Fabrication And Characteristics Of All-solid-state Supercapacitor Based On LATP Solid Electrolyte

Energy shortage and environmental pollution are two major challenges for humanity after entering the new century.However,commercialized energy storage devices mostly use liquid electrolytes to maintain their high ionic conductivity,which causes the inherent hazards of leakages and fire.The use of a solid electrolyte instead of a liquid electrolyte can effectively solve such problems.Supercapacitors have attracted wide attention due to their advantages of high capacity,high power density and long cycle life.All-solid-state supercapacitors base on solid electrolyte have great potential.In present thesis,a single phase of Li_1.3Al_0.3Ti_1.7P₃O₁₂?LATP?was synthesized by a one-step solid-state reaction,and its properties were improved by adding sintering aid.A carbon-filled three-dimensional connected electrode structure was designed to obtain a layered all-solid-state supercapacitor,and its structure and properties were studied.A single phase of LATP was synthesized by a one-step solid-state reaction using ammonium polyphosphate?APP?as a PO₄ precursor instead of NH₄H₂PO₄ to avoid the cumbersome experimental process of traditional synthesis methods.LiMnPO₄?LMP?was added as sintering aid to improve sintering properties,mechanical properties and chemical stability of LATP ceramics.The reaction dynamics showed that LATP was chemically compatible with LMP at high temperature.The density reached the maximum at a sintering temperature of 825°C by incorporating 2%of the sintering aid.At the same time,the Vickers hardness reached the maximum of 473 HV,and the ionic conductivity also got the highest value(4.9×10^-4 S cm^-1).The equivalent circuit of a single-layered dense electrolyte was analyzed by electrochemical impedance and cyclic voltammetry.The fitting result was consistent with the experimental results.The results showed that there is a typical double-layer interface capacitance behavior at the interface of electrolyte/electrode,which is expected to be used for the preparation of supercapacitors.A sandwich all-solid-state supercapacitor with a carbon-filled porous electrolyte/dense electrolyte/carbon-filled porous electrolyte was designed and tested for electrochemical performance.The porous/dense/porous layered ceramic was obtained by sintering the LATP powder with sintering aid and the LATP powder without sintering aid pressed together.A carbon-filled porous electrolyte was obtained by filling the porous ceramic with a polyimide solution and vacuum heat treatment.The analysis of mercury porosimetry proved that the average pore size and the porosity decreased after carbon-filled porous ceramics,which indicated that carbon had been effectively filled,but the filling rate still needed to be improved.Layered ceramic supercapacitor show a large capacitance of 0.13 F cm^-1 at a low scan rate of 2 mV s^-1,and a 91%of the initial capacitance after 600 cycles.In the future work,we need to design the pore structure distribution rationally,increase the carbon filling rate and improve the contact between the electrode and the solid electrolyte to improve the capacitance and discharge rate characteristics of the capacitor.