Synergy effects in blended electrodes for Li-ion batteries: A conceptual clarification

The use of electrodes with multiple active materials is considered a promising approach to develop advanced Li-ion batteries. Recent studies even point to synergistic effects in terms of rate performance. However, the origin of synergistic effects is still insufficiently understood to enable targeted material and design development and to optimize batteries accordingly. Using straightforward equivalent circuit modeling combined with electrochemical studies, we reveal that improvements in rate capability are an intrinsic property of blended electrodes. The electrical parallel connection of the components in the composite electrode allows the applied current to be distributed among the components in a way that the voltage losses become minimal. This way, rate-limiting components can still contribute to the electrode's capacity at high loads, which makes blended electrodes particularly attractive, e. g., for applications that must be able to handle high pulse loads. Based on the results, rational design principle are derived by means of a systematic sensitivity analysis, quantifying the influence of the individual active material properties. These findings greatly contribute to the understanding of the internal dynamics and synergy effects in blended electrodes and support the targeted development of advantageous material combinations and electrode designs for future Li-ion batteries.