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High-nickel ternary materials are currently the most promising lithium battery cathode materials due to their development and application potential. Nevertheless, these materials encounter challenges like cation mixing, lattice oxygen loss, interfacial reactions, and microcracks. These issues are exacerbated at high voltages, compromising their cyclic stability and safety. In this study, we successfully prepared Nb5+-doped high-nickel ternary cathode materials via a high-temperature solid-phase method. We investigated the impact of Nb5+ doping on the microstructure and electrochemical properties of LiNi0.88Co0.05Mn0.07O2 ternary cathode materials by varying the amount of Nb2O5 added. The experimental results suggest that Nb5+ doping does not alter the crystal structure but modifies the particle morphology, yielding radially distributed, elongated, rod-like structures. This morphology effectively mitigates the anisotropic volume changes during cycling, thereby bolstering the material's cyclic stability. The material exhibits a discharge capacity of 224.4 mAh g−1 at 0.1C and 200.3 mAh g−1 at 1C, within a voltage range of 2.7 V–4.5 V. Following 100 cycles at 1C, the capacity retention rate maintains a high level of 92.9%, highlighting the material's remarkable capacity retention and cyclic stability under high-voltage conditions. The enhancement of cyclic stability is primarily due to the synergistic effects caused by Nb5+ doping. Nb5+ modifies the particle morphology, thereby mitigating the formation of microcracks. The formation of high-energy Nb-O bonds prevents oxygen precipitation at high voltages, minimizes the irreversibility of the H2–H3 phase transition, and thereby enhances the stability of the composite material at high voltages. [ABSTRACT FROM AUTHOR]

Owing to the high energy density, lithium–sulfur batteries (LSBs) have attracted a lot of attention as a representative of new secondary batteries. However, LSBs also face some serious issues in practical applications such as the large volume expansion of S cathode, shuttle effect of lithium polysulfide (LPSs), and dendrite formation of lithium metal anode. In this work, hollow carbon sphere (HCS) was used as a framework, and CoSe2/Se nanorods were uniformly loaded on the HCS surface to form a 3D heterostructured composite (CS/Se/HCS). When used as an active sulfur host, the HCS is conducive to the transport of electrons and Li+; meanwhile, it can suppress the large volume expansion in the electrochemical performance. CoSe2 can effectively adsorb LPSs and accelerate the transformation of LPSs. We also investigated the effect of CoSe2/Se content on the electrochemical performance of the S electrode. Among different CS/Se/HCS samples, the CS/Se/HCS-0.3/S electrode exhibited the best electrochemical performance; at 1C rate, after 500 cycles, it presents a reversible capacity of 511 mA h g−1. This work provided a new idea for the combination of transition metal selenide and carbon materials, which can be used in LSBs and other energy storage devices. [ABSTRACT FROM AUTHOR]

The electrochemical performance of materials largely depend on the quality of precursor. Co-precipitation is an effective way to attain an excellent morphology, particle size and distribution of particles, which is still a huge challenge in pH regulation of the reaction system to influence supersaturation. Here, Ni0.8Co0.1Mn0.1 (OH)2 precursors were prepared as an example by regulating Ni2+ concentration in the supernatant instead of adjusting pH value, and the effect of preparation process parameters on microstructure of precursor was evaluated quantitatively. Particle size distribution of Ni0.8Co0.1Mn0.1(OH)2 precursor was evaluated from SEM images, and the electrochemical performance of LiNi0.8Co0.1Mn0.1O2 cathode materials were studied using LAND battery test system. The results showed that more homogeneous particle size distribution was attained in samples prepared by regulating concentration of Ni2+ in supernatant than with pH regulation. Average particle size increased from 4.1 to 5.9 μm, and peak width at half height were 1.37 and 1.16 μm, respectively. Same conclusions could also drawn from standard deviation, peak area and peak height data. Electrochemical data demonstrate that rate capabilities were 206.7, 183.2, 171, 161.8, and 145.5 mA h/g from 0.1 to 10 C, respectively and capacity retention was 86.6% after 100 cycles at 1 C, which were better than the pH regulation progress. These results indicate that regulation of concentration of Ni2+ in supernatant has better performance and is suitable for industrial applications. [ABSTRACT FROM AUTHOR]

Carbon‐layer‐coated porous Ni‐doped CoSe2 (Ni‐CoSe2/C) nanospheres have been fabricated by a facile hydrothermal method followed by a new selenization strategy. The porous structure of Ni‐CoSe2/C is formed by the aggregation of many small particles (20–40 nm), which are not tightly packed together, but are interspersed with gaps. Moreover, the surfaces of these small particles are covered with a thin carbon layer. Ni‐CoSe2/C delivers superior rate performance (314.0 mA h g−1 at 20 A g−1), ultra‐long cycle life (316.1 mA h g−1 at 10 A g−1 after 8000 cycles), and excellent full‐cell performance (208.3 mA h g−1 at 0.5 A g−1 after 70 cycles) when used as an anode material for half/full sodium‐ion batteries. The Na storage mechanism and kinetics have been confirmed by ex situ X‐ray diffraction analysis, assessment of capacitance performance, and a galvanostatic intermittent titration technique (GITT). GITT shows that Na+ diffusion in the electrode material is a dynamic change process, which is associated with a phase transition during charge and discharge. The excellent electrochemical performance suggests that the porous Ni‐CoSe2/C nanospheres have great potential to serve as an electrode material for sodium‐ion batteries. [ABSTRACT FROM AUTHOR]