SO^(2-)_4掺杂对Nasicon型Li_3Fe_2(PO_4)_3正极材料电化学性能的影响  

Effect of SO^(2-)_4 Doping on Electrochemical Properties of the Nasicon Li_3Fe_2(PO_4)_3 Cathode

作　　者：张勃[1] 何臖 华正伸 王新[1] 彭会芬[1,2] ZHANG Bo HE Jun HUA Zhengshen WANG Xin PENG Huifen(School of Material Science ＆ Engineering, Hebei University of Technology, Tianjin 300130, China Tianjin Key Laboratory of Laminating Fabrication ＆ InteoCace Control Technology for Advanced Materials, Tianjin 300130, China)

机构地区：[1]河北工业大学材料科学与工程学院,天津300130 [2]天津市材料层状复合与界面控制技术重点实验室,天津300130

出　　处：《高等学校化学学报》2017年第1期108-114,共7页Chemical Journal of Chinese Universities

基　　金：河北省自然科学基金(批准号:E2016202358)资助~~

摘　　要：采用溶胶-凝胶法用SO^(2-)_4部分代替Li_3Fe_2(PO_4)_3中的PO^(3-)_4阴离子制得Li_(3-x)Fe_2(PO4)_(3-x)(SO_4)_x(x=0~0.90)正极材料,通过X射线衍射、充放电技术、循环伏安特性测试及电化学阻抗谱表征了掺杂材料的相组成及电化学性能.结果表明,SO^(2-)_4主要以固溶形式存在于Li_3Fe_2(PO_4)_3中,产物中还伴有少量Fe_2O_3第二相析出.SO^(2-)_4掺杂使Li_3Fe_2(PO_4)_3的放电容量呈抛物线形规律变化,并在掺杂浓度x=0.60时达到最佳值,该样品在0.5C倍率下的首次放电容量为111.59 mA·h/g,比未掺杂的样品提高了18.4%;60次循环充放电后的容量保持率为96%;将该样品的放电倍率由0.5C逐渐提高至5C,再降至0.5C,并在每个倍率下循环10次,材料的最终放电容量仍能达到首次放电容量的97%.导致这些变化的原因是SO^(2-)_4掺杂使材料的氧化还原性能增强,电池内阻减小,极化程度降低及Li^+扩散系数增大.Effect of SO42- doping on electrochemical properties of the Li3Fe2 （PO4）3 cathode materials was studied. Phase constitutents and electrochemical properties of the Li3-x Fe2 （ PO4 ） 3-x （ SO4） x （ x = 0- 0. 90 ） materials were characterized by XRD, charge-discharge technology, cyclic voltammetry and electrochemical impedance spectrum. The results proved that the added SO42- anions mainly dissolved in the Li3Fe：（ PO4） 3 compound, concomitant with the secondary phase, Fe2O3. Introduction of the SO]- anions resulted in a parabolic variation of discharging capacity for the Li3Fe2（PO4）3 SO42-content（x） of 0. 60 exhibited the best performance. Its initi compound, and that the sample with the al discharging capacity was about 111.59 mA· h/g at a rate of 0. 5C, and this value was 18. 4% higher than that without any SO42-. After 60 charge- discharge cycles, its capacity retention was around 96% at a rate of 0. 5C. Moreover, 97% of the initial capacity was obtained for this material by gradually increasing discharging rates from 0. 5C to 5C, and then decreasing back to 0. 5C, together with 10 charging-discharging cycles at each rate. Above-mentioned improve- ment in electrochemical properties for the SO2- substituted samples should result from their enhanced redox ability, decreased internal resistance and polarization, and increased Li＋ diffusion coefficients of the batteries.

关 键 词：正极材料 Nasicon型Li3Fe2(PO4)3 SO(2-)4掺杂 电化学性能 

分 类 号：O646[理学—物理化学]