Controllable synthesis of borophene aerogels by utilizing h-BN layers for high-performance next-generation batteries

Borophene is emerging as a promising electrode material for Li, Na, Mg, and Ca ion batteries due to its anisotropic Dirac properties, high charge capacity, and low energy barrier for ion diffusion. However, practical synthesis of active and stable borophene remains challenging in producing electrochemical devices. Here, we introduce a method for borophene aerogels (BoAs), utilizing hexagonal boron nitride aerogels. Borophene grows between h-BN layers utilizing boron-boron bridges, as a nucleation site, where borophene forms monolayers mixed with sp²-sp³ hybridization. This versatile method produces stable BoAs and is compatible with various battery chemistries. With these BoAs, we accomplish an important milestone to successfully fabricate high-performance next-generation batteries, including Na-ion (478 mAh g^-1, at 0.5C, >300 cycles), Mg-ion (297 mAh g^-1, at 0.5C, >300 cycles), and Ca-ion (332 mAh g^-1, at 0.5C, >400 cycles), and Li-S batteries, with one of the highest capacities to date (1,559 mAh g^-1, at 0.3C, >1,000 cycles).