Operando quantification of diffusion-induced stresses in O3-type NaNi1/3Fe1/3Mn1/3O2 sodium-ion battery electrode during electrochemical cycling

Abstract

The extraction and insertion of Na⁺ ions into transition metal layered oxides based on Ni, Fe, and Mn (NFM) can introduce stresses in electrode coatings containing these materials. The magnitude and nature of such stresses generated in an NaNi_1/3Fe_1/3Mn_1/3O₂ (NFM111) electrode are investigated in this study using the substrate curvature method. A complex profile comprising both tensile and compressive stresses are observed during the electrochemical desodiation/sodiation cycles in a Na metal counter electrode cell. The peak compressive and tensile stresses experienced by the electrode during cycling in the 2.0–4.1 V range are – 4 MPa and 2.7 MPa, respectively. Similar stress profiles are obtained from measurements in two different in-plane directions, indicating that the response is an average of randomly oriented particles in the electrode coating. The stress evolution shows excellent correlations with phase changes in the oxide that result from removal and insertion of the alkali ions. The experimental data are being used to develop mechanically durable NFM electrodes for high-performance sodium-ion batteries intended for transportation and electricity-grid applications.