Interface stability of high-performance lithium metal batteries regulated by ion transport
Lithium metal batteries,boasting their ultra-high theoretical capacity and elevated working voltage,are considered the top choice for the next generation of high-capacity batteries.However,the disordered ionic transport and instability at the"electrolyte/anode"interface,which leads to lithium dendrite growth,severely restrict the commercial application.In this study,the COF@PP composite separators were obtained by a vacuum self-assembly method using sulfonic acid-based covalent organic framework materials(sulfonic acid COF-1)as raw materials.It is found that the COF layer could enhance the selectivity and rapidity of lithium ion transport,the ionic conductivity and transference number of lithium ions increase from 0.21 mS·cm-1 and 0.46 to 0.44 mS·cm-1 and 0.66,respectively.Hence,lithium ions achieve stable depositing/stripping for over 250 h without significant lithium dendrite formation."Li|LiFePO4"cell performance tests demonstrates that the COF@PP separator reduced active lithium loss,achieving a discharge specific capacity exceeding 150 mA·h·g-1 within the voltage range of 2.5-4.2V.The capacity retention rate is more than 94％after 200 cycles at 1 C,significantly outperforming conventional separator batteries.The performance enhancement is attributed to the formation of uniform nanochannels after the PP are covered by COF,inhibiting the passage of large-radius anions.Moreover,the composite separator exhibits good wettability and forms internal channels with filled electrolyte,providing a rapid pathway for ion transport.
lithium-metal batteriescovalent organic frameworkscomposite separators"electrolyte/anode"interfaceion transport regulation
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