Engineering the diphasic Li‐rich Mn‐based composite with alleviated Jahn–Teller effect for high‐energy Li‐ion batteries

Abstract The unique oxygen stacking sequence of O2‐type structures restricts the irreversible transition metal movement into Li vacancies for the delithiated Li‐rich layered oxides (LLOs) and maintains outstanding voltage stability. However, the ion‐exchange synthesis promotes the Mn‐ion valence reduction and aggravates the Jahn–Teller (J–T) distortion alongside disproportionation. Since the main oxidation state of the Mn ions is +4 in the traditional O3‐type LLOs, synergistic effects of the O2‐type and O3‐type structures are expected in the O2/O3 diphasic Li‐rich material. Herein, O2/O3 biphasic intergrowth LLOs were rationally designed, and the synergic optimization of the biphasic structure was planned to retard the J–T effect. The O2/O3 intergrowth nature was confirmed, and the percentages of the O2 and O3 phases were 56% and 44%, respectively. Density functional theory calculations demonstrated that the Mn 2+ (EC) sheath had a remarkably lower energy barrier than the Li + (EC) sheath. This finding suggests that Mn 2+ ions that are dissolved into the electrolyte accelerate the electrolyte oxidization, so the deposition of the cathode electrolyte interface for pristine O2‐LLOs causes a high electrochemical impedance. The designed O2/O3 biphasic LLOs boost the capacity stability and suppress the voltage drop upon repeated Li + de‐intercalation. The phase regulation strategy offers great potential for developing low‐cost LLOs with enhanced structural stability for advanced Li‐ion batteries.