Lithium cathode materials have been considered as promising candidates for energy storage applications because of their high power/energy densities, low cost, and low toxicity. However, the Li/Ni cation mixing limits their application as practical electrode materials. The cation mixing of lithium transition-metal oxides, which was first considered only as the origin of performance degeneration, has recently been reconsidered as a way to stabilize the structure of active materials. Here we find that as the duration of the post-synthesis thermal treatment (at 500 °C) of LiNiCoMnO (NCM) was increased, the Li/Ni molar ratio in the final product was found to decrease, and this was attributed to the reduction in nickel occupying lithium sites; the cation mixing subtly changed; and those subtle variations remarkably influence their cycling performance. The cathode material with appropriate cation mixing exhibits a much slower voltage decay and capacity fade during long-term cycling. Combining X-ray diffraction, Rietveld analysis, the Fourier transform infrared technique, field-emission scanning electron microscopy, and electrochemical measurements, we demonstrate that an optimal degree of Ni occupancy in the lithium layer enhances the electrochemical performance of layered NMC materials and that this occurs through a "pillaring" effect. The results provide new insights into "cation mixing" as a new concept for material design utilization of layered cathodes for lithium-ion batteries, thereby promoting their further application in lithium-ion batteries with new functions and properties.

SiO x /C composites with a void-reserving structure are promising anodes for lithium-ion batteries. However, the facile and controllable synthesis of uniformly dispersed SiO x and carbon components, simultaneously incorporating ample voids, still remains a great challenge. Herein, a molecular polymerization strategy is devised to construct SiO x /C hollow particles for lithium-ion batteries. 3-aminopropyltriethoxysilane and dialdehyde molecules are judiciously engineered as silicon and carbon precursors to produce the polymer hollow spheres (PHSs) through a one-step aldimine condensation without any template and additive. A range of PHSs is obtained using terephthalaldehyde, glutaraldehyde, and glyoxal as the crosslinkers, demonstrating the high tunability of the strategy. Importantly, in situ pyrolysis of the PHSs warrants the homogeneous incorporation of SiO x (<5 nm) in carbon hollow capsids at a nanocluster scale. The obtained SiO x /C hollow spheres exhibit excellent Li + -ion storage behaviors, including cycling lifespan, coulombic efficiency, and rate performance. The superior performance is attributed to the well-dispersed SiO x nanoclusters in carbon substrate and the hollow structure. This molecular polymerization approach not only enables Si-based hollow composites effective and scalable anode materials but also opens up a new avenue for the controllable synthesis of template-free hollow architectures.

Exploiting high-efficiency catalysts toward hydrogen evolution reaction (HER) is a significant assignment nowadays. We find a quick and straightforward means to produce large-scale g-C 3 N 4 , which does not use template and easily obtains uniform nanostructures. And, we fabricate onestep preparation of a non-noble-metal catalyst, consisting of carbon material and transition metal only, by coupling graphitic carbon nitride (g-C 3 N 4 ) with Ni. The results show that Ni/C 3 N 4 composite catalyst possesses coral-like structure and its unique morphology is in favor of electrochemical activity for HER. Simultaneously, the Ni/C 3 N 4 composite catalyst presented prominent activity on HER with a high exchange current density of 1.91 × 10 −4 A cm −2 , a low Tafel slope of 128 mV dec −1 and small overpotentials of 356 and 222 mV to reach current densities of 100 and 10 mA cm −2 , which are superior to those of the state-of-the-art HER-active Ni-based compositions, as well as majority other metal-free catalysts, and even rivaled the electrocatalytic property of commercial Pt/C catalyst.

Owing to the scarcity of platinum resources and their visible flaw with poor durability and severe anode methanol crossover, Pt-based catalysts for catalyzing ORR have been experiencing some problems lately. Hence, nonprecious metal catalysts which are expected to replace platinum-based catalysts have become popular green sustainable development topics. We chose a facile pyrolysis method for the synthesis of this material, making the resulting coating material present a state of effectively encapsulating all cobalt nanoparticles into slim nitrogen-doped carbon nanotubes after process optimization, and the cobalt content even reached 20.9 wt %. In the catalytic aspect, the optimized Co@NSCNTs show a half wave potential equivalent to Pt/C in alkaline medium. Then, better durability (after 60,000 s chronoamperometry, the current retention still remains 95%) and commendable resistance to methanol crossover performed than the literature confirmed. All these characteristics superior to Pt/C should be ascribed to large amounts of entire encapsulated structures and synergism between encapsulated Co nanocrystal and graphitic N-doped carbon nanotubes. The presence of abundant metal particles allows more surface carbon and nitrogen atoms to be activated, in favor of the adsorption and dissociation of O2, and then improving oxygen reduction reaction (ORR) catalysis.

Transition-metal sulfides are key cathode materials for thermal batteries used in military applications. However, it is still a big challenge to prepare sulfides with good electronic conductivity and thermal stability. Herein, we rapidly synthesized a Co-doped NiS2 micro/nanostructure using a hydrothermal method. We found that the specific capacity of the Ni1–x Co x S2 micro/nanostructure increases with the amount of Co doping. Under a current density of 100 mA cm–2, the specific capacity of Ni0.5Co0.5S2 was about 1565.2 As g–1 (434.8 mAh g–1) with a cutoff voltage of 1.5 V. Owing to the small polarization impedance (5 mΩ), the pulse voltage reaches about 1.74 V under a pulse current of 2.5 A cm–2, 30 ms. Additionally, the discharge mechanism was proposed by analyzing the discharge product according to the anionic redox chemistry. Furthermore, a 3.9 kg full thermal battery is assembled based on the synthesized Ni0.5Co0.5S2 cathode materials. Notably, the full thermal battery discharges at a current density of 100 mA cm–2, with an operating time of about 4000 s, enabling a high specific energy density of around 142.5 Wh kg–1. In summary, this work presents an effective cathode material for thermal battery with high specific energy and long operating life.