Toward an Understanding of SEI Formation and Lithium Plating on Copper in Anode-Free Batteries

Abstract

“Anode-free” batteries present a significant advantage due to their substantially higher energy density and ease of assembly in a dry air atmosphere. However, issues involving lithium dendrite growth and low cycling Coulombic efficiencies during operation remain to be solved. Solid electrolyte interphase (SEI) formation on Cu and its effect on Li plating are studied here to understand the interplay between the Cu current collector surface chemistry and plated Li morphology. A native interphase layer (N-SEI) on the Cu current collector was observed with solid-state nuclear magnetic resonance spectroscopy (ssNMR) and electrochemical impedance spectroscopy (EIS). Cyclic voltammetry (CV) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) studies showed that the nature of the N-SEI is affected by the copper interface composition. An X-ray photoelectron spectroscopy (XPS) study identified a relationship between the applied voltage and SEI composition. In addition to the typical SEI components, the SEI contains copper oxides (Cu x O) and their reduction reaction products. Parasitic electrochemical reactions were observed via in situ NMR measurements of Li plating efficiency. Scanning electron microscopy (SEM) studies revealed a correlation between the morphology of the plated Li and the SEI homogeneity, current density, and rest time in the electrolyte before plating. Via ToF-SIMS, we found that the preferential plating of Li on Cu is governed by the distribution of ionically conducting rather than electronic conducting compounds. The results together suggest strategies for mitigating dendrite formation by current collector pretreatment and controlled SEI formation during the first battery charge.

Toward Unraveling the Origin of Lithium Fluoride in the Solid Electrolyte Interphase

“…Of particular interest were the decomposition voltages (i.e., stability windows) and nature of passivation films in terms of chemical composition and physical structure. The techniques utilized included atomic force microscopy (AFM), ,, infrared spectroscopies, − electrochemical impedance spectroscopy, ,− electrochemical quartz crystal microbalance, , X-ray photoelectron spectroscopy (XPS), − ,,,,,− secondary ion mass spectroscopy (SIMS), ,, grazing incidence X-ray scattering, and X-ray reflectivity (XRR) …”

Correlative Electrochemical Microscopy for the Elucidation of the Local Ionic and Electronic Properties of the Solid Electrolyte Interphase in Li‐Ion Batteries

“…Grey et al. recently confirmed [34] that a native SEI rich in LiF is spontaneously formed which correlates with the high electronically insulating character found when using LiPF 6 . iii) Using a model Li 4 Ti 5 O 12 electrode, Abe et al [35] .…”

All‐Climate and Ultrastable Dual‐Ion Batteries with Long Life Achieved via Synergistic Enhancement of Cathode and Anode Interfaces

“…According to the mechanism of LG‐DIBs, all the working ions should theoretically come from the electrolyte; thus, it is ideal to replace the lithium electrode with the current collector. [ 26 ] However, because dead lithium is generated during cycling, a lithium source has to be provided at the negative electrode to ensure battery operation. To reduce the use of lithium resources, we applied the ESF directly as a host for lithium: ESF pre‐loaded with a certain amount of lithium could ensure stable cycling of the LG‐DIBs with 83% capacity retention after 1000 cycles ( Figure ), while the amount of lithium in the corresponding LG‐DIB is much less than that using lithium foil (in order to improve the uniformity of Li metal deposition, an ether electrolyte of 1 mol L −1 LiTFSI in DOL/DME was used in the electrodeposition process).…”