Win-Win Strategies Enable Efficient Anode-Less Zinc-Ion Hybrid Supercapacitors.

Abstract

Boosting the energy and power densities of electrochemical energy storage (EES) devices to broaden their practicality is of great significance and emergently desirable. Recently, the EES cells with an anode-free concept have been announced to realize those targets. Herein, 20 μm of a zincophilic layer prepared by blending ZIF-8 and sodium alginate (SA) is uniformly coated on Cu foil (Z8-SA@Cu) as an alternative anode for anode-less zinc-ion hybrid supercapacitors (ALZHSCs). Contributing by the distinctive features evidenced by electrochemical measurements and post-mortem analyses: (1) less nucleation barrier and overpotential, (2) limited zincate formation, (3) improved Zn²⁺ flux and (4) efficient Zn plating/stripping, the as-prepared Z8-SA@Cu is rationally considered to be a promising anode for ALZHSCs. Encouragingly, the assembled ALZHSC device not only delivers an impressive rate capability (40 mAh/g at 1 mA/cm² and 34 mAh/g at 10 mA/cm²) but also achieves the excellent cycling stability (capacity retention: 88 % after 12,000 cycles at 5 mA). Most importantly, the ALZHSC device also reveals significant increases in gravimetric energy density and high-power ability as compared to the traditional ZHSCs.