On March 11th 2011, there was the huge earthquake in Tohoku, and the severe accident occurred at Fukushima-daiichi nuclear power plant. Since then, in Japan, it has been an urgent issue to solve the problem of electric power generation, shortage of natural resources and energy supplying. In the world, at the same time, rapid population growth and economic development mainly in India and China are raising oil prices and causing a serious lack of energy.
Secondary battery, which can freely store and release electricity, is now used as battery of mobile electronic device. And recently it begins to be utilized as power source for HEV / EV. Furthermore, in the near future, it must enable us to put large-scale electricity storage system into practice, introducing sustainable energy. For such smart use of electricity, secondary battery needs to have higher energy density, higher power density, longer cycle life, more cost-effectiveness and more safety.

Fig.1 Relationship between energy density and power density of each battery.

Lithium ion battery, LIB, is the most widespread secondary battery these days because of its relatively high energy density and power density. To improve LIB aiming qualities like mentioned above, it is necessary to develop new materials for cathode and anode.

Fig. 2Constituent materials of LIB

Then we are researching Tin- and Silicon-anode and Sulfur-cathode as alternative materials to existing Graphite-anode and LiCoO2-cathode, respectively. And also, we are developing a measurement method for degradation analysis of LIB. On the other hand, we are opening up fuel cell and air cell, which are promising new clean energy devices.

1. Development of degradation analysis and comparison with destructive-analysis
1.1. Development of impedance measurement method for LIB
1.1.1. Analysis of full-cell impedance by equivalent circuit
1.1.2. Separation of LIB impedance using symmetric cell
1.1.3. Clarification of the degradation mechanism of LIB by destructive analysis
1.2. Electrochemical impedance spectroscopy (EIS) for polymer
1.2.1 Diagnosis of cathode catalyst layer in PEFC by EIS
1.2.2 EIS for the evaluation of MEA under PEFC operation
2. The Alloy Anodes for Lithium-Ion Secondary Battery (Si,Sn)
2.1. Si-O-C Composite Anode (organic/ inorganic hybrid anode)
2.2. Sn-Ni Alloy Anode
2.3. Mesoporous Sn anode
2.4. Sn-O-C Composite Anode (organic/ inorganic hybrid anode)
3. Positive Electrode for Lithium-Ion Secondary Battery (S, Li2S)
3.1. Sulfur cathode (S)
3.2. Lithium sulfide cathode (Li2S)
4. Development of a lithium metal anode for lithium-air battery