气相沉积碳源对LiFePO_4/C性能的影响

Effect of carbon sources of vapor deposition on the performance of LiFePO_4/ C

以FeC2O4·2H2O、Li2CO3和NH4H2PO4为原料，采用分步引入碳源的方式，在前驱体中加入蔗糖预烧，在烧结过程中分别引入甲炕和甲苯蒸气，将高温固相反应与化学气相沉积（CVD）相结合，制备LiFePO4／C复合材料。通过XRD、SEM、透射电子显微镜（TEM）和拉曼光谱进行结构和微观形貌分析；用循环伏安和恒流充放电测试考察电化学性能。以甲苯为气相沉积碳源制备的LiFePO4／C复合材料，没有磷化铁杂质，具有较好的晶体颗粒单分散性和较高的电导率。在2．0-4．0V放电，0．2C比容量为154．8mAh／g，5．0C比容量为0．2C时的88．2％。

LiFePO4/C composite was synthesized using FeC2O4· 2H2O, Li2CO3 and NH4H2PO4 as raw materials. The route combined high-temperature solid-phase reaction and chemical vapor deposition （CVD） methods. Sucrose and CVD carbon sources （methane or toluene）were introduced in the presintering and the CVD assisted sintering process, respectively. LiFePO4/C composites were synthesized with sucrose and methane or sucrose and methylhenzene as composite carbon respectively. The structure and morphology were characterized by XRD, SEM and transmission electron microscope （ TEM ）. The electrochemical performance was evaluated by cyclic vohammetry and galvanostatie charge-discharge tests. By using carbon sources with toluene in the CVD process, the LiFePO4/C composite with high purity, good monodispersity and high conductivity was synthesized. When discharged in 2. 0 -4.0 V,the specific capacity of 0. 2 C was 154. 8 mAh/g,while its capacity retention was 88.2% （relative to 0. 2 C）at 5.0 C rate.