Ling Licheng

Synthesis of Nitrogen Doped Graphene through Microwave Irradiation

Graphite oxide was synthesized with Staudenmaier method using natural flake graphite as carbon source.After graphite oxide was impregnated into ammonium carbonate saturated solution,NH4+ intercalated graphite oxide was given.Rapid thermal exfoliation and reduction of NH4+ intercalated graphite oxide to graphene was achieved as well as the nitrogen-doping of graphene under the condition of microwave irradiation.SEM,TEM,EDS,XRD,XPS and Raman were performed to characterize the synthesized nitrogen-doping of graphene.The synthesized nitrogen-doped graphene was transparent and wrinkled with 2 5 graphite layers.The nitrogen content of as-prepared nitrogen-doped graphene was 1.56wt%,corresponding to pyridinc N,pyrrolic N and graphitic N incorporated into the graphitic network.

Promoter action of sulphur on the stabilization of pitch spheres

Elemental sulphur was added into the starting pitch during the preparation of pitch-based spherical activated carbon in order to enhance the stabilization of pitch sphere. Pitch sphere (diameter 0.65–1.0 mm) without adding sulphur needs slow heating rate of 0.5 °C/min, high final temperature of 300 °C and long holding time of 20 h for the successful stabilization in air. While adding elemental sulphur with 2.5–10.0 wt % in total amount into starting pitch decreased the stabilization time significantly, pitch sphere containing 5.0 wt % of sulphur can be stabilized in air very easily at heating rate of 2.0 °C/min up to 270 °C without any holding time, and the successful stabilization time was only 3 h. Pitch molecules reacted with sulphur and some sulphur functional groups, such as C−SH, C−S−C, C=S, O=S=, O=S=O etc., were formed besides the oxygen functional groups under the stabilization condition. All of these sulphur functional groups acted as bridge bonds to make the pitch molecules polymerized so as to high up the softening point of pitch spheres, making the pitch spheres stabilized. Three kinds of sulfocompounds, i.e. H2S, COS and CS2 evolved in stabilization process.

SnO 2 /石墨烯锂离子电池负极材料的制备及其电化学行为研究

以氧化石墨和氯化亚锡为原料, 采用原位合成法制得SnO 2 /石墨烯纳米复合材料。该方法不需外加还原剂, 也避免了SnO 2 纳米粒子和石墨烯在机械混合过程中的团聚问题。XRD和TEM等的分析结果表明, 纳米SnO 2 颗粒都均匀地分散在石墨烯表面, 其中纳米SnO 2 的粒径和石墨烯的厚度分别为3~6 nm和1.5~2.0 nm。电化学测试结果表明: 在200 mA/g电流密度下循环100次后, SnO 2 /石墨烯负极材料的嵌锂容量可稳定在552 mAh/g, 容量保持率比单纯纳米SnO 2 提高了4.4倍; 在40、400、800 mA/g的电流密度下, SnO 2 /石墨烯负极材料的放电容量可分别保持在724.5、426.0、241.3 mAh/g, 表现出较好的倍率性能, 该结果归因于石墨烯良好的导电性及其二维纳米结构。以氧化石墨和氯化亚锡为原料, 采用原位合成法制得SnO 2 /石墨烯纳米复合材料。该方法不需外加还原剂, 也避免了SnO 2 纳米粒子和石墨烯在机械混合过程中的团聚问题。XRD和TEM等的分析结果表明, 纳米SnO 2 颗粒都均匀地分散在石墨烯表面, 其中纳米SnO 2 的粒径和石墨烯的厚度分别为3~6 nm和1.5~2.0 nm。电化学测试结果表明: 在200 mA/g电流密度下循环100次后, SnO 2 /石墨烯负极材料的嵌锂容量可稳定在552 mAh/g, 容量保持率比单纯纳米SnO 2 提高了4.4倍; 在40、400、800 mA/g的电流密度下, SnO 2 /石墨烯负极材料的放电容量可分别保持在724.5、426.0、241.3 mAh/g, 表现出较好的倍率性能, 该结果归因于石墨烯良好的导电性及其二维纳米结构。

以Fe 2 O 3 为原料通过水热–高温煅烧法合成LiFePO 4 /C纳米复合材料及其电化学性能研究

采用三氧化二铁(Fe 2 O 3 )为铁源, 抗坏血酸作碳源, 通过在200℃下水热反应并经煅烧后合成出LiFePO 4 /C纳米复合材料. 抗坏血酸在水热反应体系中不但作为最终反应产物的碳源, 而且还起到了限制LiFePO 4 颗粒生长的作用. 抗坏血酸的用量对产物的形貌、结构、碳含量有重要影响, 进而影响产物的电化学性能. 当抗坏血酸用量为1 g时, 制得的LiFePO 4 /C纳米复合材料的粒径在220~280 nm. 该材料用作锂离子电池的正极材料时, 在0.1 C 的电流密度下循环500次后其放电容量仍保持159 mAh/g, 并且具有较好的倍率性能.采用三氧化二铁(Fe 2 O 3 )为铁源, 抗坏血酸作碳源, 通过在200℃下水热反应并经煅烧后合成出LiFePO 4 /C纳米复合材料. 抗坏血酸在水热反应体系中不但作为最终反应产物的碳源, 而且还起到了限制LiFePO 4 颗粒生长的作用. 抗坏血酸的用量对产物的形貌、结构、碳含量有重要影响, 进而影响产物的电化学性能. 当抗坏血酸用量为1 g时, 制得的LiFePO 4 /C纳米复合材料的粒径在220~280 nm. 该材料用作锂离子电池的正极材料时, 在0.1 C 的电流密度下循环500次后其放电容量仍保持159 mAh/g, 并且具有较好的倍率性能.LiFePO 4 nanoparticles coated with a carbon layer were synthesized by a hydrothermal reaction-calcination process, using Fe 2 O 3 as an iron source and ascorbic acid as carbon source. The amount of ascorbic acid have an effect on the structure, phase and carbon amount of the final product. With 1 g ascorbic acid used in the reaction, the particle sizes of synthesized LiFePO 4 /C nanocomposites are in a range of 220–280 nm. Using as the cathode materials for the lithium-ion batteries, the as-prepared material shows high capacity and good cycle stability (159 mAh/g at 0.1C over 500 cycles), as well as good rate capability.

TiO 2 /C纳米复合材料的制备及其电化学性能研究

以球状钛乙醇酸盐为TiO 2 前驱体, 葡萄糖作碳源, 通过水热法制得Φ(300~400) nm的TiO 2 /C复合纳米微球. 葡萄糖的浓度对产物的形貌、结构、碳含量有重要影响, 进而影响产物的电化学性能. 当碳含量为7wt%时, TiO 2 /C纳米复合材料的晶粒大小、BET比表面积、平均孔径分别为7.1 nm、157 m 2 /g和5.2 nm; 该材料用作锂离子电池负极材料时, 在0.2 C 的电流密度下循环80次后的嵌锂容量为160 mAh/g, 并且具有较好的倍率性能.以球状钛乙醇酸盐为TiO 2 前驱体, 葡萄糖作碳源, 通过水热法制得Φ(300~400) nm的TiO 2 /C复合纳米微球. 葡萄糖的浓度对产物的形貌、结构、碳含量有重要影响, 进而影响产物的电化学性能. 当碳含量为7wt%时, TiO 2 /C纳米复合材料的晶粒大小、BET比表面积、平均孔径分别为7.1 nm、157 m 2 /g和5.2 nm; 该材料用作锂离子电池负极材料时, 在0.2 C 的电流密度下循环80次后的嵌锂容量为160 mAh/g, 并且具有较好的倍率性能.