High-entropy configuration strategy boosts excellent rate performance of layered oxide for sodium-ion batteries

Abstract

Layered oxides are considered to be potential cathodes for sodium-ion batteries based on high theoretical capacity and ease of synthesis. However, the complex phase transition caused by interlayer sliding in layered oxides leads to poor cycling stability, which will hinder their further application. Here, we designed a newly O3-type layered cathode NaNi_0.3Co_0.2Cu_0.1Mn_0.2Ti_0.2O₂ based on high-entropy to achieve highly reversible phase transition behavior. It reveals 132 mAh g⁻¹ at 0.2 C within 2–4 V increasing the energy density to 408 Wh kg⁻¹ and it shows an outstanding rate capability of 90 mAh g⁻¹ at 80 C (84.90% capacity retention after 1,500 cycles at 80 C). In-situ XRD shows that reasonable design of high-entropy components in layered material can achieve the purpose of delaying the occurrence of phase transition and DFT calculations show that the introduction of Co in transition metal layers can effectively improve the rate performance of the material. This work is of great significance in guiding the design and synthesis of highly stable layered cathode materials for sodium-ion batteries.