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Lithium-ion capacitors (LICs) represent a new type of energy-storage devices, which have combined merits of high energy density Li-ion battery and high power density supercapacitor. Nevertheless, one significant challenge for LICs is the imbalanced kinetics between the fast capacitive cathode and relatively slow intercalation anode that limit the energy-storage performance. Here, the asymmetric LIC devices were developed based on a nitrogen-doped, carbonized zeolitic imidazolate framework (ZIF-8) cathode and a three-dimensional, nano-network-structured, conversion reaction-based Ni/NiO/C anode. These nanostructures associated with both the cathode and anode enable rapid electron and ions transport in the LIC devices, which allows the asymmetric LICs to be operated on either high energy mode (energy density of 114.7 Wh/kg at power density of 98.0 W/kg) or high power mode (power density of 60.1 kW/kg at energy density of 17.6 Wh/kg). The device also exhibited long-term cycle stability with 87% capacitance retention after 12 000 cycles. These results demonstrate that the rational design of nanoporous electrode structures can deliver a balanced, high-performance-activated cZIF-8|Ni/NiO/C-based lithium-ion capacitor.

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One key limitation of lithium metal electrodes is their propensity for dendrite formation that limits their use in commercial batteries. Here, a simple surface modification method was demonstrated to improve the electrochemical stability of the lithium metal electrode through direct coating of onionlike carbon (OC) and a fluoropolymer onto the lithium metal electrode. Selective and rapid microwave heating of the OC resulted in the in situ formation of a LiF-rich composite with the simultaneous infiltration of lithium into the OC. The electrochemical stability of the modified electrode was compared with a neat lithium metal electrode using symmetric stripping/plating cells. The microwave processed surface coating acted as a robust and stable passivation layer to prevent electrolyte decomposition, while also suppressing fast dendrite growth. The potential stability during the stripping and plating was enhanced at all rates examined (0.5–2 mA/cm2) by this passivation layer. With the stripping/plating capacity of 1 mA h/cm2, the microwave processed lithium metal electrode can be cycled over 1000 h at a current density of 0.5 mA/cm2. These results demonstrated that microwave treatment is a promising method for selective modification of the lithium metal electrode to improve its performance in energy storage applications.