Na⁺-Activation Engineering in the Na₃V₂(PO₄)₃ Cathode with Boosting Kinetics for Fast-Charging Na-Ion Batteries

Abstract

Na superionic conductor-structured phosphates have attracted wide interest due to their high working voltage and fast Na+ migration facilitated by the robust 3D open framework. However, they usually suffer from low-rate capability and inferior cycling stability due to the low intrinsic electronic conductivity and limited activated Na+ ions. Herein, a doping protocol with Na+ in the V3+ site is developed to activate extra electrochemical Na+ ions and expand the migration path of Na+, leading to the improvement of the electronic conductivity and diffusion kinetics. It is also disclosed that the generated stronger Na–O bonds with high ionicity significantly conduce to the enhanced structural stability in the Na+-substituted Na3.05V1.975Na0.025(PO4)3/C cathode. The obtained composite can deliver an excellent rate capacity of 83.8 mA h g–1 at 20 C and a moderate cycling persistence of 91.3% over 1500 cycles at 10 C with great fast-charging properties. The reversible structure evolution is confirmed by the ex situ XRD, XPS, and ICP characterization. This work sheds light on awakening electroactive Na+ ions and designing phosphates with superior electrochemical stability for practical Na-ion batteries.

In Situ Constructing Ultrafast Ion Channel for Promoting High-Rate Cycle Stability of Nano-Na3V2(PO4)3 Cathode

“…The finding indicates that the carbon channel construction strategy has certain significance in synchronously achieving the rate capacity and high-rate durability. 27,38,39 In situ XRD characterization and ex situ XPS analysis are powerful characterization techniques to investigate the role of the carbon channel in the Na + storage mechanism of sodium batteries. In situ XRD tests are performed with a sampling interval of 10 min for the first cycle at a current rate of 0.5 C. The whole pattern covering the entire range is shown in Figure S20.…”

Pore-forming mechanisms and sodium-ion-storage performances in a porous Na3V2(PO4)3/C composite cathode

“…It is well known that Na + ions in the NVP lattice undergo extraction and insertion reactions during battery charging and discharging processes. 52,53 The volume of the NVP lattice also shrinks and expands along with these reactions, which further induces stress inside the lattice. Owing to the lack of buffer space for volume expansion, the stress generated inside the dense bulk NVP/C material will be concentrated and then can cause permanent damage to the NVP.…”

A zero-strain Na-deficient NASICON-type Na2.8Mn0.4V1.0Ti0.6(PO4)3 cathode for wide-temperature rechargeable Na-ion batteries

“…In addition, a tiny reduction peak (3.28 V) in the MVT-D curve indicates the disordered arrangement of Na + ions, which is also observed in other similar NASICON-type cathodes. 16,56 The reduction peak centered at 2.15 V represents the Ti 4+ /Ti 3+ reaction upon discharging, which could be maintained through the rest of the cycles. The average charging voltage increases with the introduction of Mn 2+ , while the reversibility of the reaction gradually decreases due to the structural evolution of Mn ions, which is in good accordance with the ICE values.…”

“…[10][11][12][13][14] To enrich the competitiveness of cost and performance for NASICON cathodes, plentiful explorations dedicated to low V compositions were utilized, with the introduction of electrochemically inert or active transition elements. [15][16][17][18] Substitution of an electrochemically inactive metal oen contributes to improved structural stability and triggers the potential redox of transition metals to activate the excess Na + de-intercalation. For example, the introduction of Mg 2+ not only helps increase the electrochemically active Na + content but also stabilizes the crystal structure, which facilitates surface reaction during the charging/discharging process.…”