微波辅助溶剂热法制备LiMn_(1-x)Mg_xPO_4/C正极材料
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摘要
采用微波辅助溶剂热法的合成途径,成功制备出镁掺杂的磷酸锰镁锂(LiMn_(1-x)Mg_xPO_4/C)电极材料。采用X-射线衍射、扫描电镜、恒电流充放电等测试方法对晶体结构,微观形态和电化学性能进行表征。结果表明微波辅助溶剂热样品LiMn_(1-x)Mg_xPO_4/C为具备较大比表面积和介孔结构的片层状形貌材料。该片层状纳米结构有利于锂离子脱嵌/镶嵌反应,Mg~(2+)掺杂在片层状纳米晶体合成过程中发挥着重要作用,可以提高材料的电化学活性和电化学表现。其中LiMn_(0.95)Mg_(0.05)PO_4/C材料在0.1 C和5 C倍率下最高可逆放电容量分别为141.2和95.3(mA·h)/g,具备较高的放电容量和倍率性能表现。与传统溶剂热法相比,微波辅助溶剂热法的反应时间显著降低且制备得到的材料具备优异的电化学性能表现,对于制备其他锂离子电池材料具有指导意义。
Magnesium-doped lithium manganese phosphate(LiMn_(1-x)Mg_xPO_4/C)electrode materials were successfully prepared by microwave-assisted solvothermal synthesis.X-Ray diffraction,scanning electron microscope thermogravimetry and Brunaur-Emmett-Teller method were employed to characterize crystal structures and morphology,and the electrochemical characteristics of the as-prepared materials were evaluated by galvanostatic charge/discharge,cyclic voltammetry and AC impedance method.The results showed that the plate-like LiMn_(1-x)Mg_xPO_4/C samples,which were synthesized from the microwave-assisted solvothermal method,possessed large specific surface area and well-defined mesoporous structure.In particular,Mg~(2+)doping exerts a significant effect on synthesizing flake-like nanocrystal which favors lithium-ion extraction/insertion reactions,improving the electrochemical activity and electrochemical performance of LiMnPO_4/C material.As a result,the LiMn_(0.95)Mg_(0.05)PO_4C nanoparticle exhibited a high reversible capacity of 141.2 and 95.3(mA·h)/g at 0.1 C and 5 C,respectively exhibited outstanding charge/discharge performance and rate capability.Compared to conventional solvothermal synthetic route,microwave-assisted solvothermal approach led to a significant decrease in the reaction time and the as-prepared material possessed excellent electrochemical performance.It is extraordinary and remarkable for the preparation of high-performance LiMnPO_4 cathode material,providing a new method for the preparation of electrode materials for Li-ion batteries.
Magnesium-doped lithium manganese phosphate(LiMn_(1-x)Mg_xPO_4/C)electrode materials were successfully prepared by microwave-assisted solvothermal synthesis.X-Ray diffraction,scanning electron microscope thermogravimetry and Brunaur-Emmett-Teller method were employed to characterize crystal structures and morphology,and the electrochemical characteristics of the as-prepared materials were evaluated by galvanostatic charge/discharge,cyclic voltammetry and AC impedance method.The results showed that the plate-like LiMn_(1-x)Mg_xPO_4/C samples,which were synthesized from the microwave-assisted solvothermal method,possessed large specific surface area and well-defined mesoporous structure.In particular,Mg~(2+)doping exerts a significant effect on synthesizing flake-like nanocrystal which favors lithium-ion extraction/insertion reactions,improving the electrochemical activity and electrochemical performance of LiMnPO_4/C material.As a result,the LiMn_(0.95)Mg_(0.05)PO_4C nanoparticle exhibited a high reversible capacity of 141.2 and 95.3(mA·h)/g at 0.1 C and 5 C,respectively exhibited outstanding charge/discharge performance and rate capability.Compared to conventional solvothermal synthetic route,microwave-assisted solvothermal approach led to a significant decrease in the reaction time and the as-prepared material possessed excellent electrochemical performance.It is extraordinary and remarkable for the preparation of high-performance LiMnPO_4 cathode material,providing a new method for the preparation of electrode materials for Li-ion batteries.
引文
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[29]Guo H,Wu C,Liao L,et al.Performance improvement of lithium manganese phosphate by controllable morphology tailoring with acid-engaged nano engineering[J].Inorganic Chemistry,2015,54(2):667-674.
[30]Wang L,Zhang H,Liu Q,et al.Modifying high-voltage olivinetype LiMnPO4cathode via Mg substitution in high-orientation crystal[J].ACS Applied Energy Materials,2018,1(11):5928-5935.
[31]Hu C,Yi H,Fang H,et al.Improving the electrochemical activity of LiMnPO4via Mn-site co-substitution with Fe and Mg[J].Electrochemistry Communications,2010,12(12):1784-1787.
[32]Kumar P R,Venkateswarlu M,Misra M,et al.Enhanced conductivity and electrical relaxation studies of carbon-coated LiMnPO4nanorods[J].Ionics,2012,19(3):461-469.
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[2]Dunn B,Kamath H,Tarascon J M.Electrical energy storage for the grid:a battery of choices[J].Science,2011,334(6058):928-935.
[3]Nitta N,Wu F,Lee J T,et al.Li-ion battery materials:present and future[J].Materials Today,2015,18(5):252-264.
[4]Padhi A K,Najundaswamy K S,Goodenough J B.Phosphoolivines as positive-electrode materials for rechargeable lithium batteries[J].Journal of the Electrochemical Society,1997,144(4):1188-1194.
[5]Masquelier C,Croguennec L.Polyanionic(phosphates,silicates,sulfates)frameworks as electrode materials for rechargeable Li(or Na)batteries[J].Chemical Reviews,2013,113(8):6552-6591.
[6]Aravindan V,Gnanaraj J,Lee Y S,et al.LiMnPO4-a next generation cathode material for lithium-ion batteries[J].Journal of Materials Chemistry A,2013,1(11):3518-3539.
[7]Deng Y F,Yang C X,Zou K X,et al.Recent advances of Mn-rich LiFe1-yMny PO4(0.5≤y<1.0)cathode materials for high energy density lithium ion batteries[J].Advanced Energy Materials,2017,7(13):1614-6840.
[8]Devaraju M K,Honma I.Hydrothermal and solvothermal process towards development of LiMPO4(M=Fe,Mn)nanomaterials for lithium-ion batteries[J].Advanced Energy Materials,2012,2(3):284-297.
[9]Morgan D,van der Ven A,Ceder G.Li conductivity in Lix MPO4(M=Mn,Fe,Co,Ni)olivine materials[J].Electrochemical and Solid State Letters,2004,7(2):A30-A32.
[10]Yamada A,Hosoya M,Chung S C,et al.Olivine-type cathodes:achievements and problems[J].Journal of Power Sources,2003,119-121(6):232-238.
[11]Zhao M,Fu Y,Xu N,et al.High performance LiMnPO4/Cprepared by a crystallite size control method[J].Journal of Materials Chemistry A,2014,2(36):15070-15077.
[12]Dinh H C,Mho S I,Yeo I H,et al.Superior high rate capability of size-controlled LiMnPO4/C nanosheets with preferential orientation[J].RSC Advances,2015,5(122):100709-100714.
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[14]Yan S Y,Wang C Y,Gu R M,et al.Enhanced kinetic behaviors of LiMn0.5Fe0.5PO4/C cathode material by Fe substitution and carbon coating[J].Journal of Solid State Electrochemistry,2015,19(10):2943-2950.
[15]Oh S M,Oh S W,Yoon C S,et al.High-performance carbonLiMnPO4nanocomposite cathode for lithium batteries[J].Advanced Functional Materials,2010,20(19):3260-3265.
[16]Wang F X,WangX W,Chang Z,et al.Electrode materials with tailored facets for electrochemical energy storage[J].Nanoscale Horizons,2016,1(4):272-289.
[17]Jung Y H,Park W B,Pyo M,et al.A multi-element doping design for a high-performance LiMnPO4cathode via metaheuristics computation[J].Journal of Materials Chemistry A,2017,5(19):8939-8945
[18]Lu Q,Hutchings G S,Zhou Y,et al.Nanostructured flexible Mgmodified LiMnPO4matrix as high-rate cathode materials for Liion batteries[J].Journal of Materials Chemistry A,2014,2(18):6368-6373.
[19]Wang Y,Yang H,Wu C Y,et al.Facile and controllable one-pot synthesis of nickel-doped LiMn0.8Fe0.2PO4nanosheets as high performance cathode materials for lithium-ion batteries[J].Journal of Materials Chemistry A,2017,5(35):18674-18683.
[20]Duan J G,Hu G R,Cao Y B,et al.Synthesis of high-performance Fe-Mg-co-doped LiMnPO4/C via a mechano-chemical liquidphase activation technique[J].Ionics,2016,22(5):609-619
[21]Zhang J,Luo S,Wang Q,et al.Yttrium substituting in Mn site to improve electrochemical kinetics activity of sol-gel synthesized LiMnPO4/C as cathode for lithium ion battery[J].Journal of Solid State Electrochemistry,2017,21(11):3189-3194.
[22]Wang C,Li S,Han Y,et al.Assembly of LiMnPO4nanoplates into microclusters as a high-performance cathode in lithium-ion batteries[J].ACS Applied Materials&Interfaces,2017,9(33):27618-27624
[23]Pan X,Gao Z.Hydrothermal synthesis and electrochemical properties of dispersed LiMnPO4wedges[J].Crystengcomm,2013,15(38):7808-7814.
[24]Guo H,Wu C,Xie J,et al.Controllable synthesis of highperformance LiMnPO4nanocrystals by a facile one-spot solvothermal process[J].Journal of Materials Chemistry A,2014,2(27):10581-10588.
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[26]Zhu J N,Li W C,Cheng F,et al.Synthesis of LiMnPO4/C with superior performance as Li-ion battery cathodes by a two-stage microwave solvothermal process[J].Journal of Materials Chemistry A,2015,3(26):13920-13925.
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[28]Cui Y T,Xu N,Kou L Q,et al.Enhanced electrochemical performance of different morphological LiMnPO4/C nanoparticles from hollow-sphere Li3PO4precursor via a delicate polyolassisted hydrothermal method[J].Journal of Power Sources,2014,249(3):42-47.
[29]Guo H,Wu C,Liao L,et al.Performance improvement of lithium manganese phosphate by controllable morphology tailoring with acid-engaged nano engineering[J].Inorganic Chemistry,2015,54(2):667-674.
[30]Wang L,Zhang H,Liu Q,et al.Modifying high-voltage olivinetype LiMnPO4cathode via Mg substitution in high-orientation crystal[J].ACS Applied Energy Materials,2018,1(11):5928-5935.
[31]Hu C,Yi H,Fang H,et al.Improving the electrochemical activity of LiMnPO4via Mn-site co-substitution with Fe and Mg[J].Electrochemistry Communications,2010,12(12):1784-1787.
[32]Kumar P R,Venkateswarlu M,Misra M,et al.Enhanced conductivity and electrical relaxation studies of carbon-coated LiMnPO4nanorods[J].Ionics,2012,19(3):461-469.
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