讲座题目：Extended Capacity for High Energy Lithium-Ion Batteries
主讲人：Lu Li Department of Mechanical Engineering, National University of Singapore, Singapore
In recent years, lithium-ion batteries have been extensively studied for their applications in the fields of new generation automobile applications, such as electric vehicles (EVs) and hybrid-electric vehicles (HEVs), due to their high energy density, high efficiency and long lifespan. However, currently only limited cathode materials fully meet the requirements of these devices. As reported, energy is dependent on both voltage and capacity. Among various commercial cathode materials, LiMn1.5Ni0.5O4spinel is a promising one because it has a high operating voltage of 4.7 V. In addition, this kind of material has excellent rate performance with 3D lithium diffusion pathway and it is inexpensive, stable and environmentally friendly. Although LiMn1.5Ni0.5O4suffers from its limited capacity above 3 V, doubled capacity can be obtained when it is cycled in a wider potential window of 2-5 V. However, in this case, Jahn-Teller distortion cannot be ignored and results in a fast capacity fade. On the other hand, Li rich layered-layered oxides have also attracted broad attention because of their ability to deliver a capacity of more than 250 mAh/g with good cycle stability. Li2MnO3component in the layered-layered oxides is inactive below 3V, which may help to stabilize the structure of the spinel oxides and access excellent cycling stability.
Therefore, the present study attempts to embed the layered Li2MnO3with good cycling stability into the spinel structures to extend its capacity. The resultant composite crystallized in both a layered and spinel structure with nano-domain structure. When it is used as a cathode material for lithium-ion batteries, it exhibits superior cycle stability with a high capacity after some conditioning cycles and no Jahn-Teller distortion can be identified. This kind of material shows great promise for applications in advanced lithium batteries.
Li Lu received his B.Eng and M. Eng fromTsinghua University,China, and his Ph.D from the Katholiek Universiteit Leuven,Belgium. After four years of doctoral study and two years of post-doctoral work at the Department of Metallurgy and Materials Engineering, Catholic University of Leuven, Belgium. He joined the Department of Mechanical Engineering, National University of Singapore in 1991 and is a Full Professor. He is also Adjunct Scientist in Materials Research Institute of Engineering, Singapore, Guest Professor of Peking University and Zhejiang University, China and Honorius Professor of University of Queensland, Australia.
Dr. Lu is involved in the research of functional materials, mainly in two directions: i) materials for Li-ion rechargeable batteries which include traditional bulk batteries and all-solid-state batteries, and for supercapacitors, and ii) piezoelectric and ferroelectric materials. More recent years Dr. Lu has been heavily involved in development of thin film batteries, and Li-ion conductors for all-solid-state battery and air-batteries.
Dr. Lu is Deputy Head of Mechanical Engineering for Academic Affairs. He is also the Editor-in-Chief of Functional Materials Letters, and Associate Editor of Materials Technology particularly in charge of functional materials. He is Chairman of Functional Materials Society.