Abstract
High-entropy oxides (HEOs) and medium-entropy oxides (MEOs) are new types of single-phase solid solution materials. MEOs have rarely been reported as positive electrode material for sodium-ion batteries (SIBs). In this study, we first proposed the concept of the application of MEOs in SIBs. P2-type 3-cation oxide Na2/3Ni1/3Mn1/3Fe1/3O2 (NaNMF) and 4-cation oxide Na2/3Ni1/3Mn1/3Fe1/3−xAlxO2 (NaNMFA) were prepared using the solid-state method, rather than the doping technology. In addition, the importance of the concept of entropy stabilization in material performance and battery cycling was demonstrated by testing 3-cation (NaNMF) and 4-cation (NaNMFA) oxides in the same system. Thus, NaNMFA can provide a reversible capacity of about 125.6 mAh·g−1 in the voltage range of 2–4.2 V, and has enhanced cycle stability. The capacity and decay law of the MEO batteries indicate that the configurational entropy (1.28 R (NaNMFA) > 1.10 R (NaNMF)) of the cationic system, is the main factor affecting the structural and cycle stability of the electrode material. This work emphasizes that the rational design of MEOs with novel structures and different electrochemically active elements may be the strategy for exploring high-performance SIB cathode materials in next-generation energy storage devices.
Highlights
IntroductionWith the depletion of fossil fuels worldwide and the increasing energy demand, the development of humans in various fields, such as housing, industry,
With the depletion of fossil fuels worldwide and the increasing energy demand, the development of humans in various fields, such as housing, industry, www.springer.com/journal/40145J Adv Ceram 2022, 11(1): 158–171Various positive electrode materials for sodium-ion batteries (SIBs), such as Prussian blue analogs, polyanionic compounds, and layered transition metal (TM) oxides have been investigated
The electrochemical impedance spectroscopy (EIS; Solartron 1260+1287 Electrochemical Workstation, UK) and cyclic voltammetry were collected on a Solartron 1260 + 1287 electrochemical workstation in the same voltage range corresponded to the charge/discharge testing at a scan rate of 0.1 mV·s−1
Summary
With the depletion of fossil fuels worldwide and the increasing energy demand, the development of humans in various fields, such as housing, industry,. The capacity and voltage decay of P2-NaNM are fast when P2-NaNM is cycled at a high cut-off voltage of 4.4 V Such poor stability is due to the phase transition from P2 to O2 and the sliding of the TMO2 layer after Na extraction [21,22,23,24]. Compared with single metal oxides, high-entropy oxides (HEOs), as a new type of multi-component single-phase solid solution transition metal oxides (TMO), have higher electronic conductivity and various electrochemically active components [45,46]. HEOs involve introducing high configuration entropy to stabilize the single-phase structure Another interesting discovery in Breitung’s study is that Nay(Co0.2Cu0.2Mg0.2Ni0.2Zn0.2)OCly (designated as Na(HEO)–Cl) can be prepared, which inspires the study of high-entropy cathodes for SIBs [47]. Through the phase analysis and electrochemical test, it is considered that the prepared NaNMFA cathode has a broad application prospect in high-performance SIBs
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