The tendency of Li plating at the surface of thick graphite electrodes greatly limits its application in electrical vehicle (EV) batteries for fast charging applications. To address this concern, we...

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With the advantages of high conductivity and low cost, porous carbons have been considered as the most attractive materials as hosts of sulfur cathode in lithium-sulfur batteries (LSBs). However, LSBs always suffer short cycle life due to the “shuttle effect” of lithium polysulfide species (polysulfides), which are intermediate products during the charge/discharge processes. The weak interaction between carbon and polysulfides results in the dissolution of polysulfides from the cathodes, loss of active material and eventually fast capacity fading. To overcome these drawbacks, we employed a biomass-derived carbon as the host material in sulfur cathodes. Results from X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen sorption reveals that this biomass-derived product is amorphous carbon and is composed of both large (>10 nm) and small (<5 nm) pores. Using as hosts of cathodes in LSBs, the biomass-derived carbons could deliver a high reversible capacity of > 800 mAh/g and retain >80% of initial capacity after 200 cycles. Especially, the activated carbons exhibited 80% capacity retention after 400 cycles. The promising LSB performance could be ascribed to the unique porous architecture of biomass-derived carbons. The meso/micropores in biomass-derived carbons could provide more sites to anchor sulfur and polysulfides, while macropores provide channels for fast transport of ions. This was corroborated by the results from the electrochemical impedance spectroscopy (EIS), the thermogravimetric analysis (TGA) and absorption measurements.

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The relatively low coulombic efficiency (CE), especially the high initial capacity loss (ICL), and short cycle life are two major obstacles limit the wide adoption of Si-based materials as anodes of commercial lithium-ion batteries (LIBs). In this work, we introduced an aqueous binary binder composed of polyacrylic acid (PAA) and a water-soluble polymer to a Si-based electrode. Used as anodes of LIBs, the Si-based electrodes with the binary binder exhibited lower ICL and longer cycle life than those with PAA binder. The improved battery performance is ascribed to the unique electrode structure with the binary binder. The analysis from Fourier-transform infrared spectroscopy (FTIR) reveals that the intermolecular hydrogen bonds has been formed between PAA and the new polymer. The formation of hydrogen bonds could affect the properties of slurry for electrode coating and the structure of dried electrodes. Compared to the PAA binder, the new binary binder increases the viscosity of aqueous slurries at low shear rates and prompts the shear thinning, which benefit the preparation of slurries with high stability. Observations from the electron microscopy reveal that a relative porous structure was generated in the electrodes with the binary binder, compared with those with PAA binder. The porous structure could not only facilitate the electrolyte transport, but also accommodate the large volume expansion of Si during the charge/discharge processes. In addition, a thin solid-electrolyte-interface (SEI) film was found at the surface of cycled electrodes with the binary binder. Key words: aqueous binder coulombic efficiency Si-based anode lithium-ion battery