在锂离子电池(LIBs)和钠离子电池(SIBs)中,设计同时适用的负极材料,使其具有高倍率性能和超长循环寿命是亟需解决的工作.本文采用静电纺丝技术和硫化工程技术成功制备了一种均匀分布在N,S-掺杂炭纳米纤维上的MoO2/MoS2异质结构(MoO2/MoS2@NSC).其中一维炭骨架作为导电框架可缩短Li+/Na+的扩散途径;炭纳米纤维中N/S杂原子的掺杂引入了丰富的活性位点,显著增强了离子扩散动力学.此外,在MoO2相中通过原位形成的MoS2纳米片强化了异质界面,MoO2和MoS2之间异质界面的构建使得Li+/Na+的快速传输成为实现高效储能的关键.因此,作为LIBs负极材料时,MoO2/MoS2@NSC电极在5.0 A g-1的电流密度下循环2 000圈后,仍具有640 mAh g-1的优异放电比容量,每圈的容量衰减率仅为0.002％;在10.0 A g-1的高电流密度下可达到614 mAh g-1的放电比容量.对于SIBs,在2.0Ag-1的电流密度下循环2 000圈后其可逆容量仍能达到242 mAh g-1.本工作采用一种新颖的界面调控策略来合理地设计负极材料,从而提高Li+/Na+储存动力学,实现超长寿命的循环性能.
A new anode material for high rate and long life lithium/sodium storage
It is imperative to design suitable anode materials for both lithium-ion(LIBs)and sodium-ion batteries(SIBs)with a high-rate performance and ultralong cycling life.We fabricated a MoO2/MoS2 heterostructure that was then homogeneously distrib-uted in N,S-doped carbon nanofibers(MoO2/MoS2@NSC)by electrospinning and sulfurization.The one-dimensional carbon fiber skeleton serves as a conductive frame to decrease the diffusion pathway of Li+/Na+,while the N/S doping creates abundant active sites and significantly improves the ion diffusion kinetics.Moreover,the deposition of MoS2 nanosheets on the MoO2 bulk phase pro-duces an interface that enables fast Li+/Na+transport,which is crucial for achieving high efficiency energy storage.Consequently,as the anode for LIBs,MoO2/MoS2@NSC gives an excellent cycling stability of 640 mAh g-1 for 2 000 cycles under 5.0 A g-1 with an ultralow average capacity drop of 0.002％per cycle and an exceptional rate capability of 614 mAh g-1 at 10.0 A g-1.In SIBs,it also produces a significantly better electrochemical performance(reversible capacity of 242 mAh g-1 under 2.0 A g-1 for 2 000 cycles and 261 mAh g-1 under 5.0 A g-1).This work shows how introducing a novel interface in the anode can produce rapid Li+/Na+storage kinetics and a long cycling performance.
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