Direct Observation of Interfacial Mechanical Failure in Thiophosphate Solid Electrolytes with Operando X‐Ray Tomography

Abstract

at larger scales (electric vehicle or gridscale energy storage) has been hampered by insufficient energy densities, prohibitive material costs, and safety concerns. [2] While significant progress has been made in the development of high energy density battery materials, the implementation of these materials in practical systems without sacrificing cell longevity or safety remains a pressing scientific challenge. One of the best studied approaches to improve the energy density of LIBs is to replace existing graphitic anodes (372 mA h g −1 capacity) with metallic lithium (3860 mA h g −1 capacity). [3] Unfortunately, uneven lithium plating and stripping in conventional organic liquid electrolytes promotes the growth of lithium dendrites, accelerating the formation of internal short-circuits. Additionally, the low thermal stability of electrolyte solvents (often mixtures of cyclic and linear carbonates) incurs exothermic decomposition of the electrolyte in the event of cell failure, often resulting in catastrophic thermal runaway. [4-6] While many approaches have been explored to address these issues, one of the most promising options is the elimination of the liquid electrolyte in favor of a solid electrolyte. [7] Transitioning from conventional liquid electrolytes to Li +conducting solid electrolytes (SEs) presents two primary advantages. The high mechanical rigidity of inorganic SEs may act to suppress the formation of dendrites at lithium anodes, reducing the possibility of internal short circuits. [8] Additionally, the negligible flammability of most SEs dramatically lowers the risk of uncontrolled thermal runaway in the event of cell failure. [9,10] These potential benefits motivate the search for materials with sufficiently high ionic conductivities to serve as replacements for their liquid counterparts. Among the known SE formulations, the thiophosphate class of superionic conductors exhibit exceptionally fast lithium transport at room temperature. [11] Specifically, Li 10 GeP 2 S 12 (LGPS) demonstrates an ionic conductivity of ≈10 mS cm −1 , comparable to conductivities achievable in conventional liquid electrolytes. [12] Despite the favorable ionic conductivity of LGPS, its poor chemical and electrochemical stabilities remain key challenges for practical application. The narrow window of electrochemical stability of LGPS and many other thiophosphate

2D Materials for All‐Solid‐State Lithium Batteries

“…Compared with polymerbased solid electrolyte, in situ X-ray tomography is more important for oxygen-based and sulfur-based electrolytes, the arrangement mode of the particles will have a huge impact on the conduction of lithium ions. [197] Aside from summarized technologies, some other advanced characterizations are also applied in the 2DMs used in ASSLBs, such as cryo-electron microscopy, spherical aberration electron microscopy, et al…”

Tracking lithium penetration in solid electrolytes in 3D by in-situ synchrotron X-ray computed tomography

“…In tandem with high flux sources, bespoke cell configurations have also been developed to maximise image quality and, for example in studies of Li 3 PS 4 solid electrolytes 45 . Recently, the electrochemical reduction of Li 10 GeP 2 S 12 was observed at the interface with lithium via an J o u r n a l P r e -p r o o f 4 elegant study using synchrotron X-ray CT 46 : as the original solid electrolyte pellet already contained cracks before cycling, elucidating the precise mechanism of crack propagation was challenging. By ensuring a fresh sample in absence of any cracks (to avoid a simple mechanical propagation), the crack initiation and growth that are induced by the lithium deposition during the electrochemical process can be revealed further.…”

Synchrotron X‐Ray Tomography for Rechargeable Battery Research: Fundamentals, Setups and Applications

“…[ 156–160 ] Madsen et al. [ 161 ] used synchrotron X‐ray tomography imaging to study the Li|SSE interface and they found that the addition of highly concentrated liquid electrolyte could effectively inhibit the LGPS from cracking during battery cycling. Zhou et al [ 102 ] also used this method to study the superiority of Celgard‐reinforced composite polymer electrolyte (CgCPE) in ASSLB.…”