Bidirectional Ion Transport Enabled by Ionically Open Current Collectors in Dry‐Processed Ultrahigh‐Mass‐Loading Electrodes of Lithium Batteries

While dry‐processed ultrahigh‐mass‐loading electrodes are promising for increasing the energy density of lithium batteries, their large thickness imposes severe lithium‐ion transport limitations. Here, a bidirectional ion transport (BIT) architecture is introduced by replacing conventional metallic current collectors with ionically open graphene current collectors. Unlike typical unidirectional ion transport, where ions access the electrode from only one surface, the porous graphene current collectors enable lithium‐ion transport through both surfaces of the electrode while simultaneously providing efficient electron transport. Consequently, BIT cells exhibit a more than twofold increase in the lithium‐ion diffusion coefficient, which mitigates lithium‐ion concentration polarization and promotes more uniform lithiation/delithiation behavior throughout thick electrodes, thereby improving cycling stability. Furthermore, the BIT design enables the stacking of ultrahigh‐mass‐loading electrodes (50 mg cm –2 , 10 mAh cm –2 ) in pouch cells with favorable electrochemical performance, providing an effective strategy to overcome lithium‐ion transport limitations in thick electrodes for high‐energy‐density lithium batteries.