Study On Asymmetric Electrochemical Capacitor Based On Lithium Battery Materials Li₄Ti₅O₁₂ And LiNi_1/3Co_1/3Mn_1/3O₂

Asymmetric electrochemical capacitor is a novel storage element betweensupercapacitor and battery, with higher energy density than supercapacitors andhigher power density than battery, which can overcome the defect of low powerdensity for supercapacitor and low energy density for battery. This device can wellsatisfy the requirement of the load for the energy density and power density of thepower sources. The research focused on the electrode materials of hybrid capacitorbased on Lithium battery materials and activated carbon, the specific capacitance,specific energy, specific power and cycle performance of asymmetricelectrochemical capacitors were tested and researched by constant currentcharge-discharge test.Spinel Li₄Ti₅O₁₂is a novel promising anode material for lithium-ion batteriesand supercapacitors. This material has many advantageous properties comparedwith other anode materials. Spinel Li₄Ti₅O₁₂has high specific capacity andexcellent cyclability. Importantly, it is very safe when used as electrode material inlithium-ion batteries and supercapacitors. Howerver, due to the low Li ionicelectronic conductivity in Li₄Ti₅O₁₂, the rate performance of Li₄Ti₅O₁₂is ratherpoor. LiNil/3Col/3Mnl/3O₂is the soild solution of LiNiO₂, LiCoO₂, and LiMnO₂withlayered structure and has less structural change in the lithium-ion insertion process.It has the advantages of these three materials, as long cycle life, high specificcapacity, excellent thermal stability, good safety performance and low cost.In this thesis, the Li₄Ti₅O₁₂and LiNi_1/3Co_1/3Mn_1/3O₂electrode materials wereprepared by solid state reaction. Asymmetric electrochemical capacitor wasprepared by Li₄Ti₅O₁₂and LiNi_1/3Co_1/3Mn_1/3O₂combine with active carbon. Bytesting the structures and morphologies and electrochemical performance, theconclusions were as follows:1、The Li₄Ti₅O₁₂and LiNi_1/3Co_1/3Mn_1/3O₂electrode materials were prepared bysolid state reaction. The XRD test showed they had been successfully prepared inthis work, constant current charge-discharge test showed their first dischargecapacity were177mAh/g and157.6mAh/g, after10cycles capacity remain at a rate of85.8%and85.8%.2、AC/AC symmetric electrochemical capacitor was tested by constant currentcharging-discharging at80mA/g、160mA/g and400mA/g, studying its charge anddischarge properties and cycle performance. The results showed it had goodcapacitance characteristics and cycle life, especially at80mA/g, it had the specificcapacitance value of36.1F/g and after50cycles the capacitance value remains at arate of95.2%.3、AC(LiNi_1/3Co_1/3Mn_1/3O₂)/AC asymmetric electrochemical capacitors withdifferent LiNi_1/3Co_1/3Mn_1/3O₂content were tested by constant currentcharging-discharging at80mA/g、160mA/g and400mA/g, studying their charge anddischarge properties and cycle performance. The results showed they had goodcapacitance characteristics and cycle life, at80mA/g, when the LiNi_1/3Co_1/3Mn_1/3O₂content was10%it had the specific capacitance value of26.7F/g and after50cycles the capacitance value remains at a rate of94.2%.4、AC(LiNi_1/3Co_1/3Mn_1/3O₂)/Li₄Ti₅O₁₂asymmetric electrochemical capacitorswith different LiNi_1/3Co_1/3Mn_1/3O₂content were tested by constant currentcharging-discharging at80mA/g、160mA/g and400mA/g, studying their charge anddischarge properties and cycle performance. The results showed they had goodcapacitance characteristics and cycle life, in80mA/g, when the LiNi_1/3Co_1/3Mn_1/3O₂content was10%it had the specific capacitance value of178.5F/g and after50cycles the capacitance value remains at a rate of92.5%.