Although the synthesis of mesoporous materials is well established, the preparation of TiO₂ fiber bundles with mesostructures, highly crystalline walls, and good thermal stability on the RGO nanosheets remains a challenge. Herein, a low-cost and environmentally friendly hydrothermal route for the synthesis of RGO nanosheet-supported anatase TiO₂ fiber bundles with dense mesostructures is used. These mesostructured TiO₂-RGO materials are used for investigation of Li-ion insertion properties, which show a reversible capacity of 235 mA h g⁻¹ at 200 mA g⁻¹ and 150 mA h g⁻¹ at 1000 mA g⁻¹ after 1000 cycles. The higher specific surface area of the new mesostructures and high conductive substrate (RGO nanosheets) result in excellent lithium storage performance, high-rate performance, and strong cycling stability of the TiO₂-RGO composites.

The utilization of the greenhouse gas CO₂ in energy-storage systems is highly desirable. It is now shown that the introduction of graphene as a cathode material significantly improves the performance of Li–CO₂ batteries. Such batteries display a superior discharge capacity and enhanced cycle stability. Therefore, graphene can act as an efficient cathode in Li–CO₂ batteries, and it provides a novel approach for simultaneously capturing CO₂ and storing energy.

The utilization of the greenhouse gas CO₂ in energy-storage systems is highly desirable. It is now shown that the introduction of graphene as a cathode material significantly improves the performance of Li–CO₂ batteries. Such batteries display a superior discharge capacity and enhanced cycle stability. Therefore, graphene can act as an efficient cathode in Li–CO₂ batteries, and it provides a novel approach for simultaneously capturing CO₂ and storing energy.

Mesoporous wall-structured TiO₂ on reduced graphene oxide (RGO) nanosheets were successfully fabricated through a simple hydrothermal process without any surfactants and annealed at 400 °C for 2 h under argon. The obtained mesoporous structured TiO₂–RGO composites had a high surface area (99 0307 m² g⁻¹) and exhibited excellent electrochemical cycling (a reversible capacity of 260 mAh g⁻¹ at 1.2 C and 180 mAh g⁻¹ at 5 C after 400 cycles), demonstrating it to be a promising method for the development of high-performance Li-ion batteries.

Lithium–oxygen batteries are attracting more and more interest; however, their poor rechargeability and low efficiency remain critical barriers to practical applications. Herein, hierarchical carbon–nitrogen architectures with both macrochannels and mesopores are prepared through an economical and environmentally benign sol–gel route, which show high electrocatalytic activity and stable cyclability over 160 cycles as cathodes for Li–O₂ batteries. Such good performance owes to the coexistence of macrochannels and mesopores in C–N hierarchical architectures, which greatly facilitate the Li⁺ diffusion and electrolyte immersion, as well as provide an effective space for O₂ diffusion and O₂/Li₂O₂ conversion. Additionally, the mechanism of oxygen reduction reactions is discussed with the N-rich carbon materials through first-principles computations. The lithiated pyridinic N provides excellent O₂ adsorption and activation sites, and thus catalyzes the electrode processes. Therefore, hierarchical carbon–nitrogen architectures with both macrochannels and mesopores are promising cathodes for Li–O₂ batteries.

Highly dispersed Ni nanoparticles (NPs) and abundant functional N-species were integrated into ultrathin carbon nanosheets by using a facile and economical sol–gel route. Embedded- and anchored-type configurations were achieved for the dispersion of Ni NPs in/on N-rich carbon nanosheets. The anchored-type composite exhibited outstanding pseudocapacitance of 2200 F g⁻¹ at 5 A g⁻¹ with unusual rate capability and extraordinary cyclic stability over 20 000 cycles with little capacitance decay. Aqueous asymmetric supercapacitors fabricated with this composite cathode demonstrated a high energy density of 51.3 Wh kg⁻¹ at a relatively large power density of 421.6 W kg⁻¹, along with outstanding cyclic stability. This approach opens an attractive direction for enhancing the electrochemical performances of metal-based supercapacitors and can be generalized to design high-performance energy-storage devices.