Interface Modeling via Tailored Energy Band Alignment: Toward Electrochemically Stabilized All‐Solid‐State Li‐Metal Batteries

Abstract

Interfacial instability between Li‐metal anode (LMA) and inorganic solid‐state electrolyte (SSE) is a critical issue in all‐solid‐state Li‐metal batteries (ASSLBs). Previous studies have focused on interface modification methodology to achieve long‐term cycling stability in ASSLBs. However, strategy establishment without an in‐depth understanding of the LMA–SSE interface is limited to a phenomenological solution. Also, the fact that rechargeable batteries are operated by behavior of charges inside electric field is frequently overlooked. Here, it is demonstrated for the first time that interface modeling based on energy band theory does effectively overcome the intrinsic vulnerability of SSE to LMA. The interfacial deterioration, due to undesirable electron transport from LMA to the SSE surface, is precluded by a titanium compound self‐induced interlayer (TSI), which forms an interfacial energy barrier. The Li symmetric cell with a TSI successfully maintains its constant overpotential over 1000 cycles and the significantly reduced impedance, whereas the cell having no interface modification exhibits erratic voltage profiles and is easily failed by repetitive charge–discharge process. This newly introduced approach is an informative tool to substantially reinforce the fundamental understanding of interfacial phenomena in all‐solid‐state batteries. Furthermore, rigorous stability requirements of automotive applications are expected to be fulfilled by the innovative interface modification.

Insights into the Enhanced Interfacial Stability Enabled by Electronic Conductor Layers in Solid‐State Li Batteries

“…Figure 2b shows that the interfacial impedance value increased slowly during cycling for 150 h, and then it suddenly jumped to more than 50 kΩ cm −2 at 168 h, similar to previous reports. [ 13,31–34 ] We attribute this steep increase in impedance to the formation of abundant cracks, as shown in the postmortem digital image (inset of Figure 2b). (The LATP pellet after cell tests was stored in a glovebox before the observation in air, as shown in Figure S4a, Supporting Information.).…”

Interface Analysis of LiCl as a Protective Layer of Li1.3Al0.3Ti1.7(PO4)3 for Electrochemically Stabilized All-Solid-State Li-Metal Batteries

“…The result suggests that Ti 4+ is readily reduced when LATP is brought in contact with Li and possibly followed by the decomposition of LATP . As a result, the ASSB with LATP is known to have unstable cycling performances at a prolonged time. , …”

“…13 Interfacial modification via protective layer deposition is considered a sharp measure to tackle this problem. 14,17 The protective layer is expected to block the electron transfer to LATP and thus promote excellent battery performance. For this purpose, materials with electronic insulating properties should be chosen as a protective layer.…”

“…Unlike the previously mentioned works that used electronic insulating materials, Kim et al reported the deposition of the titanium nanolayer on LATP, which transformed into the socalled titanium self-induced interlayer (TSI), which contains LiTi 2 (PO 4 ) 3 , during cycling. 14 TSI is an excellent electron potential barrier due to its lower conduction band minimum (CBM) than LATP. Despite the excellent protective performance of TSI in preventing electron transfer from the Li metal anode, the transformation of Ti to TSI may cause battery capacity fading, as the process will likely consume Li + from the electrodes.…”

A Solid Electrolyte Based on Electrochemical Active Li4Ti5O12 with PVDF for Solid State Lithium Metal Battery

“…Element doping coupled with hierarchy design also achieved visible enhancements with less side effect on ion transport. [28,29] In parallel with researches unveiling the nature and mechanism in solid state battery, numbers of investigations have been pursuing methods to stabilize their performance as well as to reduce the cost. Simple preparation and earth-abundant ingredients are preconditions for a solid state electrolyte to be suitable for scalable production.…”