An efficient electrolyte additive of quaternized hardwood kraft lignin enabling dendrite-free aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) have great application potential in large-scale grid energy storage systems. However, the practical application of AZIBs is hindered by several serious issues arising from zinc anodes, such as hydrogen evolution, corrosion, and the formation of zinc dendrites and byproducts. In this study, renewable and low-cost hardwood kraft lignin was modified by the grafting of quaternary ammonium groups. Quaternized hardwood kraft lignin (QHKL) was used as an electrolyte additive for the AZIBs. The addition of 1 wt% of QHKL to the reference electrolyte (RE) strongly contributed to the suppression of hydrogen evolution and zinc electrode self-corrosion. Moreover, it promoted even and homogeneous zinc ion deposition. The Zn//Zn symmetric battery with the electrolyte containing the QHKL additive had remarkable cycling s\ility at various current densities and exhibited highly reversible processes in zinc ion plating and stripping. Thus, the Zn//MnO2 battery with the QHKL-modified electrolyte had outstanding rate performance and remarkable cyclability and maintained a discharge specific capacity of 55.4 mAh g- 1 after 3000 cycles at a high current density of 1.5 A g- 1. This value was approximately 2.5 times greater than the discharge specific capacity of the battery with the RE under the same test conditions. More importantly, the XRD, SEM and EDS analyses revealed that the zinc anode after cycling had barely any dendrites or byproducts (3Zn(OH)2 center dot ZnSO4 center dot xH2O).