Interface Limited Lithium Transport in Solid-State Batteries

Abstract

Understanding the role of interfaces is important for improving the performance of all-solid-state lithium ion batteries. To study these interfaces, we present a novel approach for fabrication of electrochemically active nanobatteries using focused ion beams and their characterization by analytical electron microscopy. Morphological changes by scanning transmission electron microscopy imaging and correlated elemental concentration changes by electron energy loss spectroscopy mapping are presented. We provide first evidence of lithium accumulation at the anode/current collector (Si/Cu) and cathode/electrolyte (LixCoO2/LiPON) interfaces, which can be accounted for the irreversible capacity losses. Interdiffusion of elements at the Si/LiPON interface was also witnessed with a distinct contrast layer. These results highlight that the interfaces may limit the lithium transport significantly in solid-state batteries. Fabrication of electrochemically active nanobatteries also enables in situ electron microscopy observation of electrochemical phenomena in a variety of solid-state battery chemistries.

Review—Practical Challenges Hindering the Development of Solid State Li Ion Batteries

“…135 Coulombic efficiency is also negatively influenced by physical stranding of inaccessible metal caused by non-uniform plating and a low density microstructure, aptly described in the literature as 'dead Li'. 140,141 A distribution of current density will manifest as a distribution of C-rates, which may create a spectrum in depth of discharge within the cathode. In the absence of other dominant failure modes, this would result in capacity fade over long duty cycles.…”

Interphase formation on lithium solid electrolytes—An in situ approach to study interfacial reactions by photoelectron spectroscopy

“…In rechargeable lithium ion batteries (LIB), the kinetics of interfaces and interphases between the electrodes and the electrolyte are essential for the proper battery function [1]. The instability of organic electrolytes in contact with the anode material and the resulting formation of the solid electrolyte interphase (SEI) in cells using liquid electrolytes are limiting factors for the cycle life on the one hand, and reactions at the cathode surface may cause additional problems.…”

Interface reactions between LiPON and lithium studied by in-situ X-ray photoemission

“…Hence interfaces and reaction layers at the interface play a crucial role for the performance of the battery [10]. Any continuous side reaction occurring at one of the interfaces will lower the lifetime of the battery [11] due to loss of active lithium and barrier layer formation.…”

“…Nevertheless there is still a lack of knowledge about the exact nature of reaction layers and formation mechanisms between the solid electrode and the solid electrolyte. Research on the interface between the electrode and the electrolyte has been performed using analytical methods such as transmission electron microscopy [1,10], by theoretical calculations [12] or by impedance spectroscopy [13]. To our knowledge no studies on interface properties have been performed using XPS.…”