Conductive porous carbon nanofibers are promising for environmental, energy, and catalysis applications. However, increasing their porosity and conductivity simultaneously remains challenging. Here we report chemical crosslinking electrospinning, a macro–micro dual-phase separation method, to synthesize continuous porous carbon nanofibers with ultrahigh porosity of >80% and outstanding conductivity of 980 S cm−1. With boric acid as the crosslinking agent, poly(tetrafluoroethylene) and poly(vinyl alcohol) are crosslinked together to form water-sol webs, which are then electrospun into fibrous films. After oxidation and pyrolysis, the as-spun fibers are converted into B-F-N triply doped porous carbon nanofibers with well-controlled macro–meso–micro pores and large surface areas of ~750 m2 g−1. The sponge-like porous carbon nanofibers with substantially reduced mass transfer resistances exhibit multifunction in terms of gas adsorption, sewage disposal, liquid storage, supercapacitors, and batteries. The reported approach allows green synthesis of high-performance porous carbon nanofibers as a new platform material for numerous applications.
Silicon
(Si) is a promising anode material to replace the broadly
adopted graphite due to its high capacity and abundant source. However,
Si anodes suffer from severe problems of huge volume change (∼300%),
and the commonly used binders like poly(vinylidene fluoride) (PVDF)
cannot accommodate such changes. Here, we report a tough block copolymer
PVDF-b-Teflon (PTFE) binder that can coalesce pulverized
Si and thus enhance the stability of Si anodes. The suspension copolymerization
of vinylidene fluoride and tetrafluoroethylene produces elastic PVDF-b-PTFE with large breaking elongations of >250% and high
viscosity as well as high ionic conductivity and thermal stability.
We show that 5 wt % of the binder forms elastic cobweb structures
in the electrode matrix that can effectively coalesce Si particles
and conductive agents together, enabling long cycling stability (>250
cycles) and high rate performance (1 C) for electrodes at a commercial-level
Si loading of 1 mg·cm–2. The findings point
out to a promising strategy for developing highly elastic and tenacious
binders for electrodes with large volume changes during the electrochemical
reactions.
Silica is an attractive anode material for soft lithium batteries owing to its high specific capacity, but it suffers severe problems of large volume change and unstable solid-electrolyte interface. Moreover, it is a challenge to fabricate flexible silica anodes. Here, we report a low-cost and scalable strategy to create flexible anodes of N-doped carbon nanofiber-confined porous silica (p-SiO 2 @N-CNF) by developing a sol-gel electrospinning process followed by carbonization. This approach causes the p-SiO 2 nanoparticles (NPs) to be self-assembled within the N-CNFs, which act like elastomer and electrolyte barrier to accommodate volume changes and to enhance the stability of SiO 2 , whereas the NPs act as soft plasticizer providing strength to the CNF skeletons. Benefiting from the hierarchical structures, the anodes with high p-SiO 2 loadings (>1.6 mg/cm 2) exhibit exceptional cycling performance (>1,000 cycles) in terms of bending, current rate, and capacity. Moreover, the batteries remain stable when discharging at 0.5 C and charging at 2 C.
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