Film-like graphite, manufacturing method for same, and battery using same
A film-like graphite that satisfies the following condition (1) or condition (2) described below. Condition (1): a graphite crystal orientation degree P is 96% or more with respect to a film plane. Condition (2): a graphite crystal orientation degree P is 94% or more with respect to a film plane and a thickness is 42 μm or more.
1 . A film-like graphite, satisfying condition (1) or condition (2):
Condition (1): a graphite crystal orientation degree P is 96% or more and less than 100% with respect to a film plane, and a thermal conductivity b is 1,550 W/mK or more; or
Condition (2): a graphite crystal orientation degree P is 94% or more and less than 100% with respect to a film plane and a thickness is 42 μm or more and 250 μm or less, and a thermal conductivity b is 800 W/mK or more.
2 . The film-like graphite of claim 1 , further satisfying condition (5) and condition (6): condition (6),
Condition (5): when a film thickness is denoted by a in μm, and a thermal conductivity is denoted by b in W/mK, in a direction along a film plane, the film-like graphite satisfies expression (1a)
2,140≤12 a+b Expression (1a),
Condition (6): a minimum bending radius measured in a bend test is 16 mm or less.
3 . The film-like graphite of claim 1 , having a thickness of 58 μm or more.
4 . The film-like graphite of claim 1 , having a thermal conductivity b of 800 W/mK or more in a direction along the film plane.
5 . The film-like graphite of claim 1 , having a density of 1.7 g/cm 3 or more.
6 . The film-like graphite of claim 1 , having an electrical conductivity of 9,000 S/cm or more in a direction along the film plane.
7 . The film-like graphite of claim 1 , having a multilayer structure in which a plurality of layers overlap with each other,
wherein the multilayer structure has a width of 40 μm or more and a thickness of 8 μm or more, and
wherein an angle between a direction of each layer constituting the multilayer structure and a direction along the film plane is 20° or less.
8 . The film-like graphite of claim 7 , wherein each layer constituting the multilayer structure has a large number of unevenness, and
wherein adjacent layers are in contact with each other at a large number of positions.
9 . The film-like graphite of claim 7 , wherein each layer constituting the multilayer structure has a flat surface or a smooth curved surface, and
wherein adjacent layers are in close contact with each other.
10 . The film-like graphite of claim 1 , wherein a minimum bending radius measured in a bend test is 16 mm or less.
11 . The film-like graphite of claim 1 , wherein, when a pressure of 100 MPa is applied to an entire film plane of the film-like graphite to compress the entire film plane in an environment of 25° C., a T a /T b ratio of a film thickness T a after compression to a film thickness T b before compression is 0.7 or more.
12 . The film-like graphite of claim 1 , wherein in Tension-Free U-shape Folding Test, a folding number is 10,000 or more until breakage, performed at a bending radius R of 2 mm and a bending angle of 180°.
13 . The film-like graphite of claim 1 , having a thermal conductivity in a range of from 1 to 20 W/mK in a direction perpendicular to the film plane.
14 . The film-like graphite of claim 1 , wherein a surface area/film area ratio of a surface area to a film area is 1.05 or more.
15 . The film-like graphite of claim 1 , wherein a layer formed of an adhesive or a pressure-sensitive adhesive is not comprised in the film-like graphite in a film thickness direction.
16 . The film-like graphite of claim 1 , wherein an a×b product of a film thickness a in μm, and a thermal conductivity b in W/mK, in a direction along a film plane, is 88,000 or more.
17 . The film-like graphite of claim 1 , wherein a number N of a plurality of bright regions obtained from an image in a vertical cross-section of the film-like graphite with respect to a film plane, in which bright parts and dark parts observed in a polarization microscope image are binarized, a film thickness H in μm, and a film width W in μm satisfy expression (7) or (8) and (9)
N/H/W≤ 0.015 (7),
N/H/W≤ 0.04 (8),
H≥ 42 (9).
18 . A lithium-ion secondary battery or an all-solid battery, comprising:
the film-like graphite of claim 17 as a current collector or a negative-electrode active material; and
negative-electrode current collector.
19 . The film-like graphite of claim 1 , wherein an average area of a plurality of bright regions obtained from an image in a vertical cross-section of the film-like graphite with respect to a film plane, in which bright parts and dark parts observed in a polarization microscope image are binarized, is 22 μm 2 or more, or a film thickness is 42 μm or more and the average area is 9 μm 2 or more.
20 . A film-like graphite, satisfying condition (3) or condition (4):
Condition (3): a film thickness a is 58 μm or more and a thermal conductivity b is 1,550 W/mK or more in a direction along a film plane; or
Condition (4): a film thickness a is 50 μm or more, a thermal conductivity b is 1,550 W/mK or more in a direction along a film plane, and a×b≥100,000.
21 . A film-like graphite, wherein an a×b product of a film thickness a in μm, and a thermal conductivity b in W/mK, in a direction along a film plane, is 88,000 or more and 500,000 or less, and a thermal conductivity b is 1,550 W/mK or more.
22 . A film-like graphite, wherein a number N of a plurality of bright regions obtained from an image in a vertical cross-section of the film-like graphite with respect to a film plane, in which bright parts and dark parts observed in a polarization microscope image are binarized, a film thickness H in μm, and a film width W in μm, satisfy expression (7) or (8) and (9)
N/H/W≤ 0.015 (7),
N/H/W≤ 0.04 (8),
H≥ 42 (9).
23 . A film-like graphite, wherein an average area of a plurality of bright regions obtained from an image in a vertical cross-section of the film-like graphite with respect to a film plane, in which bright parts and dark parts observed in a polarization microscope image are binarized, is 22 μm 2 or more, or
wherein a film thickness is 42 μm or more and the average area is 9 μm 2 or more.
24 . A method for manufacturing a film-like graphite, the method comprising:
carbonizing a raw film made of an organic polymer to obtain a carbonized film; and
graphitizing the carbonized film to obtain a graphitized film,
wherein a film-like graphite that has a thermal conductivity of 800 W/mK or more and a minimum bending radius of 16 mm or less according to a bend test is manufactured from the raw film that has a thickness of 150 μm or more and 450 μm or less at a maximum value in a temperature increase range of 60° C. or higher during optional 30 minutes in a temperature increase pattern obtained by a monotonic temperature increase in a temperature increase history of 2,000° C. or higher in the graphitizing.
25 . The method of claim 4 , wherein a maximum heating temperature Tmax in the graphitizing is in a range of from 2,400 to 2,900° C.
26 . The method of claim 24 , wherein a laminated film in which two or more polymer films made of an organic polymer are bonded to each other by a pressure-sensitive adhesive or an adhesive is used as the raw film.
27 . A method for manufacturing a film-like graphite, the method comprising:
of carbonizing a raw film, made of an organic polymer and having a thickness of 70 μm or more, to obtain a carbonized film; and
graphitizing the carbonized film to obtain a graphitized film,
wherein the carbonizing comprises heating the raw film in a mixed gas comprising (a-1) acetylene and/or (a2) an acetylene derivative and (b) an inert gas.
28 . The method of claim 27 , wherein at least a part of the heating in the mixed gas is carried out at a temperature of T f or lower,
wherein, in a thermogravimetric analysis in which a measurement sample made of the raw film is heated to 1,000° C. at a temperature increase rate of 10° C./min while flowing nitrogen gas at a flow velocity of 200 mL/min, and a temperature and a weight of the measurement sample are recorded, T f (C) is a highest temperature among temperatures at which a weight reduction rate, in weight (reduction per unit time,) of the measurement sample observed is 10% or more of a maximum value of the weight reduction rate.
29 . The method of claim 28 , wherein a period of 30 minutes or more in which an average temperature increase rate is 5° C./min or less is included in a temperature range of T s or higher and T f or lower in a temperature increase pattern obtained by a monotonic temperature increase in a temperature increase history in the heating step in the mixed gas,
where in the thermogravimetric analysis, T s is a lowest temperature among temperatures of 100° C. or higher at which a weight reduction rate of the measurement sample observed is 0.8% or more of a maximum value of the weight reduction rate.
30 . A manufacturing method for manufacturing a film-like graphite, the method comprising:
carbonizing a raw film, made of an organic polymer and having a thickness of 120 μm or more, to obtain a carbonized film;
graphitizing the carbonized film to obtain a graphitized film having a density of less than 1.7 g/cm 3 ; and
compressing or rolling the graphitized file to obtain the film-like graphite, having a density of 1.7 g/cm 3
wherein an S g /S m ratio of an area Sg of the graphitized film to an area S m of the raw film is 0.8 or more.