Blending of lithium insertion compounds is a promising approach to design advanced electrodes for lithium-ion batteries. In spite of considerable improvements regarding the power density, some basic interactions between the constituents of the blend are still under discussion. Herein we quantify the so-called buffer effect observed in blended insertion electrodes for the first time by using a special experimental setup and a model-like blended insertion electrode. Internal dynamics of the blend are investigated during defined pulse loads and subsequent relaxation. The results reveal significant electrochemical interactions between the constituents, depending on the applied current and the overpotential, respectively. These interactions are attributed to thermodynamic factors of emerging and converging equilibrium potentials of the constituents during charging-discharging and subsequent relaxation. This buffer effect enables the preparation of electrodes with high energy density and very good rate capability by combining active materials with high specific capacity and fast kinetics.