Abstract
Recently, high entropy oxides (HEO) with special stabilization effects have been widely investigated as new anode materials for lithium-ion batteries. However, the lithium storage mechanism of HEO is still under debate. In this work, we applied a modified solution combustion synthesis method with a subsequent ball milling refinement process to prepare a six-component (FeNiCrMnMgAl)3O4 spinel high entropy oxide (6-SHEO). The novel 6-SHEO anode features outstanding electrochemical performance, enabling a stable capacity of 657 mAh g−1 at a current rate of 0.2 A g−1 after 200 cycles, and good high-rate capability with 350 mAh g−1 even at 4 A g−1. In addition, the lithium storage behavior of this 6-SHEO anode was explored in detail through in-situ XRD and ex-situ TEM approaches. Surprisingly, a reversible spinel to rock salt phase transition behavior and spinel phase residue phenomenon was firstly observed by this route. Furthermore, for better understanding of the phase change behavior in this 6-SHEO anode, a high-energy ball milling approach was applied to induce a similar spinel to rock salt phase transformation for the first time, which generates fresh insight into the mechanism of the phase change behavior in this 6-SHEO anode.
Highlights
As a key component of lithium-ion batteries, studies focused on anode materials have received much attention
Different from the above work, Nguyen et al observed a rock salt phase formation in (FeCoNiCrMn)3 O4 SHEO during the first discharge process [13]. In their ex-situ X-ray diffraction (XRD) work, the observation of the crystalline Li2 O phase is contrary to the shared understanding because the Li2 O generated during conversion reaction in transition metal oxide (TMO) should be amorphous and prone to react with CO2 in the air to form
It should be noted that the presence of Mn and Cr6+ may originate from oxidation caused by the solution combustion process at high temperatures under the air the oxidation caused by the solution combustion process at high temperatures under the atmosphere
Summary
As a key component of lithium-ion batteries, studies focused on anode materials have received much attention. The high configuration entropy induced phase stabilization effect can promote the microscopic mechanical properties of electrodes, resulting in good structure stability while reacting with lithium [8] All these advantages make it a promising next-generation anode material for lithium-ion batteries. Different from the above work, Nguyen et al observed a rock salt phase formation in (FeCoNiCrMn) O4 SHEO during the first discharge process [13] In their ex-situ XRD work, the observation of the crystalline Li2 O phase is contrary to the shared understanding because the Li2 O generated during conversion reaction in transition metal oxide (TMO) should be amorphous and prone to react with CO2 in the air to form. 6-SHEO anode, which is highly instructive for investigating the lithium storage behaviors of SHEO anode
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