Electro-Chemo-Mechanical Study of Cathode-Interface-Engineered All-Solid-State Lithium Batteries
Authors: Wang Longlong 
Published: February 2024

All-solid-state lithium batteries (ASSLBs) have been regarded as one of the most promising next-generation batteries in terms of their superior safety and great potential to meet the requirements of high energy and power density.1 However, the performance of ASSLBs based on even state-of-the-art solid electrolytes (SEs) with a high room-temperature ion conductivity of 10−2 S·cm−1 is still inferior to that of commercially available LIBs, because fast solid electrode/electrolyte interfacial lithium-ion transport remains a vital challenge in ASSLBs.2 The sluggish lithium-ion transport across the solid electrode/electrolyte interface mainly results from the electro-chemo-mechanical degradation, such as the space charge layer (SCL), interface reaction generating ionically resistive products, and poor physical contact.3,4 On the cathode side, coating high-voltage cathodes with chemically compatible and stable buffering layers with high ionic conductivity but low electronic conductivity has been widely confirmed to be an effective approach to overcome these problems.However, a mechanistic understanding of the coating functionality remains unresolved, and there is still much room for improvement regarding the methodology and associated material properties.5

Here, from electro-chemo-mechanical perspectives, we have fully studied the improvement mechanism of cathode interface engineering for ASSLBs based on the complementary analyses including calculations (e.g., first-principles, finite element methods), in-situ (e.g., differential phase contrast scanning transmission electron microscopy (DPC-STEM), Raman, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT)) and ex-situ (X-ray absorption spectra (XAS), X-ray photoelectron spectroscopy (XPS), focused-ion beam scanning electron microscopy (FIB-SEM)) characterizations. We find that discontinuous ferroelectric BaTiO3 coating can effectively suppress the SCL formation and lead to fast continuous interfacial lithium-ion conduction pathways, thus significantly improving the interfacial migration kinetics between cathode materials and the sulfide SEs.6 The bidirectionally compatible NASICON-type LixZr2(PO4)3 (LZPO) buffering layer enables the high-voltage cathode interface (4.5 V LiCoO2/Li6PS5Cl) with high chemical/electrochemical stability and fast Li-ion transport dynamics.7 Additionally, the high Young’s modulus of the coating layer (e.g., LZPO) can remarkably decrease stress inside cathodes and prevent cathode/SE interface separation, which is beneficial to mitigate microcracks in cathodes and cathode/SE interface contact loss, respectively.8 We believe these findings will help advance the fundamental scientific understanding of the coating functionality and the interfacial lithium-ion transport mechanism in ASSLBs, thus shed light on rational electrode/electrolyte interface design for high-rate performance ASSLBs.

References

Janek, J. & Zeier, W. G. A solid future for battery development. Nat. Energy
1, 16141 (2016).

Janek, J. & Zeier, W. G. Challenges in speeding up solid-state battery development. Nat. Energy, doi:10.1038/s41560-023-01208-9 (2023).

Banerjee, A., Wang, X., Fang, C., Wu, E. A. & Meng, Y. S. Interfaces and Interphases in All-Solid-State Batteries with Inorganic Solid Electrolytes. Chem. Rev.
120, 6878–6933 (2020).

Chen, R., Li, Q., Yu, X., Chen, L. & Li, H. Approaching Practically Accessible Solid-State Batteries: Stability Issues Related to Solid Electrolytes and Interfaces. Chem. Rev.
120, 6820–6877 (2020).

Culver, S. P., Koerver, R., Zeier, W. G. & Janek, J. On the functionality of coatings for cathode active materials in thiophosphate-based all-solid-state batteries. Adv. Energy Mater.
9, 1900626 (2019).

Wang, L. et al. In-situ visualization of the space-charge-layer effect on interfacial lithium-ion transport in all-solid-state batteries. Nat. Commun.
11, 5889 (2020).

Wang, L. et al. Bidirectionally compatible buffering layer enables highly stable and conductive interface for 4.5 V sulfide-based all-solid-state lithium batteries. Adv. Energy Mater.
11, 2100881 (2021).

Sun, X. et al. A Bifunctional Chemomechanics Strategy To Suppress Electrochemo-Mechanical Failure of Ni-Rich Cathodes for All-Solid-State Lithium Batteries. ACS Appl. Mater. Interfaces
14, 17674–17681 (2022).