基于MOFs原位转化的纳米级Se@y-C多孔复合材料可控构筑及其高效储锂性能研究

Li-Se battery is one of the most promising novel battery system, due to its ultra-high energy storage capacity. However, the large volume expansion, solubility of polyselenide intermediate and poor electronic/ionic transportation of Se have greatly hindered the cycling performance and rate capability of Li-Se battery. Herein, we propose a novel strategy to construct nano Se@y-C hybrid material that based on MOFs in-situ transformation, which features high electrochemical performance. In the resultant sample, nano Se is confined in the pores of the in-situ formed heteroatom-doped carbon layers. Superiorities of the nano Se@y-C are as following: the in-situ formed carbon layers can effectively prevent the aggregation of nano Se and accommodate its volume change, help to maintain its structural stability; heteroatom-doping can not only enhance the electronic/ionic conductivity of electrode, but also improve the interaction between Se and carbon layers. Mechanism of improved electrochemical performance of the nano Se@y-C hybrid is also studied, which focused on the synergistic effect of nano effect and carbon coating, influence mechanism of the heteratom-doping. The implementation of this project can provide important reference for the construction of electrode that shows high capacity, long cycling performance and excellent rate capability.

Li-Se电池具有超高的储能容量是极具研究意义的新型电池体系，但在充放电过程中Se易出现体积变化明显、多硒化物中间体脱落、电子/离子传导性较差等问题，导致其循环寿命和倍率性能不理想，限制了Li-Se电池的发展。本项目拟采用MOFs原位转化的策略构筑高性能纳米级Se@y-C多孔复合材料，产物中Se选择性的限域在碳孔径内避免表面吸附Se的存在。其优势如下：原位生成的碳基体可有效防止纳米Se的团聚和缓解充放电中Se的体积变化对电极结构的破坏，提高其循环寿命；异原子的引入能增强电极的电子/离子传导性和Se‒碳间作用力，改善其倍率性能。我们将深入研究纳米级Se@y-C多孔复合材料的高效储锂性能，阐明纳米效应及碳包覆对其性能提高的协同作用，明确异原子掺杂对Se电极的影响机理和作用规律。本项目的实施可为构筑高容量、长寿命、优倍率性能的电极提供重要借鉴。

Li-Se电池具有超高的储能容量是极具研究意义的新型电池体系，但充放电中Se的体积变化明显、多硒化物中间体易脱落且电子传导性不理想等问题直接影响了其循环稳定性和倍率性能，限制了Li-Se电池的发展。本项目采用MOFs原位转化的策略构筑了高性能的纳米级Se@异原子掺杂碳（Se@y-C）多孔复合材料，其中纳米Se被全部包裹在原位生成的氮原子掺杂碳孔径内，优势如下：原位生成的碳基体可有效防止纳米Se的团聚和缓解充放电中Se的体积变化对电极结构的破坏，提高其循环寿命；异原子的引入能增强电极的电子/离子传导性和Se‒碳间作用力，改善其倍率性能。研究表明以该方法制备的Se@void@NC材料作为电极组装的半电池在10A/g的电流密度下经4000圈循环后仍能保持324mAh/g的超高比容量。本项目的实施可为构筑高容量、长寿命、优倍率性能的电极材料提供重要借鉴。

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