Highly wrinkled graphene film (HWGF) with high packing density was synthesized by combining an electrostatically self-assembling process, a vacuum filtration-induced film assembling process and capillary compression. Fe₃O₄ nanoparticles were used as a low-cost and environment-friendly hard template. Hierarchical porosity and high packing density were achieved with the aid of capillary compression in the presence of Fe₃O₄ nanoparticles. This strategy enables integration of highly wrinkled graphene sheets to form highly compact carbon electrodes with a continuous ion transport network. The generated HWGF exhibited a high packing density of 1.53 g cm⁻³, a high specific surface area of 383 m² g⁻¹ and a hierarchically porous structure. The HWGF delivered a high capacitance of 242 F g⁻¹ and 370 F cm⁻³ at 0.2 A g⁻¹ in 6 M KOH aqueous electrolyte system with excellent rate capability (202 F g⁻¹ and 309 F cm⁻³ retained at 20 A g⁻¹). The capacity retention rate reached 97% after 10 000 cycles at 1 A g⁻¹. The HWGF-based supercapacitor exhibited a high energy density of 17 W h kg⁻¹ at the power density of 49 W kg⁻¹. Such high capacitive performances could be attributed to the highly dense but porous graphene assemblies composed of highly wrinkled graphene sheets.

A uniform Co(OH)₂ sheath was anchored on the surface of a conductive CNT by a facile strategy, exhibiting comparatively high specific capacitance and outstanding long cycle life stability.

An easy and scalable synthetic route was proposed for synthesis of a high-energy stable anode material composed of carbon-coated Si nanoparticles (NPs, 80 nm) confined in a three-dimensional (3D) network-structured conductive carbon nanotube (CNT) matrix (Si/CNT@C). The Si/CNT@C composite was fabricated via in situ polymerization of resorcinol formaldehyde (RF) resin in the co-existence of Si NPs and CNTs, followed by carbonization at 700 °C. The RF resin-derived carbon shell (~10 nm) was wrapped on the Si NPs and CNTs surface, welding the Si NPs to the sidewall of the interconnected CNTs matrix to avoid Si NP agglomeration. The unique 3D architecture provides a highway for Li⁺ ion diffusion and electron transportation to allow the fast lithiation/delithiation of the Si NPs; buffers the volume fluctuation of Si NPs; and stabilizes solid–electrolyte interphase film. As expected, the obtained Si/CNT@C hybrid exhibited excellent lithium storage performances. An initial discharge capacity of 1925 mAh g⁻¹ was achieved at 0.1 A g⁻¹ and retained as 1106 mAh g⁻¹ after 200 cycles at 0.1 A g⁻¹. The reversible capacity was retained at 827 mAh g⁻¹ when the current density was increased to 1 A g⁻¹. The Si/CNT@C possessed a high Si content of 62.8 wt%, facilitating its commercial application. Accordingly, this work provides a promising exploration of Si-based anode materials for high-energy stable lithium-ion batteries.

The electrodeposition process makes good progress to reduce the sheet resistance, which ensures the effective diffusion of Li-ions and electrons.