Overcharge Cycling Effect on the Surface Layers and Crystalline Structure of LiFePO4 Cathodes of Li-Ion Batteries

Abstract

Electrochemical cells using LiFePO4 cathode material are considered one of the safest and most resistant to overcharging among Li-ion batteries. However, if LiFePO4-based electrodes are exposed to high potentials, surface and structural changes may occur in the electrode material. In this study Li/LiFePO4 half-cells were overcharged under different modes with variable cut-off voltages and charge currents. The change in voltage profile, discharge capacity, surface layers composition, and crystalline structure were characterized after overcharge cycles. It was demonstrated that the cathode material is resistant to short-term overcharging up to 5 V, but undergoes irreversible changes with increasing overcharge time or potential. Thus, despite the well-known tolerance of LiFePO4-based batteries to overcharge, a long overcharge time or high cut-off voltage leads to destructive changes in the cathode and should be avoided.

Operando Quantified Lithium Plating Determination Enabled by Dynamic Capacitance Measurement in Working Li‐Ion Batteries

“…Due to the enormous polarization at high charging rate, the battery voltage reaches 3.6 V at the very beginning. Therefore, overcharging to a cut‐off voltage of 4.2 V is implemented to probe the Li plating behavior since the tolerance of LFP‐based batteries to short‐term overcharge has been confirmed by previous literatures [27] . The C S values show a rapid upward trend at a charging capacity of 0.6 A h, corresponding to the battery voltage of 3.93 V (Figure 5c).…”

High-Rate Layered Cathode of Lithium-Ion Batteries through Regulating Three-Dimensional Agglomerated Structure

“…Since the layered LiNi x Co y Mn z O 2 (x + y + z = 1, LNCM) cathodes materials was put forward by J.R. Dahn, it was regarded as the most promising cathode because of the large theoretical capacity of 273 mAh•g −1 to 285 mAh•g −1 , the high-voltage platform of 3.6 V and a considerable compacted density with greater than 2.6 g cm −3 [6][7][8][9]. And the Li-ion battery can be served as a power source for vehicle application or energy storage, which will improve the environment and accelerate development of the new energy resources [10].…”

Operando Quantified Lithium Plating Determination Enabled by Dynamic Capacitance Measurement in Working Li‐Ion Batteries

“…Therefore, overcharging to a cut-off voltage of 4.2 V is implemented to probe the Li plating behavior since the tolerance of LFP-based batteries to short-term overcharge has been confirmed by previous literatures. [27] The C S values show a rapid upward trend at a charging capacity of 0.6 A h, corresponding to the battery voltage of 3.93 V (Figure 5c). A safe capacity limit of 0.6 A h without Li plating is suggested for the 1.0 A h Gr j j LFP pouch cells charging at 2.0 C. After 0.6 A h, the C S values exhibit a general upward trend, but some fluctuations occur, which is distinct from the variation trend in coin cells.…”