Synthesizing Porous NaTi2(PO4)3 Nanoparticles Embedded in 3D Graphene Networks for High-Rate and Long Cycle-Life Sodium Electrodes

Sodium ion batteries attract increasing attention for large-scale energy storage as a promising alternative to the lithium counterparts in view of low cost and abundant sodium source. However, the large ion radius of Na brings about.a series of challenging thermodynamic and kinetic difficulties to the electrodes for sodiumstorage, including low reversible capacity and low ion transport, as well as large volume change. To mitigate or even overcome the kinetic problems, we develop a self-assembly route to a novel architecture consisting of nanosized porous NASICON-type NaTi2(PO4)(3) particles embedded in microsized 3D graphene network. Such architecture synergistically combines the advantages of a 3D graphene network and of OD porous nanoparticles. It greatly increases the electron/ion transport kinetics and assures the electrode structure integrity, leading to attractive electrochemical performance as reflected by a high rate-capability (112 mAh g(-1) at 1C, 105 mAh g(-1) at 5C, 96 mAh g(-1) at 10C, 67 mAh g(-1) at 50C), a long cycle-life (capacity retention of 80% after 1000 cycles at 10C), and a high initial Coulombic efficiency (>79%). This nanostructure design provides a promising pathway for developing high performance NASICON-type materials for sodium storage.