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Enriching electrode materials with definite functions is of great influence but highly challenging towards achieving high areal capacity lithium ion batteries (LIBs). Taking transition metal oxides (TMOs) as a case study, several attempts have been employed to demonstrate the large variations in lithium storage performance of TMOs, but explanation of the adsorption capability is rarely reported. Herein, the Li-ion storage chemistry of NiO nanosheets is successfully enhanced by modulating the position of the p-orbital energy level via engineering with porous N-doped carbon fiber and carbon quantum dots (CDs). The as-prepared monolithic NiO hybrid nanosheets (denoted CF/ECF/NiO/CD) exhibit high reversible areal capacity of 3.97 mA h cm−2 at 0.25 mA cm−2, excellent cyclic stability with capacity of 2.91 mA h cm−2 at 3.0 mA cm−2, as well as attractive rate capacity of 2.61 mA h cm−2 at 6.0 mA cm−2. In situ Raman analyses, XPS, and DFT calculations reveal that performance enhancement is related to the electronic modulations between NiO, porous carbon fiber and CDs that triggers the shift of the p-band towards accommodating interfacial electron transfer that helps in promoting the Li storage activity. In addition, an all-flexible lithium ion battery based on CF/ECF/NiO/CD anode is assembled and a volumetric energy density of 619.9 Wh L−1 is achieved (equivalent to an energy density of 201.7 Wh kg−1). This work opens an achievable approach for high-areal-capacity LIBs and provides relevant understanding into designing other LIB electrodes and beyond.
Huang et al. (Tue,) studied this question.