Enhanced high-rate performance in Zn/Al dual-doped LiMn2O4 with submicron truncated structure

Abstract

The Jahn-Teller effect and Mn dissolution always restrict the practical electrochemical properties of spinel LiMn2O4 cathode material. Herein, a low-temperature solid-state combustion method is employed to synthesize various truncated octahedral LiZn0.03AlxMn1.97-xO4 (x ≤ 0.08) with submicron structure. The Zn/Al dual-doping is conducive to forming {110} and {100} planes, and is also beneficial to the crystal development of LiMn2O4. It is found that as the amount of Al doping increases, the average particle size gradually decreases from 188 nm to 113 nm. In addition, the Zn/Al co-doping integrated with small particles can improve the high-rate performance. The optimal LiZn0.03Al0.03Mn1.94O4 exhibits submicron truncated octahedral morphology, high crystallinity, and good particles dispersibility. Benefiting from these structure merits, the LiZn0.03Al0.03Mn1.94O4 delivers the first discharge capacity of 113.1 mAh⋅g−1 and low capacity fade of 9.9 % after 300 cycles at 1C. It also shows the high first discharge capacity of 86.6 mAh⋅g−1 at 10C and the high capacity retention of 72.1 % after 2000 cycles. Even at ultrahigh current density of 15C and 20C, the ultralong cycling lifespans over 2000 cycles are also achieved in LiZn0.03Al0.03Mn1.94O4 cathode material. The excellent electrochemical properties are ascribed to its relatively high Li+ diffusion coefficient (1.60 × 10−11 cm2⋅s−1) and low apparent activation energy (25.45 kJ⋅mol−1) during the de-intercalation process. The Zn/Al dual-doping and submicron truncated octahedron designs of the LiMn2O4 provide a scientific reference to prepare high-performance cathode materials.