Interfacial Stability of Phosphate-NASICON Solid Electrolytes in Ni-Rich NCM Cathode-Based Solid-State Batteries

Abstract

A nondegrading, low-impedance interface between a solid electrolyte and cathode active materials remains a key challenge for the development of functional all-solid-state batteries (ASSBs). The widely employed thiophosphate-based solid electrolytes are not stable toward oxidation and suffer from growing interface resistance and thus rapid fading of capacity in a solid-state battery. In contrast, NASICON-type phosphates such as Li1+x Al x Ti2–x (PO4)3 and Li1+x Al x Ge2–x (PO4)3 are stable at high potentials, but their mechanical rigidity and high grain boundary resistance are thought to impede their application in bulk-type solid-state batteries. In this work, we present a comparative study of a LiNi0.8Co0.1Mn0.1O2 (NCM-811) cathode composite employing either β-Li3PS4 (LPS) or Li1.5Al0.5Ti1.5(PO4)3 (LATP) as a solid electrolyte. LPS is employed as a separator in both cases to assemble a functional ASSB. To avoid high-temperature processing of LATP, along with subsequent detrimental interfacial reactions with NCM materials, the ASSBs are constructed and operated in a hot-press setup at 150 °C. The cathode interfaces are investigated using in situ electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy, which reveals that the interface resistance is strongly suppressed and the chemical state of the composite is unchanged during cycling when employed with LATP. The cell using LATP is reversibly charged and discharged for multiple cycles and outperforms a comparable cell using a thiophosphate composite electrode. The results indicate that LATP in the cathode composite represents an excellent candidate to overcome interfacial challenges in bulk-type solid-state batteries.

All ceramic cathode composite design and manufacturing towards low interfacial resistance for garnet-based solid-state lithium batteries

“…Of several equivalent circuits of two to four RQ elements, that with three RQ elements showed the best fitting result (Fig. 4g and Table S1, ESI †) for this study, whereas two 21,[67][68][69] or three 70,71 RQ elements have been employed for the fitting of other battery systems. Our spectra contain two small semicircles at high ((RQ) 2 ) and low frequency ((RQ) 4 ) and one larger semicircle at mid frequency ((RQ) 3 ), which all increased; however, the main degradation originated from the process at mid frequency, (RQ) 3 .…”

Structure Design of Cathode Electrodes for Solid‐State Batteries: Challenges and Progress

“…It is worth noting that the interphase formation is the consequence of the interplay between cathode and solid electrolyte, meaning that it not only depends on the intrinsic characteristics of electrolyte but also involves cathode. [ 89,90 ] From the first‐principles study by Miara et al, the reactivity of LiFePO 4 and LiMnO 2 against Li 7 La 3 Zr 2 O 12 was much higher than LiCoO 2 within the stability window of 3.8 V, which may be a partial explanation for low interface resistance and high capacity retention within 100 cycles of LiCoO 2 in Li 6.75 La 3 Zr 1.75 Nb 0.25 O 12 ‐based battery demonstrated by Ohta and co‐workers. [ 87,91 ] Another interface in the cathode electrode that may confront interphase formation is the carbon additive/solid electrolyte interface.…”

Solid‐State Li–Metal Batteries: Challenges and Horizons of Oxide and Sulfide Solid Electrolytes and Their Interfaces

“…A similar interfacial product during charge was also reported when β-Li 3 PS 4 was used as one of the cathode components in other stu dies. [320,326,339,354,355] More specifically, the effect of different cut-off voltages from 4.0, 4.3, and 4.6-5.0 V on the interfacial resistance of the β-Li 3 PS 4 -NCM811 interface was investigated for a Li-In|β-Li 3 PS 4 |β-Li 3 PS 4 -NCM811 cell (Figure 9a). [320] Using electrochemical cycling experiments, electrochemical impedance spectroscopy (EIS), and ex situ/in situ XPS, significant interfacial resistance was shown to evolve, severely affecting the battery performance above charging voltages of 4.3 V. Furthermore, depth profiling of the forming interphase revealed that most of the decomposition occurred in direct contact with the current collector, explaining the local electric potential drop, [320] Copyright 2019, Royal Society of Chemistry.…”