Synthesis, structure, and electrochemical performance of magnesium-substituted lithium manganese orthosilicate cathode materials for lithium-ion batteries

JOURNAL OF POWER SOURCES

卷:197

Article

Gummow, R. J.¹  Sharma, N.²  Peterson, V. K.²  He, Y.¹ 

[1] James Cook Univ, Sch Engn & Phys Sci, Douglas, Qld 4811, Australia

[2] Australian Nucl Sci & Technol Org, Bragg Inst, Kirrawee Dc, NSW 2232, Australia

关键词: Magnesium substitution;    Solid solution;    Rietveld refinement;    Neutron diffraction;    X-ray diffraction;    Lithium manganese silicate;   

DOI  :  10.1016/j.jpowsour.2011.09.013

来源: Elsevier

【 摘 要 】

Magnesium-substituted lithium manganese orthosilicate (Li(2)MnSiO(4)) cathode materials with a nominal composition of Li(2)Mg(x)Mn(1-x)SiO(4), for x = 0.4 and 0.5 are synthesized by a solid-state route, at 700 degrees C in argon. The samples are characterized using powder X-ray and neutron diffraction, scanning electron microscopy, and galvanostatic cell-cycling. Rietveld analyses of the powder X-ray and neutron diffraction data show the formation of a monoclinic P2(1)/n structure related to gamma lithium phosphate with no significant impurity peaks. This structure of the Mg-substituted samples is in contrast to the unsubstituted Li(2)MnSiO(4) compound that has a Pmn2(1) structure when synthesized under the same conditions. Unit-cell volumes of the Mg-substituted materials are intermediate between those of the P2(1)/n structure of Li(2)MnSiO(4) and the isostructural low-temperature form of Li(2)MgSiO(4), indicating the formation of a solid solution. The Mg-substituted materials feature mixed Mg/Mn cation sites, although no evidence of Li/Mn, Li/Mg or Li/Mg/Mn mixed sites are found. The Li(2)Mg(x)Mn(1-x)SiO(4) cathodes show improved electrochemical performance over that reported for the unsubstituted Li(2)MnSiO(4) P2(1)/n phase. The Li(2)Mg(x)Mn(1-x)SiO(4) cathode performance remains limited by its poor electronic properties and the large particle size of the solid-state synthesized products. Optimization of the synthesis conditions is likely to lead to enhanced electrochemical performance. (C) 2011 Elsevier B.V. All rights reserved.

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