Preparation Of Solid Electrolyte/Carbon Nanotube Double-Coated Composite Electrode For Solid-State Batteries

With the continuous improvement of living standards,intelligent electronic products,portable electronic devices and electric cars are growing with the increasing demand.And the traditional liquid lithium-ion batteries cannot meet the market demand,thereby the solid-state batteries become an ideal choose for future lithium-ion batteries for their safety and energy density issues.However,the interfacial problemsin solid-state batteries seriously hinder their practical application,especially the complex solid-solid interface and electron/ion conduction on the electrode.In order to solve with these problems,this dissertation constructed a composite electrode with carbon nanotubes（CNTs）conductive network and the filled solid electrolyte.Thereby the complex solid-solid interface in the electrode was simplified,and the electron/ion transfer rate in the electrode was greatly improved.The results demonstrate the electrochemical performances of the solid-state battery were significant improved.The main results are as follows:（1）The polymerization of lithium bistrifluoromethanesulfonimide/1,3-dioxane（Li TFSI/DOL）electrolyte can be catalyzed by aluminum triflate/tetrahydrofuran（Al（OTf）₃/THF）as liquid cationic initiator,and poly（1,3-dioxane）solid electrolyte（PDOL）woud be obtained.The lithium ion migration number of PDOL electrolyte is 0.5,and the ionic conductivity is 1.78×10-4 S cm^-1 at room temperature.The electrolyte also has a high thermal stability.（2）The precursor of the mixed electrolyte can be adsorbed by the composite electrode,and the PDOL@CNTs@Li Fe PO₄（LFP）electrode with excellent bendability would be formed as the in-situ polymerization occured The active materials in the electrode are tightly wrapped by the random CNT networks,and then the PDOL electrolytes are fully wrapped outside the CNTs networks.Thereby the electron and ion transfer rates in the electrode can be greatly improved with the double-layered structure of CNTs and PDOL.The composite electrode indicates a sheet resistance of less than 4.5Ωsq^-1 and a lithium ion diffusion coefficient higher than 10^-11cm^-2 s^-1,which demonstrates excellent electronic and ionic conductivity in the electrode.（3）The half-cell of PDOL@CNTs@LFP/Li suggests a stable polarization voltage and low charge transfer resistance.Therefor,it can work normally with a discharge specific capacity of99 m Ah g^-1even at a high rate of 10 C.In addition,the composite electrode indiactes excellent flexibility even with the LFP loading of 19.4 mg cm^-2.Further,the assembled half cell also suggests a stable cycling performance,high coulomb efficiency of 99.8%,high capacity of 2.274 mAh·cm^-2 and high energy density of 241.64 Wh kg^-1.And the lithium metal pouch battery assembled with the composite electrode also showed a stable electrochemical performances,it can work 3 h even at a cutting sstate.（4）The flexible solid-state battery of PDOL@CNTs@LFP||PDOL@CNTs@LTO alsoindicates a good cycle stability after the traditional aluminum-plastic film packaging was replaced by plastic film,and the battery works normally at bent and cut state,suggesting an excellent safety.Moreover,The flexible solid-state battery with large-capacity of 288.8 m Ah also has been prepared and indicated a stable electrochemical performances.It can be sewed onto clothes and works naturally at an operation situation.