Recent progress in Li and Mn rich layered oxide cathodes for Li-ion batteries

Li and Mn rich(LMR)layered oxides,written as xLi_(2) MnO_(3)·(1-x)LiMO_(2)(M=Mn,Ni,Co,Fe,etc.),have been widely reported in recent years due to their high capacity and high energy density.The stable structure and superior performance of LMR oxides make them one of the most promising candidates for the next-generation cathode materials.However,the commercialization of these materials is hindered by several drawbacks,such as low initial Coulombic efficiency,the degradation of voltage and capacity during cycling,and poor rate performance.This review summarizes research progress in solving these concerns of LMR cathodes over the past decade by following three classes of strategies:morphology design,bulk design,and surface modification.We elaborate on the processing procedures,electrochemical performance,mechanisms,and limitations of each approach,and finally put forward the concerns left and the possible solutions for the commercialization of LMR cathodes.

Understanding Structural Evolution in the Synthesis of Advanced Energy Materials

Developing a variety of in situ characterization techniques to unravel the structural/chemical evolution during the synthesis of various advanced energy materials for studying the relationship among those experimental conditions and the structure is the key to implement the controllable synthesis of battery materials.This perspective summarizes the recent studies into structural evolution during in situ synthesis of various advanced energy materials by synchrotron X-ray diffraction technique and forecasts the more extensive applications in the future.

Interface-reconstruction Forming Bifunctional(LixTM1-x)O Rock-salt Shell for Enhanced Cyclability in Li-rich Layered Oxide

Poor cycling stability,as a long-standing issue,has greatly hindered the commercial application of Li-rich layered oxide cathodes in high-energy-density Li-ion batteries.NiO-type rock-salt phase is commonly considered electrochemically inert but stable.Herein,an ultrathin(LixTM1-x)O rock-salt shell was in situ constructed at the particle surface during the synthesis of Li-rich layered oxide cathodes through a unique soft chemical quenching method.Comprehensive structural/chemical analysis reveals that,it not only inherits the chemical stability of traditional NiO-type rock-salt phase,but also facilitates Li^+diffusion due to the co-occupancy of Li^+and TM cations.Such a bifunctional shell could efficiently prevent TM dissolution and oxygen evolution during the long-term cycling,eventually leading to the enhanced cycling stability for Li-rich layered oxides(92.7%of capacity retention after 200 cycles at 0.5 C).It provides new guidance to design and synthesize new Li-rich layered oxides with the excellent cycling stability through utilizing some electrochemically-inert phases.