In Situ High‐Temperature Phase Elucidation of Secondary Particles and Segregating Nanoparticles with Surface Coating‐Networking Architecture for High‐Voltage Cathode Life at High Rate

Secondary microparticles are synthesized using a Mn1.5Ni0.5(OH)2CO3 precursor, which undergoes thermal decomposition and calcination, releasing CO2 and H2O gaseous species. In situ high‐temperature phase elucidation confirms the least degree of disordered phase LiMn1.5Ni0.5O4 cathode without rock‐salt impurity phase and having insignificant content of Mn3+ to stable Fd m structure. Raman spectrum shows a band at 590 cm−1 (F2g(3)) without splitting, confirming spinel compound derived with disordered phase. Microscopic analyses reveal secondary microparticles and segregated primary nanoparticles having surface coating‐conducting network architecture. Cyclic voltammograms of primary nanoparticles show well‐resolved two redox peaks at 4.7 V compared to secondary microparticles, confirming superior kinetic reversibility for Ni2+ to Ni3+ and Ni3+ to Ni4+ redox process. At 20C discharge, segregated primary nanoparticles exhibit a discharge flat voltage profile at 4.3 V and deliver a high reversible capacity of 100 mAh g−1 for the 12th cycle and 86 mAh g−1 for the 1000th cycle, while secondary microparticles deliver 70 mAh g−1 for 12th cycle and declined its cycle operation at 250th cycle with the capacity of < 5 mAh g−1. Results confirm a strong potential for use as a highly durable, cobalt‐free, high‐voltage cathode capable of high‐rate discharge in LIBs.