Blended positive electrodes consisting of mixtures of LiMn2O4 spinel (LMO) and layered LiNi0.5Mn0.3Co0.2O2 (NMC) have been studied by coupling electrochemical testing to operando synchrotron based X-ray absorption and powder diffraction experiments to shed light on their redox mechanism. Blending NMC with LMO results in enhanced energy density at high rates, with the composition with 25% LMO exhibiting the best electrochemical performance. Tests with a special electrochemical setup detecting the contribution of each blend component indicate that the effective current load on each blend component can be significantly different from the nominal rate and also varies as function of SoC. Operando studies enabled to monitor the evolution of oxidation state and changes in the crystal structure, which are in agreement with the expected behaviour of the individual components considering the material specific electrochemical current loads. These findings should contribute to a deeper mechanistic understanding of blended electrodes to foster a rational driven approach for their design.

Operando experiments were performed at MSPD & CLAESS beamlines (proposal 2021035098 and 2021095303) at ALBA Synchrotron with the collaboration of ALBA staff. Authors are grateful to ALISTORE ERI and to H. Ehrenberg and his team at KIT for providing access to the 8 coin cell carousel holder. ICMAB-CSIC members thank the Spanish Agencia Estatal de Investigación Severo Ochoa Programme for Centres of Excellence in R&D, Spain (CEX2019-000917-S) and funding through grant PID2020-113805GB-I00. This work has been done in the framework of the doctorate in Materials Science of the Universitat Autònoma de Barcelona and D.C. wants to acknowledge DESTINY MSCA PhD Programme. Authors acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI). This project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No 945357.

With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

Peer reviewed