A biscuit-like separator enabling high performance lithium batteries by continuous and protected releasing of NO₃ ⁻ in carbonate electrolyte

Lithium nitrate (LiNO₃) has been widely applied as an additive to effectively protect lithium (Li) metal anode via enhancing the interfacial stability. However, few researches have been carried out to protect Li metal anode with LiNO₃ in carbonate electrolyte, because of its sparingly solubility. Herein, we propose a concept of sustainably and controllably releasing NO₃ ⁻ in carbonate electrolyte by intercalating superfluous LiNO₃ particles between bi-layer polypropylene (PP) membranes (PP/LiNO₃/PP). The sandwiched biscuit-like configuration prevents the direct attachment of non-conducting LiNO₃ to active materials, facilitating the battery operation. Moreover, this construction is conductive to form uniform and stable solid electrolyte interphase (SEI) in virtue of Li–N compounds on Li metal by slow but continuous releasing of NO₃ ⁻ from LiNO₃ particles. Li metal anode with the PP/LiNO₃/PP configuration showed a high Coulombic efficiency of over 95.3% after 550 cycles at a current density of 1 mA cm⁻². When paired with LiNi_0.80Co_0.10Al_0.10O cathode, the Li metal full cell with the intercalated LiNO₃ particles could deliver a discharge capacity of 103.8 mAh g⁻¹ at the 500th cycle at 1C current density, which is far superior to the performance of the cell without LiNO₃ additive. More profoundly, the PP/LiNO₃/PP configuration is also applicable to the commercialized anode such as Silicon-Graphite to improve the electrochemical performance prominently. This strategy is not only a facile and efficient way in protecting Li metal anode, but also a universal method enabling the additives with sparingly solubility to be widely used in modern energy industries.