A Boron Nitride Nanotube Coated Separator for Suppressing Dendritic Lithium Growth in Lithium Metal Batteries

Abstract

High-energy-density lithium metal batteries (LMBs) are emerging as key systems for energy storage applications. However, their practical implementation remains challenging due to the uncontrolled Li dendrite growth, which raises safety concerns and accelerates capacity degradation. In this context, separator modification has proven to be a versatile and feasible strategy for overcoming this issue. In this work, a boron nitride nanotube (BNNT) layer was applied onto a commercial PP separator via simple blade casting. The resulting BNNT@PP demonstrated remarkably enhanced Li+ transport due to the interaction between BNNT and TFSI-. In addition, the BNNT@PP exhibited accelerated charge transfer kinetics along with improved electrolyte wettability. These combined effects guided lithium to deposit as smooth and dense Li blocks, thereby effectively preventing the evolution of dendritic Li. Incorporating the BNNT@PP substantially improved the cycling stability of Li symmetric cells, allowing them to operate for more than twice as long as those with bare PP. The Li

LFP full cells using BNNT@PP showed superior rate capability and delivered ~15 mAh g-1 higher discharge capacities during long-term cycling at 2 C, compared with those using bare PP. As such, this study underscores the potential of separator engineering as an effective approach for regulating lithium deposition morphology, providing a viable pathway for safe and durable high-energy-density LMBs.