High-Voltage Stability of Small-Size Single Crystal Ni-Rich Layered Cathode for Sulfide-Based All-Solid-State Lithium Battery at 4.5 V

Abstract

Mechanical damage of NCM811 (LiNi0.8Co0.1Mn0.1O2), severe interfacial side reactions, and physical contact failure of cathode and solid electrolyte (SE) are the main obstacles for it to achieve high-voltage stability in all-solid-state batteries (ASSLBs). The cathode morphology effects on the structural integrity are directly related to the electrochemical performance of ASSLBs. In this work, small-size single crystal NCM811 (S-SC) is synthesized for sulfide-based ASSLBs to solve mechanical damage and contact failure issues. In addition, the interfacial stability is improved by a Li2O pre-lithiation strategy. Cross section polisher-scanning electron microscopy (CP-SEM) is applied to reveal the mechanical structure evolution behavior of NCM811 cathodes with different morphology. Electrochemical impedance spectroscopy (EIS), time of flight secondary ion mass spectrometry (TOF-SIMS), and X-ray photoelectron spectroscopy (XPS) technologies are applied to characterize the interfacial stability among cycling. As a result, with a high mass loading of 35.67 mg cm−2 and high current density of 7.13 mA cm−2, the Li2O pre-lithiated S-SC (S-SC-PL) cathode delivers extraordinarily high-voltage stability of 100% after 500 cycles at 2.72–4.4 V and 100% after 200 cycles at 2.72–4.5 V in ASSLBs. This work provides an effective cathode morphological design strategy to improve high-voltage stability of Ni-rich layered cathodes for sulfide-based ASSLBs.