Nix Mny Coz O Nanowire/CNT Composite Microspheres with 3D Interconnected Conductive Network Structure via Spray-Drying Method: A High-Capacity and Long-Cycle-Life Anode Material for Lithium-Ion Batteries

Enhanced Cycle Stability of Crumpled Graphene-Encapsulated Silicon Anodes via Polydopamine Sealing

Despite silicon being a promising candidate for next-generation lithium-ion battery anodes, self-pulverization and the formation of an unstable solid electrolyte interface, caused by the large volume expansion during lithiation/delithiation, have slowed its commercialization. In this work, we expand on a controllable approach to wrap silicon nanoparticles in a crumpled graphene shell by sealing this shell with a polydopamine-based coating. This provides improved structural stability to buffer the volume change of Si, as demonstrated by a remarkable cycle life, with anodes exhibiting a capacity of 1038 mA h/g after 200 cycles at 1 A/g. The resulting composite displays a high capacity of 1672 mA h/g at 0.1 A/g and can still retain 58% when the current density increases to 4 A/g. A systematic investigation of the impact of spray-drying parameters on the crumpled graphene morphology and its impact on battery performance is also provided.

Engineering Hierarchical CoO Nanospheres Wrapped by Graphene via Controllable Sulfur Doping for Superior Li Ion Storage

The inferior conductivity and large volume expansion impair the widespread applications of metal oxide-based anode materials for lithium-ion batteries. To address these issues, herein an efficient strategy of structural engineering is proposed to improve lithium storage performance of hierarchical CoO nanospheres wrapped by graphene via controllable S-doping (CoOS_0.1   @ G). S-doping promotes the Li⁺ diffusion kinetics of CoO by expanding the interplanar spacing of CoO, lowering the activation energy, and improving the pseudocapacitance contribution. Meanwhile, the electronic structure of CoO is adjusted by S-doping as confirmed by density functional theory calculations, thus enhancing the conductivity. Finite element analysis reveals that the produced Li₂ S during lithiation improves the structural stability of the S-doped electrode, which is further confirmed by experimental observation. As expected, CoOS_0.1   @ G exhibits excellent lithium storage performance with an initial discharge capacity of 1974 mAh g^-1 at 100 mA g^-1 , and high discharge capacity of 1573 mAh g^-1 after 400 cycles at 500 mA g^-1 . It is believed that the insights into the structural doping enlighten research to explore other metal oxides for fast and stable Li ion storage.

Micro-nano NiO-MnCo2O4 heterostructure with optimal interfacial electronic environment for high performance and enhanced lithium storage kinetics

This manuscript provides an in situ synthesis method for the self-assembly of a heterostructured NiO-MnCo2O4 micro-nano composite with a poriferous shell. The special shell structure effectively alleviated the volume variation and subsequently enhanced the diffusivity of ions in the cycling process for cyclic stability. The inner spaces among the stacked nanoparticles are conducive to electrolyte infiltration and the transfer of ion/electrons with low concentration polarization. Consequently, the optimized NiO-MnCo2O4 exhibited excellent cycle stability (718.8 mA h g-1 after 1000 cycles at 2 A g-1) and highly recoverable rate performance. On gaining insight into the heterointerface structure, it was indicated that the optimal interfacial electronic environment in the presence of the nickel content plays a key role in creating lattice defects and active sites to increase the ion diffusion rate, electron conductivity and unlock extra pseudocapacitance for ion storage. The excellent capabilities from the optimal heterointerface environment will promote the development of high-energy applications of LIBs.