Kapaev Roman R, Zhugayevych Andriy, Ryazantsev Sergey V, Aksyonov Dmitry A, Novichkov Daniil, Matveev Petr I, Stevenson Keith J
Center for Energy Science and Technology, Skolkovo Institute of Science and Technology Bolshoy Boulevard 30 bld. 1 Moscow 121205 Russia
Polymer Theory Department, Max Planck Institute for Polymer Research Ackermannweg 10 Mainz 55128 Germany.
Chem Sci. 2022 Jun 29;13(27):8161-8170. doi: 10.1039/d2sc03127b. eCollection 2022 Jul 13.
The demand for fast-charging metal-ion batteries underlines the importance of anodes that work at high currents with no risk of dendrite formation. NiBTA, a one-dimensional Ni-based polymer derived from benzenetetramine (BTA), is a recently proposed promising material for safe fast-charging batteries. However, its charge-discharge mechanisms remained unclear and controversial. Here we solve the controversies by providing the first rigorous study using a combination of advanced theoretical and experimental techniques, including and X-ray diffraction, Raman spectroscopy and X-ray absorption near-edge spectroscopy (XANES). In safe potential ranges (0.5-2.0 V M/M, M = Li, Na or K), NiBTA offers high capacities, fast charge-discharge kinetics, high cycling stability and compatibility with various cations (Li, Na, K). In the Na- and K-based cells, fast bulk faradaic processes are manifested for partially reduced states. Atomistic simulations explain the fast kinetics by facile rotations and displacements of the macromolecules in the crystal, opening channels for fast ion insertion. The material undergoes distinct crystal structure rearrangements in the Li-, Na- and K-based systems, which explains different electrochemical features. At the molecular level, the charge storage mechanism involves reversible two-electron reduction of the repeating units accompanied by a change of the absorption bandgap. The reversible reduction involves filling of the orbitals localized at the ligand moieties. No reduction of NiBTA beyond two electrons per repeating unit is observed at potentials down to 0 V M/M.
对快速充电金属离子电池的需求凸显了阳极在高电流下工作且无枝晶形成风险的重要性。NiBTA是一种由苯四胺（BTA）衍生而来的一维镍基聚合物，是最近提出的一种用于安全快速充电电池的有前景的材料。然而，其充放电机制仍不清楚且存在争议。在此，我们通过结合先进的理论和实验技术，包括X射线衍射、拉曼光谱和X射线吸收近边光谱（XANES）进行首次严谨研究，解决了这些争议。在安全电位范围（0.5 - 2.0 V M/M，M = Li、Na或K）内，NiBTA具有高容量、快速充放电动力学、高循环稳定性以及与各种阳离子（Li、Na、K）的兼容性。在基于Na和K的电池中，部分还原态表现出快速的体相法拉第过程。原子模拟通过晶体中大分子的轻松旋转和位移解释了快速动力学，为快速离子插入打开了通道。该材料在基于Li、Na和K的体系中经历了明显的晶体结构重排，这解释了不同的电化学特征。在分子水平上，电荷存储机制涉及重复单元的可逆双电子还原，伴随着吸收带隙的变化。可逆还原涉及填充位于配体部分的轨道。在低至0 V M/M的电位下，未观察到每个重复单元超过两个电子的NiBTA还原。
