摘要
采用碳热还原法以磷铁和碳酸锂为原料合成了LiFePO4,用XRD、恒流充放电法和EIS对其进行表征,用TG-DTA分析了反应过程。预焙烧过程中磷铁中的磷与碳酸锂反应形成Li4P2O7和LiFeP2O7,再与中间产物Fe2O3、Fe3O4和补充磷源NH4H2PO4进一步反应生成LiFePO4。产物具有良好的电化学性能,在0.1C时放电容量可以达到151.68mAh/g,0.2和0.5C分别循环10和20次后放电容量仍有125.94和103.51mAh/g,衰减率分别为4.23%和7.24%。不同荷电状态的EIS结果表明:放电至2.4V具有最小的溶液阻抗;界面阻抗由于充放电至3.4V时包括一部分不稳定的SEI膜,因此比充放电至2.4V时大;随着充放电过程的继续,反应过程由反应控制逐渐变为扩散控制。
LiFePO4 was synthesized by carbon thermal reduction method using Fel. s P and Li2 CO3 as raw material. XRD, galvanostatic charge/discharge and EIS were adopted to characterize the product. TG-DTA was used to investigate the reaction process. In the preheating process, the phosphorus in Fe1.5P reacted with Li2CO3 to form Li4P2O7 and LiFeP2O7 which further reacted with the intermediate product of Fe2O3, Fe3O4 and supplementary phosphorus source of NH4 H2 PO4 to produce LiFePO4. The experimental results showed the product had good electrochemical performance. The first discharge capacity could reach 151.68mAh/g at 0. 1C rate, and could remain 125.94mAh/g at 0.2C after 10 cycles and 103.51mAh/g at 0. 5C after 20 cycles. The fade ratio was 4. 23% and 7.24%, respectively. The solution resistance was the smallest when discharge to 2. 4 V; Interface resistance charge and discharge to 3.4 V was bigger than charge and discharge to 2. 4V due to the unstable SEI. With the process of charging and discharging,Control factors was changed gradually from the reaction control into diffusion control.
出处
《化工新型材料》
CAS
CSCD
北大核心
2012年第6期111-113,126,共4页
New Chemical Materials
基金
四川大学青年基金项目(07046)
