Preparation And Electrochemical Properties Of NASICON-Type Electrode Materials For Long-life Sodium Ion Batteries

Sodium-ion batteries are one kind of electrochemical energy-storage devices based on the reversible Na-(de)intercalation reaction,showing application potential in the field of scale-storage of sustainable energies due to their large specific energy,high energy efficiency and low cost.However,their lifetime needs to be further improved.This thesis aims to fabricate lifespan-long sodium-ion batteries by designing high-performance NASICON-type vanadium-based cathode material and titanium-based anode material,mainly containing following contents:?preparation and electrochemical properties of vanadium-based phosphate cathode materials:a series of Na3V2(PO4)3/C materials with various carbon contents are prepared with a traditional sol-gel method,and the effect of the carbon content on crystal structure and electrochemical performance of the material is investigated by using XRD,TGA and galvanostatic technique to have the optimized carbon content.Furthermore,Mn-doped Na3+xV2-xMnx(PO4)3/C(0?x?1)samples are prepared via a sol-gel route,and the influence of Mn doping on crystal structure,reaction kinetics and charge/discharge performance of the material is studied by coupling XRD,cyclic voltammetry and galvanostatic technique.It is found that the Na3.2V1.8Mn0.2(PO4)3/C sample delivers reversible capacities of 106.6 mAh.g-1 at 20 mA·g-1 and 91.2 mAh.g-1 at 200 mA·g-1,and a high capacity retention of 91.5%after 200 cycles.? preparation and electrochemical properties of titanium-based phosphate anode materials:ATi2(PO4)3/C(A=Li,Na and Mg)compositions are prepared with a sol-gel approach,and the effect of the composition on crystal structure,morphology,reaction kinetics,and charge/discharge performance of the material is detailedly investigated by using XRD,SEM,cyclic voltammetry,GITT,EIS,and galvanostatic technique.Experimental results suggest that the LiTi2(PO4)3/C composition renders reversible capacities of 120.4 mAh·g-1 at 20 mA·g-1 and 89.7 mAh·g-1 at 1000 mA·g-1,without capacity fading after 1000 cycles.?assembling and performance measurements of full sodium-ion batteries:full batteries are assembled by coupling as-prepared Na3.2V1.8Mn0.2(PO4)3/C cathode material and LiTi2(PO4)3/C anode material.The mass ratio of the cathode material and anode material is particularly optimized to reach the best electrochemical performance.It is revealed that the battery can deliver a working voltage of 1.3 V,a reversible capacity of 95.3 mAh.g-1,and a capacity retention of 80.1%after 100 cycles.The results in this thesis provide theoretical fundamentals for design and manufacturing of lifespan-long sodium-ion batteries.