磷酸铁锂的制备及其电化学性能

Preparation and Electrochemical Performance of LiFePO_4

以LiOH·H2O,FeSO4·7H2O和H3PO4为原料[n(Li)∶n(Fe)∶n(P)=3∶1∶1],采用水热法合成了LiFePO4(P),其结构经XRD,FE-SEM,HR-TEM和SEAD表征。考察了pH值、反应温度、反应时间和表面活性剂对P的结晶度、颗粒形貌、晶粒大小和择优取向的影响。结果表明:在pH为9.27,0.5%的聚乙烯醇为表面活性剂,于150℃反应8 h合成的P表现出规则的片状形貌,衍射峰强I(200)/I(211)为0.492 5;P在垂直b轴方向有一定的择优生长;P在ac面为最大面,b轴方向尺寸最短;采用乙炔黑为导电剂制备的P扣式电池表现出优良的电化学性能,于室温0.1 C倍率充放电,放电比容量为108.3 mAh·g-1;葡萄糖包覆改性后的扣式电池,0.1 C倍率放电比容量为148 mAh·g-1,1 C倍率放电时,放电比容量仍保持在133.9 mAh·g-1左右。

The pure phase LiFePO4（P） was prepared by hydmthermal method using LiOH · H2O,FeSO4 · 7H2O and H3PO4 as the raw materials[n（Li） ∶ n（Fe）∶ n（P） =3 ∶ 1 ∶ 1].The structures were characterized by XRD,FE-SEM,HR-TEM and SEAD.The effect of pH,reaction temperature,reaction time and surfactant on the crystallinity,particle morphology,grain size and optimizing crystal orientation of P were investigated.The results showed that P prepared under 150 ℃ for 8 h using 0.5% polyving akohol as the surfactant in pH of 9.27 shows regular laminated structure and the intensity ratio I（200）/I（211） of the diffraction peak is 0.492 5,which illustrates that the samples preferably cystallized in the perpendicular direction to b axis.The result of SEAD analysis indicated that the sample shows the biggest ac face and shortest b axis.Button cell of P with acetylene black as the conductive additive shows excellent electrochemical performance,the discharge capacity was 108.3 mnAh · g-1 at room temperature at 0.1 C and can reach to 148 mAh · g-1 and remain at 133.9 mAh · g-1 at 1 C after glucose carbon coating.