Investigation on the root cause of the decreased performances in the overcharged lithium iron phosphate battery

Abstract

The overcharge of the lithium iron phosphate (LiFePO 4 ) batteries usually leads to the sharp capacity fading and safety issues, especially under low temperature environment. Thus, investigating their root cause originated from the electrode materials is critical for the safety performance optimization and market promotion of the LiFePO 4 batteries. In this work, the electrochemical/thermal behaviors of 18650 LiFePO 4 batteries are investigated after overcharge under room and low temperature of 25°C and −20°C, respectively. The results demonstrate a decreased electrochemical performance and faster heating rate of the overcharged battery, particularly under harsh working environments such as high discharge rate and low temperature. Coupling with the analyses of the internal resistance, the crystal structure, and microstructure of the electrodes, the root cause is attributed to the damage of the crystal structure and microstructure, which reduce the electron/Li + migrating capability and electrolyte diffusion/transfer efficiency. KEYWORDS electrochemical performance, internal resistance, lithium iron phosphate battery, microstructure, overcharge

Low‐temperature reversible capacity loss and aging mechanism in lithium‐ion batteries for different discharge profiles

“…In practical applications, it is proposed that the batteries are required to operate at various temperature ranges, and the variation trend of aging rate and dominating mechanism with temperature is different . Significant performance degradation (eg, rapid capacity fading and poor rate capability) has been reported when the LIBs were operated at low‐temperature conditions . Therefore, investigation of the degradation mechanism under these conditions is essential to elucidate the reasons behind the poor long‐term usability and provide reference for designing better‐performing LIBs …”

“…5 Significant performance degradation (eg, rapid capacity fading and poor rate capability) has been reported when the LIBs were operated at low-temperature conditions. [6][7][8] Therefore, investigation of the degradation mechanism under these conditions is essential to elucidate the reasons behind the poor long-term usability and provide reference for designing better-performing LIBs. 9 So far, there is a wide variety of studies regarding the performance and aging behaviors of LIBs under lowtemperature conditions.…”

Study on degradation behavior of commercial 18650 LiAlNiCoO2cells in over‐charge conditions

“…As a promising clean‐energy storage technology, Li‐ion cells have long been a concern in many industries such as electric vehicles (EV) and hybrid electric vehicles (HEV) power supply . The rapid growth of Li‐ion industry has led to the vigorous development of the Li‐ion cell market, which has promoted greatly driven research on Li‐ion cells, especially on the failure mechanisms under abused conditions . Among all kinds of abuse conditions, overcharge can easily cause safety problems .…”

“…They include Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometry (EDS), X‐Ray Diffraction (XRD) etc . Ex‐situ electrochemical techniques are used in numerous research under overcharge conditions . Compared with ex‐situ electrochemical techniques, in‐situ electrochemical techniques such as Electrochemical Impedance Spectroscopy (EIS) and Incremental Capacity (IC) are non‐invasive characterization.…”

“…[1][2][3] The rapid growth of Li-ion industry has led to the vigorous development of the Li-ion cell market, which has promoted greatly driven research on Li-ion cells, especially on the failure mechanisms under abused conditions. 4,5 Among all kinds of abuse conditions, overcharge can easily cause safety problems. 6 Thus, the importance of fundamentally understanding the electrochemical and thermal behavior during overcharge conditions is causing great attention.…”