Five-volt-class high-capacity all-solid-state lithium batteries

Advances in battery technology have been impeded by the voltage constraints of electrolytes. Here we present a high-energy all-solid-state battery design featuring >5 V operation and an ultrahigh areal capacity of 35.3 mAh cm⁻²; these attributes were enabled by a highly conductive and ultrahigh-voltage stable fluoride solid electrolyte, LiCl–4Li₂TiF₆ (1.7 × 10⁻⁵ S cm⁻¹ at 30 °C). LiCl–4Li₂TiF₆ shields high-voltage spinel oxide cathodes, achieving 106 mAh g⁻¹ at 2C with 75.2% retention over 500 cycles for LiNi_0.5Mn_1.5O₄, sharply contrasting with the conventional LiNbO₃ counterpart, which decomposes and fails to prevent detrimental interfacial degradation. The efficacy of LiCl–4Li₂TiF₆ is validated across various systems, including LiCoMnO₄, LiFe_0.5Mn_1.5O₄ and pouch-type LiNi_0.5Mn_1.5O₄||Li (or Ag–C) all-solid-state batteries, and further demonstrated by operability down to 2.3 V with 258 mAh g⁻¹ and ultrathick 1.8-mm electrodes. This shielding layer with >5 V stability introduces a transformative design paradigm by revisiting the previously forbidden high-voltage cathodes.