Chemo-mechanical stable cathode interphase via interface in situ catalytic-conversion integrated design for all solid-state batteries†

Abstract

All-solid-state lithium batteries (ASSLBs) based on LiNi_1−x−yCo_xMn_yO₂ cathodes suffer from rock-ribbed electrolyte–cathode interface issues such as oxygen evolution and side reactions with electrolytes at high operating voltages, resulting in severe structure deterioration and rapid capacity decay. Herein, a type of synergistic “catalytic conversion”-integrated mechanism was strategically exploited to in situ construct a steerable cathode–electrolyte interface (CEI), aiming to synchronously enhance electrochemical and structural stability upon cycling. By employing functional polypyrrole (PPy) as a coating layer on high voltage-operated LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811), we revealed that the N–H bond of the polypyrrole ring can cause N–H⋯O hydrogen bonding interaction to alleviate oxygen evolution. By employing functional polypyrrole (PPy) as coating layer on high voltage-operated LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811), we unveils that the N–H bond of polypyrrole ring can product N–H⋯O hydrogen bonding interaction to alleviate oxygen evolution. Specifically, the hydrogen bonding between the nitrogen-hydrogen (N–H) groups of polypyrrole (PPy) and lattice oxygen escaped form NCM811 facilitates the reduction of protons to generate hydroxide ions (OH⁻). The resulting astray OH⁻ together with O²⁻ further coordinated with Li⁺ around the aromatic skeleton interrupted by a nucleophilic π–π interaction, thereby promoting the in situ generation of an Li₂O–LiOH-rich CEI. Finally, parasitic interfacial side reactions and oxygen evolution are considerably suppressed, endowing the NCM@PPy full cell with excellent cycling performance and a capacity retention of 81.2% after 300 cycles. This in situ-generated Li₂O–LiOH-rich CEI enables the NCM811 cathode to achieve a considerable capacity of 122 mA h g⁻¹ at 0.5C with an operating voltage of 4.3 V and a lifetime of more than 100 cycles, demonstrating its practical application potential in the energy storage field.