Negative electrode material for lithium-ion secondary battery, negative electrode for lithium-ion secondary battery, lithium-ion secondary battery and method of producing negative electrode for lithium-ion secondary battery
A negative electrode material for a lithium-ion secondary battery includes: graphitic particles having a standard deviation of degree of circularity of from 0.05 to 0.10 in a range in which a cumulative frequency of degree of circularity from a lower degree of circularity is from 10% by particle to 90% by particle in a cumulative frequency distribution with respect to a degree of circularity obtained using a flow-type particle analyzer; and carbon particles having an average degree of circularity of 0.94 or less, the average degree of circularity being obtained using a flow-type particle analyzer.
1 . A negative electrode material for a lithium-ion secondary battery, the negative electrode material comprising:
graphitic particles that are synthetic graphite particles produced by a process including burning a raw material comprising at least one selected from the group consisting of a resin material and a pitch-based material, the graphitic particles having an average degree of circularity of 0.85 or more and having a standard deviation of degree of circularity of from 0.05 to 0.10 in a range in which a cumulative frequency of degree of circularity from a lower degree of circularity is from 10% by particle to 90% by particle in a cumulative frequency distribution with respect to a degree of circularity obtained using a flow-type particle analyzer; and
carbon particles that are natural graphite particles having an average degree of circularity of from 0.90 to 0.94, the average degree of circularity being obtained using a flow-type particle analyzer.
2 . The negative electrode material for a lithium-ion secondary battery according to claim 1 , wherein the graphitic particles have a degree of circularity of from 0.70 to 0.91 at the cumulative frequency of 10% by particle.
3 . The negative electrode material for a lithium-ion secondary battery according to claim 1 , wherein the graphitic particles have a volume average particle diameter of from 2 to 30 μm.
4 . The negative electrode material for a lithium-ion secondary battery according to claim 1 , wherein the carbon particles have a volume average particle diameter of from 0.5 to 15 μm.
5 . The negative electrode material for a lithium-ion secondary battery according to claim 1 , wherein the carbon particles have a smaller volume average particle diameter than a volume average particle diameter of the graphitic particles.
6 . The negative electrode material for a lithium-ion secondary battery according to claim 1 , wherein a ratio of volume average particle diameters between the graphitic particles and the carbon particles (graphitic particles:carbon particles) is from 10:0.5 to 10:5.
7 . The negative electrode material for a lithium-ion secondary battery according to claim 1 , wherein the graphitic particles have a Raman R value of from 0.10 to 0.60, the R value representing a ratio (ID/IG) of a peak intensity observed in a range of from 1300 cm −1 to 1400 cm −1 (ID) to a peak intensity observed in a range of from 1580 cm −1 to 1620 cm −1 (IG) in Raman spectrometry, the graphitic particles being irradiated with a laser light at 532 nm.
8 . The negative electrode material for a lithium-ion secondary battery according to claim 1 , wherein a mass ratio between the graphitic particles and the carbon particles (graphitic particles:carbon particles) is from 51:49 to 99:1.
9 . A negative electrode for a lithium-ion secondary battery, the negative electrode comprising:
a current collector; and
a negative electrode material mixture layer disposed on a surface of the current collector,
the negative electrode material mixture layer comprising:
graphitic particles that are synthetic graphite particles produced by a process including burning a raw material comprising at least one selected from the group consisting of a resin material and a pitch-based material, the graphitic particles having an average degree of circularity of 0.85 or more and having a standard deviation of degree of circularity of from 0.05 to 0.10 in a range in which a cumulative frequency of degree of circularity from a lower degree of circularity is from 10% by particle to 90% by particle in a cumulative frequency distribution with respect to a degree of circularity obtained using a flow-type particle analyzer; and
carbon particles that are natural graphite particles having an average degree of circularity of from 0.90 to 0.94, the average degree of circularity being obtained using a flow-type particle analyzer.
10 . A lithium-ion secondary battery comprising the negative electrode for a lithium-ion secondary battery according to claim 9 .
11 . A method of producing a negative electrode for a lithium-ion secondary battery, the method comprising:
preparing a negative electrode material mixture comprising:
graphitic particles that are synthetic graphite particles produced by a process including burning a raw material comprising at least one selected from the group consisting of a resin material and a pitch-based material, the graphitic particles having an average degree of circularity of 0.85 or more and having a standard deviation of degree of circularity of from 0.05 to 0.10 in a range in which a cumulative frequency of degree of circularity from a lower degree of circularity is from 10% by particle to 90% by particle in a cumulative frequency distribution with respect to a degree of circularity obtained using a flow-type particle analyzer; and
carbon particles that are natural graphite particles having an average degree of circularity of from 0.90 to 0.94, the average degree of circularity being obtained using a flow-type particle analyzer; and
disposing the negative electrode material mixture on a surface of a current collector.