Defects and nanostrain gradients control phase transition mechanisms in single crystal high-voltage lithium spinel

Abstract

Lithiation dynamics and phase transition mechanisms in most battery cathode materials remain poorly understood, because of the challenge in differentiating inter- and intra-particle heterogeneity. In this work, the structural evolution inside Li1−xMn1.5Ni0.5O4 single crystals during electrochemical delithiation is directly resolved with operando X-ray nanodiffraction microscopy. Metastable domains of solid-solution intermediates do not appear associated with the reaction front between the lithiated and delithiated phases, as predicted by current phase transition theory. Instead, unusually persistent strain gradients inside the single crystals suggest that the shape and size of solid solution domains are instead templated by lattice defects, which guide the entire delithiation process. Morphology, strain distributions, and tilt boundaries reveal that the (Ni2+/Ni3+) and (Ni3+/Ni4+) phase transitions proceed through different mechanisms, offering solutions for reducing structural degradation in high voltage spinel active materials towards commercially useful durability. Dynamic lattice domain reorientation during cycling are found to be the cause for formation of permanent tilt boundaries with their angular deviation increasing during continuous cycling.

In-situ and wavelength-dependent photocatalytic strain evolution of a single Au nanoparticle on a TiO2 film

“…To investigate the propagation of surface changes inward to the bulk region of the AuNP, we calculated the absolute variation in average lattice spacing ( ), where represents to the initially measured pristine AuNP (Fig. 4a, b ) 30 , 61 . Under the pristine condition, no significant changes in were observed during the BCDI measurement.…”

Surface engineering for stable electrocatalysis

“…107 Notably, the state-of-the-art BCDI boasts a picometer strain sensitivity (1 Â 10 À4 ), allowing the structural impact of individual crystal defects to be resolved and quantified. 108,109 BCDI has been extensively employed to track subtle strain dynamics under various conditions, revealing the underlying processes, such as redox reaction, 100,110 adsorption, 111 phase transition, 108,112,113 and dissolution. 114,115 For example, Sheyfer et al utilized BCDI to monitor the electrochemically-induced strain on Pt (111) grain when exposed to polarization in 0.1 M HClO 4 , using a nanopipette setup (Fig.…”

Na-deficient P2-type layered oxide cathodes for practical sodium-ion batteries

“…In the case of deep discharge to 1.5 V, an orthogonal phase was found to be produced and co-existed with P2 phase [46] . The repeated phase transition and separation processes can break down electrode particles by inducing numerous intragranular cracks due to the massive strain at phase boundaries [47][48][49] , plaguing the electrochemical performance.…”