Improved capacity retention and ultralong cycle performance of Ni-Fe co-doped LiMn2O4 cathode material at high current densities

At high current density, low capacity and rapid capacity decay of spinel LiMn 2 O 4 cathode material during the cycle limit its application. Herein, element doping approach to restrain Jahn-teller effect combined with crystal plane regulation to mitigate Mn dissolution is employed to synthesize a series of truncated octahedron LiNi 0.02 Fe x Mn 1.98−x O 4 (x ≤ 0.12) which provide high exposure {111} surfaces as well as a small portion of {110} and {100} facets for offering Li + ion rapid diffusion channel. Many characterizations such as XRD , SEM and TEM show that Ni-Fe co-doped can effectively promote the development of crystal and the preferential growth of crystals planes. Electrochemical test results imply that at 1 C the difference between capacity and capacity retention ratio in terms of LiNi 0.02 Mn 1.98 O 4 (LNMO) and Ni-Fe co-doping samples are not obvious. With the increasing of current densities, Ni-Fe co-doping samples exceptional rate capability and cycle stability become apparent. The optimal LiNi 0.02 Fe 0.05 Mn 1.93 O 4 (LNFMO-5) and LNMO can keep 76.9% and 74.6% of their original capacity of 113.4 mAh·g ‐1 as well as 116.2 mAh·g ‐1 after 500 cycles at 1 C, respectively. At 10 C, the LNFMO-5 sample delivers the capacity of 89.3 mAh·g ‐1 and a higher capacity retention ratio of 72.9% after 2000 cycles, while the LNMO sample is only 63 mAh·g ‐1 and 67.2%. Even at 20 C, The LNFMO-5 sample still reaches a high specific capacity of 84.9 mAh·g ‐1 and a higher capacity retention ratio of 76.1% after 2000 cycles, which are much higher than the LNMO sample (63.0 mAh·g ‐1 ) and 57.4% capacity retention rate. CV and EIS analysis manifest that the LNFMO-5 has a higher D Li + and a lower E a than that of the LNMO. A unique Ni-Fe co-doped truncated octahedral LiMn 2 O 4 material with exceptional electrochemical property will be an attractive candidate for the preparation high-performance and long-cycle spinel LiMn 2 O 4 cathode materials.