Study On The Modification Of V-based,ni-based Cathode And Bi-based Anode Materials For Aqueous Secondary Batteries

With the rapid development and wide use of high-performance energy storage equipment,higher requirements are put forward for its environmental protection and safety.Aqueous secondary battery has recently attracted wide attention because of its high conductivity,excellent rate performance,low-cost and environmental protection,safety and so on.However,compared with organic batteries system,the poor cycle stability and energy density of aqueous batteries limit their further development.The electrode material constituted the battery is the key to improving the electrochemical performance of the secondary battery.Therefore,the synthesis methods and electrochemical performance of cathode and anode materials with high capacity and long cycle life were discussed in detail,which were modified and applied to the electrochemical analysis of aqueous secondary batteries.In addition,in order to further verify its application ability,the prepared materials were used to assemble gel-electrolyte-based flexible wearable energy storage devices,and a series of destructive tests were carried out to verify the safety and damage resistance of these devices.The main contents of this work are as follows:（1）Preparation and properties of an in-situ grown Ca V₃O₇ nanobelts（CVO_x）cathode with rich oxygen defects for aqueous zinc ion batteries.Ca V₃O₇ nanobelts（CVO）were prepared by adding Ca Cl₂ in the hydrothermal process.Then,the above-mentioned sample was placed in H₂ atmosphere and reacted at a high temperature of 200°C for 2 hours to obtain CVO_x nanobelts.After that,the proportion of oxygen defects and active sites in the CVO_x nanobelts were increased significantly,thereby improving its electrical conductivity and ion diffusion rate,effectively inhibiting structural collapse and chemical dissolution during the cycle test,and achieving a stabilization of 400 cycles with 82%capacity retention.An aqueous rechargeable CVO_x//Zn battery based on the as-fabricated CVO_x nanobelts cathode,zinc foil anode and 1 M Zn SO₄ electrolyte shows high mass capacity(471.04 m Ah g^-1),area capacity(2.26 m Ah cm^-2)and high energy density(363.9 Wh kg^-1),which is significantly superior than that of the CVO sample before modification.A quasi-solid-state CVO_x//Zn battery with long life,high rate performance and excellent safety based on the prepared CVO_x sample,zinc foil and PVA/Zn SO₄ gel electrolyte was assembled.The quasi-solid-state battery has shown excellent capacity retention in a series of bending and twisting experiments.（2）The PVO@C nanorods with phosphorus-doping and rich oxygen-defects were used as the anode of aqueous/quasi-solid-state zinc-ion batteries and their electrochemical performance was studied.The addition of Na H₂PO₂ in the hydrothermal process was used to introduce phosphorus-doping and oxygen defects（denoted as PVO@C）in the VO sample,and thereby significantly improving its electron mobility and increasing the number of active sites.The above results are further verified by DFT simulation.Compared with the VO electrode without Na H₂PO₂,the PVO@C electrode shows a lower adsorption energy for Zn²⁺during the charge and discharge process,which will be more conducive to the insertion and extraction of Zn²⁺,so as to achieve high-voltage discharge.The aqueous PVO@C//Zn battery based on the PVO@C cathode,zinc nanosheets anode,and 1 M Zn SO₄ electrolyte,exhibit high capacity(385.34 m Ah g^-1),excellent rate performance and long-term cycle stability（with 86.1%capacity retention after 5000 cycles）.In addition,the quasi-solid flexible zinc battery based on PVO@C positive electrode,electrodeposited Zn negative electrode and PAM/Zn SO₄ gel electrolyte,show high power density,high energy density and excellent cycle performance.More importantly,the quasi solid-state battery displayed excellent capacity retention in a series of destructive experiments,such as piercing,soaking,bending,sewing,washing,shearing,and hammering.The above result proves that this quasi-solid battery has excellent safety,water resistance,impact resistance and abrasion resistance.（3）Preparation and electrochemical performance of aqueous zinc ion battery based on H-Ni Mn_xO_y ultra-thin nanoflake cathode with rich oxygen defects was studied.In situ Ni Mn_xo_y nanosheets were obtained by hydrothermal reaction at 120℃for 5 hours,and then were placed in H₂ atmosphere at 200°C for 2 hours to obtain H-Ni Mn_xO_ynanosheets with rich oxygen defects.The introduction of oxygen defects in the H-Ni Mn_xO_y sample weakens the attraction of Ni²⁺,Ni³⁺and Mn²⁺to the three-dimensional electrons,and reduces the electron transfer energy in the redox reaction,significantly promoting the reaction kinetics and surface activity.Therefore,the three-electrode system assembled with carbon rods,Hg/Hg O electrodes,H-Ni Mn_xO_y electrodes,and a mixed electrolyte of 1 M Zn SO₄ and 20 m M KOH,exhibit high capacity and excellent cycle stability（the cycling test of 6000 cycles without capacity attenuation）.In addition,the aqueous rechargeable nickel-zinc battery constructed with H-Ni Mn_xO_y electrodes cathode and zinc foil anode,display high capacity retention rate of 88.5%after 5500 cycles,as well as remarkable rate performance and excellent energy density(energy density of 1.13 m Wh cm^-2 at the power density of 3.34 m W cm^-2).（4）The construction and research of Bi-based materials with highly reversible redox kinetics and wide potential window were used for aqueous Ni//Bi battery.A three-dimensional nano-flowers-like metal Bi electrode was prepared by one-step electrodeposition method by using foamed nickel as the substrate.During the cycle test,the active material would structural collapse and fall off.Therefore,the rapid pressing method was used to form a"sandwich"structure,which alleviates these problems and significantly improves its cycle life.The nano-flowers-like TL-Bi electrode owns higher specific surface area and more active sites,which is conducive for the three electrode system based on TL-Bi electrode,carbon rod,Hg/Hg O,and 1 M KOH to exhibit high power density,excellent rate performance and long life（82.1%capacity reserved after14000 cycles）.In addition,the Ni@Ni O electrode with core-shell structure obtained by a simple ultrasonic activation method and the as-prepared TL-Bi electrode was used to assemble an aqueous Ni//Bi battery and this battery displays long-term cycling performance（94.1%capacity retained after 4500 cycles）,remarkable rate performance and high capacity.