▎ 摘　　要

NOVELTY - A positive temperature coefficient (PTC) material comprises polymer matrix material and graphene microspheres with a multi-branched structure. The mass ratio of the polymer matrix material to the multi-branched graphene microspheres is 49:1-4:1. The graphene microspheres with a multi-branched structure are prepared by (1) preparing graphene oxide suspension, (2) performing ultrasonic atomization treatment on the graphene oxide suspension of step (1), heating the droplets after ultrasonic atomization, (3) graphitizing the product of step (2). USE - Positive temperature coefficient material used in battery application, coating on surface of current collector or active material, and conductive coating for current collector and electrode material (all claimed). ADVANTAGE - The PTC material has high strength (the strength refers to the ratio of the maximum resistance of the material to the internal resistance at room temperature), and can better realize the improvement of the safety of the lithium ion battery from the inside. Under normal temperature conditions, the branch structures of the graphene microspheres are in contact with each other and connected to form a cross-linked conductive network structure to ensure that the PTC material has a low resistivity. In the PTC material, the cross-linked branch structure separates and the resistivity rises sharply with rise in temperature. When graphene microspheres with multi-branched structures are added to the PTC material as a conductive agent, the problem of weaker strength of the PTC material is effectively eliminated. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) preparation of the PTC material, which involves dissolving polymer matrix material in organic solvent to obtain a mixed system, adding graphene microspheres with a multi-branched structure to the mixed system, ball milling, and drying; (2) use of the PTC material for coating on surface of current collector, or for coating on surface of active material e.g. (1) coating on the negative electrode current collector copper foil and/or coating on the positive electrode current collector aluminum foil, (2) coating on the positive active material layer and/or coating on the negative active material layer, (3) coating on the positive electrode active material layer and the negative electrode active material layer, (4) coating on the anode active material layer and the anode current collector copper foil, (5) coating on the anode active material layer and the anode current collector aluminum foil, (6) coating on the positive electrode active material layer and the negative electrode current collector copper foil, and (7) coating on the positive electrode active material layer and the positive electrode current collector aluminum foil; (3) conductive coating, which comprises the PTC material; (4) preparation of the conductive coating; (5) current collector, which comprises the conductive coating and current collector substrate. The conductive coating is coated on the surface of the current collector substrate; and (6) electrode material, which comprises the conductive coating and the active material layer. The conductive coating is coated on the surface of the active material layer.