Suppress oxygen evolution of lithium-rich manganese-based cathode materials via an integrated strategy

Improving the reversibility of anionic redox and inhibiting irreversible oxygen evolution are the main challenges in the application of high reversible capacity Li-rich Mn-based cathode materials.A facile synchronous lithiation strategy combining the advantages of yttrium doping and LiYO_(2) surface coating is proposed.Yttrium doping effectively suppresses the oxygen evolution during the delithiation process by increasing the energy barrier of oxygen evolution reaction through strong Y–O bond energy.LiYO_(2) nanocoating has the function of structural constraint and protection,that protecting the lattice oxygen exposed to the surface,thus avoiding irreversible oxidation.As an Li^(+) conductor,LiYO_(2) nano-coating can provide a fast Li^(+) transfer channel,which enables the sample to have excellent rate performance.The synergistic effect of Y doping and nano-LiYO_(2) coating integration suppresses the oxygen release from the surface,accelerates the diffusion of Li^(+)from electrolyte to electrode and decreases the interfacial side reactions,enabling the lithium ion batteries to obtain good electrochemical performance.The lithium-ion full cell employing the Y-1 sample(cathode)and commercial graphite(anode)exhibit an excellent specific energy density of 442.9 Wh kg^(-1) at a current density of 0.1C,with very stable safety performance,which can be used in a wide temperature range(60 to-15℃)stable operation.This result illustrates a new integration strategy for advanced cathode materials to achieve high specific energy density.

S-O bond chemically constrained NiS2/rGO nanocomposite with enhanced Na-ion storage capacity

NiS2 has become a research hotspot of anode materials for Na-ion batteries due to its high theoretical specific capacity.However,the volume effect,the dissolution of polysulfide intermediates and the low conductivity during the charge/discharge process lead to the low specific capacity and poor cycling stability.NiS2/rGO nanocomposite was prepared by a facile two-step process:GO was prepared by modified Hummers method,and then NiS2/rGO nanocomposite was synthesized by L-cys assisted hydrothermal method.NiS2/rGO nanocomposite shows excellent cycle performance and rate performance,which could be attributed to the mesoporous structure on the graphene skeleton with high conductivity.Besides,the chemical constraint of a unique S—O bond on NiS2 could inhibit the dissolution of intermediates and the loss of irreversible capacity.