Abstract

Average discharge voltage of the P-type-layered oxides cathode materials is one of the key factors that determine the sodium-ion batteries (SIBs) performance, especially for the high energy density performance. Inspired by the strategy of lithium and magnesium doping in the transition metal layer to promote the anionic oxygen redox and the synergistic effect of composite materials for SIBs, we develop a layered P2/P3-Na_0.75Li_0.2Mg_0.05Al_0.05Mn_0.7O₂ composite cathode material enabled by the anionic oxygen redox. The synthesized composite delivers a reversible capacity of 180 mAh g⁻¹ between 2.0 and 4.5 V at 0.2 C and keep ≈ 3.1 V stable average voltage above 2.5 V the discharge cutoff voltage. With a combination of the electrochemical performance, hard and soft X-ray absorption spectroscopy, we demonstrate that the irreversible anionic oxygen activity in the high-voltage region results in the capacity fading and the irreversible cationic manganese activity in the low-voltage region is responsible for the voltage decay. These findings provide a simple and effective method for designing low-voltage decay and high-energy density Na-deficient layered oxide composite.

Graphic abstract

中文翻译：

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用于钠离子电池的具有低电压衰减的P2 / P3复合层状阴极材料

摘要

P型层氧化物阴极材料的平均放电电压是决定钠离子电池（SIB）性能（特别是对于高能量密度性能而言）的关键因素之一。受过渡金属层中锂和镁掺杂促进阴离子氧氧化还原的策略以及SIBs复合材料的协同作用的启发，我们开发了一种层状P2 / P3-Na _0.75 Li _0.2 Mg _0.05 Al _0.05 Mn _0.7 O ₂复合阴极材料可通过阴离子氧还原来实现。合成的复合材料的可逆容量为180 mAh g ^-1在0.2 C时为2.0至4.5 V之间的电压，并保持≈3.1 V的稳定平均电压高于2.5 V的放电截止电压。结合电化学性能，硬和软X射线吸收光谱，我们证明了高压区域中不可逆的阴离子氧活性导致容量衰减，而低压区域中不可逆的阳离子锰活性是负责任的对于电压衰减。这些发现为设计低电压衰减和高能量密度的缺Na层状氧化物复合材料提供了一种简单有效的方法。

图形摘要