Nonaqueous secondary battery, method for making negative electrode component therefor, and apparatuses for evaluating and making graphite material for negative electrode component
View Patent ↗A negative electrode of a nonaqueous secondary battery is formed of a carbonaceous material. The ratio RG=Gs/Gb of the degree of graphitization Gs of the carbonaceous material, determined by a surface-enhanced Raman spectrum, to the degree of graphitization Gb, determined by a Raman spectrum measured using argon laser light, is at least 4.5. Alternatively, the carbonaceous material has a peak in a wavelength range above 1,360 cm −1 in a surface-enhanced Raman spectrum which is measured by the same surface-enhanced Raman spectrum. The deterioration of the nonaqueous secondary battery is suppressed during use in high-temperature environments and high capacity is maintained for long periods.
1. A method for making a negative electrode carbonaceous material comprising the steps of:
(a) carbonizing a raw material,
(b) heating the product of step (a) at a temperature of at most 200° , in the presence of an oxidizer; and
(c) graphitizing the product of step (b), wherein a ratio RG=Gs/Gb of the product of step (c) is at least 4.5, wherein:
Gb=Hbb/Hba ; and
Gs=Hsb/Hsa ;
wherein:
Hba is the height of a peak lying in a range of 1,580 cm −1 to 1,620 cm −1 in a first Raman spectrum, said first Raman spectrum being measured by means of an argon laser Raman spectrometer of a wavelength of 514.5 nm and a wavelength resolution of 4 cm −1 ;
Hbb is the height of a peak lying in a range of 1,350 cm−1 to 1,400 cm−1 in a second Raman spectrum, said second Raman spectrum being measured by means of an argon laser Raman spectrometer of a wavelength of 514.5 nm and a wavelength resolution of 4 cm −1 ;
Hsa is the height of a peak lying in a range of 1,580 cm −1 to 1,620 cm −1 in a first surface-enhanced Raman spectrum, said first surface-enhanced Raman spectrum being measured by means of an argon laser Raman spectrometer of a wavelength of 514.5 nm and a wavelength resolution of 4 cm −1 when silver having a thickness of 10 nm is deposited on the product of step c.; and
Hsb is the height of a peak lying in a range of 1,350 cm −1 to 1,400 cm −1 in a second surface-enhanced Raman spectrum, said second surface-enhanced Raman spectrum being measured by means of an argon laser Raman spectrometer of a wavelength of 514.5 nm and a wavelength resolution of 4 cm −1 when silver having a thickness of 10 nm is deposited on the product of step c.
2. A method for making a negative electrode carbonaceous material, comprising the steps of:
(a′) carbonizing a raw material,
(b′) heating the product of step (a′) to a temperature of at most 200° C. in the presence of an oxidizer; and
(c′) graphitizing the product of step (b′), wherein a surface-enhanced Raman spectrum of the product of step (c′) comprises a peak in a wavelength range above 1,360 cm −1 , said surface-enhanced Raman spectrum being measured by means of an argon laser Raman spectrometer of a wavelength of 514.5 nm and a wavelength resolution of 4 cm −1 when silver having a thickness of 10 nm is deposited on the product of step c′.