主题:充电电池介绍 -- 积吉
Our synthesis strategy has been to create an appropriate off-stoichiometry in the starting materials so that the coating constituents phase-separate from LiFePO4 as it forms during the heat treatment, thereby creating the active storage material and coating in a single process. Here we describe results with an iron:phosphorus deficiency ratio of 2:1 (for example LiFe1-2yP1-yO4-delta, y = 0.05), as indicated by arrow A in Supplementary Fig. 1. We note that the more common one-to-one iron:phosphorus deficiency (arrow B in Supplementary Fig. 1, equivalent to lithium excess22) creates a mixture of Li3PO4 and iron oxides, which are not likely to conduct well under the synthesis conditions used to prepare LiFePO4.
LiFe0.9P0.95O4-delta was synthesized by ball-milling Li2CO3, FeC2O4dot2H2O and NH4H2PO4 in appropriate amounts, heating the mixture at 350 °C for 10 h and then heating at 600 °C for 10 h under argon. X-ray diffraction (Fig. 1a and Supplementary Fig. 2) shows that despite the off-stoichiometric starting mixture, stoichiometric LiFePO4 forms with lattice parameters (a = 10.3134 , b = 6.002 and c = 4.691 ) very similar to those reported in the literature23. No crystalline Fe2P can be observed in the X-ray pattern of the material synthesized at 600 °C, but a small amount of Fe2P is present in the material synthesized at 700 °C (Fig. 1a). However, amorphous FeP or Fe2P created by the reducing atmosphere cannot be excluded24. Mssbauer spectroscopy (Supplementary Fig. 4) indicates that apart from the major LiFePO4 component, around 10% of the Fe is present in some other environment. The isomer shift (0.464 mm s-1) and quadrupole splitting (0.798 mm s-1) of this second component fall in the region of values given in the literature for Fe3+ in pyrophosphate (P2O7-containing) glasses, although recent work24 argues that iron monophosphides also give a Mssbauer signal in this range. To distinguish between the two possibilities, as-made material was discharged. The large discharge capacity found (Supplementary Fig. 5) is consistent with the presence of reducible Fe3+ rather than FeP in the material. Furthermore, in subsequent charge–discharge cycles we consistently find 15–18 mA h g-1 capacity in the 3.2–2.0 V voltage window, in agreement with the approx10% proportion of iron
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🙂我更正一下,是‘纳米’加‘非结晶体的焦磷酸包覆‘技术 1 积吉 字745 2009-03-13 08:45:49
🙂这个么,大家都在用同样的掺杂 大袋鼠 字20 2009-06-10 06:33:02
🙂谢谢,看起来是‘纳米’加‘碳包覆’ 1 积吉 字659 2009-03-12 10:04:46
🙂这是部分原文,他们应该是改了制造工艺
🙂锂铁电池现在关键是成本,他们的新工艺不知量产后 积吉 字12 2009-03-12 10:42:28
🙂看文章,好像工艺流程改变不大,主要是 二胡 字630 2009-03-12 10:57:27
🙂大功率充电器材比亚迪早就有了,并正在和电网谈判 积吉 字339 2009-03-12 11:28:54
🙂那个聚合物是polyethylenetetrafluor 二胡 字397 2009-03-12 11:39:52