Synthesis And Properties Of High Performance Electrode Materials For Aqueous Zn-ion Batteries

With the acceleration of global industrialization,environmental degradation and the reduction of fossil fuel reserves,the demand for clean and renewable energy is becoming increasingly urgent.In the face of this dilemma,the use of new energy forms such as solar energy,wind energy,biomass energy,tidal energy and geothermal energy is an effective way.However,these new energy forms are difficult to store and transport directly,and the high intermittence restricts their further development.The development of energy storage systems(ESSs)provides a more stable energy supply for personal,household and industrial applications.At present,battery plays an important role in all energy storage systems.It has become an indispensable part of portable electronic products,electric vehicles and even power grid.Among them,lithium-ion batteries(LIBs)are widely used because of their high energy density.However,due to limited lithium resources and harsh assembly conditions,the cost of commercial lithium-ion batteries is further increased.In addition,flammable and toxic organic electrolytes and highly active lithium also greatly hinder the further application of lithium-ion batteries.Zinc ion batteries(ZIBs)have attracted extensive attention in the field of electrochemical energy storage due to their low cost,high safety and high bulk energy density.Although the aqueous zinc ion battery can achieve higher specific capacity and energy density due to the transfer of polyvalent ions,there are many problems in the electrode materials,including irreversible dendrite of metal negative electrode and poor electrochemical performance of positive materials.Electric field concentration and oxidation will occur during stripping and coating of metal anode,which restricts the electrochemical performance of the whole battery.It is very common to use manganese based and vanadium based transition metal oxides with large interlayer spacing as cathode materials for water-based zinc ion batteries.The electrode materials with high capacity and high rate can be obtained by ion pre insertion in the synthesis process,which breaks the limitation of inherent crystal structure.The type of ions in electrolyte has a great influence on the performance of battery electrode,and the relationship between the type of pre intercalated ion vanadium compounds and electrolyte has not been explored.Traditional transition metal oxides have been restricted by the poor electronic/ionic conductivity,which is difficult to meet the practical application.Traditional coating methods inevitably increase the internal resistance between the active material and the collector.Therefore,electrodeposition is an effective method to improve the contact area and material utilization of the electrode.By using these methods,we can effectively improve the performance of aqueous zinc ion battery electrode,and realize the performance of water zinc ion battery.This paper focuses on the following aspects1.Lamellar Zn Al eutectic alloy as reversible dendrite free anode for aqueous zinc ion batteriesMetal zinc anode has the advantages of high theoretical capacity and low cost,which is an attractive anode material for aqueous zinc ion battery.However,the existing zinc anode has some problems such as low coulomb efficiency and serious dendrite growth in the stripping/electroplating process,which hinders its practical application.Therefore,a new kind of eutectic Zn/Al alloys with alternate Zn and Al layered nanostructures as reversible dendrite free anode materials significantly improve the electrochemical performance of aqueous rechargeable zinc manganese oxide batteries.The unique layered structure promotes the reversibility of zinc stripping/electroplating.The intergranular nano patterns with Al/Al₂O₃core/shell structure are formed in situ by using the symbiotic and inexpensive aluminum sheets.Among them,Al can prevent the irreversible by-products of Zn O or Zn(OH)₂,while the insulating Al₂O₃shell prevents the electroreduction of Zn²⁺ions on the Al/Al₂O₃pattern,which leads to the electrodeposition on the precursor Zn sites and basically eliminates the formation and growth of Zn dendrites.The results show that the eutectic Zn₈₈Al₁₂(at%)alloy has good dendrite free plating/striping behavior in Zn SO₄aqueous solution without O₂,and its over potential is significantly low and stable.The excellent electrochemical performance enables the AR-ZIB consisting of eutectic Zn₈₈Al₁₂alloy anode and K_xMn O₂cathode to provide an energy density of about 230 Wh kg^-1(based on the mass of K_xMn O₂cathode)at high power,while maintaining 100%capacity after 200 hours.Eutectic alloying strategy opens up a new way for the development of high performance metal anodes for the next generation of secondary batteries.2.Ultrahigh-energy and-power aqueous rechargeable Zinc-ion microbatteries based on highly cation-compatible vanadium oxidesAs a substitute of lithium-ion battery,aqueous zinc ion battery has a broad development prospect.MEMS can be used in small electronic products,which has attracted people's attention.However,the traditional aqueous zinc ion battery uses excessive zinc as anode,which makes the battery vulnerable to dendrite and oxidation,resulting in battery failure.In addition to the advantages of bipolar and high theoretical capacity,the pre intercalated vanadium oxide can effectively improve the conductivity and ionic conductivity of the electrode,provide more ion diffusion pathways and more regulatory sites.Herein,we demonstrate that high compatibility of layered TMO hosts with hydrated cation guests can boost their kinetics of intercalation/deintercalation associated with redox reactions to offer high practical capacities and rate capabilities,based on a model system of layered vanadium oxides with the preintercalation of hydrated M cations(M_xV₂O₅,M=Li,Na,K,Mg,Zn),which are seamlessly integrated on three-dimensional bicontinuous nanoporous Au current microcollectors.The electroactive M_xV₂O₅exhibits its highest specific capacity when operated in the electrolyte containing compatible M cation,generally resting with the optimal ratio(h/d)of the interlayer spacing(h)and the diameter of hydrated metal ions(d).By virtue of nanoporous Au microcollectors enabling fast electron transfer and ion transport,the constituent Zn_xV₂O₅shows superior specific capacity and rate performance in 1 M Zn SO₄aqueous electrolyte compared with the other M_xV₂O₅(M=Li,Na,K,Mg).It reaches as high as 527 m Ah g^-1(which is?90%of the maximum theoretical value of 589 m Ah g^-1)at 5 m V s^-1and retains?300 m Ah g^-1at 200 m V s^-1.The outstanding performance enlists aqueous rechargeable zinc-ion microbatteries(AR-ZIMBs)constructed with symmetric nanoporous Zn_xV₂O₅/Au interdigital microelectrodes as anode and cathode to exhibit high-density energy of?358 m Wh cm^-3at high levels of power delivery.3.Zn_xV₂O₅self-supporting electrode controlled by structure tuning is used as cathode material of flexible aqueous system zinc ion batteryTraditional transition metal oxides,such as Mn based and V based materials,have been limited by low conductivity and low ionic conductivity as cathode materials for aqueous zinc ion batteries.In practical application,these materials can not reach the application requirements.Therefore,we designed a kind of pre intercalated Zn_xV₂O₅nanobelt loaded on flexible carbon paper,and prepared integrated CFP/Zn_xV₂O₅material for high performance aqueous zinc ion battery cathode.Through the pre intercalation method,the hydrated zinc ions and water molecules are intercalated into the vanadium pentoxide layers to expand the interlayer spacing,generate more active sites,increase more capacity,and obtain stable Zn-ion diffusion channels.By integrating the active material on the conductive substrate,the internal resistance of the electrode was minimized,and the conductivity of the electrode and ion was improved.Thanks to the above material design,the CFP/Zn_xV₂O₅aqueous zinc ion battery has the capacity of 365 m Ah g^-1at the current density of 0.05Ag^-1.At the discharge rate of 5 Ag^-1,it can still maintain 120 mAh g^-1for 1000 cycles,which is 80.5%of the initial capacity.