Operando Visualization of Morphological Dynamics in All‐Solid‐State Batteries

Abstract

materials generates volume changes. [2,3] In conventional lithium-ion batteries (LiBs) employing liquid electrolytes, volume expansion dissipates in the electrode matrix (carbon/binder) and depends only on the intrinsic properties of the active material. [4,5] The mechanical fracture of the active material particles and mechanical disintegration of the electrode might be even more severe for all-solid-state batteries (SSBs) as the battery needs to maintain its mechanical integrity for proper cycling.Research in the field of SSBs is motivated by their promised high power and energy density on the cell level compared to conventional LiBs. [6] In particular, inorganic glassy and ceramic solid electrolyte (SE), for example, the thio-LiSICON family [6][7][8] and garnet-type (Li 5 La 3 M 2 O 12 ) conductors, [9] with high room-temperature ionic conductivity up to 10 mS cm −1 , moved the performance of SSBs close to and beyond that of the state-of-the-art LiB. [6] Among all superionic conductors, amorphous Li 2 S-P 2 S 5 (LPS) stands out due to its low Young's modulus (E = 18.5 GPa) [10] and its ability to be well densified by cold pressing. [11] Theoretically, the elasticity of LPS is beneficial for accommodating the stress caused by the volume change of the active material during cycling. However, All-solid-state batteries (SSBs) are considered as attractive options for next-generation energy storage owing to the favorable properties (unit transference number and thermal stabilities) of solid electrolytes. However, there are also serious concerns about mechanical deformation of solid electrolytes leading to the degradation of the battery performance. Therefore, understanding the mechanism underlying the electromechanical properties in SSBs is essentially important. Here, 3D and time-resolved measurements of an all-solid-state cell using synchrotron radiation X-ray tomographic microscopy are shown. The gradient of the electrochemical reaction and the morphological evolution in the composite layer can be clearly observed. Volume expansion/compression of the active material (Sn) is strongly oriented along the thickness of the electrode. While this results in significant deformation (cracking) in the solid electrolyte region, organized cracking patterns depending on the particle size and their arrangements is also found. This study based on operando visualization therefore opens the door toward rational design of particles and electrode morphology for all-solid-state batteries. BatteriesThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

Ni‐Rich Layered Cathode Materials with Electrochemo‐Mechanically Compliant Microstructures for All‐Solid‐State Li Batteries

“…Even after the subsequent discharge, the structure of the secondary particles of FCG75 remains intact (Figure 3g). Moreover, the void spaces between active material particles and SEs disappear . After 100 cycles, the difference in mechanical integrity between the NCA80 and FCG75 electrodes becomes more amplified (Figure 3h,i).…”

Interfaces and Interphases in All-Solid-State Batteries with Inorganic Solid Electrolytes

“…Wu et al studied operando lithiation/delithiation dynamics of Sn particles with LPS SE including interfacial crack formation and propagation. 148 The difference in X-ray attenuation (due to different densities) helped to distinguish between Sn, lithiated Sn, LPS, and voids/cracks (Figure 20f). Using this technique, they made a few observations: (i) anisotropic expansion and contraction happens during lithiation and delithiation of Sn and some lithiated Sn becomes electrochemically disconnected, meaning it can no longer participate in the redox process, (ii) there is preferential interfacial crack formation and propagation through the bulk of the LPS SE which could be due to more compressive stresses at the interface, (iii) permanent cracks are present at the Sn−LPS interface after full delithation which explains the low first cycle CE and poor capacity retention, and (iv) cracks in LPS that originate from volume expansion of Sn particles almost completely disappear after full delithation, which could be due to the adequate elasticity of LPS to accommodate the volume change (8%) of the working composite electrode.…”

Engineering of Sn and Pre‐Lithiated Sn as Negative Electrode Materials Coupled to Garnet Ta‐LLZO Solid Electrolyte for All‐Solid‐State Li Batteries

“…The electrochemical investigations were conducted using a galvanostatic cycle coupled to a potentiostatic step applied at the cut‐off potentials (so called CCCV protocol for constant current‐constant voltage). As the Sn electroactive material is known for its poor Li diffusion especially in big particles (core‐shell process), we tested two different Sn particle sizes, 44 μm and 100 nm, both reported in Figure . For the Sn nanoparticles, it is well known that the surface is covered by a native surface layer of SnO 2 .…”