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

Synthesis and Properties of Spinel LiMn_(2-x)Mg_xO_(3.97)F_(0.03)(x=0.05,0.1) as Cathode Material for Li-ion Battery

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LiMn2-xMgxO3．97F0．03（x=0．05，0．1）（x=0．05，0．1）；煅烧温度为700，750和800℃。通过XRD时样品进行测试，样品为单一尖晶石结构的物相；并用SEM测试，时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一放电性能测试，测试条件为3．3～4．3V和0．2mA／cm^2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℃样品LiMn1．9Mg0.1O3.97F0.03初始容量高达108mAh／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。

Spinel LiMn2-xMgxO3.97F0.03（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℃ 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 LiMn2-xMgxO3.97F0.03（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 eletrochemical properties were improved with the amount of metal substituted. LiMnl.9 Mg0.1 O3.97 F0.03 synthesized at 800℃ gave an discharge capacity of 108 mAh/g for the first cycle and sti!! retained 81% of the initial capacity after 60 cycles at room temperature, showing an excellent cycling stability and a high capacity.