Synthesis of Co-Free Ni-Rich Single Crystal Positive Electrode Materials for Lithium Ion Batteries: Part II. One-Step Lithiation Method of Mg-Doped LiNiO₂

Abstract

This second study in a two part series investigates the synthesis of Co-free single crystalline Mg-doped LNO via the one-step lithiation method. The synthesized materials were characterized by scanning electron microscopy, X-ray diffraction and particle size analysis to understand the impact of synthesis conditions. Higher heating temperatures promoted grain growth but also increased the Ni content in the Li layer. Increasing the Li/TM ratio does not seem to have an effect on grain growth at lower temperatures but influences the formation of Li2O impurity. The separation of particle aggregates is required to improve the cycling performance of the material. The utilization of a lower temperature step after the calcination step can reduce the Ni content in the Li layer below what would be expected at the calcination temperature, and this can be used to grow larger grains while keeping an acceptable amount of Ni in the Li layer. However, all single crystalline materials are still not yet electrochemically competitive with polycrystalline materials and have lower capacities, higher irreversible capacities and similar cycling fade. The lower capacities of single crystalline materials stem from increased kinetic hindrances to Li diffusion. Cycling single crystalline materials at 55 °C can recover ∼20 mAh g−1 of discharge capacity and yield similar irreversible capacity compared with polycrystalline cells cycled at 30 °C.

Designing Cathodes and Cathode Active Materials for Solid‐State Batteries

“…It is worth noting, that most of the investigated SC NCM materials do not exhibit a pure single crystalline morphology, but rather consist of agglomerates of micrometer-sized monolithic grains, as synthesizing fully separated single crystals is very challenging. [104,115,116] In theory, such SC NCM CAMs should prevent particle cracking but still be susceptible to loss of contact with the SE as a result of the unit-cell volume changes during (de-)lithiation. Indeed, several reports have shown the favorable mechanical behavior of SC CAMs in SSBs, leading to much improved morphological integrity and better capacity retention.…”

Single step synthesis of W-modified LiNiO2 using an ammonium tungstate flux

“…34 Some authors have also achieved this morphology in Ni-rich compositions, beginning from spherical precursor materials, by using a multi-step annealing process. [35][36][37][38] However, this has yet to be reported for the LNO end-member composition, because its structure is quite sensitive to synthesis conditions. The parameters which favour particle growth, higher temperatures and longer annealing times can result in the formation of LNO with higher off-stoichiometry between the Li and Ni sites (Li 1Àz Ni 1+z O 2 ), which leads to poor electrochemical performance.…”

Dynamics of particle network in composite battery cathodes

“…Alleviation of the active particle damage has focused on understanding and tuning the morphological and chemical characteristics at the microscale ( 9 – 12 ), such as particle size, elongation and sphericity ( 13 , 14 ), crystallographic arrangement ( 15 , 16 ), mesoscale kinetics ( 17 , 18 ), grain boundary properties ( 19 , 20 ), and compositional variation ( 21 – 24 ). For instance, reducing the primary particle size is an effective approach to improving the fast-charging performance because smaller particles have shorter ion diffusion paths ( 25 , 26 ).…”