Janus in situ formed CoO/Li2CO3/LiF interlayer between LiCoO2 and Li6PS5Cl solid electrolytes boosting the 4.5 V performance of sulfide-based all-solid-state batteries

Abstract

Sulfide-based all-solid-state lithium-ion batteries (ASSLBs) hold promise in realizing improved safety and high energy density. In this study, we present the innovative use of polyvinylidene difluoride (PVDF) polymer as a sacrificial agent for heat reduction of LiCoO₂ (LCO), which facilitates the bidirectional interfacial compatibility between the composite LCO–Li₆PS₅Cl (LPSCl). An in situ formed CoO/Li₂CO₃/LiF interlayer on the LCO surface not only improves the cathode's performance 4.5 V but also allows for increased cathode loading. The initial capacity of PVDF-treated LCO (145.3 mA h g⁻¹) is substantially higher than that of bare-LCO, with the latter experiencing a sharp capacity decline after 100 cycles. ASSLBs with high cathode loading (16.63 mg cm⁻²) could deliver an areal capacity over 1.96 mA h cm⁻² (162.8 mA h g⁻¹) at 0.3C and retain 80.33% capacity retention after 80 cycles at 0.3C. The in situ phase transformation CoO interphase derived from lattice LCO reinforces the stability and structural integrity of the particles, thereby keeping intact the cathode particle. The Li₂CO₃/LiF interphase greatly enhances the interface stability and reduces side reactions between LCO and LPSCl. This cost-effective and efficient strategy offers a significant advancement in developing high-performance cathodes for ASSLBs.