Negative electrode active material layer with controlled reflectance and lithium ion secondary battery
A negative electrode includes a negative electrode current collector and a negative electrode active material layer that is provided on the negative electrode current collector and includes a negative electrode active material. The negative electrode active material includes a carbon material, and a surface of the negative electrode active material layer has a reflectance Ra in a range of 7.0≤Ra≤14.8% at a wavelength of 550 nm. A lithium ion secondary battery includes the negative electrode, a positive electrode, a separator, and a nonaqueous electrolyte solution. The nonaqueous electrolyte solution includes a nonaqueous solvent and an electrolyte, the nonaqueous solvent contains ethylene carbonate, and the ethylene carbonate is contained in a range of 10 to 30 vol. % in the entire nonaqueous solvent.
1. A negative electrode comprising a negative electrode current collector and a negative electrode active material layer that is provided on the negative electrode current collector and includes a negative electrode active material, wherein:
the negative electrode active material includes a carbon material; and
a surface of the negative electrode active material layer has a spectral reflectance Ra in a range of 7.0≤Ra≤14.8% at a wavelength of 550 nm.
2. The negative electrode according to claim 1 , wherein the carbon material contains a carbon material with a graphite structure.
3. The negative electrode according to claim 1 , wherein the negative electrode active material layer has a density da in a range of 1.35≤da≤1.62 g/cm 3 .
4. The negative electrode according to claim 1 , wherein the negative electrode active material layer has a porosity Pa in a range of 26.5≤Pa≤31.3%.
5. The negative electrode according to claim 1 , wherein the negative electrode active material layer has a supporting quantity La per unit area in a range of 4.5≤La≤12.5 mg/cm 2 .
6. A lithium ion secondary battery comprising the negative electrode according to claim 1 , a positive electrode, a separator, and a nonaqueous electrolyte solution, wherein:
the nonaqueous electrolyte solution includes a nonaqueous solvent and an electrolyte;
the nonaqueous solvent contains ethylene carbonate; and
the ethylene carbonate is contained in a range of 10 to 30 vol. % in the entire nonaqueous solvent.
7. The lithium ion secondary battery according to claim 6 , wherein:
the nonaqueous solvent contains propylene carbonate;
the propylene carbonate is contained in a range of 10 to 20 vol. % in the entire nonaqueous solvent; and
a ratio of a content Le of the ethylene carbonate to a content Lp of the propylene carbonate, Le/Lp, is in a range of 1.0≤Le/Lp≤3.0.