A graphite sheet having a ratio of thermal diffusivity in horizontal and vertical directions of 300 or more is disclosed. Also, a graphite sheet having a ratio of thermal diffusivity in a vertical direction of 2.0 mm.sup.2/s or less is disclosed. The graphite sheet has excellent thermal conductivity in horizontal and vertical directions and excellent flexibility at the same time and can be produced at low manufacturing cost, thereby holding an economic advantage.

A graphite sheet having a ratio of thermal diffusivity in horizontal and vertical directions of 300 or more is disclosed. Also, a graphite sheet having a ratio of thermal diffusivity in a vertical direction of 2.0 mm.sup.2/s or less is disclosed. The graphite sheet has excellent thermal conductivity in horizontal and vertical directions and excellent flexibility at the same time and can be produced at low manufacturing cost, thereby holding an economic advantage.

This application discloses a negative-electrode active material and a preparation method thereof, a secondary battery, and a battery module, a battery pack, and an apparatus that include such secondary battery. The negative-electrode active material includes a core and a coating layer covering at least part of a surface of the core, where the core includes artificial graphite, the coating layer includes amorphous carbon, a volume-based particle size distribution of the negative-electrode active material satisfies D.sub.v99≤24 μm, a volume-based median particle size D.sub.v50 of the negative-electrode active material satisfies 8 μm≤D.sub.v≤15 μm, D.sub.v99 is a particle size corresponding to a cumulative volume distribution percentage of the negative-electrode active material reaching 99%, and WO is a particle size corresponding to a cumulative volume distribution percentage of the negative-electrode active material reaching 50%.

A method for producing carbon or graphite foam parts with high purity level for high-temperature insulation under vacuum or protective gas, as insulating material or as filter material, includes the following steps: introducing dry, foamable starch (1) into an open-top container (2) having a round or angular cross section, until the base (3) of the container (2) is covered amply and uniformly with starch (1); introducing the container (2) partly filled with starch (1) into an oven (4), and heating the container (2) to a foaming temperature of >180° C. over a prolonged period of several hours to foam the starch (1), until the container (2) has filled completely with carbon foam (6); withdrawing the container (2) from the oven (4) and extracting the carbon foam (6) after sufficient cooling, and optionally portioning the carbon foam (6) into carbon foam parts (6.1).

A method for producing carbon or graphite foam parts with high purity level for high-temperature insulation under vacuum or protective gas, as insulating material or as filter material, includes the following steps: introducing dry, foamable starch (1) into an open-top container (2) having a round or angular cross section, until the base (3) of the container (2) is covered amply and uniformly with starch (1); introducing the container (2) partly filled with starch (1) into an oven (4), and heating the container (2) to a foaming temperature of >180° C. over a prolonged period of several hours to foam the starch (1), until the container (2) has filled completely with carbon foam (6); withdrawing the container (2) from the oven (4) and extracting the carbon foam (6) after sufficient cooling, and optionally portioning the carbon foam (6) into carbon foam parts (6.1).

A process for producing a material in the form of nanosheets by ball milling of crystals of the material, wherein the ball milling takes place in the presence of a reactive gas.

A process for producing a material in the form of nanosheets by ball milling of crystals of the material, wherein the ball milling takes place in the presence of a reactive gas.

Disclosed herein are a polyimide film for graphite sheets, a method of fabricating the same, and a graphite sheet fabricated using the same. The polyimide film is fabricated by imidizing a polyamic acid formed by reaction between a dianhydride monomer and a diamine monomer, wherein the reaction is carried out in the presence of a metal compound and the polyamic acid forms a chelate with metal ions.

Disclosed herein are a polyimide film for graphite sheets, a method of fabricating the same, and a graphite sheet fabricated using the same. The polyimide film is fabricated by imidizing a polyamic acid formed by reaction between a dianhydride monomer and a diamine monomer, wherein the reaction is carried out in the presence of a metal compound and the polyamic acid forms a chelate with metal ions.

Disclosed herein are a polyimide film for graphite sheets, a method of fabricating the same, and a graphite sheet fabricated using the same. The polyimide film is fabricated by imidizing a polyamic acid formed by reaction between a dianhydride monomer and a diamine monomer, wherein the reaction is carried out in the presence of particles of a metal compound having an average particle diameter (D.sub.50) of about 1 μm to about 6 μm.