An ultrasound-triggered cation chelation and reassembly route to one-dimensional Ni-rich cathode material enabling fast charging and stable cycling of Li-ion batteries

Abstract

Ni-rich oxides, LiNixMnyCozO2 (NMC), are among leading candidates for cathode materials in Li-ion batteries. However, they are mostly fabricated by coprecipitation approach under complex conditions, which usually produces large secondary particles composed of aggregated primary particles. Undesirable cation mixing and crack propagation upon cycling block ion and electron transport, result in fast capacity fading and poor rate capability. Herein, we present an ultrasound-triggered cation chelation and reassembly route for synthesizing one-dimensional precursor with homogeneous element distribution at the atomic level. This process is accomplished by the synergistic combination of ultrasound and surfactant, which can disperse reactants and remove hydration shells surrounding cations so as to accelerate chelating reaction, and then separate and assemble chelates into one dimensional structure. The whole synthesis time is only 20 min (8.9 min of ultrasonic working time) in an open vessel under natural ambient conditions. One-dimensional LiNi0.6Mn0.2Co0.2O2 has a high reversible capacity (184 mAh·g−1 at 0.1 C) and long cycling stability (95.1% and 82.4% capacity retention for 100 and 1000 cycles, respectively). The short charging time of 76 s is realized at super high current rate of 20 C, which is very important to improve the competitiveness of electric vehicles relative to fuel vehicles. Our synthetic approach can provide a general strategy for the growth of mixed-metal-EDTA chelate precursors by changing the feeding ratio of Ni2+, Mn2+ and Co2+ cations in reaction for fabricating NMC cathode materials with other compositions.