Preparing LiNi0.5Mn1.5O4 nanoplates with superior properties in lithium-ion batteries using bimetal–organic coordination-polymers as precursors

Abstract

LiNi_0.5Mn_1.5O₄ nanoplates were prepared using a two-step method composed of a hydrothermal method and a solid-state reaction. At first, bimetal–organic coordination-polymers containing Ni²⁺ and Mn²⁺ were synthesized using the ligand 3,4,9,10-perylenetetracarboxylic dianhydride (ptcda) by a template-assisted self-assembly method in a hydrothermal atmosphere. This was followed by thermal treatment to remove the organic components and then calcination with lithium acetate, and nanoplate-stacked LiNi_0.5Mn_1.5O₄ was obtained. The nanoplate structure shortens the diffusion path of the lithium ions in the bulk of LiNi_0.5Mn_1.5O₄ and then promotes fast charge–discharge properties of the material. In addition, an amorphous Li₂CO₃ layer with nanometer thickness in situ generated on the surface of the LiNi_0.5Mn_1.5O₄ particles was confirmed by TEM and XPS. This is helpful for suppressing the interfacial side reactions and thereby improving the cycling stability of the material. Owing to these advantages, the LiNi_0.5Mn_1.5O₄/Li₂CO₃ material exhibits excellent rate capability and cycling stability. The as-prepared material delivers 129.8 mA h g⁻¹ at a 1 C rate and retains 86.4% of the initial capacity even after 1000 cycles of charge–discharge at 25 °C. Even at a high discharge rate of 40 C, the specific capacity of the material is 120.9 mA h g⁻¹, and the capacity retention is 84.7% over 500 cycles. The high-temperature stability of the material is also superior. When operating at 55 °C, the capacity loss by cycle is only 0.037% throughout 250 cycles.