▎ 摘　　要

NOVELTY - A composite graphite material comprises main particles and coating layer (2) on at least a portion of the surface of the main particles. The main particles are secondary particles formed by more than two primary particles (101). The main particles comprise artificial graphite. The coating layer comprises amorphous carbon. The air oxidation temperature (T0) of the composite graphite material is 630-730℃, preferably 660-710℃. The air oxidation temperature (T0) is the temperature corresponding to the intersection of two tangent lines at two points at two points on the thermogravimetric curve of the composite graphite material respectively corresponding to 500℃ and temperature (T1). The temperature (T1) is the peak temperature of the largest area peak in the differential thermogravimetric curve of the composite graphite material. USE - Composite graphite material used in negative electrode of secondary battery (all claimed). ADVANTAGE - The composite graphite material can make the secondary battery have high energy density, and also have improved fast charging performance and low-temperature power performance. DETAILED DESCRIPTION - A composite graphite material comprises main particles and coating layer on at least a portion of the surface of the main particles. The main particles are secondary particles formed by more than two primary particles. The main particles comprise artificial graphite. The coating layer comprises amorphous carbon. The air oxidation temperature (T0) of the composite graphite material is 630-730℃, preferably 660-710℃. The air oxidation temperature (T0) is the temperature corresponding to the intersection of two tangent lines at two points at two points on the thermogravimetric curve of the composite graphite material respectively corresponding to 500℃ and temperature (T1). The temperature (T1) is the peak temperature of the largest area peak in the differential thermogravimetric curve of the composite graphite material. The thermogravimetric curve and the differential thermogravimetric curve can be obtained by thermogravimetric analysis under the following conditions: sample mass is 10±0.05 mg, purge gas is air, air flow rate is 60 mL/minute, heating rate is 5℃/minute, and the test temperature is 35-950℃. INDEPENDENT CLAIMS are included for the following: preparation of the composite graphite material; and negative electrode sheet, which comprises negative electrode current collector and negative electrode film layer arranged on at least one surface of the negative electrode current collector. The negative electrode film layer comprises the composite graphite material and additive comprising one or more of hard carbon, micro-expanded graphite, expanded graphite and graphene. The interlayer distance d002 of the additive (002) crystal plane is ≥ 0.3358 nm, preferably 0.3359-0.3366 nm. DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the composite graphite material. 101Primary particles 102Coating layer 103Kinetic carbon material