Oxide‐Based Solid‐State Batteries: A Perspective on Composite Cathode Architecture

Abstract

The garnet‐type phase Li7La3Zr2O12 (LLZO) attracts significant attention as an oxide solid electrolyte to enable safe and robust solid‐state batteries (SSBs) with potentially high energy density. However, while significant progress has been made in demonstrating compatibility with Li metal, integrating LLZO into composite cathodes remains a challenge. The current perspective focuses on the critical issues that need to be addressed to achieve the ultimate goal of an all‐solid‐state LLZO‐based battery that delivers safety, durability, and pack‐level performance characteristics that are unobtainable with state‐of‐the‐art Li‐ion batteries. This perspective complements existing reviews of solid/solid interfaces with more emphasis on understanding numerous homo‐ and heteroionic interfaces in a pure oxide‐based SSB and the various phenomena that accompany the evolution of the chemical, electrochemical, structural, morphological, and mechanical properties of those interfaces during processing and operation. Finally, the insights gained from a comprehensive literature survey of LLZO–cathode interfaces are used to guide efforts for the development of LLZO‐based SSBs.

Low Interfacial Resistance and Superior Suppression to Li-Dendrite Penetration Facilitated by Air-Stable and Mechanically Robust Al/Mg-Co-Doped Li-La-Zirconate as Electrolyte for Li-Based Solid-State Cells

“…Ensuring good interfacial contact between Li and LLZO is a must, since poor interfacial contact not only accrues the charge transfer resistance ( R ct ), which leads to lowering of the power density of the solid-state cell, but also partly facilitates the formation/growth of Li-dendrites at lower current density. ,,,,− Good contact at the Li/LLZO interface is likely to be achieved and maintained primarily if the LLZO remains stable and, thus, free of impurity phases at the surface (such as Li 2 CO 3 , La 2 O 3 , and La 2 Zr 2 O 7 ) and concomitantly at the Li/LLZO interface, which is expected to be better for our air-stable Al/Mg-co-doped LLZO than for the simply Al-doped LLZO. − …”

Recent Advances in Developing High-Performance Solid-State Lithium Batteries: Interface Engineering

“…These challenges may be overcome by looking at solid electrolytes (SEs), which have recently been a major focus in the advancement of solid-state batteries (SSBs). When it comes to mechanical and electrochemical stability, SEs outperform LEs; they may be made from solid polymers, inorganic compounds, or hybrids. − Research into ionic transport channels of SEs, electrochemical stability windows, and mechanical characteristics have been the subject of a plethora of experimental and theoretical efforts. − With focus on SSBs as an alternative to conventional LIB technology, a higher energy density with improved safety and lower costs can be achieved. SSBs require SEs with good chemical stability, wide electrochemical voltage windows, high ionic conductivities, and satisfactory mechanical properties. − It is difficult to achieve all of these parameters, and most reported SEs have limitations.…”

A guideline to mitigate interfacial degradation processes in solid-state batteries caused by cross diffusion

“…Despite the promising prerequisites of LLZO its integration into a battery is associated with the formation of complex solid-to-solid interfaces that arise as the main bottlenecks to achieve high power density, rate capacity, and capacity retention of SSBs, which impede their ultimate commercial usage. 7,8 Whereas for the Li | LLZO interface significant improvements have been achieved, 9 the cathode side still suffers from technical challenges such as poor contact between the LLZO and the cathode or contact loss during cycling due to volume changes within the cathode. 10,11,12,13,14 A stable interface contact is a key requirement for high initial discharge capacities, this however, requires high temperature processing.…”