Comparative kinetic study of olivine LixMPO4 (M = Fe, Mn)
Comparative kinetic study of olivine LixMPO4 (M = Fe, Mn)
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DOI：
10.1149/1.1773731
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发表时间：
2004-01-01
影响因子：
3.9
通讯作者：
Kanno, R
中科院分区：
文献类型：
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作者：
Yonemura, M;Yamada, A;Kanno, R
定量地研究了橄榄石LixMPO4(M=Fe，Mn)的动力学差异。在相同的外部条件下，对比测量了LixFePO4和LixMnPO4的恒电流放电曲线和逐级阳极过电压的电流弛豫(计时电流法)，并通过Rietveld X射线衍射谱的精细化、扫描电子显微镜的直接织构观察、Brunauer-Emmett-Teller表面积测量和敲击密度测量对其进行了仔细的控制和确认。目前LixMnPO4的耐久性比LixFePO4低一个数量级，这显然是由于它们固有的结晶学和输运性质的差异造成的。认为位于Mn3+位上的重极化子空穴是一个重要的速率限制因素。尽管橄榄石骨架中Mn3+/Mn2+的开路电压(4.05V)高于Fe3+/Fe2+的开路电压(3.45V)，但由于LiMnPO4的有效能量密度比LiFePO4低得多，反常的大极化可能会使LiMnPO4不再作为实用的锂电池正极。(C)2004年电化学会。
A huge kinetic difference in olivine LixMPO4 (M = Fe, Mn) is demonstrated in a quantitative manner. Galvanostatic discharge profiles and the current relaxation to the stepwise anodic overvoltage (chronoamperometry) are comparatively measured for the LixFePO4 and LixMnPO4 under identical extrinsic conditions, which are carefully controlled and confirmed using Rietveld refinement for the X-ray diffraction profiles, direct texture observation by scanning electron microscope, Brunauer-Emmett-Teller surface area measurements, and tap density measurements. The current durability for LixMnPO4 is orders-of-magnitude inferior to that of LixFePO4, the origin of which is clearly attributed to their intrinsic crystallographic and transport property differences. Heavy polaronic holes localized on the Mn3+ sites are suggested as an important rate-limiting factor. In spite of the higher open-circuit voltage of Mn3+/ Mn2+ (4.05 V) compared to that of Fe3+/Fe2+ (3.45 V) in the olivine framework, the abnormally large polarization may eliminate pure LiMnPO4 as a practical lithium battery cathode due to much lower effective energy density than LiFePO4. (C) 2004 The Electrochemical Society.