Using High-Entropy Configuration Strategy to Design Na-Ion Layered Oxide Cathodes with Superior Electrochemical Performance and Thermal Stability

Abstract

Na-ion layered oxide cathodes (Na x TMO 2 , TM = transition metal ion(s)), as an analogue of lithium layered oxide cathodes (such as LiCoO 2 , LiNi x Co y Mn 1−x−y O 2 ), have received growing attention with the development of Na-ion batteries. However, due to the larger Na + radius and stronger Na + −Na + electrostatic repulsion in NaO 2 slabs, some undesired phase transitions are observed in Na x TMO 2 . Herein, we report a high-entropy configuration strategy for Na x TMO 2 cathode materials, in which multicomponent TMO 2 slabs with enlarged interlayer spacing help strengthen the whole skeleton structure of layered oxides through mitigating Jahn−Teller distortion, Na + /vacancy ordering, and lattice parameter changes. The strengthened skeleton structure with a modulated particle morphology dramatically improves the Na + transport kinetics and suppresses intragranular fatigue cracks and TM dissolution, thus leading to highly improved performances. Furthermore, the elaborate high-entropy TMO 2 slabs enhance the TM−O bonding energy to restrain oxygen release and thermal runaway, benefiting for the improvement of thermal safety.

Homeostatic Solid Solution in Layered Transition-Metal Oxide Cathodes of Sodium-Ion Batteries

“…1−4 This is more evident with the extraction and insertion of large-sized Na + from and into the cathode materials to induce inferior structure rearrangement and mechanical degradation. 5,6 Simultaneously, the large lattice distortion impacts the electronic structure and redox reactions of transition-metal (TM) ions. 7 These dictate the electrochemical behaviors of electrode materials.…”

“…Two-phase transformation is a quite common phenomenon in electrochemical reactions of electrode materials. It usually involves additional kinetic barriers for initiation of a new phase and its boundary propagation. − This is more evident with the extraction and insertion of large-sized Na + from and into the cathode materials to induce inferior structure rearrangement and mechanical degradation. , Simultaneously, the large lattice distortion impacts the electronic structure and redox reactions of transition-metal (TM) ions . These dictate the electrochemical behaviors of electrode materials.…”

Strong Anionic Repulsion for Fast Na Kinetics in P2‐Type Layered Oxides

“…Significantly, the average interlayer distance of NTMNO calculated from the operando synchrotron XRD patterns was larger (5.64 Å) than that of NMNO (5.57 Å), which allowed a wider Na + diffusion pathway during the (de)sodiation and enhanced Na + kinetics and diffusivity during the cycling. [ 43 ] Figure 4j displays the cycle performances of NTMNO and NMNO at 0.5 and 3 C. In line with the superior rate capability of NTMNO, the cycle fading became relatively low as the C‐rate increased from 0.5 C to 3 C during the cycling. In contrast, NMNO experienced drastic capacity fading under the same conditions.…”

High‐entropy oxide: A future anode contender for lithium‐ion battery

“…28 Similar conceptions could even be generalized to sodium-ion batteries. [29][30][31] Also, Al has been deployed as a structural pillar, 32 as Al substitution is found to pronouncedly alleviate the structural deformation of the cathode material under deep charged state. 33 It is worth mentioning that the retention of spinel framework was also observed in (FeCoNiCrMn) 3 O 4 without inert elements.…”