Design Of Aqueous Zn Battery Materials And Research Of Their Performance

With the advantages of high safety,high energy density,low cost,and environmental-friendliness,aqueous Zn batteries have attracted much attention for large-scale energy storage.The research of aqueous Zn batteries has made great progress so far,but they still face many challenges such as low areal capacity of cathode materials,serious side reactions and low utilization of Zn anodes.In this thesis,to address the above issues,we improve the areal capacity of MnO₂ cathode by realizing a composite mechanism of single and double electron transfer in its cathode;design a polydopamine-polyacrylamide（PDAB）Zn anode protection layer to suppress the side reactions;and develop a three-dimensional copper nanocollector modified by zincophilic Sb（ZA@3D-nano Cu）for anode-free Zn batteries.Specific research works are as follows:1.The areal capacity of MnO₂cathode is significantly increased by modulating the simultaneous H⁺and Zn²⁺de-embedding reactions and Mn²⁺/MnO₂deposition/dissolution reactions in MnO₂ cathode.The MnO₂ cathode based on the composite mechanism can achieve a high areal capacity of 37 m Ah cm^-2.The Zn-MnO₂battery assembled with this cathode has good rate performance and can operate in the current density range of 5 m A cm^-2 to 80 m A cm^-2 at an areal capacity of 20 m Ah cm^-2.And the battery always maintains a Coulomb efficiency higher than 80%.In addition,the Zn-MnO₂ battery based on the cathodic composite mechanism can stably cycle over300 cycles at a high areal capacity of 20 m Ah cm^-2 with a 91%capacity retention rate.The battery has the potential for further scale-up and has potential applications.2.To cope with the instability of Zn anode in aqueous electrolytes,we synthesized a PDAB membrane with abundant catechol groups and amino groups for the protection of Zn anode.Density flooding calculations and experimental results show that PDAB membranes have strong interactions with Zn²⁺and H₂O molecules,mostly in a PDAB-Zn-H2O structure with a relatively water-deficient local configuration.It can not only make the Zn²⁺flux uniformly distributed and induce Zn uniform deposition,but also reduce the water activity and thus prolong the service life of Zn anode by reducing the resulting parasitic side reactions.Therefore,the cycle stability and cycle life of the Zn@PDAB|MnO₂ battery assembled with the composite mechanism-based MnO₂cathode are improved.In addition,the scaled-up Zn@PDAB|MnO₂ pouch cell can be stably cycled for nearly 220 cycles（～1750 h）at a capacity of 80 m Ah.This design strategy significantly improves the cycle stability of aqueous Zn batteries,and extends the lifetime of aqueous Zn batteries,providing a highly referenced alternative for large-scale energy storage in smart grids.3.To achieve high utilization of Zn,this section develops a stable three-dimensional copper nanowire collector modified with zincophilic Sb nanoparticles for anode-free Zn batteries.COMSOL simulations and electrochemical tests show that the three-dimensional structure can uniform surface electric field distribution and its large internal space can mitigate the volume change problem that occurs during Zn deposition.In addition,the zincophilic Sb layer provides abundant nucleation sites with low barriers to nucleation.The synergistic effect of the two significantly inhibits dendrite growth.As a result,the ZA@3D-nano Cu|Zn half-cells exhibit enhanced cycling performance at 100%high zinc utilization.The ZA@3D-nano Cu@PDAB|MnO₂battery with PDAB protective layer and composite mechanism type MnO₂ cathode has a high initial specific capacity of 450 m Ah g^-1_{Mn O2} and still has a high capacity retention rate of 89%after 1000 cycles.In addition,the ZA@3D-nano Cu|Br₂ battery can be stably cycled more than 1000 times at a high areal capacity of 10 m Ah cm^-2.The ZA@3D-nano Cu|Br₂ pouch cell still exhibits a high Coulomb efficiency of over 96.2%at a capacity of 200 m Ah.This strategy provides a new approach to realize high-capacity anode-free Zn batteries and provides novel opportunity for the industrialization of aqueous Zn batteries.