硅酸盐学报

磷酸铁锂-石墨电池贮存性能衰减机理

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母亚豪 ¹ , 乔昕 ¹^,² , 裴波 ² , 彭健 ¹ , 王硕 ¹

硅酸盐学报 | 青年视角 2025,53(7): 2032-2039

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硅酸盐学报 |青年视角 2025 , 53 (7) : 2032 -2039

磷酸铁锂-石墨电池贮存性能衰减机理

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母亚豪¹, 乔昕¹^,², 裴波², 彭健¹, 王硕¹

作者信息

^1．武汉理工大学材料科学与工程学院，材料复合新技术国家重点实验室智能材料与器件中心，武汉 430070

^2．武汉船用电力推进装置研究所，武汉 430064

通讯作者:

王硕（1996—），男，副教授；

彭健（1990—），男，研究员；

裴波（1985—），男，高级工程师。

作者简介:

母亚豪（2000—），男，硕士研究生。

Unravelling the Storage Degradation Mechanism of LiFePO₄-Graphite Batteries

Yahao MU¹, Xin QIAO¹^,², Bo PEI², Jian PENG¹, Shuo WANG¹

Affiliations

^1.Center of Smart Materials and Devices, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, School of Material Science and Engineering, Wuhan University of Technology, Wuhan 430070, China

^2.Wuhan Institute of Marine Electric Propulsion, Wuhan 430064, China

Corresponding Author:

WANG Shuo (1996-), male, Associate Professor. E-mail: shuowang@whut.edu.cn;

PENG Jian (1990-), male, Professor. jianpeng@whut.edu.cn;

PEI Bo (1985-), male, Senior Engineer. peibohfy@163.com

MU Yahao (2000-), male, Master candidate. E-mail: muyahao@whut.edu.cn

出版时间: 2025-07-20 doi: 10.14062/j.issn.0454-5648.20240812

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摘要

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不同温度和荷电状态对磷酸铁锂电池贮存性能有较大的影响。为了提供理论依据来改善电池的循环性能且延长使用寿命，研究了磷酸铁锂-石墨体系扣式电池在不同贮存温度（0、25、50 ℃）和荷电状态［50%、100%荷电状态（SOC）］下的贮存性能衰减机理。结果表明：高温和高SOC条件下贮存会导致电池容量衰减加剧。通过多种表征技术，揭示了贮存过程中正负极材料结构、形貌以及正极电解质界面相（CEI）和固体电解质界面相（SEI）的演变规律。结果显示：石墨负极表面无序程度增加；随着SOC和温度的增加，电解液分解加剧，CEI和SEI层中的LiF含量增加，其中温度对SEI/CEI的影响更为显著，负极侧SEI层中Li₂CO₃由于分解导致其相对含量降低。

关键词

磷酸铁锂-石墨电池 / 贮存性能 / 温度 / 荷电状态 / 固体电解质界面相

Abstract

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Introduction

Lithium iron phosphate-graphite (LFP-C) batteries are widely used in various fields due to their high energy density, low cost, high safety, good rate performance, long cycle life, and environmental friendliness. However, prolonged calendar aging leads to increased internal resistance and capacity decay, thereby shortening their service life. In this work, the impacts of storage temperature and SOC on the calendar aging performance of LFP-C batteries were investigated. The results show that the capacity decay is more severe under high temperature and high SOC conditions. The structural evolution of the anode and cathode materials, as well as the cathode-electrolyte interphase (CEI) and solid electrolyte interphase (SEI) layers were analyzed. It is indicated that the structure of LiFePO₄ cathode remains stable, while the degree of disorder in the graphite anode increases. The decomposition of the liquid electrolyte leads to an increase of LiF content in the CEI and SEI layers with decreasing Li₂CO₃ content in the SEI layer at 50 ℃.

Methods

In an inert atmosphere glove box, several LFP-C CR2025 coin cells were assembled. The cells were charged to the targeted SOC, and then divided into six groups and stored under different conditions (i.e., at 0°C-50%SOC, 0 ℃-100%SOC, 25 ℃-50%SOC, 25 ℃-100%SOC, 50 ℃-50%SOC, and 50 ℃-100%SOC) for one month. After storage, each group of cells was cycled at 1C to assess the impact of different storage conditions on the electrochemical performance of the cells. Other cells were disassembled, and then cleaned to obtain the positive and negative electrodes. The capacity degradation mechanisms of batteries during calendar aging were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy dispersive X-Ray spectroscopy (SEM-EDX), and X-ray photoelectron spectroscopy (XPS).

Results and discussion

After 1-month storage, the LFP - graphite coin cells are charged and discharged at 1 C for 300 cycles. The results show that the cells stored at 50 ℃ cannot deliver any capacity. The cells stored at 0 ℃ exhibit a significantly higher discharge capacity, compared to the cells stored at 25 ℃. The cycling performance results of the cells after storage at different states of charge (SOC) indicate that the discharge capacity of coin cells stored at 50% SOC is higher than that of cells stored at 100% SOC.

It is revealed that there is a slight difference in the XRD patterns of LFP electrodes stored under various temperatures and SOC conditions, indicating that the structure of LFP maintains a high stability under various storage conditions. The XRD patterns of the graphite anodes also remain unchanged, and only the peaks attributed to the graphite and current collector Cu foil appear.

The results by Raman spectroscopy indicate that the LFP material remains stable after storage, while the degree of disorder in the graphite anode increases significantly and becomes more pronounced with the increase of storage temperatures and SOC. The results by FTIR reveal the side reaction products on the surfaces of both the cathode and anode materials (i.e., Li₂CO₃, (CH₂OCOOLi)₂, and ROCO₂Li).

The results by SEM-EDX indicate that there is a slight change in the elemental ratio on the surface of the cathode electrodes after storage under different conditions, further validating the stability of the LFP material. The surface of graphite particles becomes rough after storage, and the content of fluorine and phosphorus elements on the surface of graphite anodes increases under high-temperature and high-SOC conditions.

The results by XPS show that the content of LiF in the CEI layers increases with increasing the temperature and SOC. The storage temperature shows a more pronounced effect on the composition of the CEI rather than the SOC. The relative content of LiF and P—F in the SEI layers significantly increases, while the relative content of Li₂CO₃ decreases due to decomposition as the storage temperature increases.

Conclusions

LiFePO₄-graphite coin cells with different SOC (i.e., 50% and 100%) were stored at various temperatures (i.e., 0, 25 ℃ and 50 ℃) and for one month and then charged and discharged for 300 cycles. The results showed that cells stored at 50°C were completely inoperative. The battery capacity retention followed an order of 0 ℃-50%SOC > 0 ℃-100%SOC > 25 ℃-50%SOC > 2 ℃-100%SOC.

It was revealed that the LFP cathode exhibited a structural stability as the storage temperature and SOC increased. Conversely, the degree of disorder of graphite anode increased, having a detrimental effect on the lithium ion migration. It was evident that the temperature could have a dominant influence on the composition of the CEI rather than SOC. The relative content of Li₂CO₃ decreased, while the relative content of LiF decreased within the CEI layers as the storage temperatures and SOC increased. In addition, the relative content of LiF and P—F increased in the SEI layers with temperature, and the temperature had a more significant effect rather than SOC on the SEI layer.

Key words

lithium iron phosphate-graphite batteries / calendar aging performance / storage temperature / state of charge / solid electrolyte layer

引用本文

母亚豪, 乔昕, 裴波, 彭健, 王硕. 磷酸铁锂-石墨电池贮存性能衰减机理. 硅酸盐学报, 2025 , 53 (7) : 2032 -2039 . DOI: 10.14062/j.issn.0454-5648.20240812

Yahao MU, Xin QIAO, Bo PEI, Jian PENG, Shuo WANG. Unravelling the Storage Degradation Mechanism of LiFePO₄-Graphite Batteries[J]. Journal of the Chinese Ceramic Society, 2025 , 53 (7) : 2032 -2039 . DOI: 10.14062/j.issn.0454-5648.20240812

基金

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国家自然科学基金青年基金项目(52302305)
湖北省重点研发计划项目(2022BAA069)

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2025年第53卷第7期

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文章信息

doi: 10.14062/j.issn.0454-5648.20240812

接收时间：2024-12-24
首发时间：2026-10-21
出版时间：2025-07-20

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出版历史

收稿日期：2024-12-24
修回日期：2025-01-11

基金

国家自然科学基金青年基金项目(52302305)

湖北省重点研发计划项目(2022BAA069)

作者信息

^1．武汉理工大学材料科学与工程学院，材料复合新技术国家重点实验室智能材料与器件中心，武汉 430070

^2．武汉船用电力推进装置研究所，武汉 430064

通讯作者:

王硕（1996—），男，副教授；

彭健（1990—），男，研究员；

裴波（1985—），男，高级工程师。

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https://castjournals.cast.org.cn/joweb/gsyxb/CN/10.14062/j.issn.0454-5648.20240812

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2种不同金属材料的力学参数

科 Family	属数 Number of genus	种数 Number of species	占总种数比例 Percentage of total species (%)	属 Genus	种数 Number of species	占总种数比例 Percentage of total species (%)
鹅膏菌科Amanitaceae	2	11	5.26	鹅膏菌属 Amanita	10	4.78
小菇科 Mycenaceae	2	12	5.74	丝盖伞属 Inocybe	5	2.39
多孔菌科 Polyporaceae	8	14	6.70	蜡蘑属 Laccaria	5	2.39
红菇科 Russulaceae	3	23	11.00	小皮伞属 Marasmius	6	2.87
				小菇属 Mycena	11	5.26
				光柄菇属 Pluteus	5	2.39
				红菇属 Russula	17	8.13
				栓菌属 Trametes	5	2.39

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