Employing cationic kraft lignin as electrolyte additive to enhance the electrochemical performance of rechargeable aqueous zinc-ion battery

Rechargeable Zn//MnO2 batteries, the most widely studied aqueous zinc-ion batteries, suffer from poor electrochemical performance due to a series of issues on the zinc anode including corrosion, dendrites, and passivation. In this study, abundant and low-cost kraft lignin is used as a raw material to synthesize quaternized lignin (QL(80)), which is upgraded to an electrolyte additive for the Zn//alpha-MnO2 battery (ReZMB). According to corrosion and chronoamperometry tests, the electrolyte containing 1 wt% of the QL(80) (named as 1 % QL(80)) has the lowest corrosion on the zinc electrode and is best able to promote the homogenous zinc deposition. Consequently, the ReZMB using the 1 % QL(80) records the highest open-circuit voltage after storage at full charge state and the optimal rate capability, and meanwhile, the Zn//Zn symmetric battery exhibits an extended lifespan of 200 h at 5 mA.cm(-2), 5 mAh.cm(-2). In addition, the passivation of the zinc anode is highly prevented because no byproducts appear on the zinc anode of the ReZMB with 3000 cycles at 1.5 A.g(-1), according to the results of XRD and SEM characterizations. Ultimately, the ReZMB using the 1 % QL(80) presents more outstanding cyclability (more stable operation and similar to 74.5 % higher discharge capacity after 3000 cycles at 1.5 A.g(-1)) than that of the battery using the reference electrolyte (2 M ZnSO4 + 0.2 M MnSO4). This study paves the new way for designing green lignin-derived electrolyte additives for advanced rechargeable zinc-ion batteries.