Thermal Recovery of the Electrochemically Degraded LiCoO₂/Li₇La₃Zr₂O₁₂:Al,Ta Interface in an All-Solid-State Lithium Battery

Abstract

All-solid-state lithium batteries are promising candidates for next-generation energy storage systems. Their performance critically depends on the capacity and cycling stability of the cathodic layer. Cells with a garnet Li7La3Zr2O12 (LLZO) electrolyte can show high areal storage capacity. However, they commonly suffer from performance degradation during cycling. For fully inorganic cells based on LiCoO2 (LCO) as cathode active material and LLZO, the electrochemically induced interface amorphization has been identified as an origin of the performance degradation. This study shows that the amorphized interface can be recrystallized by thermal recovery (annealing) with nearly full restoration of the cell performance. The structural and chemical changes at the LCO/LLZO heterointerface associated with degradation and recovery were analyzed in detail and justified by thermodynamic modeling. Based on this comprehensive understanding, this work demonstrates a facile way to recover more than 80% of the initial storage capacity through a thermal recovery (annealing) step. The thermal recovery can be potentially used for cost-efficient recycling of ceramic all-solid-state batteries.

Aqueous Processing of LiCoO2–Li6.6La3Zr1.6Ta0.4O12 Composite Cathode for High-Capacity Solid-State Lithium Batteries

“…As there is in fact Al (diffused from alumina substrate) existing in the LCO phase of the cathode, the impact of Al on the battery performance requires further investigation. In this regard, additional experiments by sintering on different substrates can be done for a comparison to evaluate the effect of Al-doping in LCO for the LCO-garnet composite cathodes …”

“…In this regard, additional experiments by sintering on different substrates can be done for a comparison to evaluate the effect of Al-doping in LCO for the LCO-garnet composite cathodes. 45 Other degradation contributions could relate to the anode. As shown in our previous study, the Coulombic efficiency of the LFP-based SSLBs with indium anode was 96−98%, while the one of SSLBs with Li anode was 99%.…”

High Cathode Loading and Low‐Temperature Operating Garnet‐Based All‐Solid‐State Lithium Batteries – Material/Process/Architecture Optimization and Understanding of Cell Failure

“…[47] Ihrig et al reported that amorphous interphases are formed on the interfaces between LCO and LLZT after charge/discharge cycles, [61] which could be recovered by thermal treatment. [62] It is known that element interdiffusion is induced by electrochemical processes for sulfide-based ASSBs. [63] However, in our studies, such interphases could not be confirmed even after six cycles (Figure 4).…”

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

“…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. To form sufficient bonding between the individual components in an all-oxide cathode composed by LLZO and LiCoO2 (LCO) temperatures from 600 to 1050 °C are required (see Table 1).…”