(1. 深圳大學(xué) 化學(xué)與化工學(xué)院，深圳 518060；
2. 哈爾濱工業(yè)大學(xué)深圳研究生院 材料科學(xué)與工程學(xué)院，深圳 518055)
摘 要: 采用基于密度泛函理論的第一性原理研究鋰離子電池正極材料LiFePO4摻雜Ni和Mg的電子結(jié)構(gòu)。結(jié)果表明：Ni氧化物的電子結(jié)構(gòu)和能量性質(zhì)受d軌道中電子影響，用于摻雜改性時(shí)，結(jié)構(gòu)穩(wěn)定，帶隙降低使電子電導(dǎo)率增加，充放電速率提高；Mg摻雜改性時(shí)，當(dāng)摻雜在Li位時(shí)，帶隙和總能均降低，同時(shí)Li離子的擴(kuò)散運(yùn)動(dòng)也提高，有利于改性，而在Fe位摻雜時(shí)，費(fèi)米面附近Fe-d軌道中電子影響能帶，使帶隙增加，不利于電子電導(dǎo)，鍵的布居分析也表明Li-O共價(jià)性增強(qiáng)，不利于離子擴(kuò)散，即不利于改性。因此，通過摻雜可對LiFePO4的微觀結(jié)構(gòu)產(chǎn)生影響，從而影響其電化學(xué)性能，但這種微觀結(jié)構(gòu)主要受d軌道中電子運(yùn)動(dòng)對費(fèi)米面附近能帶的影響，而與摻雜離子的化合價(jià)和半徑無關(guān)。
關(guān)鍵字: LiFePO4；鎳摻雜；鎂摻雜；電子結(jié)構(gòu)；第一性原理
（1. College of Chemistry and Chemical Engineering, Shenzhen University, Shenzhen 518060, China;
2. School of Materials Science and Engineering, Harbin Institute of Technology Shenzhen Graduate School,
Shenzhen 518055, China）
Abstract:LiFePO4 doped with Ni and Mg was simulated by using the first-principles. Through the energy band, PDOS and population analysis, it shows that, when the transition metal element Ni is used as dopant, the structure is becomes stable and the band gap reduces when Ni is doped on either Li(M1) or Fe(M2) sites, which results in the increase of the electronic conductivity and the discharge-recharge rate, because the electronic structure and energy properties of the transition metal oxides are greatly affected by the electrons in orbital d. When non-transition metal element Mg is doped at Li-site, both the band gap and total energy decrease, and the lithium ion diffusivity improves. When Mg is doped at Fe-site, the band gap increases because of the influence of electronics in Fe-d orbitals near the Fermi level, which is not beneficial to the electronic conductivity. The covalent interaction between Li and O strengthens through the analysis of population, which is not benefit for the lithium ion diffusivity and modification. So, the electrochemical properties of LiFePO4 are influenced by the changes of microstructure which are affected by dopants. The electrons in orbital d mainly affect the electronic structure near the Fermi level, while has no relative with the chemical valence and atomic radius of dopant.
Key words: LiFePO4; Ni-doping; Mg-doping; electronic structures; first principles
