High-energy all-solid-state lithium batteries enabled by Co-free LiNiO₂ cathodes with robust outside-in structures

A critical current challenge in the development of all-solid-state lithium batteries (ASSLBs) is reducing the cost of fabrication without compromising the performance. Here we report a sulfide ASSLB based on a high-energy, Co-free LiNiO₂ cathode with a robust outside-in structure. This promising cathode is enabled by the high-pressure O₂ synthesis and subsequent atomic layer deposition of a unique ultrathin Li_xAl_yZn_zO_δ protective layer comprising a Li_xAl_yZn_zO_δ surface coating region and an Al and Zn near-surface doping region. This high-quality artificial interphase enhances the structural stability and interfacial dynamics of the cathode as it mitigates the contact loss and continuous side reactions at the cathode/solid electrolyte interface. As a result, our ASSLBs exhibit a high areal capacity (4.65 mAh cm⁻²), a high specific cathode capacity (203 mAh g⁻¹), superior cycling stability (92% capacity retention after 200 cycles) and a good rate capability (93 mAh g⁻¹ at 2C). This work also offers mechanistic insights into how to break through the limitation of using expensive cathodes (for example, Co-based) and coatings (for example, Nb-, Ta-, La- or Zr-based) while still achieving a high-energy ASSLB performance.