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采用基于密度泛函理论的第一性原理方法, 计算了不同Mn掺杂浓度LiFe1-xMnxPO4 (x=0,0.25,0.50,0.75) 的电子结构. 同时采用流变相辅助高温固相碳热还原法制备了LiFe1-xMnxPO4 (x= 0,0.25,0.50,0.75) 材料. 理论计算表明: LiFePO4具有Eg = 0.725 eV的带隙宽度, 为半导体材料. 通过Fe位掺杂25%的Mn离子可最大程度地 减小材料带隙宽度、降低FeO键及LiO键键能, 进而提高材料的电子电导率及锂离子扩散速率. 实验结果亦表明, 当Mn掺杂量x=0.25时, 材料具有最优的电化学性能, 其具有约为158 mAh g-1的放电比容量以及551 Wh kg-1的能量密度. 理论计算与实验结果非常符合.The electronic structures of pure and Mn-doped LiFePO4 are studied using density functional theory (DFT). The results demonstrate that the pure LiFePO4 has a band gap of 0.725 eV, while the 25% Mn doped LiFe0.75Mn0.25PO4 has the smallest band gap (0.469 eV), and the weakest FeO and LiO bond, which indicates that the electronic conductivity and the ionic conductivity of the doped LiFePO4 are improved due to doping. On the other hand, the experimental results also show that the LiFe0.75Mn0.25PO4 has the best electrochemical performance and it delivers a very high capacity of 158 mAh? g-1 and a high energy density of 551 Whkg-1.
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Keywords:
- LiFePO4 /
- Li-ion batteries /
- first principles /
- density functional theory
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[2] Shin H C, Nam K W, Chang W Y 2011 Electrochem. Acta 56 1182
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[16] Xu J, Chen G 2010 Physica B 405 803
[17] Ouyang C Y, Wang D Y, Shi S Q, Wang Z X, Li H, Huang X J, Chen L Q 2006 Chin. Phys. Lett. 23 61
[18] Yamada A, Chung S C, Hinokuma K 2001 J. Electrochem. Soc. 148 A224
[19] Zhang H, Tang Y H, Zhou W W, Li P J, Shi S Q 2010 Acta Phys. Sin. 59 5135 (in Chinese) [张华, 唐元昊, 周薇薇, 李沛娟, 施思齐 2010 59 5135]
[20] Gao F, Tang Z Y 2008 Electrochem. Acta 53 5071
[21] Chen C H, Liu J, Amine K 2001 J. Power Sources 96 321
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[1] Padhi A K, Nanjundaswamy K S, Goodenough J B 1997 J. Electrochem. Soc. 14 1188
[2] Shin H C, Nam K W, Chang W Y 2011 Electrochem. Acta 56 1182
[3] Huang F, Liu Y, Lei Y, Fan L X 2010 J. Wuhan Univ. Sci. Technol. 33 532 (in Chinese) [黄峰, 刘芸, 雷艳, 范丽霞 2010 武汉科技大学学报 33 532]
[4] Liu H, Feng Y, Wang Z H, Wang K, Xie J Y 2008 Powder Technol. 184 313
[5] Jin S F, Han E S, Liu J Y, Zhang J P 2011 Chin. J. Powder Sources 35 263 (in Chinese) [靳素芳, 韩恩山, 刘吉云, 张俊平 2011 电源技术 35 263]
[6] Ren Z G, Qu M Z, Yu Z L 2010 J. Inorg. Mater. 25 230 (in Chinese) [任兆刚, 瞿美臻, 于作龙 2010 无机材料学报 25 230]
[7] Long Y F, Wang F, Lü X Y, Yang K D, Wen Y X 2011 J. Inorg. Mater. 26 625 (in Chinese) [龙云飞, 王凡, 吕小艳, 杨克迪, 文衍宣 2011 无机材料学报 26 625]
[8] Zhang W K, Hu Y L, Tao X Y, Huang H, Gan Y P, Wang C T 2010 J. Phys. Chem. Solids 71 1196
[9] Xin X G, Chen X, Zhou J J, Shi S Q 2011 Acta Phys. Sin. 60 028201 (in Chinese) [忻晓桂, 陈香, 周晶晶, 施思齐 2011 60 028201]
[10] Hou X H, Hu S J 2010 Chin. Sci. Bull. 55 3222
[11] Liu Z J, Huang X J, Wang D S 2008 Solid State Commun. 147 505
[12] Xu F W, Xue W D, Su R, Wang M X 2008 J. Sichuan Normal Univ. (Nat. Sci.) 31 224 [许芳伟, 薛卫东, 苏荣, 王明玺 2008 四川师范大学学报 (自然科学版) 31 224]
[13] Liu H, Xie J Y 2009 J. Mater. Process. Technol. 209 477
[14] Oh S M, Oh S W, Yoon C S, Scrosati B, Amine K, Sun Y K 2010 Adv. Funct. Mater. 20 3260
[15] Li G H, Azuma H, Tohda M 2002 Electrochem. Solid-State Lett. A 5 135
[16] Xu J, Chen G 2010 Physica B 405 803
[17] Ouyang C Y, Wang D Y, Shi S Q, Wang Z X, Li H, Huang X J, Chen L Q 2006 Chin. Phys. Lett. 23 61
[18] Yamada A, Chung S C, Hinokuma K 2001 J. Electrochem. Soc. 148 A224
[19] Zhang H, Tang Y H, Zhou W W, Li P J, Shi S Q 2010 Acta Phys. Sin. 59 5135 (in Chinese) [张华, 唐元昊, 周薇薇, 李沛娟, 施思齐 2010 59 5135]
[20] Gao F, Tang Z Y 2008 Electrochem. Acta 53 5071
[21] Chen C H, Liu J, Amine K 2001 J. Power Sources 96 321
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