Research On Energy Storage Devices For Alkali Metal Ion Batteries

With the rapid development of modern industry,due to the reserves of lithium metal are constanly decreasing（0.002 wt.%）.Therefore,alternative materials of lithium metal energy storage are eagerly to be studies.Sodium metals（2.36 wt.%）and potassium metals（2.09 wt.%）are potential for their high element abundance and they are similar to lithium in physical and chemical properties.The standard reduction electrode potential of sodium is-2.71 V,and that of potassium is-2.93 V,compared with that of lithium,the standard reduction electrode potential of lithium is-3.04 V,which has similar electrochemical properties.Therefore,it gradually comes into the field of view of researchers.In the past ten years,the excellent performance of the new alkali metal battery energy storage devices with sodium and potassium metal anode has also made a satisfactory result.In order to construct an excellent new alkaline metal battery system,researchers have practiced many strategies,such as designing electrode structure to enhance the electrode reaction kinetics,constructing nanoparticles,nanorods,nanosheets,etc.Preparation of carbon conducting materials for coating and protection of electrode materials,such as graphene loading,carbon matrix coating,etc.to increase the life of the electrode.The electrolyte is designed to stabilize the solid electrolyte film,such as the addition of electrolyte additives such as vinyl fluorocarbonate.In addition,the development of new alkaline metal battery system is also a new method.In chapter 2,a simple one-step hydrothermal method was used to compound the caged Sb/Fe precursor micron rods with GO,which was then freeze-dried and reduced at high temperature to obtain Sb/Sb₂O₄/Fe₃C/r GO（SSFG）.Nanoparticles were dispersed in the grapheme laminate without obvious agglomeration.Fe₃C catalyst adsorbed potassium ions and promoted the formation of solid electrolyte components,which improved the efficiency and cycle life of potassium ion batteries.The capacity is 234 m Ah/g after 280 charge/discharge cycles at 500 m A/g,and 108m Ah/g after 1244 charge/discharge cycles at 2000 m A/g.In chapter 3,the free radical polymerization of butyl acrylic acid（AA）was initiated by initiator,and then the cross-linking degree was increased by adding three-dimensional cross-linking agent acetylacetone aluminum to prepare the self-healing polymer matrix,it can realize self-healing after mechanical damage.The Na-K alloy electrode was used to repair the damage caused by external forces during the cycle.Through the joint action of the self-healing polymer electrolyte and the self-healing sodium-potassium alloy electrode,the electrode/electrolyte interface exists stably during the deposition and dissolution process.The stable solid electrolyte membrane generated protects the electrode and inhifies the generation and growth of dendrite through“dendrite creep”,thus increasing the battery life.The smooth and non-porous interface of the gel polymer electeolyte inhibits the uneven distribution of sodium ions through the common porous membrane and avoids the formation of uneven interface of the sodium metal electrode.At 0.5 m Ah/cm²and0.5 m A/cm²,the polarization voltage of the Na-K alloy symmetric battery with self-healing gel polymer electeolyte was about 0.49 V after 624 h reversible deposition and dissolution,and the polarization voltage of the control Na-K alloy symmetric battery with glass fiber membrane immersed in liquid electrolyte was0.57 V after 624 h under the same test conditions.The cycle life of the self-repairing polymer electrolyte was about 860 h,while the cycle life of the control glass fiber disphragm liquid electrolyte was only about 640 h.