Dual Modification of P3-Type Layered Cathodes to Achieve High Capacity and Long Cyclability for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) have garnered extensive attentions in recent years as a low-cost alternative to lithium-ion batteries. However, achieving both high capacity and long cyclability in cathode materials remains a challenge for SIB commercialization. P3-type Na0.67Ni0.33Mn0.67O2 cathodes exhibit high capacity and prominent Na+ diffusion kinetics but suffer from serious capacity decay and structural deterioration due to stress accumulation and phase transformations upon cycling. In this work, a dual modification strategy with both morphology control and element doping is applied to modify the structure and optimize the properties of the P3-type Na0.67Ni0.33Mn0.67O2 cathode. The modified Na0.67Ni0.26Cu0.07Mn0.67O2 layered cathode with hollow porous microrod structure exhibits an excellent reversible capacity of 167.5 mAh g-1 at 150 mA g-1 and maintains a capacity above 95 mAh g-1 after 300 cycles at 750 mA g-1. For one thing, the specific morphology shortens the Na+ diffusion pathway and releases stress during cycling, leading to excellent rate performance and high cyclability. For another, Cu doping at the Ni site reduces the Na+ diffusion energy barrier and mitigates unfavorable phase transitions. This work demonstrates that the electrochemical performance of P3-type cathodes can be significantly improved by applying a dual modification strategy, resulting in reduced stress accumulation and optimized Na+ migration behavior for high-performance SIBs.

Air-Stable and High-Voltage Layered P3-Type Cathode for Sodium-Ion Full Battery.

The development of highly efficient and stable cathodes for sodium-ion batteries (SIBs) is strategically critical to achieving large-scale electrical energy storage. Creating air-stable and high-voltage layered cathodes for sodium-ion full batteries still remains a challenge. Herein, we describe a rational design and preparation of a stable P3-Na2/3Ni1/4Mg1/12Mn2/3O2 cathode. The cathode displays a satisfactory working voltage of 3.6 V and excellent cyclic stability over 100 cycles at a 1 C rate without obvious capacity fading. The results of ex situ X-ray diffraction (XRD) demonstrate that the P3-type structure is well retained even when charged to 4.4 V. Furthermore, the structural characterization by XRD Rietveld refinement, scanning electron microscopy, and electrochemical testing certifies that the cathode maintains its structure commendably even when soaked in water for 12 h. In particular, the P3- Na2/3Ni1/4Mg1/12Mn2/3O2∥hard carbon full battery exhibits a desired competitively high voltage of 3.45 V and an attractive energy density of up to 412.2 W h kg-1 based on the cathode. The comprehensive results achieved by the specially designed strategy provide guidance toward the exploration of stable cathodes in the application of SIBs as modern energy-storage devices.