碳包覆Ti2Nb2O9纳米片的制备及其储钠性能

具有两种不同阳离子的二元金属氧化物在钠离子电池中可发生可逆的多电子反应,是一类非常具有应用前景的高容量负极材料。在本项工作中,通过离子交换法和化学剥离法得到HTiNbO5纳米片,采用水热法将其与蔗糖复合再经由后续热处理得到碳包覆的Ti2Nb2O9纳米片材料。碳包覆的Ti2Nb2O9纳米片可用作钠离子电池的负极材料,具有更高的电子导电性和多的反应活性点以及快速的离子传输通道,在50 mA∙g^−1的电流密度下具有265.2 mAh∙g^−1的可逆容量。在0.5 A∙g^−1的大电流密度下,循环200圈之后比容量为160.9 mAh∙g^−1(容量保持率75.3%)。研究结果表明Ti2Nb2O9/C纳米片在钠离子电池中具有出色的充放电性能和循环稳定性,为钠离子电池负极材料提供了可行的新选择。

Niobium Tungsten Oxide in a Green Water‑in‑Salt Electrolyte Enables Ultra‑Stable Aqueous Lithium‑Ion Capacitors

Aqueous hybrid supercapacitors are attracting increasing attention due to their potential low cost,high safety and eco-friendliness.However,the narrow operating potential window of aqueous electrolyte and the lack of suitable negative electrode materials seriously hinder its future applications.Here,we explore high concentrated lithium acetate with high ionic conductivity of 65.5 mS cm−1 as a green“water-in-salt”electrolyte,providing wide voltage window up to 2.8 V.It facilitates the reversible function of niobium tungsten oxide,Nb18W16O93,that otherwise only operations in organic electrolytes previously.The Nb18W16O93 with lithium-ion intercalation pseudocapacitive behavior exhibits excellent rate performance,high areal capacity,and ultra-long cycling stability.An aqueous lithium-ion hybrid capacitor is developed by using Nb18W16O93 as negative electrode combined with graphene as positive electrode in lithium acetate-based“water-in-salt”electrolyte,delivering a high energy density of 41.9 W kg−1,high power density of 20,000 W kg−1 and unexceptionable stability of 50,000 cycles.

Potassium ion pre‑intercalated MnO_(2)for aqueous multivalent ion batteries

Manganese dioxide(MnO_(2)),as a cathode material for multivalent ion(such as Mg^(2+)and Al^(3+))storage,is investigated due to its high initial capacity.However,during multivalent ion insertion/extraction,the crystal structure of MnO_(2)partially collapses,leading to fast capacity decay in few charge/discharge cycles.Here,through pre-intercalating potassium-ion(K+)intoδ-MnO_(2),we synthesize a potassium ion pre-intercalated MnO_(2),K_(0.21)MnO_(2)·0.31H_(2)O(KMO),as a reliable cathode material for multivalent ion batteries.The as-prepared KMO exhibits a high reversible capacity of 185 mAh/g at 1 A/g,with considerable rate performance and improved cycling stability in 1 mol/L MgSO_(4)electrolyte.In addition,we observe that aluminum-ion(Al^(3+))can also insert into a KMO cathode.This work provides a valid method for modifcation of manganesebased oxides for aqueous multivalent ion batteries.

Improved flexible Li-ion hybrid capacitors： Techniques for superior stability

Flexible power devices play an increasingly crucial role in emerging flexible electronics. To improve the electrochemical performance of flexible power devices, novel electrode structures and new energy-storage systems should be designed. Herein, a novel flexible Li-ion hybrid capacitor （LIC） is designed based on an anode comprising Li4TisO12 nanoplate arrays coated on carbon textile （LTO/CT） and a cathode comprising a flexible N-doped graphene/carbon-nanotube composite （NGC） film. The LTO/CT anode is fabricated by directly growing Li4TisO12 nano- plates on CT with robust adhesion using a simple one-pot hydrothermal reaction. Considering the volume of a real-device flexible LIC, the NGC//LTO/CT con- figuration delivers high volumetric energy and power densities of 2 mWh·cm-3 and 185 mW·cm-3, respectively. Furthermore, the flexible LIC shows excellent flexibility and electrochemical stability, with extremely small capacity fluctuation under different bending states. This work demonstrates a scalable route to assemble flexible LICs as high-performance power devices.

超低浓度电解液助力K0.486V2O5高性能质子存储

高浓度电解液被认为是一种很有前景的拓宽电解液电化学稳定窗口和提高水系电池电化学性能的方法.但是高浓度电解液也存在高成本、高粘度、低电导率等棘手问题.因为特殊的Grotthuss机制,质子电池能够在低浓度电解液中获得足够的动力学性能.基于此,我们采用罕见的超低浓度硫酸电解液(0.01 mol L^(-1))助力K~+预嵌的VO(KVO,KVO)电化学稳定性.在50 mA g^(-1)的低电流密度下,KVO电极具有129 mA h g^(-1)的比容量;在1 A g^(-1)的电流密度下,循环20,000圈的容量保持率为78%.超低浓度电解液策略为开拓耐用的、低成本的水系能源存储系统提供了一种新的路径.