(1. 中南大學(xué) 冶金與環(huán)境學(xué)院，長沙 410083；
2. 長沙理工大學(xué) 物理與電子科學(xué)學(xué)院，長沙 410004)
摘 要: 以硫酸為表面修飾劑，采用浸漬法對(duì)天然石墨進(jìn)行表面修飾改性。傅里葉變換紅外光譜儀(FTIR)分析結(jié)果表明，硫酸表面修飾的天然石墨表面—OH和C=C消失，—COO-數(shù)量增多。電化學(xué)性能測試結(jié)果表明，經(jīng)硫酸表面修飾的天然石墨的循環(huán)性能和倍率性能均得到提高。經(jīng)3 mol/L H2SO4處理12 h的天然石墨(NGS3)在0.5C下20次循環(huán)后脫鋰容量為320.5 mA？h/g；而未經(jīng)表面修飾的天然石墨(NG)在相同條件下的脫鋰容量僅為299.9 mA？h/g。采用交流阻抗譜對(duì)石墨進(jìn)行嵌脫鋰動(dòng)力學(xué)研究，結(jié)果顯示，經(jīng)硫酸表面修飾的天然石墨膜電阻(RSEI)和電荷轉(zhuǎn)移電阻(Rct)均減小，膜電容(CSEI)和雙電層電容(CCPE)增加，多次循環(huán)后RSEI保持穩(wěn)定，NG的活化能(Ea)為87.7 kJ/mol，NGS3的Ea為77.2 kJ/mol，表明 H2SO4修飾有利于鋰離子去溶劑化能力的提高，并有利于形成穩(wěn)定的固體電解質(zhì)界面(Solid electrolyte interface，SEI)。
關(guān)鍵字: 天然石墨；表面修飾；負(fù)極；固體電解質(zhì)界面；交流阻抗；活化能
（1. School of Metallurgy and Environment, Central South University, Changsha 410083, China;
2. School of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410004, China）
Abstract:The natural graphite was modified by impregnation method with sulfuric acid as surface modification agent. FTIR results show that —OH and C=C bonds on the surface of natural graphite disappear while the number of —COO- increases after sulfuric acid surface-modification. The electrochemical performance reveals that the cycle performance and ratio performance are improved. The lithium-deinsertion capacities of natural graphite impregnated by 3 mol/L H2SO4 for 12 h (NGS3) and unmodified natural graphite (NG) are respectively 320.5 and 299.9 mA？h/g after 20 cycles at 0.5C. AC impedance was used to investigate kinetics on lithium ion insertion/ deinsertion. It is found that the membrane resistance (RSEI) and charge transfer resistance (Rct) decrease, while the membrane capacitance (CSEI) and extracted capacitance (CCPE) increase. Moreover, RSEI keeps constant after several cycles. The activation energies of NG and NGS3 are 87.7 and 77.2 kJ/mol, respectively, which indicates that sulfuric acid treatment is beneficial to the improvement of the desolvation of lithium ion from solvent molecules and the formation of a stable solid electrolyte interface (SEI).
Key words: natural graphite; surface-modification; anode; solid electrolyte interface; alternating impedance; activation energy
