Zinc-ion batteries (ZIB) present great potential in energy storage due to low cost and high safety. However, the poor stability, dendrite growth, and narrow electrochemical window limit their practical application. Herein, we develop a new eutectic electrolyte consisting of ethylene glycol (EG) and ZnCl 2 for dendrite-free and long-lifespan ZIBs. The EG molecules participate in the Zn 2 + solvation via coordination and hydrogen-bond interactions. Optimizing the ZnCl 2 /EG molar ratio (1 : 4) can strengthen intermolecular interactions to form [ZnCl(EG)] + and [ZnCl(EG) 2 ] + cations. The dissociation-reduction of these complex cations enables the formation of a Cl-rich organic-inorganic hybrid solid electrolyte interphase film on a Zn anode, realizing highly reversible Zn plating/stripping with long-term stability of � 3200 h. Furthermore, the polyaniline j j Zn cell manifests decent cycling performance with � 78 % capacity retention after 10 000 cycles, and the assembled pouch cell demonstrates high safety and stable capacity. This work opens an avenue for developing eutectic electrolytes for high-safety and practical ZIBs.

developing advanced electrochemical energy storage devices with high energy/ power density and long lifespan. [1] Among them, lithium-ion batteries (LIBs) and supercapacitors (SCs) are two most promising devices for chemical energy storage. [2] However, there has been an obvious research boundary between them owing to their different charge-storage mechanisms. Generally, LIBs provide high energy density but relatively low power density on basis of insertion-, conversion-, and alloying-type mechanisms, while SCs exhibit high power density and relatively good cycling stability but low energy density via a fast physisorption and/or shallow redox reaction on the electrode/electrolyte interface. [3] Therefore, to meet the market need and conquer the energy storage barrier, developing advanced LIBs with supercapacitor-like rate performance that combines both merits is a very challenging research direction with vital importance in the near future. [4] There is no doubt that the intrinsic phase structures of electrode materials play a crucial role in improving battery performance. [5] Compared with conversion-/ alloying-type materials, most insertion-type materials have robust crystalline skeletons and relatively high diffusion efficiency during charging and discharging, which can endow LIBs with long-term cycling stability and high rate capability. [6] Niobium pentoxides (Nb 2 O 5 ) have attracted extensive interest for ultrafast lithium-ion batteries due to their impressive rate/capacity performance and high safety as intercalation anodes. However, the intrinsic insulating properties and unrevealed mechanisms of complex phases limit their further applications. Here, a facile and efficient method is developed to construct three typical carbon-confined Nb 2 O 5 (TT-Nb 2 O 5 @C, T-Nb 2 O 5 @C, and H-Nb 2 O 5 @C) nanoparticles via a mismatched coordination reaction during the solvothermal process and subsequent controlled heat treatment, and different phase effects are investigated on their lithium storage properties on the basis of both experimental and computational approaches. The thin carbon coating and nanoscale size can endow Nb 2 O 5 with a high surface area, high conductivity, and short diffusion length. As a proof-ofconcept application, when employed as LIB anode materials, the resulting T-Nb 2 O 5 @C nanoparticles display higher rate capability and better cycling stability as compared with TT-Nb 2 O 5 @C and H-Nb 2 O 5 @C nanoparticles. Furthermore, a synergistic effect is investigated and demonstrated between fast diffusion pathways and stable hosts in T-Nb 2 O 5 for ultrafast and stable lithium storage, based on crystal structure analysis, in situ X-ray diffraction analysis, and density functional theoretical calculations. Therefore, the proposed synthetic strategy and obtained deep insights will stimulate the development of Nb 2 O 5 for ultrafast and long-life LIBs.

With high theoretical capacity and applicable operating voltage, layered transition metal oxides are potential cathode for potassium-ion batteries (PIBs). However, K+/vacancy ordered structure in these oxides limits the K+ transport...

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Mn‐based layered oxides are one of the most appealing cathodes for potassium‐ion batteries (PIBs) because of their high theoretical capacity. However, the Jahn–Teller effect of Mn3+ induces detrimental structural disorder and irreversible phase transition, leading to inferior cycling stability. Herein, an efficient strategy to suppress the Jahn–Teller effect in Mn‐based layered oxides by regulating the Mn average valence is demonstrated. To verify this strategy, Ti4+ and Mg2+ ions are chosen and introduced into the layered oxides (K0.5Mn0.7Co0.2Fe0.1O2), which can enhance the structural stability but have opposite effects on the regulation of Mn3+/4+ valence. The K0.5Mn0.6Co0.2Fe0.1Mg0.1O2 with a higher Mn valence (4+) exhibits long‐term cycling stability as a PIB cathode compared to the K0.5Mn0.6Co0.2Fe0.1Ti0.1O2 with a lower Mn valence (3.667+). Meanwhile, the detrimental phase transition from P3 to O3 caused by Jahn–Teller effect is completely suppressed, and is replaced by a highly reversible single‐phase solid solution reaction for K0.5Mn0.6Co0.2Fe0.1Mg0.1O2. The enhanced cycling stability and single‐phase reaction are attributed to the suppressed Jahn–Teller effect via Mn valence regulation, confirmed by first‐principles calculations. Therefore, this discovery paves the way for the development of advanced layered cathodes for the next‐generation high‐performance PIBs.

great attention as alternatives to LIBs, in order to provide new opportunities for the substantial improvement of energy storage systems. [5][6][7][8][9][10][11][12] The alkali metals (Li, Na, and K) are located at the first group in the periodic table, possessing similar physicochemical properties. However, it is generally accepted that the larger cation radius of Na + (1.02 Å) and K + (1.33 Å) causes the sluggish diffusion kinetics, thus limiting the development of SIBs and PIBs. [6] Compared to the mature technology of LIBs, the developments of SIBs and PIBs are still at an initial stage.The common electrode materials in LIBs are generally not applicable to SIBs and PIBs. [13][14][15][16][17][18] Advanced electrode materials that can store large-sized Na + and K + are urgently desired. 2D layered transition metal dichalcogenides (TMDs), which are fundamentally and technically interesting, have been widely researched in energy storage field. [19][20][21] Vanadium disulfide (VS 2 ) is a typical family member of TMDs, which has attracted wide attention due to its layered structure with a large interlayer spacing of 0.57 nm together with excellent electric conductivity and weak van der Waals interlayer interaction. [22,23] The unique structure and properties of VS 2 make it an ideal host for the insertion/extraction of alkali metalions. Recently, the literature regarding the potential of VS 2 as an electrode for alkali metal-ion (Li + , Na + , and K + ) batteries with outstanding performance has been reported. [24][25][26][27][28][29] However, less attention has been paid to the relationship between the electrochemical performance and the storage mechanism in alkali metal-ion batteries. Revealing the detailed energy storage mechanisms, including the structural evolution, phase transition reactions, and ion diffusion kinetics, is highly significant for a deeper understanding of the electrochemistry about VS 2 and further optimization of its electrochemical performance in alkali metal-ion batteries.In this work, we systematically revealed and compared the electrochemical behaviors of the layered VS 2 cathode in three battery systems (LIBs, SIBs, and PIBs), including electrochemical performance, detailed structural evolution, and reaction kinetics during the alkali metal-ions insertion/extraction. In situ X-ray diffraction (XRD), ex situ transmission electron microscope (TEM), together with density functional theory (DFT) analysis were employed to accurately track the structural evolution of VS 2 during the discharging/charging processes, VS 2 is one of the attractive layered cathodes for alkali metal-ion batteries. However, the understanding of the detailed reaction processes and energy storage mechanism is still inadequate. Herein, the Li + /Na + /K + insertion/ extraction mechanisms of VS 2 cathode are elucidated on the basis of experimental analyses and theoretical simulations. It is found that the insertion/ extraction behavior of Li + is partially irreversible, while the insertion/extraction behavior of Na + /K...

Considered as an imperative alternative to the commercial LiFePO4 battery, the potassium metal battery possesses great potential in grid-scale energy storage systems due to the low cost, low standard redox potential, and high abundance of potassium. The potassium dendrite growth, large volume change, and unstable solid electrolyte interphase (SEI) on the potassium metal anode have, however, hindered its applications. Although conductive scaffolds coupling with potassium metal have been widely proposed to address the above issues, it remains challenging to fabricate a uniform composite with uncompromised capacity. Herein, we propose a facile and efficient strategy to construct dendrite-free and practical carbon-based potassium composite anodes via amine functionalization of the carbon scaffolds that enables fast molten potassium infusion within several seconds. On the basis of experiments and theoretical calculations, we show that highly potassiophilic amine groups immediately transform carbon scaffolds from nonwetting to wetting to postassium. Our carbon-cloth-based potassium composite anode (K@CC) can accommodate volume fluctuation, provide abundant nucleation sites, and lower the local current density, achieving nondendritic morphology with a stable SEI. The fabricated K0.7Mn0.7Ni0.3O2|K@CC full cell displays excellent rate capability and an ultralong lifespan over 8000 cycles (68.5% retention) at a high current of 1 A g–1.

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