Synthesis of micro-nano hierarchical structured LiFePO4/C composite with both superior high-rate performance and high tap density

Abstract

Efforts were made to synthesize LiFePO₄/C composites showing both high rate capability and high tap density. First, monoclinic phase FePO₄·2H₂O with micro-nano hierarchical structures are synthesized using a hydrothermal method, which are then lithiated to LiFePO₄/C also with hierarchical structures by a simple rheological phase method. The primary structures of FePO₄·2H₂O are nanoplates with ∼30 nm thickness, and the secondary structures of the materials are intertwisted micro-scale rings. The LiFePO₄/C materials lithiated from these specially structured precursors also have hierarchical structures, showing discharge capacities of more than 120, 110, and 90 mAh g⁻¹ at rates of 5 C, 10 C and 20 C, respectively, and high tap density of 1.4 g cm⁻³ as cathode materials for lithium ion batteries. Since tap density is an important factor that needs to be considered in fabricating real batteries in industry, these hierarchical structured LiFePO₄/C moves closer to real and large-scale applications.