Building Ionic/Electronic Three-Dimensional Conductive Framework to Enhance the Electrochemical Performance of LiVPO4f Cathode for Lithium Ion Batteries

LiVPO₄F has high charge-discharge plateau and good safety, making it a promising high-voltage cathode material for lithium ion batteries (LIBs).^{1, 2} Nevertheless, LiVPO₄F suffers low electronic and ionic conductivity, which brings poor rate capability as well as cycle performance. Moreover, the reaction at the electrode/electrolyte interface at high voltage with high oxidative V⁴⁺ causes low cycle property and low initial coulombic efficiency.³ Therefore, mastering the electrode/electrolyte interface is of great significance for application of LiVPO4F. Surface coating and bulk doping are usually used to overcome these issues in some well-known electrode materials. Coating with highly disperse graphene is able to effectively improve the electronic conductivity of the materials.^{4, 5} Li₃PO₄ is a fast ionic conductor and is also used as inorganic coating material to enhance the ionic transmission of the electrode materials for LIBs.⁶ Also, Li₃PO₄ is expected to act as a barrier that restrains the side reaction at the electrode/electrolyte interface at high voltage.⁷ In this report, we construct the ionic/electronic 3D conductive framework to enhance the comprehensive performance of LiVPO₄F. As shown in the schematic diagram (Fig. 1), in this ideal architecture, the nano Li₃PO₄ are dispersed in the space of thin graphene layers, and the LiVPO₄F particles are well wrapped by graphene. We expect the Li₃PO₄ and graphene co-coated LiVPO4F to deliver impressive electrochemical performance, including superior cycle performance, good rate capability, and high initial coulombic efficiency.

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