COMPOSITE GRAPHITE PARTICLES FOR NON-AQUEOUS SECONDARY BATTERIES, NEGATIVE ELECTRODE MATERIAL CONTAINING THE SAME, NEGATIVE ELECTRODES, AND NON-AQUEOUS SECONDARY BATTERIES

摘要

A subject is to provide a nonaqueous secondary battery which is sufficiently low in charge/discharge irreversible capacity in initial cycling even when an active-material layer comprising a negative-electrode material and formed on a current collector has been densified for capacity increase. The subject has been accomplished with composite graphite particles for a nonaqueous secondary battery which comprise a composite of spherical graphite particles and a binder graphite and which at least satisfy any requirement selected from the group consisting of the following requirements (a) to (g):
(a) the composite graphite particles include composite graphite particles in which at least part of the spherical graphite particles is exposed at the surface thereof; (b) the composite graphite particles include composite graphite particles which have an imperfect laminate structure of the spherical graphite particles near the surface thereof; (c) when the median diameter of the spherical graphite particles and the median diameter of the composite graphite particles are expressed by a and b, respectively, then the ratio c=a/b is 0.93 or larger; (d) the composite graphite particles have a Raman R value of 0.15-0.25, an average degree of circularity of 0.85 or higher, a tap density of 0.87-1.25 g/cm 3 , and a BET specific surface area of 2.5-8 m 2 /g; (e) a volume of 0.01-2 µm pores as measured with a mercury porosimeter, is 0.05-1 mL/g;
(f) the amount of CO groups present on the surface normalized with the BET specific surface area is 1.15-5 µmol/m 2 ; and (g) when an electrode is produced by preparing a slurry using the composite graphite particles and a specific electrolytic solution is dropped onto the electrode, then the average time period required for the electrolytic solution to disappear completely from the electrode surface is 180 seconds or shorter.