Zinc Ion Battery Electrode/Electrolyte Interface Modification And Performance Study

Today’s society is being subjected to the tremendous pressure for energy security and environmental protection,and it is urgent to develop new energy storage devices with high safety factor as well as low cost and high efficiency.The aqueous zinc ion batteries（ZIBs）,with its own safety and price advantages,has become one of the best choices for large-scale energy storage applications.Vanadium-based compounds are one of the widely used cathode materials in aqueous ZIBs.Among them,two-dimensional vanadium sulfide（2D VS₂）nanoplates have received great attention due to their unique two-dimensional channels,but VS₂ has poor electrical conductivity and a hard skeleton,which can lead to structural damage and rapid capacity decay under high charge and discharge currents.In addition,for ZIBs,the solventization of Zn²⁺and the local unevenness of the Zn surface usually lead to many side reactions during the charging and discharging process,resulting in the corrosion of the zinc sheet and the generation of dendrites.In addition to forming"dead zinc",zinc dendrites can penetrate the diaphragm and lead to serious short circuit accidents.In this thesis,a new electrolyte and composite electrode materials are developed based on the design and mechanism analysis of zinc ion batteries to address these problems.The conclusions achieved are as follows:1.To enhance the structural stability and conductivity of VS₂ and improve the cathode/electrolyte interface properties,vanadium sulfide@polyaniline（VS₂@PANI）composites were designed.The addition of PANI effectively increased the interlayer spacing of VS₂,which promoted the embedding/deembedding of Zn²⁺,and enhanced its diffusion kinetics.Meanwhile,the interlayer PANI effectively supports the lamellar structure and avoids the structural collapse of the cathode material.Using VS₂@PANI as the cathode material,a high specific capacity of 315.6 m Ah g^-1 can be generated at a current density of 0.1 A g^-1,and a capacity retention of 89.34%can still be achieved after 1000 cycles at 1.0 A g^-1.Compared with the pure VS₂ material(155.9 m Ah g^-1),the zinc storage performance is substantially improved.2.To regulate the ion migration of Zn²⁺more effectively and to optimize the electrode/electrolyte interface properties,an electrolyte of zinc fluoride（ZnF₂）was used as a dendrite inhibitor.Fluoride ions produced by dissolving ZnF₂ in zinc sulfate electrolyte（2M Zn SO₄）interact with Zn²⁺to inhibit its solventization,and at the same time,fluoride ions are a good ion conductor,accelerating Zn²⁺ion migration.On the other hand,the ZnF₂ layer on the anode electrode surface can support electrostatic shielding like a solid electrolyte interface（SEI）,which guides ions to deposit uniformly in the same direction,inhibits zinc dendrite growth,increases interfacial stability and optimizing the cycling performance.The full cell with0.03%ZnF₂ in the electrolyte at a current density of 1.0 A g^-1 showed excellent cycling performance up to 1000 cycles with 91.76%capacity retention.3.The anode,as one of the components of a battery,plays an important role in energy storage and conversion.To improve the anode/electrolyte interface properties,a PVA film was coated on the zinc anode to prepare a PVA@Zn metal（PVA@Zn）anode.The PVA coating on the surface of zinc flakes forms a cladding layer that acts as a physical anticorrosion layer on the one hand,and on the other hand,a large number of polar groups in PVA have strong interactions with zinc ions to desolvate them.As a result,the dendritic inhibition effect and corrosion resistance of zinc flakes are significantly enhanced.The battery assembled with the PVA@Zn composite electrode as anode can remain stable at a current density of 1.0 A g^-1,and the capacity retention rate reaches 92.12%after 1000 turns of charging and discharging.