富锂层状正极材料Li2MnO3的表面改性及其电化学性能研究

doi:10.13208/j.electrochem.190524

摘要/Abstract

摘要：

Li₂MnO₃正极材料具有较高的理论容量（459 mAh·g ^-1）,不仅安全无毒还能够大大降低电池的制造成本,从而受到越来越多的关注. 然而,较低的首圈库仑效率和较差的循环性能妨碍了其在锂电池中的实际应用. 在此,作者研究了MgF₂涂层对Li₂MnO₃正极材料的电化学性能. 结果表明,MgF₂涂层诱导部分层状Li₂MnO₃向尖晶石相转化,从而降低了首圈不可逆容量,提高库仑效率. 重量比为0.5%、1.0%和2.0%的MgF₂涂层电极的初始库仑效率分别为70.1%、77.5%和84.9%,而原始电极仅为57.7%. 充放电曲线表明,1.0wt.%MgF₂涂层改性的Li₂MnO₃具有最高的充放电容量和最佳的循环稳定性. 40个循环后1.0wt.%MgF₂涂层样品的容量保持率为81%,远高于原始样品的容量保持率（53.6%）. 电化学阻抗谱结果表明MgF₂涂层减少了不利成分的快速沉积,并改善了电极的循环稳定性.

关键词: Li₂MnO₃正极材料, 氟化镁涂层, 循环稳定性, 库仑效率

Abstract:

Cathode material Li₂MnO₃ has received more and more attention owing to its high theoretical capacity (459 mAh·g ^-1). However, the low initial coulombic efficiency and the poor cycle stability hamper its practical application in lithium-ion batteries. Herein, we investigated the crystal structure and electrochemical performance of Li₂MnO₃ by introducing MgF₂ coating layer. The results indicated that the conversion of partial layer Li₂MnO₃ to spinel phase induced by MgF₂ coating could reduce the initial irreversible capacity and improve the first cycle efficiency. The initial coulombic efficiencies of the 0.5wt.%, 1.0wt.%, and 2.0wt.% MgF₂-coated electrodes were 70.1%, 77.5% and 84.9%, respectively, compared with 57.7% of the pristine cathode. The charge-discharge curves showed that the 1.0wt.% MgF₂-modified Li₂MnO₃ delivered the highest charge and discharge capacities, and exhibited the best cycle stability. The capacity retention rate of the 1.0wt.% MgF₂-coated sample was 81% after the 40th cycles, which was much higher than that of the pristine sample (53.6%). The electrochemical impedance spectroscopic data revealed that the MgF₂ coating reduced the rapid deposition of the resistive component and improved the cycle stability of the electrodes.

Key words: Li₂MnO₃ cathode, MgF₂ coating, cycle stability, coulombic efficiency

中图分类号:

O646.21

王杜丹, 王非, 翟欢欢, 李玉鹏, 杨纳川, 陈康华. 富锂层状正极材料Li₂MnO₃的表面改性及其电化学性能研究[J]. 电化学（中英文）, 2020, 26(2): 289-297.

WANG Du-dan, WANG Fei, ZHAI Huan-huan, LI Yu-peng, YANG Na-chuan, CHEN Kang-hua. Electrochemical Performance Improvement of Li₂MnO₃ Cathode Materials by MgF₂ Coating[J]. Journal of Electrochemistry, 2020, 26(2): 289-297.

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链接本文: https://electrochem.xmu.edu.cn/CN/10.13208/j.electrochem.190524

https://electrochem.xmu.edu.cn/CN/Y2020/V26/I2/289

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Reagent	Purity	Manufacturer
LiCH₃COO·2H₂O	AR	Aladdin
Mn(CH₃COO)₂·4H₂O	AR	Aladdin
MgCl₂	AR	Aladdin
NH₄F	AR	Aladdin
C₆H₈O₇·H₂O	AR	Aladdin

Name	Model	Factory
Electronic balance	ALC-210.4	ACCULRB sartorius group
Blast drying oven	101	Beijing Guangming Medical Co., Ltd.
Tube furnace	TCW-32B	Yixing Opry Furnace Industry
Magnetic heating stirrer	DF-101S	Zhengzhou Changcheng Branch Industry and Trade Co., Ltd.
LAND test system	CT2001A	Wuhan Landian Electronics Co., Ltd.
Electrochemical workstation	CHI660A	Shanghai Zhenhua Instrument Company

Li₂MnO₃ sample	Charge capacity/ (mAh·g^-1)	Discharge capacity/(mAh·g^-1)	First cycle efficiency/%
Pristine	200.9	116.1	57.7
0.5wt.%-MgF₂	178.2	125.6	70.1
1wt.%-MgF₂	178.5	138.2	77.5
2wt.%-MgF₂	129.7	110	84.9

R_sf	Pristine	0.5wt.%-MgF₂	1wt.%-MgF₂	2wt.%-MgF₂
0	180.8	157.8	108	146
40th	424.9	406.3	195.4	352.2

富锂层状正极材料Li₂MnO₃的表面改性及其电化学性能研究

Electrochemical Performance Improvement of Li₂MnO₃ Cathode Materials by MgF₂ Coating

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