(1. 四川大學(xué)材料科學(xué)與工程學(xué)院，成都610065；
2. 四川大學(xué)化學(xué)工程學(xué)院，成都610065)
摘 要: 采用溶膠-凝膠法合成Li3V2(PO4)3/C正極材料，采用X射線衍射(XRD)、掃描電子顯微鏡(SEM)、充放電循環(huán)測試、電化學(xué)阻抗譜(EIS)、循環(huán)伏安(CV)等手段研究極片面密度和壓實密度對Li3V2(PO4)3/C電化學(xué)性能的影響。結(jié)果表明：Li3V2(PO4)3/C的倍率性能隨著面密度的增加而變差，且面密度越大極化現(xiàn)象越嚴(yán)重，20C時放電比容量差距高達(dá)22.8 (mA·h)/g。EIS分析結(jié)果表明：隨著面密度的增加，電荷轉(zhuǎn)移阻抗增大，鋰離子表觀擴(kuò)散系數(shù)降低。當(dāng)極片壓實密度過高或過低時，Li3V2(PO4)3/C的倍率性能均較差，壓力為 20 MPa時放電比容量最高，20C時放電比容量為 94.0 (mA·h)/g，而0和35 MPa時放電比容量僅70 (mA·h)/g 左右。EIS和CV測試結(jié)果表明：極片壓實密度較小和較大的情況均不利于電荷和鋰離子的轉(zhuǎn)移。
關(guān)鍵字: Li3V2(PO4)3/C；面密度；壓實密度；倍率性能；鋰離子；擴(kuò)散系數(shù)
（1. School of Materials Science and Engineering, Sichuan University, Chengdu 610065, China;
2. School of Chemical Engineering, Sichuan University, Chengdu 610065, China）
Abstract:Li3V2(PO4)3/C anode material was prepared by sol-gel method. The effects of surface density and press density of the cathode electrode on electrochemical performance of Li3V2(PO4)3/C were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), galvanostatic charge-discharge test, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The results show that the rate capability of Li3V2(PO4)3/C electrode becomes worse with the increase of surface density, delivering a discharge specific capacity gap of as high as 22.8 (mA·h)/g at 20C, and is accompanied by a more severe polarization. The EIS results show that the charge transfer resistance increases and apparent lithium ion diffusion coefficient decreases with the increase of surface density. Besides, the rate capability of Li3V2(PO4)3/C is poor when the press density is either too low or too high. It is evidenced that Li3V2(PO4)3/C electrode pressed at the pressure of 20 MPa can provide the highest discharge capacity of 94.0 (mA·h)/g at 20C, but only about 70 (mA·h)/g at 0 and 35 MPa. The results of EIS and CV show that it is not conductive to the transformation of charge and lithium ion under too high or too low press density.
Key words: Li3V2(PO4)3/C; surface density; press density; rate capability; lithium ion; diffusion coefficient
