Complexation of Conductive Agents to Cathode Active Materials of Lithium-Ion Batteries Using the Poly–Ion Complex Formation Reaction

Electrodes of lithium-ion batteries are currently deposited by the slurry method. However, in the slurry method, the materials that make up the electrodes, that is, active materials, conductive agents, and binders, are subject to problems such as segregation and aggregation. This problem can be solved by generating composite particles of the active material, the conductive agent, and the binder. Composite particles that combine these three functions can be synthesized by forming a poly–ion complex (PIC) consisting of organics containing amino groups and graphene oxide on the surface of lithium transition metal oxide, the cathode active material. The formation mechanism of these particles is discussed, and their potential as a battery material is investigated by examining the conductivity of the electrode film. The conductivity of the electrode film using these composite particles is approximately 35% higher than that of the film in which Li­(Ni0.34Co0.33Mn0.33)­O2 (NCM), carbon black (CB), and polyvinylidene fluoride (PVDF) are mechanically mixed. This is understood as a result of the direct bonding between PIC and NCM. The conductive agent and binder are highly dispersed around the NCM particles without segregation/aggregation. In addition, when a dry film is formed using only the composite particles without adding PVDF, the adhesion to the collector foil is good and the conductivity improves compared to the sample with PVDF.