Operando analysis of the molten Li|LLZO interface: Understanding how the physical properties of Li affect the critical current density

Challenges and Opportunities for Fast Charging of Solid-State Lithium Metal Batteries

“…The morphological stability of the anode and electrochemical performance of the SSB depend on the kinetics of transport and reaction, and hence the thermal environment in the vicinity of different solid–solid interfaces within the system. Temperature-dependent mechanisms such as vacancy diffusion and viscoplasticity (creep) of lithium play a pivotal role in preserving the anode morphology during electrochemical operation. − Additionally, further enhancement in ionic transport within the solid electrolyte has also been considered beneficial toward achieving homogenized reaction distributions at the anode interface and improved ionic percolation within the cathode microstructure. , …”

“…With the high current densities (10–20 mA/cm 2 ) necessary for sub 10 min charging, such risks of system failure are further exacerbated. Above the CCD, filamentary growth/short circuiting has been observed across a wide range of solid electrolytes including the garnet-based Li 7 La 4 Zr 2 O 12 , Li 3 PS 4 , Li 6 PS 5 Cl, and Li 2 S-P 2 S 5 . , Recent studies have highlighted the dependence of CCD on different aspects such as external pressure, temperature, , interface resistance, and discharge conditions . Preferential plating at surface flaws and electrode edges has been observed at fast charging rates, leading to crack formation and mechanical failure of the solid electrolyte …”

“…To address this challenge, larger stack pressures and temperatures have been shown to enhance the ability to maintain a continuous contact area and enable higher discharge rates. , This points toward the critical role of the mechanical properties of Li metal in determining both void formation during stripping and CCD. In particular, the viscous flow of Li, in the form of either viscoplastic deformation in the solid phase , or fluid flow of molten Li, has been shown to be a critical parameter to increase the rate capability of Li metal–solid electrolyte interfaces . Furthermore, increasing temperature also affects the interfacial kinetics and ionic transport in the solid electrolyte, which can reduce current focusing and counteract the driving force for fracture …”

An Investigation of Chemo‐Mechanical Phenomena and Li Metal Penetration in All‐Solid‐State Lithium Metal Batteries Using In Situ Optical Curvature Measurements

“…[1,4,5,7,8,[16][17][18][19][20][21][22][23] Some recent studies of LLZO have proposed that the Li flux during plating can create significant stresses in surface flaws and/or porosity. [4][5][6][7][8]18,[24][25][26][27][28][29][30] Figure 1 shows a schematic of this type of process, where current focusing near the tip accentuates stress build up inside of a surface flaw. A second, related hypothesis is that these stresses are large enough to fracture a SE, and that this is an important mechanism that leads to short circuits via Li metal penetration.…”

“…To address this, a novel experimental configuration is employed to permit in situ bending measurements during lithium plating. The technique established here contrasts to prior art in the field where the evolution of Li-dendrites is typically probed by either optical microscopy, [6,8] X-ray tomography, [33,34] or neutron depth profiling. [35,36] These methods make it possible to image Li metal penetration, but they do not provide direct information about mechanical deformation during electrochemical cycling.…”