始放电容量有逐渐增加的趋势,但充放电循环的容量损失也逐渐增加;氟掺杂量一定,镁掺杂量较多时,对应温度下煅烧的样品的结晶程度较好,样品的电化学性能也较好。在800下°C样品Li Mn1.9Mg0.1O3.97F0.03初始容量高达108 mAh/g,60次充放电循环后,其容量保持率高达81%,具有优良的循环稳定性能。

Synthesis and Properties of Spinel LiMn2-xMgxO3.97F0.03 (x=0.05, 0.1) as Cathode Material for Li-ion Battery

Spinel LiMn_(2-x)Mg_xO_(3.97)F_(0.03)(x=0.05,0.1) as cathode materials for lithium-ion batteries was synthesized by a "melting-impregnation" method.The calcinating temperatures were 700,750,and 800(°C),respectively.Their morphology and microstructure were examined by powder XRD analysis and SEM.The XRD spectra showed that the samples had pure spinel structure.Their electrochemical properties were studied by constant current charge-discharge testing between 3.3～4.3 V and at a current density of 0.2 mA/cm~(2).The initial discharge capacity of LiMn_(2-x)Mg_xO_(3.97)F_(0.03)(x=0.05,0.1) increased with rising calcinating temperature.Their capacity loss also increased gradually.When the amount of fluorine doped was constant,the crystallinity and the elctrochemical properties were improved with the amount of metal substituted.LiMn_(1.9)Mg_(0.1)O_(3.97)F_(0.03) synthesized at 800(°C) gave an discharge capacity of 108 mAh/g for the first cycle and still retained 81% of the initial capacity after 60 cycles at room temperature,showing an excellent cycling stability and a high capacity.