高电压磷酸钴锂正极材料性能调控研究

doi:10.11949/0438-1157.20211076

摘要/Abstract

摘要：

高性能、高安全储能电池的迫切需求加速了橄榄石型高电压正极材料的研究步伐。为了改善高电压磷酸钴锂(LiCoPO₄)的综合电化学性能，采用溶剂热法研究了溶剂比、过渡元素(Fe、Mn)单掺杂和双掺杂(掺杂元素总量占10%)对正极材料形貌、尺寸、反位缺陷和电化学性能的影响。结果表明，当溶剂比为2.3时，未掺杂LiCoPO₄在0.1C下表现出163.1 mAh·g^-1的最高理论比容量；双掺杂LiCo_0.9Mn_0.05Fe_0.05PO₄正极材料具有突出的循环性能，在0.5C电流密度下，循环100圈后的容量保持率为78.9%，循环稳定性得到明显改善。

关键词: 磷酸钴锂, 溶剂热法, 混合溶剂, 元素掺杂

Abstract:

The urgent need for high-performance, high-safety energy storage batteries has accelerated the pace of research on olivine-type high-voltage cathode materials. Lithium cobalt phosphate (LiCoPO₄) with different Fe and Mn doping contents (10% of the total doping elements) was synthesized by using solvothermal method with diethylene glycol (DEG) and H₂O as mixed solvent. The effects of the solvent ratio and element doping contents on the morphology, size, antisite defects and electrochemical properties of as-prepared cathode materials were discussed. The results show that LiCoPO₄ demonstrated the highest discharge capacity of 163.1 mAh·g^-1 when the solvent ratio of 2.3 was used and LiCo_0.9Mn_0.05Fe_0.05PO₄ cathode material prepared under the solvent ratio of 2.3 had outstanding cycling performance and the capacity retention after 100 cycles was 78.9% at 0.5C.

Key words: lithium cobalt phosphate, solvothermal method, mixed solvent, element doping

中图分类号:

TQ 150

崔声睿, 董林涛, 金永成, 向兰. 高电压磷酸钴锂正极材料性能调控研究[J]. 化工学报, 2021, 72(12): 6380-6387.

Shengrui CUI, Lintao DONG, Yongcheng JIN, Lan XIANG. Studies on the performance of high voltage LiCoPO₄ cathode materials[J]. CIESC Journal, 2021, 72(12): 6380-6387.

图/表 10

图1 LiCo1-x-yMnxFeyPO4/C复合正极材料的XRD谱图

Fig.1 XRD patterns of a series of LiCo1-x-yMnxFeyPO4/C composite materials

表1 LiCo1-x-yMnxFeyPO4/C复合正极材料的晶胞参数

Table 1 The lattice parameters of LiCo1-x-yMnxFeyPO4/C composite material

样品	M₂		M₁		晶胞参数
样品	Co1	Li2	Li1	Co2	a	b	c
LCP-2.3	0.956	0.044	0.956	0.044	10.2088	5.9273	4.7039
LCFP-2.3	0.871	0.029	0.971	0.029	10.2113	5.9289	4.7038
LCFP-3.0	0.875	0.025	0.975	0.025	10.2142	5.9326	4.7041
LCMP-2.3	0.880	0.020	0.980	0.020	10.2317	5.9453	4.7068
LCMP-3.0	0.879	0.021	0.979	0.016	10.2299	5.9447	4.7071
LCMFP-2.3	0.882	0.018	0.982	0.018	10.2203	5.9351	4.7052

图2 LiCo1-x-yMnxFeyPO4/C复合正极材料的Raman谱图

Fig.2 Raman spectra of LiCo1-x-yMnxFeyPO4/C composite material

图3 LiCo1-x-yMnxFeyPO4/C复合正极材料的傅里叶变换红外光谱图

Fig.3 FTIR spectra of LiCo1-x-yMnxFeyPO4/C composite cathode materials

图4 LiCo1-x-yMnxFeyPO4/C复合正极材料的SEM图

Fig.4 SEM images of LiCo1-x-yMnxFeyPO4/C composite material

图5 正极材料的TEM图

Fig.5 TEM images of cathode materials

图6 LiCo1-x-yMnxFeyPO4/C活化后首圈充放电曲线及CV曲线

Fig.6 Charge-discharge curves of the first cycle after LiCo1-x-yMnxFeyPO4/C and CV curves

图7 LiCo1-x-yMnxFeyPO4/C正极材料电化学性能

Fig.7 The electrochemical performance of LiCo1-x-yMnxFeyPO4/C composite material

图8 LCP-2.3 [(a)、(b)]和LCMFP-2.3 [(c)、(d)]在循环前、后的SEM图

Fig.8 SEM images of LCP-2.3 [(a)，(b)] and LCMFP-2.3 [(c)，(d)] before and after cycling

图9 正极材料的交流阻抗谱图(a)； Z'与ω-1/2线性拟合图(b)

Fig.9 Electrochemical impedance spectrum (a); The liner relation of Z' and ω-1/2 (b)

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