The present invention provides a positive-electrode active material for a lithium-ion secondary cell or a sodium-ion secondary cell, which can effectively exhibit more excellent charge/discharge characteristics; and a method for manufacturing the positive-electrode active material. Namely, the present invention relates to a positive-electrode active material for a secondary cell comprising an oxide represented by formula (A): LiFe.sub.aMn.sub.bM.sub.cPO.sub.4, formula (B): LiFe.sub.aMn.sub.bM.sub.cSiO.sub.4, or formula (C): NaFe.sub.gMn.sub.hQ.sub.iPO.sub.4; and carbon derived from a cellulose nanofiber supported thereon.

The present invention provides a positive-electrode active material for a lithium-ion secondary cell or a sodium-ion secondary cell, which can effectively exhibit more excellent charge/discharge characteristics; and a method for manufacturing the positive-electrode active material. Namely, the present invention relates to a positive-electrode active material for a secondary cell comprising an oxide represented by formula (A): LiFe.sub.aMn.sub.bM.sub.cPO.sub.4, formula (B): LiFe.sub.aMn.sub.bM.sub.cSiO.sub.4, or formula (C): NaFe.sub.gMn.sub.hQ.sub.iPO.sub.4; and carbon derived from a cellulose nanofiber supported thereon.

This invention innovates a low cost method to synthesize carbon fibers through graphene composites, which are fabricated through chemical treatment of graphite. This invention also is related to the applications of thereof carbon fibers in different fields. Several examples of such fields would be to use carbon fibers to manufacture carbon fiber tubes, pipes or risers, or car/airplane/computer parts, bicycles, and sports supplies and many additional applications.

A method for producing a carbon fiber, the method comprising: (i) subjecting a continuous carbon fiber precursor having a polymeric matrix in which strength-enhancing particles are incorporated to a stabilization process during which the carbon fiber precursor is heated to within a temperature range ranging from the glass transition temperature to no less than 20° C. below the glass transition temperature of the polymeric matrix, wherein the maximum temperature employed in the stabilization process is below 400° C., for a processing time within said temperature range of at least 1 hour in the presence of oxygen and in the presence of a magnetic field of at least 1 Tesla, while said carbon fiber precursor is held under an applied axial tension; and (ii) subjecting the stabilized carbon fiber precursor, following step (i), to a carbonization process. The stabilized carbon fiber precursor, resulting carbon fiber, and articles made thereof are also described.

A method includes a freezing process in which a solution or gel containing cellulose nanofibers is frozen to obtain a frozen component, a drying process in which the frozen component is dried in a vacuum to obtain a dry component, and a carbonizing process in which the dry component is heated and carbonized in a non-combustible atmosphere, and in the carbonizing process, the dry component is heated together with a reducing catalyst and also a material that generates a reducing gas by thermal decomposition.

A method includes a freezing process in which a solution or gel containing cellulose nanofibers is frozen to obtain a frozen component, a drying process in which the frozen component is dried in a vacuum to obtain a dry component, and a carbonizing process in which the dry component is heated and carbonized in a non-combustible atmosphere, and in the carbonizing process, the dry component is heated together with a reducing catalyst and also a material that generates a reducing gas by thermal decomposition.

A problem to be solved by the present invention is to provide a new form of adsorbent suitable for a motor vehicle canister. An activated carbon fiber sheet satisfies one or two or more of conditions for indices, such as a specific surface area, a pore volume of pores having a given pore diameter, and a sheet density. An embodiment, for example, may have: a specific surface area ranging from 1400 to 2300 m.sup.2/g; a pore volume ranging from 0.20 to 0.70 cm.sup.3/g for pores having pore diameters of more than 0.7 nm and 2.0 nm or less; an abundance ratio R.sub.0.7/2.0, which is a ratio of a pore volume of micropores having pore diameters of 0.7 nm or less occupied in a pore volume of micropores having pore diameters of 2.0 nm or less, ranging from 5% to less than 25%, and a sheet density ranging from 0.030 to 0.200 g/cm.sup.3.

A problem to be solved by the present invention is to provide a new form of adsorbent suitable for a motor vehicle canister. An activated carbon fiber sheet satisfies one or two or more of conditions for indices, such as a specific surface area, a pore volume of pores having a given pore diameter, and a sheet density. An embodiment, for example, may have: a specific surface area ranging from 1400 to 2300 m.sup.2/g; a pore volume ranging from 0.20 to 0.70 cm.sup.3/g for pores having pore diameters of more than 0.7 nm and 2.0 nm or less; an abundance ratio R.sub.0.7/2.0, which is a ratio of a pore volume of micropores having pore diameters of 0.7 nm or less occupied in a pore volume of micropores having pore diameters of 2.0 nm or less, ranging from 5% to less than 25%, and a sheet density ranging from 0.030 to 0.200 g/cm.sup.3.

An object is to provide a new form of adsorbent suitable for a high performance canister. An adsorbent including activated carbon is used as the adsorbent for the canister and satisfies the following conditions. P.sub.0.2/100 expressed by Equation 1:

P.sub.0.2/100=X÷Y×100  (Equation 1)

is 18% or more, in Equation 1, X represents an amount of adsorbed n-butane gas per 100 parts by weight of the adsorbent at 25° C. under an atmosphere where a gas pressure of n-butane gas is 0.2 kPa, and Y represents an amount of adsorbed n-butane gas per 100 parts by weight of the adsorbent at 25° C. under an atmosphere where a gas pressure of n-butane gas is 100 kPa.

An object is to provide a new form of adsorbent suitable for a high performance canister. An adsorbent including activated carbon is used as the adsorbent for the canister and satisfies the following conditions. P.sub.0.2/100 expressed by Equation 1:

P.sub.0.2/100=X÷Y×100  (Equation 1)

is 18% or more, in Equation 1, X represents an amount of adsorbed n-butane gas per 100 parts by weight of the adsorbent at 25° C. under an atmosphere where a gas pressure of n-butane gas is 0.2 kPa, and Y represents an amount of adsorbed n-butane gas per 100 parts by weight of the adsorbent at 25° C. under an atmosphere where a gas pressure of n-butane gas is 100 kPa.