Design,fabrication And Application Of Electrodes For Aqueous Zn Ion Batteries

Energy storage technology can provide stable energy supply for industry and society,as well as solid support and protection for achieving the goal of ‘Carbon Neutrality’,which has become a necessary part of modern life.Among the currently available energy storage technologies,Li ion batteries(LIBs)dominate the energy storage markets due to their long cycle life,high energy density,and high power density.However,the scarcity of electrode materials and the toxicity and flammability of electrolytes in LIBs limit their further development in the fields of large-scale energy storage and safely wearable electronics.In the era of ‘post LIBs’,aqueous Zn ion batteries(ZIBs)have gained tremendous attention due to their unique advantages of safety,non-toxicity,low cost,and high theoretical capacity.Among aqueous ZIBs,the electrode is one necessary component,whose design and manufacturing have a crucial impact on the stability of electrode and the overall performance of battery.The optimization design and controllable manufacturing of electrode can improve the electrochemical stability and mechanical stability of the electrode,thereby improving the overall stability of battery,effectively promoting the practical application of aqueous ZIBs in the wearable electronic devices.This paper focuses on the limited electrochemical stability and mechanical stability of electrode in aqueous ZIBs,starts from the optimal structural design,fabricates structurally ordered and controllable electrodes by combining micro/nanomanufacturing with electrochemical processing,improves the stability of electrodes and batteries,and develops high-safety and high-stability flexible ZIBs and micro ZIBs.The paper mainly aims at the optimization design of micro-nano structures,the controllable manufacturing of electrodes,the energy storage enhancement mechanism of electrodes,the research of electrochemical properties,and the flexible and miniaturized applications of aqueous ZIBs.The relevant researches are carried out around the following three aspects:(1)The uneven Zn deposition in Zn anode is a crucial factor affecting the stability of aqueous ZIBs.Aiming at the low utilization rate,uneven deposition,and dendrite growth of traditional Zn anodes,this work designs and fabricates a flexible ultrathin and ultralight Zn micromesh anode with orderly aligned cellular microholes by combining photolithography with electrodepositing.The Zn micromesh anode with specially designed microholes structure can promote the homogeneous Zn deposition and avoid the dendrite growth,thus significantly improving the safety and stability of aqueous ZIBs.Furthermore,numerical simulations and visual in-situ microscopic observation system certify the special regulation effect of Zn micromesh anode on the ion concentration distribution and current density distribution,where Zn ions preferentially nucleate and deposit on the inner walls of microholes,enabling homogeneous,orientated and spatially selective Zn deposition.The assembled flexible ZIBs based on Zn micromesh anode manifest superb flexible property and durable stability under bending and folding conditions.This work provides a new idea for future flexible batteries and wearable electronic devices,enabling great scientific and engineering significance.(2)Following the last work of Zn micromesh anode,this work further proposes a topology optimization strategy that optimizes the vertex structure of the regular polygon into smooth circular structure,and fabricates the biomimetic honeycomb Zn anode with optimized circular holes.Verified by the multi-field numerical simulations and theory calculations,the biomimetic honeycomb circular microholes structure after optimization can enable homogeneously distributed and smoothly transitional multifield regulation effects(structural stress,current density,and surface heat)for the electrode,which achieves uniform Zn deposition and avoids the formation of Zn dendrite.In addition,the theory calculation,ex-situ microscopic observation and insitu infrared observation verify the superior zincophilic and electrochemical stability of biomimetic honeycomb Zn anode,which realizes the in-situ formed alloying interface during the cycling process and is beneficial for the stable and dendrite-free Zn deposition.Further,the flexible ZIBs composed of biomimetic honeycomb Zn anode exhibit excellent cycling stability and integrate the heart rate sensor as a selfpowered sensing system.This self-powered system realizes reliable heart rate monitoring and can be used in the field of wearable sensing devices.The design strategy and manufacturing process demonstrated in this work are expected to be extended to the development of other metal electrodes and to promote the application of flexible batteries and flexible electronics.(3)With the rapid development of flexible electronics and microelectromechanical systems,the demand for high-safety and high-performance microbattery is becoming more and more urgent.This work constructs the highperformance micro ZIBs based on the 3D nanocone arrays architecture via combining laser scribing with multi-step electroplating.The unique conductive 3D nanocone arrays structure effectively improves the conductivity and wettability of the microelectrode,enabling the faster electron transfer and shorter ion transport path.Compared with planar microelectrode,the specially designed electrode achieves a higher loading amount and a closer contact with the active materials.In addition,the electrochemical kinetic analysis further discovers that the capacitance contribution mainly comes from the surface pseudocapacitive behavior.Also,the stability and discharging ability of the flexible quasi-solid-state microbattery based on gel electrolyte is investigated.This work develops the high-performance micro ZIBs by introducing the 3D nanocone arrays structure,which provides a new idea for the development of miniaturized energy storage devices in flexible electronics and microsystem energy field.