Applied Technology

Series Progress on Developing Electrode Materials for Li-Ion Batteries

Rencently, Prof. Guo Yuguo and Prof. Wan Lijun’s groups from the Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, CAS, made series progress on the development of high-performance electrode materials for lithium-ion batteries. On the invitation of the editor of Accounts of Chemical Research, they have published a review article titled “Nanocarbon Networks for Advanced Rechargeable Lithium Batteries”. In the Account paper, they summarized recent progress in the structural design, chemical synthesis, and characterization of the electrochemical properties of nanocarbon networks for Li-ion batteries and the next generation rechargeable lithium batteries, such as Li-S and Li-O2 batteries. In addition, they also addressed the ways, in which nanocarbon networks can expand the applications of rechargeable lithium batteries into the emerging fields of stationary energy storage and transportation (Acc. Chem. Res., 2012, 45, 1759). Through systematic studies, the group found that the nanoporous three-dimensional conducting networks, which are formed by various nanocarbon building blocks (carbon nanoparticle, carbon nanotube, graphene and nanoporous carbon), can effectively disperse the nanoparticles of the active electrode materials to prevent them from agglomerating, provide rapid pathways for Li ions and electrons to reach the surface of each active nanoparticle, and hence make full use of the potential kinetic advantages of the nanostructured electrode materials. In this way, they developed many electrode materials with high specific capacities and favorable high-rate performances for Li-ion batteries. With this concept, the researchers made series progress in using graphene to build the three-dimensional conducting networks in hybrid cathode and anode materials, and developing many efficient assembly methods for such structures. Recently, they have proposed a double-protection design concept for high-capacity alloy anode material. To be specific, they used a core-shell structured nanocarbon shell in combination with the three-dimensional graphene network to solve the issues concerning the high-capacity alloy anode material (i.e., dramatic volume expansion, and surface/interface and kinetic problems). For example, they developed a Ge@C/graphene nanocomposite anode material with high specific capacity, long cycle life and excellent high-rate performance (J. Am. Chem. Soc., 2012, 134, 2512).

Substantial Step in Industrialization of DMM

A medium test for the production of polyoxymethylene dialkyl ethers (abreviated as DMM) with capacity of 100 tons/year was successfully completed based on the lab experiment and a scale-up test of 15 tons/year in the Baiying Test Base by Prof. Chen Jing’s research group of the Lanzhou Institute of Chemical Physics, CAS. The relevant technological package for 1 million tons production has been also designed, which marks the industrial production of DMM is now put on the right track. The successful completion of the technological package will open not only a new channel for the development of the cleaner energy resources as an auternative for the coal resources, but will also provide a new strategy for the effective solution of the over production of methanol, as production of methanol reached 50 million tons in China, of which 60% are extracted from coal.

Major Progress in Electrical Nanogap Devices

Recently, Prof. Liu Jinhuai, and Huanmg Xingjiu's group from the Institute of Intelligent Machines, CAS proposed two new strategies for developing electrical nanogap devices. For detecting substances that are invisible to the human eye or nose, and particularly those biomolecules, pollutants in environment, etc, the devices must have very small feature sizes, be compact and provide a sufficient level of sensitivity, often to a small number of molecules that are just a few nanometres in size. The most charming feature of the devices is to directly transduce events of objective molecules specific binding into useful electrical signals such as resistance/impedance, capacitance/dielectric, or field-effect. The relevant research results have been publicated on Willey journal Small, and selected as the front cover (Small, 2012, 8, 3274-3281). At the same time, the researchers have also demonstrated a strategy of specific inhibition of charge transport to polychlorinated biphenyls detection coupled with a 34-nm gold nanogap. The selectivity and sensitivity of this strategy is due to the specific binding of PCBs to the cavities of β-CD. The lower detection limit reaches at least 1 nM for PCBs. Besides the gap size, d, the relative dielectric constant of the gap area, εi, is the dominant factor in detecting the decrease in the tunneling current. Such a device having “traps” between the gaps addresses the fundamental problem in that it is difficult to force a “solution” containing the target species to be detected into the small size of the nanogap. In addition, it is expected that such CD-modified nanogap device will have the capability to detect a number of organic compounds in solution which could be captured by the hydrophobic inner cavity of CDs. In this work, the researchers have designed not only a convenient PCBs sensor in this study, but also a methodology for more extensive application of the nanogap sensor in detection of other persistent organic pollutants having chemical inertness, insulating, and hydrophobicity properties. These results have been publicated on ACS journal Analytical Chemistry. (2012, 84, 9818-9824).