过渡金属离子掺杂对磷酸铁锂性能的影响
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摘要
以碳酸锂、草酸亚铁、磷酸二氢铵、葡萄糖为原料,添加不同的过渡金属乙酸盐(乙酸锰、乙酸钴、乙酸镍、乙酸锌),在氩气保护下采用高温固相法制备LiFePO_4/C复合材料。采用X射线衍射、扫描电子显微镜、同步热分析、恒电流充放电、电化学阻抗、循环伏安等方法研究掺杂金属离子及掺杂量对LiFePO_4/C晶体结构和电化学性能的影响。结果表明,LiFe_(0.9)M_(0.1)PO_4/C(M=Mn、Co、Ni、Zn)样品的晶体结构均与橄榄石型LiFePO_4相同。掺杂过渡金属阳离子可以提高LiFePO_4/C的还原电位,降低氧化电位,缩小氧化还原峰间距,提高化学反应的可逆性。掺杂后的样品在5C下的放电性能较好,以LiFe0.9Ni0.1PO4/C的放电容量最高,达到89mAh/g。
By adding different transition metal acetates(manganese acetate,cobaltous acetate,nickel acetate,zinc acetate),LiFePO_4/C composite materials were synthesized for lithium rechargeable batteries by high temperature solid-state reaction under the protection of argon,using Li_2CO_3,FeC_2O4·2H_2O,NH_4H_2PO_4,C_6H_(12)O_6(glucose)as raw materials.Effect of doping transition metal ions on crystal structure and performance of the sample was investigated by using X-ray diffraction,scanning electron microscopy,thermogravimetric analysis,galvanostatic charge discharge and electrochemical impedance spectroscopy,cyclic voltammetry.The results indicated that LiFe_(0.9)M_(0.1)PO_4/C(M=Mn,Co,Ni,Zn)and LiFePO_4 have the same crystal structure of olivine-style.Doping transition metal ions can increase the reduction potential of LiFePO_4/C,decrease the oxidation potential,reduce the distance between redox peaks,and improve the reversibility of the chemical reaction.The doped samples have a better discharge performance at 5C,especially LiFe_(0.9)Ni_(0.1)PO_4/C which has the highest discharge specific capacity reaching 89mAh/g.
By adding different transition metal acetates(manganese acetate,cobaltous acetate,nickel acetate,zinc acetate),LiFePO_4/C composite materials were synthesized for lithium rechargeable batteries by high temperature solid-state reaction under the protection of argon,using Li_2CO_3,FeC_2O4·2H_2O,NH_4H_2PO_4,C_6H_(12)O_6(glucose)as raw materials.Effect of doping transition metal ions on crystal structure and performance of the sample was investigated by using X-ray diffraction,scanning electron microscopy,thermogravimetric analysis,galvanostatic charge discharge and electrochemical impedance spectroscopy,cyclic voltammetry.The results indicated that LiFe_(0.9)M_(0.1)PO_4/C(M=Mn,Co,Ni,Zn)and LiFePO_4 have the same crystal structure of olivine-style.Doping transition metal ions can increase the reduction potential of LiFePO_4/C,decrease the oxidation potential,reduce the distance between redox peaks,and improve the reversibility of the chemical reaction.The doped samples have a better discharge performance at 5C,especially LiFe_(0.9)Ni_(0.1)PO_4/C which has the highest discharge specific capacity reaching 89mAh/g.
引文
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2 Prosini P P,Lisi M,Zane D,et al.Determination of the chemical diffusion coefficient of lithium in LiFePO4[J].Solid State Ionics,2002,148(1-2):45.
3 Zaghib K,Charest P,Guerfi A,et al.LiFePO4safe Li-ion polymer batteries for clean environment[J].J Power Sources,2005,146(1-2):380.
4 Striebel K,Shim J,Sierra A,et al.The development of low cost LiFePO4-based high power lithium-ion batteries[J].J Power Sources,2005,146(1-2):33.
5 Chen Z Y,Zhu H L,Zhu W,et al.Electrochemical performance of carbon nanotube-modified LiFePO4cathodes for Li-ion batteries[J].Trans Nonferrous Metals Soc China,2010,20(4):614.
6 Zhang X S,Tang R H,Xiao F M,et al.Effects of Cr doping on structure and electrochemical performance of LiFePO4/C[J].Mater Rev:Res,2014,28(8):44(in Chinese).章兴石,唐仁衡,肖方明,等.Cr3+对LiFePO4/C材料结构和电化学性能的影响[J].材料导报:研究篇,2014,28(8):44.
7 Feng X S,Mo X Y,Yu C J,et al.Study on preparation and modification of LiFePO4/C cathode material for lithium rechargeable batteries doping metal ions[J].Mater Rev:Res,2012,26(10):33(in Chinese).冯晓叁,莫祥银,俞琛捷,等.锂离子电池LiFePO4/C复合正极材料掺杂金属离子的制备及改性研究[J].材料导报:研究篇,2012,26(10):33.
8 Wang Y,Huang W H,Xiao Z P,et al.Study on synthesis and performances of lithium iron phosphate as cathode materials by Mg-doping[J].Mater Rev:Res,2013,27(12):40(in Chinese).王英,黄文浩,肖志平,等.镁掺杂改性磷酸铁锂正极材料及其性能研究[J].材料导报:研究篇,2013,27(12):40.
9 Cheng F,Wan W,Tan Z,et al.High power performance of nanoLiFePO4/C cathode material synthesized via lauric acid-assisted solid-state reaction[J].Electrochim Acta,2011,56(8):2999.
10 Liu Y,Cao C,Li J.Enhanced electrochemical performance of carbon nanospheres-LiFePO4composite by PEG based sol-gel synthesis[J].Electrochim Acta,2010,55(12):3921.
11 Konarova M,Taniguchi I.Physical and electrochemical properties of LiFePO4nanoparticles synthesized by a combination of spray pyrolysis with wet ball-milling[J].J Power Sources,2009,194(2):1029.