All-Solid-State Li Batteries with NCM–Garnet-Based Composite Cathodes: The Impact of NCM Composition on Material Compatibility

Abstract

Garnet-based all-solid-state batteries (ASBs) with high energy density require composite cathodes with high areal loading and high-capacity cathode active materials. While all ceramic cathodes can typically be manufactured via cosintering, the elevated temperatures necessary for this process pose challenges with respect to material compatibility. High-capacity cathode active materials like Ni-rich LiNi x Co y Mn1–x–y O2 (NCM) show insufficient material compatibility toward the solid electrolyte Li6.45Al0.05La3Zr1.6Ta0.4O12 (LLZO:Ta) during cosintering, leading to the formation of highly resistive interphases. We investigated this secondary phase formation both experimentally and via density functional theory calculation to get a mechanistic understanding of the cosintering behavior of LLZO:Ta with NCM111 and Ni-rich NCM811. Furthermore, we employed B doping of both NCM materials in order to assess its impact on the cation interchange and subsequent secondary phase formation. While secondary phases were formed for all four NCM materials, their onset temperature, nature, and amount strongly depend on the NCM composition and doping. Surprisingly, Ni-rich NCM811 turned out to be the most promising cathode active material for the combination with garnet-type LLZO:Ta. As proof of concept, fully inorganic, ceramic all-solid-state lithium batteries featuring only a Li-metal anode, an LLZO:Ta separator, and a composite cathode, consisting of LLZO:Ta, Li3BO3, and NCM811, were prepared by conventional sintering. The purely inorganic full cells delivered a high specific areal discharge capacity of 0.7 mA h cm–2 in the initial cycle.

Zero-Strain Cathodes for Lithium-Based Rechargeable Batteries: A Comprehensive Review

“…Because ASSBs comprise all-solid-state components, including solid electrolytes, intimate contacts between the active materials and at the electrolyte/electrode interface are essential for the stable operation of ASSBs. Similar to LIBs, CAMs in ASSBs degrades owing to irreversible phase transition, microcrack formation, and TM migration. , However, unlike LIBs, where the liquid electrolyte penetrates into microcracks and develops an excessive CEI layer, the strain and microcracks of CAMs in ASSBs cause contact loss within the CAM and in the electrolyte/CAM interface. These contact losses impede Li-ion transport and increase interfacial resistance, which is the most significant issue in ASSBs.…”

Low-cobalt active cathode materials for high-performance lithium-ion batteries: synthesis and performance enhancement methods

“…Roitzheim et al have performed a detailed study on secondary phase formation during the co-sintering of NCM111/NCM811 and LLZO : Ta electrolytes with and without B-doping. 222 It was found that the interchange between Zr and Mn is more favorable compared to the interchange with Ni and Co as well as La ↔ Ni and La ↔ Co. It leads to the formation of a La-based, Mn-rich secondary phase of LaCo 1−3 , which is predominant in NCM111.…”

Assessing Coulombic Efficiency in Lithium Metal Anodes

“…More recently, anode-free lithium metal batteries (AFBs), obtained by removing the metallic lithium anode at the initial state, have shown a potential to further increase battery energy density. − The low CE and poor cycling reversibility reported in the literature for these systems, however, are not satisfactory compared to those of LMBs, mainly because there is no lithium reservoir to replenish lost lithium. Similar to LMBs, AFBs also suffer from problems originating from the creation of high surface area lithium and the formation of inactive lithium, which is directly correlated with low CE. − Over the past few decades, extensive efforts have been devoted to understanding the mechanism of the formation of high surface area lithium deposition − and developing strategies to achieve high CE in LMBs and AFBs, such as developing new electrolyte/additives, − electrochemical treatments, − surface engineering, − solid-state electrolytes, − and lithium host modification , and so on. , …”