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Transition metal oxides (TMOs) are considered favorable anode materials for lithium-ion batteries (LIBs); however, their poor conductivity, low-rate performance, and abrupt lithiated volumetric expansion make them unviable materials for a practical Li-ion full cell. As a prospective solution, a facile method of fabricating peanut-like porous carbon fibers (CFs) consisting of hollow carbon-coated NiCo–metal/oxide (NiCo–MO) spheres as high-performance anode (NiCo-MO@CFs) is reported. This synthesis route is simple and eco-friendly compared with the complicated synthesis of hollow TMOs, such as the hard template method, multistep route, or use of toxic reagents. The hollow structure can accommodate the abrupt lithiated volume variation of NiCo–MO, and the CFs can ensure structural durability during the discharge/charge process, offering a double buffering for the stress during volumetric fluctuation. A mechanistic study suggests that the hollow structure is formed by the typical Kirkendall diffusion, where encapsulation by CFs is a prerequisite. Outstanding Li-ion storage performance is supported by good rate capability and prolonged durability for 500 cycles at 1 A g−1 of NiCo-MO@CFs electrode. Remarkably, it shows a reversible discharge capacity of 894 mA h g−1 after the consecutive rate capability study and a successive discharge-charge process for 92 cycles at 0.1 A g−1. The computational study confirms that the most favorable Li adsorption sites for hybrid NiCo-MO@CFs surface are CoO-bridges and the hybrid surface provides enhanced Li adsorption energies and conductivity. Furthermore, a full cell was constructed using LiFePO 4 (cathode) and NiCo-MO@CFs (anode), which exhibits a discharge capacity of 616 mA h g−1 (anode-based) at 0.1 A g−1 with 66 % capacity retention after 100 cycles. [Display omitted] • Hollow NiCo-metal/oxide (MO)@carbon fibers (CFs) was made as anodes for LIBs. • NiCo-MO@CFs delivered the stable discharge capacities of 832 mA h g−1 at 0.1 A g−1. • After 500 cycle, NiCo-MO@CFs exhibited 96 % of capacity retention at 1 A g−1. • DFT shows fast charge-discharge rate with suitable diffusion energy barrier for Li+. • NiCo-MO@CFs-based full-cell shows a capacity 616 mA h g−1 and good stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrochemical reduction of CO 2 on Cu(1 1 1) surface and Cu/G catalysts. • The potential-limiting step (E barr) strongly prefers the favorable (COOH/HCOO) pathways. • Electronic properties and binding nature explains the reason for selective end products. • Graphite-supported single atom copper catalyst (Cu/G) prefers CH 3 OH as final end product. First-principles study explores the catalytic performance of the Cu(1 1 1) and Cu/G catalysts for the electrochemical CO 2 reduction using computational hydrogen electrode model. Two different pathways, determined based on the initially generated intermediates (COOH* and HCOO*), as well as successive intermediates and the end products, were investigated. Although the two catalysts promote both pathways, Cu(1 1 1) surface favors "COOH pathway" and Cu/G catalyst strongly promotes the "HCOO pathway" with an free energy barrier of 0.83 eV (CO* → CHO*) and 0.87 eV (HCOO* → H 2 COO*). Electronic properties and binding nature of the final intermediate (CH 3 O*) on both catalysts sheds light on the fundamental reason for the selective end products (CH 4 on the Cu(1 1 1) surface and CH 3 OH on the Cu/G catalyst). CH 3 OH is predominantly produced with the Cu/G catalyst because the C O bond of CH 3 O* is stronger than the bond between the single Cu atom and O of CH 3 O*, given that the energy of the d-band center of the single Cu atom is relatively highly negative. The current study explores the different electrochemical reduction pathways on the Cu(1 1 1) and Cu/G catalyst, providing insight for the design of highly efficient catalysts that afford selective end products. [ABSTRACT FROM AUTHOR]