Electrolytes Design For Aqueous Ion Batteries And Their Electrochemical Performances

"Clean energy+smart grid" is known as the fourth industrial revolution.Energy storage technology is one of the core technologies urgently needed to realize the popularization of grid-connected applications of solar,wind and other renewable energy generation and smart grid construction.Aqueous batteries are becoming one of the promising new generation of large-scale energy storage systems because of the advantages of safety and reliability,environmental friendliness and low cost.However,the narrow electrochemical window of the water-induced electrolyte,the low capacity and poor cycling stability of the full-cell system in aqueous ion batteries still hinder their commercial application.In this thesis,a multi-component aqueous electrolyte,solvation-regulated electrolyte and additive-assisted electrolyte are designed from aqueous electrolytes to widen the electrochemical stability window of the electrolyte,suppress interfacial side reactions and improve the energy and cycling stability of the full cell by regulating the solvation structure and in situ formation of interfacial layers.In addition,the tuned Zn²+solvation structure and the formed interfacial layer induce uniform zinc deposition and inhibit interfacial hydrogen evolution reactions,thus hindering the growth of zinc dendrites and improving the cell lifetime.To this end,this thesis focuses on the following aspects:1)Study of multicomponent electrolyte in aqueous sodium ion battery.A multicomponent,highly concentrated aqueous electrolyte named Na-H₂O-Urea-DMF was designed.This electrolyte is non-flammable,low cost,wide operating temperature range and non-toxic.The electrochemical stability window of the electrolyte reaches 2.8 V due to the participation of urea in the solventized structure forming a complex solvent sheath.at the same time,during the electrochemical cycle,the solventized structure is preferentially reduced and decomposed,generating a homogeneous interfacial SEI layer containing the inorganic salt Na₂CO₃ and other organic components on the negative electrode surface.The assembled Na₃V₂(PO₄)₃/NaTi₂(PO₄)₃(NVP/NTP)full cell exhibited high electrochemical stability.The aqueous sodium ion full cell matched with Ni-based Prussian blue analogues and sodium titanium phosphate retained 80%of capacity for 2000 cycles at 2 C.2)The investigation of solvation structure-regulated electrolytes in aqueous sodium-zinc hybrid ion batteries.A low-cost,high-concentration aqueous electrolyte with a new Zn²+ solventization structure and a unique distribution of electrolyte components in the inner Helmholtz layer near the ZnHCF cathode is reported.In this electrolyte,the H₂O-encircled Zn²+solvent sheath is replaced by abundant anions to form a new solventized structure,which further suppresses the hydrogen precipitation side reactions and ZnO generation on the Zn cathode surface and promotes the reversible deposition/dissolution of Zn,thus achieving excellent Zn cathode reversibility.The symmetric Zn cell exhibited a coulombic efficiency of approximately 99.96%after 1600 h of deposition/dissolution and 700 cycles.The assembled ZnHCF//Zn full cell showed an average voltage of 1.76 V and a capacity retention of 98%after 2000 cycles at 5 C rates.3)Additive-induced in situ formation of solid electrolyte interface layer(SEI)of zinc cathode for use in aqueous lithium-zinc hybrid ion batteries.The introduction of N,N dimethylformamide(DMF)greatly reduces the strong hydrogen bonding effect of water,which effectively reduces the hydrogen precipitation reaction on the zinc anode surface and promotes the uniform deposition of zinc,thus inhibiting dendrite growth.More importantly,the DMF additive deeply changes the Zn²+solvation structure and induces the anion reduction in situ to form an organic-inorganic composite solid electrolyte interface(SEI),which ensures highly reversible zinc deposition/exfoliation and excellent cycling stability of the symmetric cell.The electrolyte-based assembled lithium manganate(LMO)//Zn hybrid battery exhibits a high voltage of 1.8 V and a discharge specific capacity of 143.5 mAh g-1 at 0.1 C,with 93%capacity retention for 200 cycles at 0.5 C and an average Coulomb efficiency of 99.6%.