Influence of conductive additives in a nano-impact electrochemistry study of single LiMn2O4 particles

Abstract

The application of traditional cathode materials for metal-ion batteries in suspensions is recognized as an effective way of enhancing the volumetric energy density of flow batteries. These additives are called solid boosters. We have studied the influence of conducting additives on the rate-limiting steps (i.e. ion or electron transfer) for intercalating LiMn2O4 materials in suspensions. We analyzed the charge distribution and the maximum current resulting from a single particle of LiMn2O4 colliding with an electrode (i.e. nano-impact electrochemistry) and compared the results to studies with added carbon nanotubes in the water to ensure fast mixed ion/electron transfer. LiMn2O4 nanoparticles 76 nm in size were synthesized via a solution combustion method, then mixed with 30 wt% carbon nanotubes as a composite suspension. Electron transfer from the LiMn2O4 particle to the electrode was found to be the critical factor affecting the response during the single-particle collision. With an increase in the potential, the average charge observed for deintercalation from the composite particles increased nonlinearly and reached 47 % deintercalation at 1.1 V vs. Ag/AgCl. At the same time, only 5 % of lithium can be extracted from LiMn2O4 particles when no carbon nanotube additive is present. Therefore, the addition of a conductive component is essential for the effective investigation of intercalation materials in suspensions and in nano-impact electrochemistry studies.