合成及其性能
(中南大學(xué) 化學(xué)化工學(xué)院， 長沙 410083)
摘 要: 以LiOH·H2O、 V2O5和NH4H2PO4為原料， C為還原劑， 采用高溫固相法合成了鋰離子電池正極材料磷酸釩鋰（Li3V2(PO4)3）。考察了合成溫度等條件對產(chǎn)物組成和晶相的影響。 結(jié)果表明： 隨著焙燒溫度的升高， 雜相的衍射峰相對強(qiáng)度逐漸減弱， 當(dāng)煅燒溫度達(dá)到800 ℃時(shí)， 雜相衍射峰消失， 所得樣品為純相的Li3V2(PO4)3樣品； 按Li、 V、 P的摩爾比為3∶2∶3將原料在800 ℃下焙燒24 h， 合成得到正極材料。 該材料在0.1 C充放電制度下， 首次充電比容量達(dá)到135 mA·h/g， 首次放電比容量130 mA·h/g， 充放電效率達(dá)96.3％； 經(jīng)過20次循環(huán)后， 放電容量仍然高達(dá)110 mA·h/g。 對經(jīng)過20次循環(huán)后的樣品進(jìn)行了X射線衍射分析，結(jié)果發(fā)現(xiàn)， 經(jīng)過20次循環(huán)后樣品仍然具有單斜晶體結(jié)構(gòu)， 樣品各主要衍射峰強(qiáng)度都急劇減弱， 說明樣品在充放電過程中晶體結(jié)構(gòu)發(fā)生了變化；采用最小二乘法對樣品充放電前后的晶胞參數(shù)進(jìn)行了計(jì)算， 發(fā)現(xiàn)樣品在經(jīng)過充放電循環(huán)后晶胞參數(shù)都有不同程度的增加， 晶胞體積增大0.6％左右。
關(guān)鍵字: Li3V2(PO4)3；正極材料； NASCION結(jié)構(gòu)
cathode materials Li3V2(PO4)3 for
lithium-ion batteries
（ School of Chemistry and Chemical Engineering,
Central South University, Changsha, 410083, China）
Abstract: The cathode material Li3V2(PO4)3 was prepared by solid-state reaction of LiOH·H2O, V2O5 and NH4H2PO4, with carbon as the reduction agent. The effects of reaction conditions such as temperature on the structure were investigated by X-ray diffractrometry. The results show that the sample synthesized from the raw materials with molar ratio of Li, V and P of 3∶2∶3 at 800 ℃ for 24 h has a pure monoclinic crystal structure, which derives a initial discharge specific capacity of 130 mA·h/g. After charged/discharged at 0.1 C rate for 20 cycles, the sample retaines a discharge specific capacity of 110 mA·h/g. XRD patterns show that it retains monoclinic crystal structure, but the intensity of diffraction declines sharply. Least square method was used to calculate the unit-cell parameters of the sample before and after cycling, it is found that all of the parameters increase to some extend, and the unit-cell volume increases by 0.6%.
Key words: Li3V2(PO4)3; cathode materials; NASCION structure
