Crystal Facet Design in Layered Oxide Cathode Enables Low-Temperature Sodium-Ion Batteries

Abstract

Layered transition metal oxides (LTMOs) have been identified as promising cathodes for alkali metal-ion batteries. However, their low-temperature performance is generally restricted by the sluggish ion diffusion kinetics within the LTMOs' host. Nanostructured materials have been developed to enhance ion diffusion kinetics but often significantly reduce the tap density. Herein, using NaCrO 2 as a model cathode material, from the aspect of crystallography, we report a large-sized monocrystalline NaCrO 2 with abundant Na + active facets exposed by a straightforward acetate-assisted solid-state reaction, which addresses the dilemma between the volumetric energy density and ion diffusion kinetics and enables excellent lowtemperature performance. Specifically, the synthesized NaCrO 2 cathode showcases a high specific capacity of 94.7 mAh g −1 at a high rate of 20C under room temperature and displays good capacity retention of 97.2% after 100 cycles at 1C under −20 °C. Additionally, the full-cell device demonstrates a remarkable initial capacity of 113.0 mAh g −1 at a rate of 0.1C and exhibits excellent cyclic performance, retaining 84.2% of its capacity after 100 cycles at 0.2C under −10 °C. This study opens up new possibilities to design LTMOs with improved ion diffusion kinetics for alkali metalion batteries.

Boosting the electrochemical performance and moisture stability of O3-type NaNi1/3Fe1/3Mn1/3O2 cathodes using novel Na2MoO4 coatings prepared via a polyvinylpyrrolidone-anchored complex coating process

“…During the charge and discharge cycles, the structure of the O3-type NaTMO 2 cathode material may gradually collapse or undergo phase transitions due to the insertion and extraction of sodium ions. 51,52 This can affect the ionicity of the TM–O bond and the overall electrochemical performance of the material. 3,53–55 After 100 cycles at 0.1C, the average discharge voltage of pristine NFM decreased significantly from 3.04 V to 2.71 V vs. Na/Na + (Δ V = 0.33 V).…”

Bismuth-doping boosting Na+ diffusion kinetics of layered oxide cathode with radially oriented {010} active lattice facet for sodium-ion batteries

“…To alleviate the problems, exposing sufficient {010} facets of primary particles is one effective way to provide additional ion transport channels for enhancing Na + diffusion kinetics. , A surfactant-assisted synthesis method was used to effectively promote inducing the growth of the exposed {010} active planes, by lowering the high surface energy of the {010} facets with the addition of surfactants of sodium dodecyl sulfate and polyvinylpyrrolidone. , A surfactant-free coprecipitation method was able to construct a porous and hollow architecture with exposed {010} facets. − Furthermore, rationally designing secondary microparticles assembled with primary nanoparticles is effective at improving diffusion kinetics by shorting the ion diffusion pathway. , However, the diffusion of Na + into the electrolyte is difficult as it entails crossing through multiple grain boundaries due to the random agglomeration of primary particles . In addition, the nanoparticles with large specific surface areas in secondary microparticles easily initiate surface parasitic reactions with electrolyte, accelerate the degradation of the cathode material, and thus result in capacity decay after long cycling. − Therefore, simultaneous combination of the oriented crystal facets and the nanoplatelet-containing microspheres could greatly enhance both the structural stability and Na + diffusion kinetics.…”

Air Stable O3-Type Cathode Material with Nanometer Size for Durable Low-Temperature Sodium-Ion Batteries

“…To overcome the above-mentioned shortcomings, many strategies have been introduced, such as cationic substitution, surface modification, gradient doping, and composition of multiple phases. − ,− Sb doping was employed in NaNi 0.5 Mn 0.5 O 2 to enhance structural stability and rate capability by adjusting chemical bonds and expending Na + transport channels . The optimized P3–OP2 phase transition together with negative lattice expansion was achieved to reduce volume variations in Na 0.9 Ni 0.4 Fe 0.1 Mn 0.5 O 2 through codoping of Zn 2+ and Ti 4+ , ultimately enabling an excellent cycling performance to pouch-type SIBs .…”