Engineering durable interphases for high-voltage Li-ion batteries under thermal stress

Achieving stable cycling of high-voltage cathodes at elevated temperatures remains a critical challenge due to intensified interfacial side reactions and the accelerated dissolution of the cathode electrolyte interphase (CEI). In this work, based on theoretical calculations, Li₂SO₃ with desirable thermal stability and adhesiveness is proposed as a thermally stable binding agent between the selected CEI components (LiF and Li₃PO₄, where Li₃PO₄ facilitates fast Li⁺ transport and thermal stability, while LiF serves as a stable, electron-blocking framework) to prevent undesirable dissolution. This is achieved by leveraging electrolyte engineering to modulate the solvation environment and promote the in-situ formation of the aforementioned CEI architecture. Owing to its structural and compositional stability at elevated temperatures, the constructed CEI effectively mitigates interfacial side reactions even under elevated temperature conditions. As a result, the uncommon achievement of stable cycling for LiCoO₂ at 4.6 V and 45°C was realized, demonstrating 81.9% capacity retention over 500 cycles. This work provides a transformative pathway for designing a durable CEI layer tailored to high-voltage and elevated temperature applications, paving the way for lithium-ion batteries to operate reliably in extreme environments.