通过调节 Na/Mn 反位缺陷触发 O3 型阴极中的可逆阴离子氧化还原化学,Energy & Environmental Science

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通过调节 Na/Mn 反位缺陷触发 O3 型阴极中的可逆阴离子氧化还原化学
Energy & Environmental Science ( IF 32.4 ) Pub Date : 2023-01-04 , DOI: 10.1039/d2ee03874a
Yang Yu _{1,

2} , Jicheng Zhang ₁ , Rui Gao ₁ , Deniz Wong ₃ , Ke An ₄ , Lirong Zheng ₅ , Nian Zhang ₆ , Christian Schulz ₃ , Xiangfeng Liu _{1,

2}

Affiliation

氧阴离子氧化还原 (OAR) 在钠离子电池中氧化物正极的容量和稳定性中起着至关重要的作用，但对其内在机制知之甚少。如何触发和稳定 OAR 具有挑战性，特别是对于 O3 型过渡金属 (TM) 氧化物阴极。在此，我们阐明了 Na/Mn 反位缺陷主要触发 O3-NaMn _1/3 Fe _1/3 Ni _1/3 O ₂正极中的 OAR，并且可以通过调节 Na/Mn 反位缺陷来增强 OAR 活性和可逆性Ho掺杂的位点缺陷。用Ho ³⁺取代Fe ³⁺位置会促进更多的Na/Mn反位缺陷，使更多的O孤对电子参与电荷补偿。同时，Ho ³⁺^{扩大了O-O键和∠O-TM-O角，维持了(O −} )-TM-(O ⁻ )的单电子氧空穴构型，抑制了O-O因电子损失而缩短，避免形成(O ₂ ) ²⁻二聚体。此外，Ho ^{3+诱导费米能级以上的TM 3d轨道能带分裂，产生Mn e}_g *和Ni e _g *的低能轨道，促进O孤对电子和Ni e _g *的跃迁轨道电子，同时激活阴离子和阳离子的氧化还原活性。调节后，容量从146.8增加到184.9 mA hg ^-1容量保留率从 40.3% 提高到 90.0%。这项研究揭示了 O3 型阴极中的 OAR 机制，并提出了如何触发和稳定 OAR 的见解。

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Triggering reversible anion redox chemistry in O3-type cathodes by tuning Na/Mn anti-site defects

Oxygen anion redox (OAR) plays a crucial role in the capacity and stability of oxide cathodes in sodium-ion batteries but the intrinsic mechanism is poorly understood. How to trigger and stabilize OAR is challenging, particularly for O3-type transition metal (TM) oxide cathodes. Herein, we clarify that Na/Mn anti-site defects mainly trigger OAR in the O3-NaMn_1/3Fe_1/3Ni_1/3O₂ cathode, and OAR activity and reversibility can be enhanced by tuning Na/Mn anti-site defects with Ho doping. Replacing the Fe³⁺ site by Ho³⁺ promotes more Na/Mn anti-site defects, enabling more O lone-pair electrons to participate in charge compensation. Meanwhile, Ho³⁺ enlarges the O–O bond and ∠O–TM–O angle, and maintains the single-electron oxygen hole configuration of (O⁻)–TM–(O⁻) and inhibits O–O shortening caused by electron loss, avoiding forming an (O₂)²⁻ dimer. Furthermore, Ho³⁺ induces the splitting of the TM 3d orbital energy band above the Fermi level and generates low energy orbitals of Mn e_g* and Ni e_g*, which promotes the transition of O lone-pair electrons and Ni e_g* orbital electrons, and simultaneously activates the redox activity of anions and cations. After regulation, the capacity increases from 146.8 to 184.9 mA h g⁻¹ and the capacity retention increases from 40.3 to 90.0%. This study reveals the OAR mechanism in the O3-type cathode and presents insights into how to trigger and stabilize OAR.

更新日期：2023-01-04

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