Ma Liang, Li Jinliang, Li Zhibin, Ji Yingying, Mai Wenjie, Wang Hao
Guangdong Provincial Key Laboratory of Micro/Nano Optomechatronics Engineering, College of Mechatronics and Control Engineering, Shenzhen University, Shenzhen 518060, China.
Siyuan Laboratory, Guangdong Provincial Engineering Technology Research Center of Vacuum Coating Technologies and New Materials, Department of Physics, Jinan University, Guangzhou 510632, China.
Nanomaterials (Basel). 2021 Apr 27;11(5):1130. doi: 10.3390/nano11051130.
As a promising energy storage system, potassium (K) ion batteries (KIBs) have received extensive attention due to the abundance of potassium resource in the Earth's crust and the similar properties of K to Li. However, the electrode always presents poor stability for K-ion storage due to the large radius of K-ions. In our work, we develop a nitrogen-doped carbon nanofiber (N-CNF) derived from bacterial cellulose by a simple pyrolysis process, which allows ultra-stable K-ion storage. Even at a large current density of 1 A g, our electrode exhibits a reversible specific capacity of 81 mAh g after 3000 cycles for KIBs, with a capacity retention ratio of 71%. To investigate the electrochemical enhancement performance of our N-CNF, we provide the calculation results according to density functional theory, demonstrating that nitrogen doping in carbon is in favor of the K-ion adsorption during the potassiation process. This behavior will contribute to the enhancement of electrochemical performance for KIBs. In addition, our electrode exhibits a low voltage plateau during the potassiation-depotassiation process. To further evaluate this performance, we calculate the "relative energy density" for comparison. The results illustrate that our electrode presents a high "relative energy density", indicating that our N-CNF is a promising anode material for KIBs.
作为一种有前景的储能系统，钾（K）离子电池（KIBs）因其在地壳中钾资源丰富以及K与Li性质相似而受到广泛关注。然而，由于K离子半径较大，电极在储存K离子时稳定性总是较差。在我们的工作中，我们通过简单的热解过程开发了一种由细菌纤维素衍生的氮掺杂碳纳米纤维（N-CNF），它能够实现超稳定的K离子存储。即使在1 A g的大电流密度下，我们的电极在KIBs经过3000次循环后仍表现出81 mAh g的可逆比容量，容量保持率为71%。为了研究我们的N-CNF的电化学增强性能，我们根据密度泛函理论提供了计算结果，表明碳中的氮掺杂有利于在钾化过程中K离子的吸附。这种行为将有助于提高KIBs的电化学性能。此外，我们的电极在钾化-去钾化过程中表现出低电压平台。为了进一步评估这种性能，我们计算了“相对能量密度”进行比较。结果表明我们的电极具有高“相对能量密度”，这表明我们的N-CNF是一种有前景的KIBs负极材料。
