Fluorination of Graphite Oxide and Application to Lithium Battery

采用Hummers法、Staudenmeier法和Brodie法合成了氧化石墨，并在20 ^ C ~ 200^ C的温度下，用氟气体和VF_5+F_2和SbF_5+F_2的混合物进行了氟化。Hummers法、Staudenmeier法和Brodie法制备的氧化石墨的最佳氟化温度依次从50^ C升高到100^ C。完全氟化是困难的，但x射线衍射显示，氟化氧化石墨沿c轴的重复距离为8.5-9 A，与阶段2型氟化石墨（c_2F）_n几乎相同。同时，沿A轴的晶格参数从2.48 A增加到2.50 A，与（C_2F）_n一致。红外光谱显示在1200cm处有较强的吸收，对应于C-F键。这些数据与氧化石墨的第二阶段结构模型相吻合。用Li负极研究了氟化氧化石墨在碳酸丙烯酯-1 M LiCLO_4溶液中的阴极行为。随着氧化石墨结晶度的提高，氟化氧化石墨的容量和放电电位的平整度得到改善。对过渡金属氟化物和氧化物氟化物与氧化石墨的离子插层化合物结构的比较表明，氧化石墨的C-O键共价不如氟化石墨高。

Graphite oxide has been synthesized by Hummers, Staudenmeier and Brodie methods and fluorinated by fluorine gas and mixtures of VF_5+F_2 and SbF_5+F_2 at temperatures between 20 ^ﾟC and 200^ﾟC. Optimum fluorination temperature increased from 50^ﾟC to 100^ﾟC for graphite oxide prepared by Hummers, Staudenmeier and Brodie methods in that order. Perfect fluorination was difficult, but X-ray diffraction showed that the repeat distance along c-axis of fluorinated graphite oxide was 8.5-9 A, almost the same as that of stage 2 type graphite fluoride (c_2F)_n. At the same time the lattice parameter along a-axis increased from 2.48 A to 2.50 A consistent with that for (C_2F)_n. IR spectrum indicated a strong absorption at 1200 cm corresponding to C-F bonding. These data coincide with the stage 2 type structure model of graphite oxide.The cathodic behavior of fluorinated graphite oxide has been investigated in propylene carbonate-1 M LiCLO_4 solution with Li negative electrode. With increasing crystallinity of graphite oxide, the capacities and flatness of the discharge potentials of fluorinated graphite oxide were impro ved.Comparison of the structures of ionic intercalation compounds of transition metal fluorides and oxide fluorides with that of graphite oxide suggested that the covalency of C-O bond in graphite oxide is not as high as that of graphite fluoride.