Analysis of the Degradation of High‐Temperature Cycle Life Based on the Dual‐Voltage Characteristics of Lithium Manganese Iron Phosphate/Carbon

With the growing demand for energy, lithium‐ion batteries are required to achieve higher energy density, improved safety, and reduced cost. Lithium manganese iron phosphate (LMFP) precisely meets these requirements. LMFP is anticipated to replace lithium iron phosphate(LFP) as a cathode material owing to its high voltage, high energy density, and low cost. However, the Jahn–Teller effect of Mn shortens its high‐temperature cycle life. Herein, 5 Ah lithium manganese iron phosphate/carbon pouch batteries were fabricated at typical formation temperatures. The inherent dual discharge voltage plateaus of LMFP during high‐temperature cycling were separately analyzed to elucidate the capacity fading mechanism. The fading mechanism, distinct from lithium iron phosphate/carbon batteries, was proposed. In the early cycle, capacity decays mainly in the low‐voltage region (≤3.5 V); later, manganese dissolution in the high‐voltage region (>3.5 V) causes some Li + to enter the low‐voltage region instead of original sites of these Li + . Notably, elevating the formation temperature can restrain this phenomenon, enhancing the high‐temperature cycle life.