5 research outputs found
Electrolyte Coatings for High Adhesion Interfaces in Solid-state Batteries from First Principles
We introduce an adhesion parameter that enables rapid screening for materials
interfaces with high adhesion. This parameter is obtained by density functional
theory calculations of individual single-material slabs rather than slabs
consisting of combinations of two materials, eliminating the need to calculate
all configurations of a prohibitively vast space of possible interface
configurations. Cleavage energy calculations are used as an upper bound for
electrolyte and coating energies and implemented in an adapted contact angle
equation to derive the adhesion parameter. In addition to good adhesion, we
impose further constraints in electrochemical stability window, abundance, bulk
reactivity, and stability to screen for coating materials for next-generation
solid-state batteries. Good adhesion is critical in combating delamination and
resistance to Lithium diffusivity in solid-state batteries. Here, we identify
several promising coating candidates for the Li7La3Zr2O12 and sulfide
electrolyte systems including the previously investigated electrode coating
materials LiAlSiO4 and Li5AlO8, making them especially attractive for
experimental optimization and commercialization
Correlative analysis of structure and chemistry of LixFePO4 platelets using 4D-STEM and X-ray ptychography
Lithium iron phosphate (LixFePO4), a cathode material used in rechargeable
Li-ion batteries, phase separates upon de/lithiation under equilibrium. The
interfacial structure and chemistry within these cathode materials affects
Li-ion transport, and therefore battery performance. Correlative imaging of
LixFePO4 was performed using four-dimensional scanning transmission electron
microscopy (4D-STEM), scanning transmission X-ray microscopy (STXM), and X-ray
ptychography in order to analyze the local structure and chemistry of the same
particle set. Over 50,000 diffraction patterns from 10 particles provided
measurements of both structure and chemistry at a nanoscale spatial resolution
(16.6-49.5 nm) over wide (several micron) fields-of-view with statistical
robustness.LixFePO4 particles at varying stages of delithiation were measured
to examine the evolution of structure and chemistry as a function of
delithiation. In lithiated and delithiated particles, local variations were
observed in the degree of lithiation even while local lattice structures
remained comparatively constant, and calculation of linear coefficients of
chemical expansion suggest pinning of the lattice structures in these
populations. Partially delithiated particles displayed broadly core-shell-like
structures, however, with highly variable behavior both locally and per
individual particle that exhibited distinctive intermediate regions at the
interface between phases, and pockets within the lithiated core that correspond
to FePO4 in structure and chemistry.The results provide insight into the
LixFePO4 system, subtleties in the scope and applicability of Vegards law
(linear lattice parameter-composition behavior) under local versus global
measurements, and demonstrate a powerful new combination of experimental and
analytical modalities for bridging the crucial gap between local and
statistical characterization.Comment: 17 pages, 4 figure