On the mechanisms of stress relaxation and intensification at the lithium/solid-state electrolyte interface
- PDF / 1,124,729 Bytes
- 24 Pages / 584.957 x 782.986 pts Page_size
- 51 Downloads / 219 Views
On the mechanisms of stress relaxation and intensification at the lithium/solid-state electrolyte interface Erik G. Herbert1,a),b), Nancy J. Dudney2, Maria Rochow1, Violet Thole1, Stephen A. Hackney1 1
Department of Materials Science and Engineering, Michigan Technological University, Houghton, Michigan 49931, USA Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA a) Address all correspondence to this author. e-mail: [email protected] b) This author was an editor of this journal during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs.org/editor-manuscripts/. This paper has been selected as an Invited Feature Paper. 2
Received: 23 May 2019; accepted: 17 September 2019
Under electrochemical cycling, stress intensification and relaxation within small volumes at the lithium/solidstate electrolyte (SSE) interface are thought to be critical factors contributing to mechanical failure of the SSE and subsequent short-circuiting of the device. Nanoindentation has been used to examine the diffusion-limited pressure lithium can support in the absence of active dislocation sources at high homologous temperatures. Based on the underlying physics of this deformation mechanism, a simple perturbation model coupling local current density, elastic stress, and diffusional creep relaxation is introduced. Combining this analysis with the indentation results, it is possible to describe a defect length scale which is too large for effective diffusional creep relaxation, but too small for efficient dislocation multiplication. In this instance, the properties of the SSE may become critical, and relevant indentation results of the SSE are described. The final outcome of the proposed analysis is a newly developed deformation mechanism map.
Introduction Motivated by recent experimental observations showing that on electrochemical cycling, metallic lithium can propagate through the oxide garnet commonly known as LLZO, global research efforts are underway to better understand the complex coupling that exists between electrochemical cycling conditions and the state of stress at the lithium/solid electrolyte interface [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]. Of particular interest is developing an understanding of how and why on electrochemical cycling a small volume of metallic lithium, which has an elastic modulus, E, of ;9 GPa and a bulk yield strength, ry, of ;0.5 MPa, is physically capable of locally infiltrating and propagating completely through the solid-state electrolyte (SSE) separator LLZO, which has an elastic modulus of ;150 GPa (17 times higher than polycrystalline lithium) and a bulk plane strain fracture toughness, KIc, of ;1.25 MPa m1/2, indicating a normal stress of 315 MPa is required to propagate a surface crack with a length of 5 lm (assuming Y 5 1.0) [7, 8, 12, 15]. Among the recent studies addressing this issue, Porz et al., Herbert et al., Wang et al., and Swamy et al. have independentl
Data Loading...
