Regulating the Electron Structure of Covalent Organic Frameworks by Strong Electron-Withdrawing Nitro to Construct Specific Li+ Oriented Channel,Advanced Energy Materials

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Regulating the Electron Structure of Covalent Organic Frameworks by Strong Electron-Withdrawing Nitro to Construct Specific Li+ Oriented Channel
Advanced Energy Materials ( IF 24.4 ) Pub Date : 2023-05-26 , DOI: 10.1002/aenm.202300725
Yongxin Yang ₁ , Conghui Zhang ₁ , Genfu Zhao ₁ , Qi An ₁ , Zhi‐yuan Mei ₁ , Yongjiang Sun ₁ , Qijun Xu ₁ , Xiaofeng Wang ₁ , Hong Guo ₁

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The growth of disordered lithium dendrite and the notorious reaction between Li and electrolyte hamper the practical application of Li metal batteries (LMBs). Herein, an artificial solid electrolyte interphase (ASEI) constructed by a nitro-functionalized covalent organic framework (NO₂-COF) is designed to regulate Li⁺ deposition and stable Li anodes. Strong electron-withdrawing nitro groups can gather the surrounding electrons of connected monomer by the donor-acceptor (D-A) effect, thus regulating the electron structure of the covalent organic framework (COF) and constructing a specific cation-oriented channel. The uniform Li⁺ deposition and inhibition of Li dendrites are achieved under such a high-selective Li⁺ transportation channel and regulated surface electric charge. In addition, the nitro can also be reduced to NO₂⁻ and further react with Li to produce high ionic-conductivity Li₃N and LiN_xO_y during the charging/discharging, which contributes to the migration of Li⁺. As a result, NO₂-COF-modified symmetrical batteries realize an ultra-long cycling life of more than 6000 h under a current density of 5 mA cm⁻² compared to bare Li and TpBD-COF/Li (without nitro). The full cells coupled with LiFePO₄ stably cycle 1000 times with a capacity retention of 91%. Hence, effectively optimizing electron structure by the donor-acceptor (D-A) effect provides a better platform to elevate the performance of LMB.

中文翻译：

强吸电子硝基调节共价有机骨架的电子结构构建特定的Li+取向通道

无序锂枝晶的生长以及锂与电解质之间臭名昭著的反应阻碍了锂金属电池（LMB）的实际应用。_{在此，由硝基功能化共价有机框架（NO 2} -COF ）构建的人造固体电解质中间相（ASEI）被设计用于调节Li ⁺沉积和稳定的Li阳极。强吸电子硝基可以通过供体-受体（DA）效应聚集连接单体周围的电子，从而调节共价有机骨架（COF）的电子结构并构建特定的阳离子导向通道。在这种高选择性的Li ^{+作用下，实现了Li}⁺的均匀沉积和Li枝晶的抑制运输通道和调节表面电荷。此外，硝基在充放电过程中还可被还原为NO ₂^-并进一步与Li反应生成高离子电导率的Li ₃ N和LiN _x O _y^{，从而有助于Li +}的迁移。结果，与裸锂和TpBD-COF/Li（不含硝基）相比， NO _{2 -COF修饰的对称电池在5 mA cm}^-2的电流密度下实现了超过6000小时的超长循环寿命。_{与 LiFePO 4}耦合的全电池稳定循环1000次，容量保持率91%。因此，通过供体-受体（DA）效应有效优化电子结构为提升LMB的性能提供了更好的平台。

更新日期：2023-05-26

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