| With the development of the information society and the needs of energy transformation,electrochemical energy storage elements are developing towards higher energy density and higher safety.Solid-state lithium metal secondary batteries are one of the most likely development paths.However,under solid-state interface conditions,the huge volume change of lithium caused by high areal capacity cycling will cause the interface between the electrolyte and lithium to fall off,resulting in battery failure.The strategy of preparing structured composite lithium anode can form a framework support to alleviate its volume change,and at the same time,it can increase the contact area between lithium and electrolyte,reduce the current density,and inhibit the growth of lithium dendrites.Aiming at the above problems,based on these ionic and electronic conductors such as inorganic solid electrolytes,gel polymer electrolytes and carbon cloth,a variety of composite lithium anodes with three-dimensional structures were prepared by infiltration,physical winding and electrodeposition processes.The effects of the composition,structure,and morphology of the structured lithium composite anode on the electrochemical performance were investigated,and the plating/stripping characteristics of lithium in the structured lithium composite anode under high-capacity cycling conditions were explored.The main work is as follows:1.Research on structured lithium composite anode with inorganic solid electrolyteIn this paper,a Lithium composite anode with a dispersed structure was prepared by a thermal coating method.The study shows that when solid-state electrolyte forms a continuous stable phase in the material,it has the dual roles of ion transport and framework support.And the reasons for the failure of composite lithium anodes with different solid-state electrolyte contents were analyzed.The porous solid-state electrolyte framework with improved lithophilicity by alumina was prepared by template method,and lithium-solid electrolyte（LAS）composite anode was prepared by infiltration method.The research shows that when the porosity is 48.1%,the LAS composite anode can cycle for 231 h at a high capacity of 5m Ah cm-2,showing good high-capacity cycling performance.This is mainly because the inorganic solid-state electrolyte plays a supporting role during cycling,maintaining the structural stability of the composite lithium anode in high-capacity cycling.However,due to the high density of solid-state electrolyte,the overall gram capacity of the LAS composite anode is low.2.Research on structured composite lithium anode with gel polymer electrolyteAiming at the problem of high density of solid-state electrolyte,a lithium-gel polymer electrolyte（LG）vertical structured composite anode with large contact interface was designed and fabricated by direct winding method using gel polymer electrolyte with low density.The results show that this structure reduces the actual current density of the composite lithium anode,while the stable SEI layer enables the reversible stripping and plating of metallic lithium along the direction of the electrolyte interlayer during cycling,maintaining the stability and reversibility of the overall structure.Tests show that the LG composite anode can cycle stably for about 785 h at a capacity of 5 m Ah cm-2;it can cycle stably for more than 540 h at the ultra-high capacity of 15 m Ah cm-2;the 4.62 m Ah cm-2 high-capacity LG//LFP full battery can be cycled stably for more than 20 cycles.3.Research on carbon cloth/gel polymer electrolyte dual-conductor structured lithium composite anodeThis paper investigates the relationship between stripping/plating and ionic/electron conductivity ratio in mixed conductors with electronic/ionic biconductive network structure.It is shown that when the ionic and electronic conductivities differ within two orders of magnitude,the mixed conductor can play the role of both ionic and electronic conductors,and metallic lithium can be plated in the mixed conductor.On this basis,a gel polymer electrolyte-lithium-carbon cloth structure（GLC）composite anode was prepared by using carbon cloth with a continuous structure as the skeleton.The test found that the GLC composite anode has better cycle performance at low capacity,and the reasons for its poor performance at high capacity cycle were analyzed.The paper uses alumina-coated carbon fibers to improve its affinity for lithium,and prepares S-GLC composite anodes using the strategy of reserved plating space.The analysis shows that the alumina on the surface of the carbon fiber in the S-GLC composite anode has good lithiophilic properties,and the pre-plated lithium builds a stable SEI layer,and the stable three-dimensional framework ensures the reversible plating/stripping of the composite lithium anode at high capacity.The S-GLC composite anode can cycle stably for nearly 4870 h at a high capacity of 12 m Ah cm-2.It exhibits excellent high-capacity cycling performance.Meanwhile,the S-GLC composite anode has excellent resistance to external pressure. |
