Carbon aerogel based materials for secondary batteries

Carbon aerogels first proposed in 1989 have attracted great attention in the area of secondary batteries due to their hierarchical porous nanonetworks, adjustable surface area, good conductivity and excellent electrochemical stability. Carbon aerogels can not only serve as electroactive materials for secondary batteries, but also can serve as carbon matrices to disperse electroactive materials or to confine electroactive materials. According to the type of carbon precursors employed in the area of secondary batteries, carbon aerogels can be divided into four kinds, that is phenolic resin derived carbon aerogels, carbon nanotube aerogels, graphene aerogels and biomass derived carbon aerogels. In this review, we first provide a brief review on the synthesis of these carbon aerogels in sequence. The preparation of phenolic resin derived carbon aerogels usually involves five steps: (1) sol formation; (2) gelation; (3) solvent exchange; (4) drying; (5) carbonization. For the successful preparation of carbon nanotube aerogels, surfactant assistance or surface functionalization is necessary. Resorcinol-formaldehyde derived carbons, carbon nanotubes, biopolymers were usually employed as crosslinkers to enhance physical and chemical properties of graphene aerogels. Natural biomass could be converted into carbon aerogel by a hydrothermal treatment, freeze-drying and post-pyrolysis process. Next, we summarize the recent progress and advances on carbon aerogels and carbon aerogel based materials for secondary batteries, focusing on lithium ion batteries and lithium-sulfur batteries. For lithium ion batteries, most of researches concentrated on carbon aerogel based nanocomposites as anode materials. For lithium-sulfur batteries, carbon aerogels, heteroatoms doped carbon aerogels and carbon aerogel based nanocomposites were used as hosts for immobilization of sulfur species and as interlayers to further block the penetration of lithium polysulfides.