Improving the interfacial stability of ultrahigh-nickel cathodes with PEO-based electrolytes by targeted chemical reactions

Abstract

Benefiting from high energy density of ultrahigh-nickel cathode materials and good safety of PEO-based electrolytes, PEO-based ultrahigh-nickel solid-state lithium batteries (SLMBs) are considered to be new-generation energy storage devices. However, the incompatibility of ultrahigh-nickel cathode materials and PEO-based electrolytes is the main challenge due to serious interfacial side reactions. Therefore, the modification of the cathode/electrolyte interface is crucial. Herein, the residual lithium on the surface of LiNi_0.9Co_0.06Mn_0.04O₂ is utilized to construct an interfacial coating layer by reacting with H₃BO₃. The in situ formed xLi₂O-B₂O₃ coating layer (LBO1-NCM) with high ionic conductivity can be regulated with different crystal structures during the sintering process. Besides, an all-solid-state three-electrode cell is fabricated, which verifies that the xLi₂O-B₂O₃ coating can effectively stabilize the interface. Astonishingly, uneven Li anode deposition is observed in SLMBs, which is caused by the breakage of PEO molecular chains due to the strong oxidation of the cathode, while this crosstalk is also suppressed by the xLi₂O-B₂O₃ coating layer. Consequently, Li|PEO|LBO1-NCM achieves a substantially improved electrochemical performance, exhibiting 90.5% of capacity retention after 100 cycles for the coin cell and 80.3% of capacity retention after 200 cycles for the pouch cell. Apparently, the targeted modification of interfaces should be paid as much attention as electrolyte optimization in SLMBs.