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Insights into P2-Type Layered Positive Electrodes for Sodium Batteries: From Long- to Short-Range Order.
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2020-01-15 , DOI: 10.1021/acsami.9b18109 Jun Wang 1 , Dong Zhou 2 , Xin He 3 , Li Zhang 2 , Xia Cao 1 , De Ning 2 , Bo Yan 3 , Xin Qi 1 , Jinke Li 3 , Vadim Murzin 4, 5 , Elie Paillard 3 , Xinzhi Liu 6 , Gerhard Schumacher 2 , Martin Winter 1, 3 , Jie Li 1
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2020-01-15 , DOI: 10.1021/acsami.9b18109 Jun Wang 1 , Dong Zhou 2 , Xin He 3 , Li Zhang 2 , Xia Cao 1 , De Ning 2 , Bo Yan 3 , Xin Qi 1 , Jinke Li 3 , Vadim Murzin 4, 5 , Elie Paillard 3 , Xinzhi Liu 6 , Gerhard Schumacher 2 , Martin Winter 1, 3 , Jie Li 1
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P2-type Fe- and Mn-based layered sodium transition metal oxides are promising positive electrode materials for sodium batteries due to their high energy density and low costs of the constituting transition metals. However, poor structural reversibility and fast capacity decay have prevented their breakthrough so far. Herein, the real-time dynamic phase transitions and capacity fading mechanism of the P2 Na0.67Fe0.5Mn0.5O2 positive electrode are revealed by operando X-ray diffraction, operando/ex situ X-ray absorption spectroscopy, neutron powder diffraction, and neutron pair distribution functions. Upon the desodiation process, a layered OP4 phase with long-range order is found as an intermediate state. With further deep desodiation, the formation of a Na-depleted ramsdellite phase with a short coherent length of 30 Å is observed for the first time. However, the transition from OP4 to ramsdellite is considered to be irreversible due to the breakdown of the layered structural characteristics, resulting in poor cycling performance in a variety of Fe-based layered sodium transition metal oxides. This work suggests that stabilizing the crystal structure by substitution or chemical modification can be a favorable strategy to avoid the degradation of positive electrodes and thus to improve the cycling performance.
中文翻译：
钠电池P2型分层正极的见解：从长到短顺序。
P 2型铁和锰基层状钠过渡金属氧化物由于其高能量密度和构成过渡金属的低成本而成为有前途的钠电池正极材料。但是，到目前为止，结构不良的可逆性和快速的容量衰减都阻止了它们的突破。本文通过操作X射线衍射，操作/非原位X射线吸收光谱，中子粉末衍射和中子揭示了P2 Na0.67Fe0.5Mn0.5O2正极的实时动态相变和容量衰减机理。对分布函数。在脱硝过程中，发现具有长程有序的分层OP4相为中间状态。随着进一步的深入灭绝，首次观察到短相干长度为30的缺钠斜方锰矿相的形成。然而，由于层状结构特征的破坏，认为从OP4到斜方锰矿的转变是不可逆的，从而导致在多种Fe基层状钠过渡金属氧化物中循环性能差。这项工作表明，通过取代或化学修饰来稳定晶体结构可能是避免正极降解从而改善循环性能的一种有利策略。
更新日期：2020-01-16
中文翻译：
钠电池P2型分层正极的见解：从长到短顺序。
P 2型铁和锰基层状钠过渡金属氧化物由于其高能量密度和构成过渡金属的低成本而成为有前途的钠电池正极材料。但是，到目前为止，结构不良的可逆性和快速的容量衰减都阻止了它们的突破。本文通过操作X射线衍射，操作/非原位X射线吸收光谱，中子粉末衍射和中子揭示了P2 Na0.67Fe0.5Mn0.5O2正极的实时动态相变和容量衰减机理。对分布函数。在脱硝过程中，发现具有长程有序的分层OP4相为中间状态。随着进一步的深入灭绝，首次观察到短相干长度为30的缺钠斜方锰矿相的形成。然而，由于层状结构特征的破坏，认为从OP4到斜方锰矿的转变是不可逆的，从而导致在多种Fe基层状钠过渡金属氧化物中循环性能差。这项工作表明，通过取代或化学修饰来稳定晶体结构可能是避免正极降解从而改善循环性能的一种有利策略。
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