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For lithium ion batteries (LIBs), low electronic conductivity of CuO leads to rapid capacity decay and poor structural stability. Herein, we successfully fabricate three-dimensional CuO nanoflake arrays coated Cu foam by facile and efficient electrochemical oxidation. When being applied as anode material for LIBs, the CuO electrodes deliver stable reversible capacities of 523.9 mA h g −1 at 0.5 A g −1 , 376.1 mA h g −1 at 1.0 A g −1 and 322.7 mA h g −1 at 2.0 A g −1 with high coulombic efficiency (>99%) after 100 cycles. A long cycle life of up to 400 cycles at 2.0 A g −1 is also achieved with the retention capacity of 193.5 mA h g −1 . Moreover, the electrode exhibits excellent rate capability and can regain its original capacities as reversing to the low current densities. Noticeably, on-line differential electrochemical mass spectrometry and in situ Raman measurements confirm the formation of solid electrolyte interface film and the conversion mechanism for the CuO electrodes, respectively. The superior lithium storage performance can be attributed to the favorable nanoflake structures with high surface area and the perfect electrical contact between CuO and Cu substrate. [ABSTRACT FROM AUTHOR]

Low electronic conductivity and drastic volume change during cycling of transition metal oxides, as anodes for lithium ion batteries (LIBs), lead to rapid capacity decay and poor structural stability. Herein, nanostructured NiCo 2 O 4 anchored on carbon sheets was synthesized by a facile hydrothermal method with following thermal treatment. The wrinkled carbon substrate in the composite derives from the carbonization of pomelo peels, which can be mass-produced for the large-scale application. This composite shows mesoporous structures with high specific surface areas and intimate NiCo 2 O 4 /carbon interfaces, which favors the alleviation of the volume expansion/shrink during charging/discharging process and improves the electron/mass transport, enhancing the capability and stability for LIBs. This composite delivers a high reversible capacity of 473.7 mA h g−1 after 210 cycles at a current density of 500 mA g−1. A long cycle life of up to 1100 cycles at 2000 mA g−1 is achieved with the retention capacity of 363 mA h g−1. The electrode also exhibits excellent rate capability and can regain its original capacities as reversing to the low current densities. This work highlights the biomass-derived carbon-supported metal oxides as an environmentally friendly and economic strategy for advanced LIBs. • Carbon substrate as buffer for anode materials can be derived from pomelo peels. • Cycling stability of NiCo 2 O 4 is improved by depositing it on carbon substrate. • Faster Li+ diffusion coefficients are obtained with the existence of carbon. [ABSTRACT FROM AUTHOR]