O3-type Ni/Mn/Fe-based layered oxides are very promising cathode materials for Na-ion batteries (SIBs) due to their high redox potential of Ni²⁺/Ni⁴⁺ and Jahn–Teller inactive centers (Ni²⁺, Fe³⁺, and Mn⁴⁺). However, their electrochemical performances are inferior for practical applications due to complex multi-phase transitions and structural instability at high voltages, Na⁺/vacancy ordering and transition-metal migration. Herein, we tailor a Li/Ti co-substituted high-entropy oxide (HEO)-Na_1.0Li_0.1Ni_0.3Fe_0.1Mn_0.25Ti_0.25O₂ (NFMTO) cathode material, which exhibits highly reversible O3–P3–OP2 phase transitions with enhanced structural stability. Accordingly, the HEO-NFMTO cathode retains 88% and 77% of its initial capacity after 200 and 400 cycles at 1C and 2C rates, respectively. The co-substitution strategy also enhances Na⁺-ion diffusivity, resulting in good rate performances of NFMTO (102.5 and 78 mA h g⁻¹ at 2C and 5C rates). A full Na-ion cell with an NFMTO cathode and hard carbon anode is fabricated, which retains 62% of its initial capacity even after 1000 cycles at 0.5C rate. The co-substitution strategy holds enormous potential for designing HEO cathode materials for practical SIBs.

中文翻译：

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具有可逆相变和优异电化学性能的钠离子电池高熵O3-Na1.0Li0.1Ni0.3Fe0.1Mn0.25Ti0.25O2正极

^{O3型Ni/Mn/Fe基层状氧化物由于其Ni 2+} /Ni ⁴⁺的高氧化还原电位和Jahn-Teller非活性中心（Ni ²⁺ , Fe ³⁺、Mn ⁴⁺ )。然而，由于复杂的多相转变和高电压下的结构不稳定、Na ⁺ /空位有序化和过渡金属迁移，它们的电化学性能在实际应用中较差。在此，我们定制了一种Li/Ti共取代高熵氧化物（HEO）-Na _1.0 Li _0.1 Ni _0.3 Fe _0.1 Mn _0.25 Ti _0.25 O ₂（NFMTO）正极材料，该材料表现出高度可逆的O3–P3–OP2相变具有增强的结构稳定性。因此，HEO-NFMTO 正极在 1C 和 2C 倍率下循环 200 次和 400 次后分别保留了 88% 和 77% 的初始容量。共取代策略还增强了Na ⁺离子扩散率，从而导致NFMTO具有良好的倍率性能（2C和5C倍率下为102.5和78 mA hg ^-1 ）。制造了具有 NFMTO 阴极和硬碳阳极的全钠离子电池，即使在 0.5C 倍率下循环 1000 次后，其仍保留了 62% 的初始容量。共替代策略在为实际 SIB 设计 HEO 正极材料方面具有巨大潜力。