Lithium-rich layered oxide materials are extremely important for improving the energy density of lithium-ion batteries. However, the electrochemical kinetics and cycle stability of these materials are still not good enough for further industrial application. Here, the effects of Nb doping on the crystalline structure, surface chemistry, cycle stability, and electrochemical kinetics of Li1.13Mn0.52Ni0.26Co0.10O2 are studied. Results show that Nb doping can significantly promote the cycle stability and electrochemical kinetics of Li1.13Mn0.52Ni0.26Co0.10O2. After 200 cycles, the discharge capacity retention increases from 59.2% (pristine material) to 78.8% (1% Nb element doping) with obvious enhanced rate performance. Via X-ray diffraction, scanning electron microscope, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and galvanostatic intermittent titration analysis, it is confirmed that Nb element has been successfully doped into the bulk of Li1.13Mn0.52Ni0.26Co0.10O2. Doping sites of Nb element in structure and influence on lithium migration has also been studied by the Rietveld refinement and first principle theoretical calculation methods. Doped Nb element efficiently changes the lattice parameters, inhibits the resistance rise, accelerates lithium ion diffusion, and finally promotes the cycle stability, and electrochemical kinetics of Li1.13Mn0.52Ni0.26Co0.10O2.

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High-energy storage devices are in demand for the rapid development of modern society. Until now, many kinds of energy storage devices, such as lithium-ion batteries (LIBs), sodium-ion batteries (NIBs), and so on, have been developed in the past 30 years. However, most of the commercially exploited and studied active electrode materials of these energy storage devices possess a single phase with low reversible capacity or unsatisfied cycle stability. Continuous and extensive research efforts are made to develop alternative materials with a higher specific energy density and long cycle life by element doping or surface modification. A novel strategy of forming composite-structure electrode materials by introducing structure units has attracted great attention in recent years. Herein, based on previous publications on these composite-structure materials, some important scientific points focusing on the design of composite-structure materials for better electrochemical performances reveal the distinction of composite structures based on average and local structure analysis methods, and an understanding of the relationship between these interior composite structures and their electrochemical performances is discussed thoroughly. The lithiation/delithiation mechanism and the remaining challenges and perspectives for composite-structure electrode materials are also elaborated.

Advanced anode materials possessing high performance, excellent stability, and low cost are quite insufficient for sodium ion batteries (NIBs), and there is a call for huge progress to meet the prerequisites toward practical applications. Herein, a silicon diphosphide (SiP2)/carbon composite anode was synthesized by a facile ball milling method to improve the NIBs performance. The well-constructed composite comprised of uniformly distributed SiP2 nanocrystallites within a conductive carbon framework greatly enhanced the electrode conductivity and structural compatibility to repeated sodiation/desodiation conversions and thus generated an excellent cyclability of >80% capacity retention for 500 cycles, a high Coulombic efficiency of 99%, and a promising fast-rate capability. In-situ/ex-situ X-ray diffraction and in-situ transmission electron microscopy investigations on the reversible electrochemical conversion of SiP2 showed the formation of Na3P and NaSi6 as the main sodiation products. This study sheds light on the realization of large-scale, high-performance NIBs through superior phosphorus-based anode materials.