Overcoming Anode Instability in Solid‐State Batteries through Control of the Lithium Metal Microstructure

Abstract

Enabling the lithium metal anode (LMA) in solid‐state batteries (SSBs) is the key to developing high energy density battery technologies. However, maintaining a stable electrode–electrolyte interface presents a critical challenge to high cycling rate and prolonged cycle life. One such issue is the interfacial pore formation in LMA during stripping. To overcome this, either higher stack pressure or binary lithium alloy anodes are used. Herein, it is shown that fine‐grained (d = 20 µm) polycrystalline LMA can avoid pore formation by exploiting the microstructural dependence of the creep rates. In a symmetric cell set‐up, i.e., LiǀLi6.25Al0.25La3Zr2O12(LLZO)ǀLi, fine‐grained LMA achieves > 11.0 mAh cm−2 compared to ≈ 3.6 mAh cm−2 for coarse‐grained LMA (d = 295 µm) at 0.1 mA cm−2 and at moderate stress of 2.0 MPa. Smaller diffusion lengths (≈ 20 µm) and higher diffusivity pathway along dislocations (Dd ≈ 10−7 cm2 s−1), generated during cell fabrication, result in enhanced viscoplastic deformation in fine‐grained polycrystalline LMA. The electrochemical performances corroborate well with estimated creep rates. Thus, microstructural control of LMA can significantly reduce the required stack pressure during stripping. These results are particularly relevant for “anode‐free” SSBs wherein both the microstructure and the mechanical state of the lithium are critical parameters.

Kinetics and Pore Formation of the Sodium Metal Anode on NASICON‐Type Na3.4Zr2Si2.4P0.6O12 for Sodium Solid‐State Batteries

“…[46,47] Additionally, the grain size and dislocation density affect the mechanical properties such as yield strength and therefore influences the interfacial kinetic behavior. [48] Superposition of different phenomena like interfacial degradation, charge transfer, current constriction, as well as regeneration under current load may take place simultaneously at the Na|NZSP0.4 interface. However, a systematic study to distinguish these processes is still missing in literature.…”

“…[ 46,47 ] Additionally, the grain size and dislocation density affect the mechanical properties such as yield strength and therefore influences the interfacial kinetic behavior. [ 48 ]…”

Less is more: a perspective on thinning lithium metal towards high-energy-density rechargeable lithium batteries

“…59,119,120,133,136,140 Thus, the as-fabricated thin Li can deliver excellent performance without being affected by, or even benefiting from the different microstructures. 164 Reviewing the thin Li fabrication technologies mentioned above, most of them are physical methods and a few correlate with chemistry or electrochemistry. It is envisioned that mechanical engineers, metallurgists, electrochemists, experts in thin film processing, and other fields, can all participate in this field and create new possibilities.…”

“…59,119,120,133,136,140 Thus, the as-fabricated thin Li can deliver excellent performance without being affected by, or even benefiting from the different microstructures. 164…”

Halide solid-state electrolytes for all-solid-state batteries: structural design, synthesis, environmental stability, interface optimization and challenges

“…146,147 However, due to the low electronegativity of Li, almost all SSEs containing transition metal components were reduced upon contact with a bare Li anode. 148,149 Although a more stable interface could be obtained by replacing Li metal with a Li–In alloy, it came at the expense of capacity.…”