Tsutomu Sugiura

Coke powder heat-treated with boron oxide using an Acheson furnace for lithium battery anodes

Abstract Coal tar pitch-based coke power was heat-treated with B 2 O 3 using an Acheson furnace. The heat-treated coke powder contained nitrogen and oxygen probably derived from BN and B 2 O 3 , respectively, and exhibited a large irreversible capacity in the first charge–discharge (lithium dope–undope) cycle. The large irreversible capacity was decreased not by the decomposition of BN or B 2 O 3 but drastically by the increase of dissolved boron concentration. The discharge capacity also correlated well with the concentration of dissolved boron.

Structure of coke powder heat-treated with boron

Abstract Coal tar pitch-based coke powder with a fine mosaic texture was heat-treated with various concentrations of boron powder at 2900°C. Increasing the boron amount led to smaller d 002 and larger d 110 , and made the original fine texture coarser. Some small particles showed specific structures of polyhedrons, of which surfaces are 002 planes of graphite lattice, after heat treatment with boron. The size of the polyhedron increased with boron content. Boron concentration was lower at the surface than at the inner portions of particles for a powder heat-treated with a higher amount of boron, while it depended less on the depth for that heat-treated with a lower amount of boron. The formation mechanism of the polyhedron particle is discussed.

Process for the preparation of graphite intercalation compound and novel graphite intercalation compound

A graphite intercalation compound enjoying high stability is produced by a method characterized by using a previously synthesized acceptor type graphite intercalation compound as a raw material and intercalating therein a substance different from the substance intercalated in the graphite intercalation compound and capable of forming an acceptor type graphite intercalation compound. The representative substance to the newly intercalated in the production mentioned above is a metal halide selected from the group consisting of ferric chloride, cupric chloride, aluminum chloride, cobalt chloride, nickel chloride, calcium chloride, barium chloride, silver chloride, zinc chloride, zirconium chloride, molybdenum chloride, tantalum chloride, and hafnium chloride.

Irreversible and Discharge Capacities Depending on Dissolved Boron Concentration of Coke Powder

Well-graphitized coke powder was further heat-treated at 2200°C with various amounts of boron in Ar to prepare coke powders containing different amounts of dissolved boron. The particle size distribution, specific surface area, crystallite size, and the texture observed with transmission electron microscopy were less dependent on the concentration of residue boron, [B] res , after the heat-treatment. The dissolved boron concentration, [B] sol , was quantitatively estimated from the potential curve of the first lithium doping. [B] sol was equal to [B] res when [B] res ≤1.0 wt % and slightly decreases with the increase of [B] res when [B] res ≥ 1.0 wt %. The irreversible capacity of the first lithium dope-undope cycle monotonously decreased, became minimum at about 0.4-0.5 wt % [B] sol , and again slightly increased with the increase of [B] sol . The discharge capacity of the first cycle was monotonously raised with the increase of [B] sol . The mechanisms of irreversible capacity and discharge capacity depending on [B] sol are discussed.