198th Meeting of 
The Electrochemical Society 
October 22-27
2000 Phoenix Civic Plaza Arizona, USA

            Zhang Ruifen (Ph.D. candidate) and Ng Say Boon (M.Eng. candidate) attended the 198^th Meeting of the Electrochemical Society (ECS) in Phoenix, Arizona from 22-27 October, 2000. The ECS meeting is held twice a year and more than 1500 participants attended this event. The participants reflect a global mix of representatives from industries, national research centres and various academic institutions.  The Chemical Engineering Department from NUS has been regularly represented and has contributed original research since 1996.

             The meeting opened with the Plenary Lecture by Prof. Carl Djerassi  on NO on Electrochemistry. Prof. Djerassi, from the Chemistry Department at Stanford University, has received 18 honorary doctorates together with numerous honours including the first Wolf Prize in Chemistry and the American Chemical Society’s highest award, the Priestly Medal. In recent years, he has turned to fiction writing mostly in the genre of science-in-fiction.

             Electrochemistry is a broad field involving many areas of research and application. As such, the meeting is divided into several symposiums such as Battery/Energy Technology, Corrosion, Electronics, Electrodeposition, Luminescent Display Materials and Sensors. Each symposium is further subdivided into technical sessions to discuss very specific topics. Ruifen and Say Boon participated in the oral presentation of the Rechargeable Lithium Batteries group. Specifically, they reported their new findings on the modifications of the battery anode materials.

             Most commercial lithium ion (rechargeable lithium) batteries use carbonaceous materials as anodes due to their excellent cycleability. Research was presented at the Meeting on various types of carbon, modifications on carbon, as well as the mechanisms of lithium intercalation into graphite.

Metals such as tin, silicon, zinc and aluminium are known to alloy reversibly with lithium to result in materials of even higher capacities than carbonaceous anodes. An oral session was dedicated to the studies of these metals and their oxides by different preparatory pathways. Audience participated actively via question and answer sessions following the presentations.

           The topic of Say Boon’s presentation was Gel encapsulated silicon-graphite composites as a negative electrode material for lithium-ion batteries and Ruifen’s topic was The effects of preparation conditions on the performance of tin oxide electrodes in lithium-ion batteries. Though metals such as tin and silicon are able to deliver high specific capacities, the cycleabilities of these materials are often rather poor due to material expansion and contraction that occur during cycling, and most current efforts are focussed on solutions to overcome such deficiencies.

             Say Boon’s work involved synthesizing an Si-O network on silicon-graphite composite via sol-gel transformation to restrain the volume changes in lithium insertion and de-insertion reactions. Prof Y.M. Chiang (MIT professor in material science) was intrigued by the approach nd provided several interesting suggestions for future work.

Figure 1: Scanning electron micrograph (X1000) of HCl catalyzed gel-encapsulated graphite-silicon composite powder.

            Ruifen prepared tin oxides via several novel methods. One of the oxides she obtained showed outstanding cycleability (i.e., cycle number is the number of charge/discharge cycles that an electrochemical cell has gone through) and high capacity (~600 mAh/g) in the 0-1 V potential window. The capacity is about twice the value of carbonaceous materials currently used in commercial cells. As a result, her work has attracted keen interest from industrial representatives, particularly from Japan.

Figure 2: Discharge capacity of SnO_x as a function of cycle number.

            Poster sessions were conducted in the evening. Research on materials engineering, optimization of lithium batteries as well as fundamental studies of the structures of lithiated alloys and mechanisms reaction pathways were presented during the poster sessions.