Although organic p-type cathode materials with high redox potential (>3.5 V vs. Li/Li⁺) are sustainable alternatives to transition metal oxide cathodes for lithium-ion batteries, only a limited number of these materials have been investigated to date. Therefore, the discovery of new p-type redox centers is essential for further development of successful organic cathodes. Herein, we report phenoxazine (PXZ) as a new p-type redox center for high-voltage cathode materials. Negligible structural reorganization of this PXZ center facilitates a kinetically faster electrochemical pathway, leading to a narrow voltage plateau, full utilization of the capacity, and superior rate capability in a new PXZ-based cathode material, PXZ trimer (3PXZ). The 3PXZ cathode delivered a specific capacity of 112 mA h g⁻¹ at 1C with a high average discharge voltage of 3.7 V vs. Li/Li⁺ in a Li-organic cell; moreover, even at a high rate of 20C, 73% capacity retention (76 mA h g⁻¹) was achieved. In addition, a 3PXZ composite with mesoporous carbon CMK-3 exhibited a capacity of 100 mA h g⁻¹ with high stability, losing only 0.044% capacity per cycle over 500 cycles at 5C. As 3PXZ outperforms most reported p-type cathodes in terms of both rate capability and stability, we suggest the adoption of the PXZ unit as a novel and promising redox center for high-performance and sustainable energy storage systems.

中文翻译：

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苯恶嗪作为有机电池正极材料的高压p型氧化还原中心：结构重组小，充电速度更快，工作电压更窄

尽管具有高氧化还原电势（> 3.5 V vs. Li / Li ⁺）的有机p型阴极材料是锂离子电池过渡金属氧化物阴极的可持续替代品，但迄今为止，仅对其中几种材料进行了研究。因此，发现新的p型氧化还原中心对于进一步开发成功的有机阴极至关重要。在本文中，我们报告了吩恶嗪（PXZ）作为高压阴极材料的新型p型氧化还原中心。该PXZ中心的结构重组可忽略不计，从而促进了动力学上更快的电化学途径，从而导致电压平台更窄，容量的充分利用以及新型PXZ的超高倍率性能阴极材料，PXZ三聚体（3PXZ）。所述3PXZ阴极递送112毫安Hg的比容量^-1在1C与3.7伏特的高平均放电电压与对于Li / Li ⁺在Li-有机细胞; 此外，即使在20℃的高速率下，也实现了73％的容量保持率（76mA hg ^-1）。另外，具有中孔碳CMK-3的3PXZ复合材料表现出100mA hg ^-1的容量和高稳定性，在5℃下500次循环中每循环仅损失0.044％。作为3PXZ在速率能力和稳定性方面都胜过大多数报道的p型阴极，我们建议采用PXZ单元作为高性能和可持续储能系统的新型且有希望的氧化还原中心。