摘要
以二氧化锗和二水合醋酸锌为原料,采用水热法制备了锗酸锌纳米棒,并将其与氧化石墨烯复合,制备了石墨烯包覆的锗酸锌纳米棒三维复合材料.SEM等测试表明,锗酸锌纳米棒均匀地穿插在石墨烯片中,阻止了石墨烯片之间相互堆垛,而石墨烯片层之间相互连接,形成三维的空间导电网络,提高了材料的电子导电性.电化学测试表明,石墨烯片作为稳定的框架,能够有效缓冲活性物质在脱嵌锂过程中产生的体积变化,在500 m A·g^(-1)电流密度下循环190次后,Zn_2GeO_4@RGO复合材料的嵌锂容量仍有1189.5 m Ah·g^(-1);在3.2 A·g^(-1)的大电流密度下,嵌锂容量达到449.5m Ah·g^(-1),表明该复合材料具有优异的长循环稳定性和良好的倍率性能.
Commercial graphite anode material for lithium-ion batteries（LIB） with a theoretical specific capacity of 372 m Ah·g^-1 is unable to satisfy the requirements of increasing mobility and high energy demands. Therefore, it is necessary to develop alternative anode material with high specific capacity. In recent years, a large amount of research has been worked out in the area of high capacity anode materials, for example, silicon（Si） and germanium（Ge）. However, the large volume changes of Si and Ge during the charge and discharge process result in the cracking and pulverization of active material and delamination from the current collector, leading to a rapid decay during the cycling. As a semiconductor, Zn2GeO4 possesses a high capacity of 1443 m Ah·g^-1 which is 90.19% as high as Ge. Nevertheless, the weight rate of germanium element in Zn2GeO4 is only 27.15%, which can effectively cut down the cost of anode material. In this work, Zn2GeO4 nanorods were synthesized through a hydrothermal method by using GeO2 and Zn（CH3COO）2·2H2O and combined with RGO to form a 3D composite. In a typical synthesis, 1.10 g Zn（CH3COO）2·2H2O and 0.52 g GeO2 was added into 15 m L deionized（DI） water and the p H of the mixture was adjusted to 7-8 by using NaOH aqueous solution. Then, the hydrothermal treatment was performed at 140 ℃ for 24 h in an oven to obtain Zn2GeO4 nanorods. Finally, the Zn2GeO4 nanorods were filtrated with GO to form a uniform membrane and reduced by hydrazine hydrate. The Zn2GeO4 nanorods and Zn2GeO4@RGO composite were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, high-resolution transmission electron microscopy（HRTEM）, Raman spectroscopy, etc. SEM and TEM testified that Zn2GeO4 nanorods were firmly adhered on the surface of graphene sheets, which can effectively avoid the stacking of graphene sheets. The graphene sheets connected with each other to form an electric conductive network, which can improve the electrical conductivity of the composite. Furthermore, the electrodes are fabricated without conductive additive that can improve the weight ratio of the active material in the whole electrodes. The excellent electrochemical performance showed that the 3D architecture electrode which worked as a stable framework to accommodate the volume change of active material during Li＋ insertion/extraction. It delivers a specific capacity of 1189.5 m Ah·g^-1 at 500 m A·g^-1 after 190 discharge/charge cycles. When at different current densities of 0.8, 1.6, 3.2 A·g^-1, the capacities were found to be about 880, 700, 450 m Ah·g^-1, respectively. Even at a high current density of 6.4 A·g^-1, the capacity can maintain about 250 m Ah·g^-1. These results indicate that the composite possesses outstanding cycling stability and excellent rate performance.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
2016年第2期185-190,共6页
Acta Chimica Sinica
基金
国家重点基础研究发展计划(973项目)(No.2014CB239701)
国家自然科学基金(Nos.21173120
51372116)
江苏省自然科学基金(BK2011030)
中央高校基本科研业务费专项资金(NP2014403
NJ20140004)
江苏高校优势学科建设工程项目资助~~
关键词
锂离子电池
负极材料
锗酸锌纳米棒
还原氧化石墨烯
水热法
lithium-ion batteries
anode materials
zinc germanate nanorod
reduced graphene oxide
hydrothermal method
