Next-Next-Generation Rechargeable Batteries and Electric Storage Device Technologies "Key Devices for Low Carbon Society and Decentralized Energy Systems"/CRDS-FY2011-SP-04
Executive Summary

One of the central challenges in green innovation is the development of technologies for storing electric energy. Focusing on such technologies and taking a long-term view for 2030 and beyond, this proposal advocates an R&D strategy for creating next-nextgeneration rechargeable batteries and electric storage device technologies, which will be significantly superior in terms of performance, functionality, and cost effectiveness to the various types of rechargeable batteries that are currently being researched.*

Following the Great East Japan Earthquake on March 11, 2011 and the accident at the Fukushima Daiichi Nuclear Power Plant, it is imperative to comprehensively reexamine Japan's future energy policy as well as the relevant strategies for energy R&D. From around 1 year before the earthquake, the Center for Research and Development Strategy (CRDS) of the Japan Science and Technology Agency (JST) has been considering and discussing the R&D strategies for power storage technologies of the future, with the participation of top researchers and engineers from both academia and industry. Taking the current situation into consideration, the Center has now summarized this work into a proposal on future challenges in R&D and issues in promoting R&D. This proposal focuses on rechargeable batteries and electric storage device technologies, which are considered key in drastically reducing fossil energy use in the transportation sector and in realizing decentralized energy systems aimed at the efficient use of new energies and the securing of emergency power sources. Such batteries and device technologies can be used in the following: (1) automobiles, other types of vehicles, and transportation machines (large capacity, transportable); (2) stationary decentralized energy systems (large/super-large, stationary); and (3) mobile devices (small capacity, portable). This proposal mainly discusses the first two areas. As future innovative electric energy storage will not necessarily take the form of current rechargeable batteries, this proposal also considers the possibility of creating new and different storage devices.

Conditions surrounding society and the industries and academia involved in battery technologies are drastically changing. Japan has traditionally maintained an internationally advantageous position in the field in terms of comprehensive technological and industrial competitiveness, but with increased demand for batteries and an expansion of the market, this position is being threatened by intense competition from Asian countries that have cost advantages. As a result, the share in the international market of Japanese manufacturers of batteries and related parts and materials has gradually declined, despite being still at a top level. Also, in terms of the number of research papers published in relevant academic fields, Japan’s position has been falling as other countries are strategically implementing R&D policies. Although Japan is currently promoting the development of next-generation rechargeable batteries through active implementation of policies by the Ministry of Economy, Trade and Industry (METI) and New Energy and Industrial Technology Development Organization (NEDO), the country cannot be said to be sufficiently prepared for the development of next-next-generation technologies further into the future.

Industry is continuing to lead the development of batteries for electric automobiles in response to strong demand in the market. It is hoped that the results of such efforts will lead to the development of stationary storage batteries that afford a stable electric power supply. This will be crucial when natural energy generation, such as photovoltaic generation and wind power generation which have unstable output, is introduced. Moreover, such small decentralized power sources acting as emergency power sources can play an important role in maintaining a safe and reliable social system. In any event, such batteries must be safe and small, have high capacity, and be of significantly low cost. At present, an energy density of 700 Wh/kg is the goal set in order to achieve widespread adoption of electric automobiles (METI 2006). This goal cannot be achieved with an extension of the current lithium-ion battery technology (which is said to have an upper limit of energy density of 250–300 Wh/kg). As there is no prospect of achieving such a goal, including the need for safety improvement, through the work currently being undertaken in various development projects, we must strengthen basic research activities, such as those focusing on clarifying basic phenomena, constructing theoretical models, and creating new concepts based on them, as well as strengthen R&D activities aimed at achieving realistic goals of the moment. The battery is a comprehensive system consisting of various technologies and, at each stage from basic research through to practical application, it requires technological development in a wide range of areas, encompassing materials, devices, circuits theory, system interconnection, and power management. It is important, therefore, to connect the roles played by industry, academia, and government in solving the technological issues involved.

The metal-air rechargeable battery, s-block metal rechargeable battery, and polyvalent cation rechargeable battery are the types of batteries we believe will emerge after the advent of the next-generation batteries currently being researched and developed. Shown below are the challenges in R&D that must be met in order to create core technologies for the future, including electric storage device technologies based on new structures and new concepts. To meet these challenges and achieve practical application of next-next-generation, innovative (ubiquitous) rechargeable batteries and electric storage devices, it is necessary for Japan as a nation to create a comprehensive system for research and promote it strategically. In particular, the following activities will be significant in discovering the seeds of innovations that will far surpass current expectations: improving the systems of basic/core research for understanding various phenomena, promoting cross-field integrative research, providing a continuous investment of resources, engaging in long-term training of researchers, and connecting the roles of basic/core research with application development research.

The important future challenges in R&D will be divided into three fields.
Development of new materials (development of new electrode materials; optimal design and control of nanoscale, three-dimensional structures near the interface of electrode materials; development of new electrolyte materials that achieve a balance between safety and high voltage; development of new separator materials)
Development of new technologies for storage device systems (development of technologies for combining new materials; development of design and manufacturing technologies for macrosystems based on an understanding of nanoscale phenomena; development of technologies for safety systems)
Understanding of cell reactions and development of theories and models (direct observation of cell reactions and development of measurement technologies; understanding of performance decline and degradation mechanisms; development of models of cell reaction theories; research on the application of computational science)

Battery research in Japan has traditionally made progress mainly in the field of electrochemistry. In contrast, this proposal emphasizes the field of physics, especially integrative research conducted by specialists in theoretical physics and solid-state physics, synthesis chemists, and experts in molecular design. Moreover, the collaboration of researchers specialized in measurement technology and computational science is required, as remarkable progress has been seen in both fields in recent years. It is hoped that the integration of these fields will be actively promoted.

Following the Great East Japan Earthquake and accident at the Fukushima Daiichi Nuclear Power Plant, Japan has experienced limited energy supply. This has dealt a serious blow to industry and to people’s lives. Decentralized energy systems were planned before the earthquake disaster as a way of contributing to the realization of an energy-saving society in the future. Today, the importance of these systems is even more pronounced and there are high expectations for their early realization. It is essential, therefore, to develop high-capacity, high-density electric storage devices that are so advanced that they are noted as ‘next-next-generation’. Although industries facing severe international competition are making investments in R&D activities for next-generation products, there is a lack of strategic investment in the creation of basic/core technologies that will lead us into the next-next-generation. In battery R&D especially, which takes time, strategic R&D with a long-term perspective should be promoted by universities, public research institutes, and industry, with the first two types of organizations playing a central role.

* Next-next-generation rechargeable batteries and electric storage devices This proposal regards batteries with an energy density 3 to 5 times higher than that of the current lithium-ion batteries as “next-generation rechargeable batteries” and batteries that have greater potentials and are expected to be realized for practical use in 2030 or later as “next-next generation rechargeable batteries and electric storage devices”. The latter includes the lithium (metal) air rechargeable battery, all-solidstate lithium rechargeable battery, s-block metal rechargeable battery, polyvalent cation rechargeable battery, new types of rechargeable batteries, batteries based on new concepts, and electric storage devices such as capacitors.