Role of negative electrode porosity in long-term aging of NMC//Graphite Li-Ion batteries
Résumé
Electrochemical energy storage associated to renewable energy sources requires devices with very long lifespan. In this work we simulated the long-term aging of Li(Ni2/5Mn2/5Co1/5)O2 (NMC)//graphite lithium-ion batteries by standardized accelerated aging tests in tough storage and cycling conditions. Aging mechanisms taking place at the graphite electrode/electrolyte interface were characterized by X-ray Photoelectron Spectroscopy (XPS) and Electrochemical Impedance Spectroscopy (EIS). Besides usual aging processes commonly admitted, we highlight the role of electrode porosity. A model is proposed to describe the electrical behavior of the electrodes taking into account the influence of electrochemically blocking pores. The blocking effect of pores is believed to be caused by confinement of Li2CO3 and/or gaseous CO2 inside the narrow pores, which do not allow lithium ions to diffuse and insert into graphite. In these pores, lithium can only participate to SEI growth which decreases the capacity by lithium consumption. © 2015 The Electrochemical Society.
Mots clés
Accelerated aging test
Carbon dioxide
Cycling conditions
Electrical behaviors
Electric batteries
Electrochemical electrodes
Electrochemical energy storage
Electrochemical impedance spectroscopy
Electrode/electrolyte interfaces
Electrode porosity
Electrodes
Graphite
Graphite electrodes
Ions
Lithium
Lithium alloys
Lithium compounds
Lithium-ion batteries
manganese
Negative electrode
Porosity
Renewable energy resources
Renewable energy source
Secondary batteries
Testing
X ray photoelectron spectroscopy
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