Preventing chemo-mechanical degradation of high voltage cathode and Li metal anode by amorphous lithium silicon oxide coating and hybrid solid electrolytes

Abstract

Solid-state batteries leveraging high-voltage cathodes and lithium (Li) metal anodes enhance safety and energy density; however, instability within the cathode, solid electrolyte, and Li components, along with their interfaces, restricts electrochemical performance, especially above 4.3 V vs Li/Li+. This work presents a comprehensive study on improving the stability of high-voltage LiNi<inf>0.8</inf>Mn<inf>0.1</inf>Co<inf>0.1</inf>O<inf>2</inf> (NMC 811) cathodes and Li metal anodes in solid-state lithium metal batteries (SSLMBs) through a dual strategy of amorphous lithium silicon oxide (LSO) coating and an active-inert filler-rich hybrid solid polymer electrolyte (AIFRHSPE) design. The AIFRHSPE exhibits high ionic conductivity (1.10 mS cm−1), a wide electrochemical stability window (>5 V) at 30 °C, and forms a Li<inf>3</inf>N- LiF-rich gradient anode electrolyte interphase in situ on Li metal. To stabilize high-voltage cathodes, we utilize a novel in-house synthesized single precursor for atomic layer deposition and deposit a ∼5 nm amorphous LSO coating on NMC 811, enhancing initial Coulombic efficiency (90.68 % vs. 84.44 %), rate capability (3 × higher accessible capacity at 1C rate), and cycling stability (>88 % retention after 250 cycles). Operando X-ray Absorption Near-Edge Spectroscopy (XANES) and ex-situ analyses reveal suppressed cation mixing, oxygen release, and inactive phase formation, mitigating chemo-mechanical degradation and particle cracking in LSO-coated samples. This integrated strategy addresses critical challenges in SSLMBs, including cell polarization, interfacial instability, chemo-mechanical degradation, and electrolyte decomposition by incorporating LSO as a cathode coating material and AIFRHSPE membrane for both electrolyte function and Li metal passivation, proving transformative for high-voltage SSLMB applications. © 2025