Stabilized interface with high discharge voltage in lithium solid-state batteries with an organic cathode

Pyrene-4,5,9,10-tetraone (PTO), with a high theoretical capacity of 409 mAh g⁻¹, is a promising cathode material. However, its use with liquid electrolytes leads to active material dissolution and rapid capacity loss. Coupling PTO cathode with a solid-state electrolyte enhances cycling stability, but low active material mass loading in solid-state batteries (SSBs) significantly limits the specific energy. To address this issue, we have developed a composite electrolyte of polyethylene oxide (PEO) and sulfide (Li_5.6PS_4.6I_1.4) that shows high ionic conductivity of 1.26 × 10⁻⁴ Ω⁻¹ cm⁻¹ at 40^o C. Using composite electrolyte enables increase in the active mass fraction of PTO to 45 wt %. As a result, specific capacity of 342.3 mAh g⁻¹ at 0.3C is achieved which is 106 % higher than the previous reports on SSBs with PTO cathode (at 0.3C) and corresponds to 83.6 % PTO active mass utilization. The composite of sulfide glass ceramic and PEO provides improved interfacial contact with the cathode, resulting in a high discharge potential of 2.8V, compared to ∼2.0V reported in previous SSBs using PTO cathodes. Consequently, this cell demonstrates outstanding cycling stability over 500 cycles, retaining more than 93 % of its capacity and achieving >98 % coulombic efficiency.