In Situ Observation of Sodium Dendrite Growth and Concurrent Mechanical Property Measurements Using an Environmental Transmission Electron Microscopy–Atomic Force Microscopy (ETEM-AFM) Platform

Abstract

Akin to Li, Na deposits in a dendritic form to cause a short circuit in Na metal batteries. However, the growth mechanisms and related mechanical properties of Na dendrites remain largely unknown. Here we report real-time characterizations of Na dendrite growth with concurrent mechanical property measurements using an environmental transmission electron microscopy–atomic force microscopy (ETEM-AFM) platform. In situ electrochemical plating produces Na deposits stabilized with a thin Na2CO3 surface layer (referred to as Na dendrites). These Na dendrites have characteristic dimensions of a few hundred nanometers and exhibit different morphologies, including nanorods, polyhedral nanocrystals, and nanospheres. In situ mechanical measurements show that the compressive and tensile strengths of Na dendrites with a Na2CO3 surface layer vary from 36 to >203 MPa, which are much larger than those of bulk Na. In situ growth of Na dendrites under the combined overpotential and mechanical confinement can generate high stress in these Na deposits. These results provide new baseline data on the electrochemical and mechanical behavior of Na dendrites, which have implications for the development of Na metal batteries toward practical energy-storage applications.

Nano-scale mechanism of crack nucleation/propagation and lithium penetration in solid electrolyte

“…The origin of lithium deposition and growth through the bulk LPS and the necessary conditions to avoid it are still disputed. 32,33 However it has been theorized that lithium can accumulate in the SSE, 27,34 and if near a large-enough crack, 35 the force due to enough accumulation can pry the crack open, propagating crack growth 36,37 . Cracks formed via lithium plating encourage more lithium plating in that particular area, which in turn increases local electronic conductivity, lowering the energy barrier and promoting more dendrite growth and propagation.…”

Modulating Nanoinhomogeneity at Electrode–Solid Electrolyte Interfaces for Dendrite‐Proof Solid‐State Batteries and Long‐Life Memristors

“…How the mechanical response and electrochemical performance correlates is yet to be answered. [ 37–40 ] Especially, since the stress is generated locally during lithium deposition, its characteristic effective length may well go down to nanometers. This leads to difficulty in direct measurements using conventional macroscopic electrochemical setups as shown in Figure 1 a,b.…”

In Situ Electrochemical Study of Na–O2/CO2 Batteries in an Environmental Transmission Electron Microscope

“…The stability of the discharge products against the electron beam arose from the formation of the surface Na 2 CO 3 layer, which acted as a solid electrolyte interface (SEI) layer, protecting the inner discharge product. In fact, such SEI protection enabled us to conduct mechanical tests of the discharge product . All of our in situ experiments were carried out at 17.9 e Å –2 s –1 , which is much lower than the critical dose rate of 424 e Å –2 s –1 .…”