Non-aqueous secondary battery-use graphite composite particle, cathode active substance material containing IT, cathode and non-aqueous secondary battery
View Patent ↗To provide a nonaqueous secondary battery ensuring that a charge-discharge irreversible capacity at an initial cycle is sufficiently small even when an active material layer comprising a negative electrode active material on a current collector is increased in a density for obtaining a high capacity. This object is attained by a graphite composite particle for a nonaqueous secondary battery, which satisfies the requirements (1) and (2): (1) D L /D S is more than 1 and 2 or less, wherein D L μm means a volume-based median size measured by a laser diffraction/scattering-type particle size distribution measuring apparatus, and D S μm means an average circle-equivalent particle size which is determined from a measured area S of particles each having a contour not overlapped with a contour of another particle in a SEM; and (2) a Raman R value is 0.04 or more and 0.14 or less, wherein the Raman R value means an intensity ratio I B /I A between an intensity I A of a maximum peak of 1580 cm −1 around and an intensity I B of a maximum peak of 1360 cm −1 around in a Raman spectrum.
1. A graphite composite particle for a nonaqueous secondary battery, which satisfies the following requirements (1) and (2):
(1) D L /D S is more than 1 and 2 or less, wherein D L μm means a volume-based median size which is measured by suspending 10 mg of the particle in 10 mL of 0.2 mass % polyoxyethylene sorbitan monolaurate aqueous solution, introducing the suspension into a commercially available laser diffraction/scattering-type particle size distribution measuring apparatus, and irradiating the suspension with an ultrasonic wave of 28 kHz at a power of 60 W for 1 minute, and D S μm means an average circle-equivalent particle size which is determined by selecting 100 particles each having a contour not overlapped with a contour of another particle at an observation using a scanning electron microscope, and determining an average value of the circle-equivalent particle size of the 100 particles determined from a measured area S of individual particles according to 2×(S/3.14) 0.5 ; and
(2) a Raman R value is 0.04 or more and 0.14 or less, wherein the Raman R value means an intensity ratio I B /I A between an intensity I A of a maximum peak of 1580 cm −1 around and an intensity I B of a maximum peak of 1360 cm −1 around in a Raman spectrum.
2. The graphite composite particle for a nonaqueous secondary battery as claimed in claim 1 , which has an average degree of circularity of 0.8 or more and 0.95 or less.
3. The graphite composite particle for a nonaqueous secondary battery as claimed in claim 1 , which has a tap density of 0.7 g/cm 3 or more and 1.5 g/cm 3 or less.
4. The graphite composite particle for a nonaqueous secondary battery as claimed in claim 1 , wherein the graphite composite particle has a structure where a calcined binder connects to at least a part of the graphite particle formed by calcining a carbonaceous particle.
5. The graphite composite particle for a nonaqueous secondary battery as claimed in claim 4 , wherein the carbonaceous particle is a spheronized graphite.
6. A negative electrode active material for a nonaqueous secondary battery, comprising the graphite composite particle for a nonaqueous secondary battery claimed in claim 1 .
7. The negative electrode active material for a nonaqueous secondary battery as claimed in claim 6 , which further comprises one or more kinds of carbonaceous active material particles selected from the group consisting of natural graphite, artificial graphite, amorphous carbon coated graphite, resin-coated graphite and amorphous carbon.
8. The negative electrode active material for a nonaqueous secondary battery as claimed in claim 6 , wherein an active material layer is formed by blending 100 parts by weight of the negative electrode active material, 2 parts by weight as a solid content of a water dispersion of styrene butadiene rubber, and 1 part by weight as a solid content of an aqueous solution of carboxymethyl cellulose having a weight average molecular weight of 250,000 to 300,000 to form an aqueous slurry; coating the aqueous slurry on a 18 μm-thick copper foil by using a doctor blade to have a dry film thickness of 10±0.1 mg/cm 2 ; drying; and forming an active material layer having a width of 5 cm by using a roll press having a roller of 20 cm in diameter while adjusting a press load so as to have a density of 1.73±0.03 g/cm 3 by pressing once, in which said press load is 200 kgf/5 cm or more and 1200 kgf/5 cm or less.
9. A negative electrode for a nonaqueous secondary battery, comprising a current collector and an active material layer formed thereon, wherein said active material layer is formed by using at least the negative electrode active material for a nonaqueous secondary battery claimed in claim 6 .
10. A nonaqueous secondary battery comprising: an electrolyte; and positive and negative electrodes capable of occluding and releasing a lithium ion, wherein said negative electrode is the negative electrode for a nonaqueous secondary battery claimed in claim 9 .