The Design And Failure Analysis Of Aqueousorganic Self-stratified Batteries

Solar and wind power generation are easily affected by intermittent and random changes in the environment,requiring energy storage technology to realize the centralized storage and release of energy,and reduce the power fluctuations of the grid.Among various energy storage technologies,electrochemical energy storage technology has received widespread attention due to its short response time,high energy conversion efficiency,and high power density.However,the existing electrochemical energy storage technologies such as lithium-ion batteries,lead-acid batteries,and flow batteries still cannot consider the key indicators such as cycle life,safety,and cost thoughtfully,and it’s not good enough to meet the needs of energy storage applications.Therefore,the research and development of new energy storage batteries is crucial to the development of the renewable energy industry.In order to solve the above problems,a new type of aqueous-organic self-stratified battery technology is proposed.The battery has an aqueous-organic self-stratified structure that is very different from mainstream batteries,contains immiscible organic catholyte and aqueous electrolyte,and can automatically layer by gravity.The battery has extremely low manufacturing cost,excellent cycling stability and safety,it has application potential in the field of large-scale energy storage.However,as a brand-new battery system,there are still many problems in its formulation principles,architecture design principles,performance optimization methods,and reaction mechanisms.On these issues,this dissertation conducts a systematic study,proposes two new low-cost aqueous-organic self-stratified battery design schemes,and analyzes their failure mechanisms.These are specific research results:1.We design a new aqueous-organic zinc-iodine self-stratified battery,and propose the cation shuttle mechanism of the battery.Using Li⁺as the shuttle ion has better battery performance.We establish a layered structure of the aqueous and organic phases in the battery through the Zn SO₄ salting-out effect,which achieves an obvious layering effect.By adding Li₂SO₄ or Na₂SO₄ to the battery,the ionic conductivity of the organic phase is improved,while the redox overpotential and charge transfer resistance of the positive electrode are reduced,and the cycling stability and rate performance of the battery are improved.The optimization effect of Li⁺is better than Na⁺.By ion concentration analysis and molecular dynamics simulation,the charge-discharge reaction process of the zinc-iodine self-stratified battery is clarified,and we propose the cation shuttle mechanism,that is,during the charge-discharge process of the battery,metal cations shuttle at the liquid-liquid interface to maintain the balance of the two phases charge,and its shuttle ability affects the speed of electrode reaction kinetics.In the self-stratified iodine zinc battery,Li⁺has the strongest shuttle ability which benefits from the smallest difference in free energy of solvation of Li⁺in the two phase solutions.Through the battery failure analysis,it’s found that the increasing ionic conductivity of the organic phase and reducing the volatilization of the electrode material are the keys to the stability of battery capacity.2.We design an aqueous-organic sodium ion self-stratified battery and propose a new battery structure that puts the anode material in the organic phase,which enlarges the range of the anode material’s potential selection.We use sodium titanium phosphate（NTP）with the potential of-0.42 V（vs.SHE）as the anode material for sodium storage,and synthesize the NTP@C by carbon coating method,which enhances the electronic conductivity and sodium storage stability of NTP.Sodium ferrocyanide（Na₄Fe（CN）₆）and NTP@C are used to assemble the sodium ion self-stratified battery.The anode and cathode of the battery have high redox reversibility,but the capacity utilization and coulombic efficiency of the battery are very low.By battery failure analysis,we found that the electrode swelling by the organic electrolyte causes the NTP@C to peel off from the current collector.so,using a strong anti-swelling binder in the electrode is the key to improving the cycle performance of the battery.