Trends of R&D on Materials for High-power and Large-capacity Lithium-ion Batteries for Vehicles Applications

Introduction With the goal of promoting energy conservation and exploring forms of energy alternative to petrified sources, as well as of reducing environmental burden, much effort has been spent on developing new breeds of vehicles. These include Hybrid vehicles (HV) that run on a combined system of a fossil fuel engine and an electric motor, Plug-in HVs (PHVs) that allow recharging of the in-vehicle battery using a commercial electric source, and Electric Vehicles (EVs). As the electric source to drive these vehicles, the development and introduction of a high-power, large capacity secondary battery is a challenge of urgent concern, and the lithium-ion battery has become the focus of attention. The lithium-ion battery, with its advantage of high energy density, has scored impressive advances in the field of information communication and the home appliance sector, especially as a portable power source. Against the backdrop of widespread proliferation of mobile phones and notebook PCs, global shipments of lithium-ion batteries amounted to \390 billion in FY 2008. The lithium-ion battery has a host of advantages including: that next to no side reaction occurs when a lithium ion intercalates into or desorbs from the positive/negative electrode material, the possibility that energy efficiency may be further enhanced by the lowering of the battery's inner resistance, a small self-discharge, and no memory effect. Research and development, up to the present, has focused on upgrading the energy density. Japan put the lithium-ion into practical use ahead of all other countries, and has maintained the global lead in terms of both technological edge and production. For highly efficient use of energy for automobiles 1 in the future, full use of the secondary batteries should be an integral part of automobile development. The battery provides electric power for driving, while enabling instantaneous recovery and storage of braking energy in quick response to the running conditions. Among in-vehicle secondary batteries, the lithium-ion battery is the most promising because of its superior characteristics in terms of power and energy density per unit weight or volume. The majority of the currently used secondary batteries are nickel-hydrogen type, and the shipment value as of FY 2009 is expected to reach \220 billion. This value is based on the market size forecast for HVs in 2009 (approximately 1.1 million vehicles [3]) and assuming a battery price of \200,000 per unit. [2] According to a Nomura Research Institute forecast, the HVs market size will grow …