Study On Interface Modification And Performance For Aqueous Zinc-ion Batteries

Rechargeable aqueous zinc-based batteries are emerging as a promising alternative to fire-prone lithium-ion batteries in some specific fields(for example submarine)due to high theoretical capacity(820 mAh g-1,and 5854 mAh cm-3),low equilibrium potential(-0.76 V vs.standard hydrogen electrode(SHE))and high hydrogen overpotential(1.2 V vs.SHE),low cost and high safety.In contrast to the organic electrolyte,aqueous electrolyte demonstrates 2-3 orders of magnitude higher ionic conductivity,which offers the capability of fast charging and high power densities for AZIBs.Nevertheless,cathode materials experiences a series of problems such as structural collapse,dissolution,water-induced side reaction,leading to rapid capacity fading and limited cycle life,which is attributed to the interaction of water molecules and cathode.Thus it is crucial to exploit how cathode wettability influences electrochemical kinetics for development high-performance cathode in AZIBs.including ions diffusion and charge transfer at cathode-electrolyte interface.Besides,the use of Zn metal anodes for AZIBs is still facing great challenges including dendrite,corrosion,shape change and passivation,leading to inferior reversibility and limited cycling life.Both of these problems are closely related to the electrode interface.In this paper,we employed cellulose nanowhisker and graphene to modify the electrode interface,improving the electrochemical performance of AZIBs.The specicfic content is as follows:1?The effect of cathode wettability in aqueous zinc-ion batteries(AZIBs)on the zinc-ion diffusion and charge transfer based on a research platform of cellulose nanowhiskers(CNWs)/graphene/MnO2 wire-in-scroll nanowires with water contact angles turning from 64.70 ± 3.72° to 115.85 ± 3.36° as cathodes for AZIBs has been investigated,where the corresponding battery performance shows a parabola trend with the peak in 103.04 ± 2.91°.The cathode achieves a high capacity of 384 mAh g-1 at 1 C and features an ultra-long lifetime of over 5000 cycles at 20 C,representing excellent Zn storage performance.A combination of experimental measurements and density functional theory calculations suggests that increased cathode hydrophobicity forces hydrated Zn2+ desolvation at electrode-electrolyte interface,facilitating zinc-ion insertion into host materials,yet extremely hydrophobic cathode leads to sluggish electrochemical kinetics.This study opens a new idea in the design of promising candidates for developing low cost and long lifespan batteries for aqueous systems.2?A bifunctional cellulose nanowhisker-graphene(CNG)membrane was constructed to regulate the zinc-ions deposition.Experimental analysis and molecular dynamics simulation reveal that the CNG membrane,functioning as a desolvation layer to preclude H2O molecules encountering the Zn anode.retards the water-induced corrosion reaction.This CNG layer with negative surface charges can simultaneously generate a deanionization shock by spreading cations but screening anions to obtain redirected Zn deposition parallel to the(0002)Zn plane.Furthermore,the flexible and toughened CNG membrane could withstand a strong tensile force(8.54 N)and a great puncture force(0.10 N)to favorably accommodate the Zn anode surface fluctuation during plating/stripping.Accordingly,CNG/Zn anode delivers an enhanced CE(99.4%)and a longer cycle life(?5500 h),over 27 times that of a bare Zn anode.A full MnO2/graphene-CNG/Zn battery exhibits a high discharge capacity(307 mAh g-1)and maintains a high capacity retention of 87.8%at 5 C after 5000 cycles.3?On the basis of the above work,a low-cost Janus separator was prepared by a simple drip coating method,that is,constructing a oriented graphene and cellulose nanowhisker in layers on the surface of glass fiber separator to obtain a flat surface.The two sides of Janus separator have completely opposite properties,the side toward the cathode is hydrophilic and the other side is hydrophobic,which can induce Zn2+to form(0002)zn texture on the Zn anode surface.The principle has the same the regulated mechanism for Zn2+as the CNG interface layer,including both desolvation and deanionization effects.More particularly,the Janus separator possesses sieve function for cations to screen H+to contact Zn anode,inhibiting hydrogen evolution reaction.