Entropy Stabilization Effect and Oxygen Vacancies Enabling Spinel Oxide Highly Reversible Lithium-Ion Storage

Abstract

High-entropy materials are an emerging kind of solid-solution material, demonstrating various exotic physicochemical properties, that have led to increased research activity as electrode materials for rechargeable batteries. Here, a kind of high-entropy spinel oxide, (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)3O4 (CCFMNO), was successfully fabricated via a solution combustion method. Due to the entropy stabilization effect and the intrinsic high mechanical strength of CCFMNO, an excellent cycling stability can be achieved. In addition, the fruitful oxygen vacancies in CCFMNO increase extra Li-ion accommodation sites, accelerating electronic conductivity and promoting Li-ion migration, thus enabling a high rate performance of 428 mAh g–1 at a high current density of 10 A g–1. More impressively, CCFMNO electrodes demonstrate excellent temperature adaptability with no capacity degeneration after 50 cycles at 0, 25, and 50 °C. Meanwhile, a full cell based on a CCFMNO anode and LiFePO4 cathode delivers an impressive high energy density of 372 Wh kg–1. All these impressive lithium storage performances strongly suggest that CCFMNO could be a promising anode material for lithium-ion batteries.

Kinetically Accelerated Lithium Storage in High‐Entropy (LiMgCoNiCuZn)O Enabled By Oxygen Vacancies

“…[ 34 ] The O 1s fine scan spectra (Figure 3d) can be fitted with three Gaussian peaks: lattice oxygen, defective oxygen, and adsorbed oxygen. [ 35 ] As expected, Li‐MO has a higher proportion of defective oxygen. Besides, the adsorbed oxygen peaks show noticeable shifts between MO and Li‐MO.…”

High-Entropy Sn0.8(Co0.2Mg0.2Mn0.2Ni0.2Zn0.2)2.2O4 Conversion-Alloying Anode Material for Li-Ion Cells: Altered Lithium Storage Mechanism, Activation of Mg, and Origins of the Improved Cycling Stability

“…According to the XPS data, the oxidation states of all other cations in the material are +2, except for Mn 3+ . Also, based on the fitted O 1s spectrum, it can be stated that the content of oxygen vacancies (at least on the surface) is rather negligible, contrary to some of the other high-entropy spinels. ,, Additionally, we conducted synchrotron-based XAS measurements. X-ray absorption near-edge structure (XANES) spectra for the Mg K-edge and Mn, Co, Ni, Zn L 3 -, and L 2 -edges collected in PFY mode are presented in Figure f, together with the reference spectra for single oxides.…”

Charge–Discharge Mechanism of High‐Entropy Co‐Free Spinel Oxide Toward Li+ Storage Examined Using Operando Quick‐Scanning X‐Ray Absorption Spectroscopy

“…[ 14 , 15 ] The entropy‐derived phase stabilization effects can improve electrode reversibility and cycleability. [ 16 , 17 , 18 ] Moreover, the HEO lattice is distorted due to the different sizes of the constituent atoms, which creates a lattice residual stress that can alter material properties. [ 19 ] Rock‐salt‐structure HEO anodes have been proposed since 2018.…”

“…[ 16 ] Recently, spinel‐structure HEOs have attracted much attention because of their two Wyckoff sites and abundant oxygen vacancies, which are favorable for reversible Li + storage. [ 17 , 22 , 23 ] A spinel (CrMnFeCoNi) 3 O 4 anode synthesized via a surfactant‐assisted hydrothermal method was found to have a great charge–discharge capacity of 1235 mAh g −1 and 90% capacity retention after 200 cycles. [ 22 ] It is worth noting that most of the reported HEO anodes include cobalt (Co), which provides high conductivity and ensures stable charge–discharge performance.…”