Hiroshi Nemoto

100 Wh Large size Li-ion batteries and safety tests

Abstract 100 Wh large size Li-ion battery with safety structures were developed. Specific energy and energy density of the battery were 110 Wh/kg and 200 Wh/l, respectively. Safety tests: nail penetration test, external short circuit test, overcharge test and externally heating test were carried out to determine the fundamental safety level of the battery. Behavior such as ignition and explosion of the battery were not observed during the safety tests. The battery is considered to be applicable to electric vehicles and hybrid electric vehicles.

Nanostructure criteria for lithium intercalation in non-doped and phosphorus-doped hard carbons

Abstract Hard carbons from various precursors heat-treated at 1000–2000 °C follow a common rule with regard to their structure-capacity correlation for lithium intercalation. A nanostructure containing a large fraction of highly strained carbon layers with large interlayer spacings and small crystallite sizes is a prerequisite to achieve reversible capacities in the range 300–450 mAh/g. P-doping of carbon derived from a polymer precursor causes a softening of the hard carbon structure by decreasing the strain on carbon layers, reducing interlayer spacing and increasing the crystallite sizes. It also induces a reduction of the number of nanopores which become larger in size. The amount of space reduction by the softening effect, however, is more than compensated by the dopant so that capacities of 550 mAh/g and first cycle efficiencies improved up to 83% are achieved.