Search

Sodium-ion storage technologies are promising candidates for large-scale grid systems due to the abundance and low cost of sodium. However, compared to well-understood lithium-ion storage mechanisms, sodium-ion storage remains relatively unexplored. Herein, we systematically determine the sodium-ion storage properties of anatase titanium dioxide (TiO2(A)). During the initial sodiation process, a thin surface layer (~3 to 5 nm) of crystalline TiO2(A) becomes amorphous but still undergoes Ti4+/Ti3+ redox reactions. A model explaining the role of the amorphous layer and the dependence of the specific capacity on the size of TiO2(A) nanoparticles is proposed. Amorphous nanoparticles of ~10 nm seem to be optimum in terms of achieving high specific capacity, on the order of 200 mAh g-1, at high charge/discharge rates. Kinetic studies of TiO2(A) nanoparticles indicate that sodium-ion storage is due to a surface-redox mechanism that is not dependent on nanoparticle size in contrast to the lithiation of TiO2(A) which is a diffusion-limited intercalation process. The surface-redox properties of TiO2(A) result in excellent rate capability, cycling stability and low overpotentials. Moreover, tailoring the surface-redox mechanism enables thick electrodes of TiO2(A) to retain high rate properties, and represents a promising direction for high-power sodium-ion storage.

Zinc metal is a promising anode material for zinc-ion batteries (ZIBs), but severe side reactions and dendrite formation hinder its commercialization. In this study, starch is introduced into the ZnSO4 electrolyte for stabilizing the Zn anode. With abundant hydroxyl groups, starch can reconstruct the H-bond system in the electrolyte, suppressing side reactions. Moreover, the unique ring and double-helix structures of starch show strong interactions with Zn2+ ions. The large molecule structure also exhibits a steric hindrance effect, regulating the diffusion and reduction of Zn2+. Additionally, starch molecules can adsorb onto the Zn anode, promoting the formation of a solid–electrolyte interphase (SEI) and resulting in uniform Zn deposition along the (002) plane. Consequently, this approach enhances the stability and reversibility of the Zn anode. [ABSTRACT FROM AUTHOR]

Aqueous ammonium ion batteries (AAIBs) have attracted considerable attention due to their high safety and rapid diffusion kinetics. Unlike spherical metal ions, NH4+ forms hydrogen bonds with host materials, leading to a unique storage mechanism. A variety of electrode materials have been proposed for AAIBs, but their performance often falls short in terms of future energy storage needs. Hence, there is a critical need to design and develop advanced electrode materials for AAIBs. 2D materials, with their tunable interlayer spacing, remarkable interfacial chemistry and abundant surface functional groups, are an ideal choice for electrode materials for NH4+ storage. This review highlights the latest research on 2D electrode materials for AAIBs, providing insights into their working principles, NH4+ storage mechanisms and control strategies for designing high-performance AAIBs. Furthermore, a summary and future perspectives on 2D electrode materials in the development of AAIBs are provided, aiming to promote the advancement of high-performance AAIBs. [ABSTRACT FROM AUTHOR]

Additive manufacturing of (quasi−) solid‐state (QSS) electrochemical energy storage devices (EES) highlights the significance of gel polymer electrolytes (GPEs) design. Creating well‐bonded electrode‐GPEs interfaces in the electrode percolative network via printing leads to large‐scale production of customized EES with boosted electrochemical performance but has proven to be quite challenging. Herein, we report on a versatile, universal and scalable approach to engineer a controllable, seamless electrode‐GPEs interface via free radical polymerization (FRP) triggered by MXene at room temperature. Importantly, MXene reduces the dissociation enthalpy of persulfate initiators and significantly shortens the induction period accelerated by SO4−, enabling the completion of FRP within minutes. The as‐formed well‐bonded electrode‐GPEs interface homogenizes the electrical and concentration fields (i.e., Zn2+), therefore suppressing the dendrites formation, which translates to long‐term cycling (50,000 times), high energy density (105.5 Wh kg−1) and power density (9231 W kg−1) coupled with excellent stability upon deformation in the zinc‐ion hybrid capacitors (ZHCs). Moreover, the critical switch of the rheological behaviours of the polymer electrolyte (as aqueous inks in still state and become solids once triggered by MXene) perfectly ensures the direct all‐printing of electrodes and GPEs with well‐bonded interface in between, opening vast possibilities for all‐printed QSS EES beyond ZHCs. [ABSTRACT FROM AUTHOR]

Aqueous zinc‐ion batteries (ZIBs), lauded for their low cost, eco‐friendliness, and high safety, have garnered significant attention. However, their commercial viability is hindered by the challenges of dendrite growth and side reactions during the Zn2+ reduction reaction process. Electrolyte as the indispensable component of batteries has a close relationship with the issues mentioned above. With the feature of simplicity, effectiveness, and scalability, regulating electrolytes is a particularly promising, feasible, and straightforward approach to stabilizing the Zn anode. The solvation design with less solvated water, interface optimization with water‐poor and pH‐stable interface, and kinetics regulation with fast Zn2+ transport, uniform Zn2+ flux, and orientational Zn growth can contribute to uniform Zn deposition with restrained corrosion. This review encapsulates the cutting‐edge advancements in electrolytes to stabilize the Zn anode. The mechanisms underlying these advancements, encompassing solvation structure design, Zn‐electrolyte interface optimization, and kinetics regulation are elucidated. Finally, this paper outlines current challenges and prospects in electrolyte development for ZIBs, providing valuable insights for future endeavors in this field. [ABSTRACT FROM AUTHOR]

Carbon materials, owing to their low cost, high conductivity, and good thermal and chemical stability, have been deemed as a promising anode candidate for potassium‐ion batteries. However, anomalous low‐voltage discharge situations in crystalline carbon materials imply uncertainty in the potassium storage mechanism. Herein, an overlooked scenario, i.e., potassium metal underpotential deposition (PMUPD), is disclosed in crystalline carbon materials for the first time. The study unveils the induction of interlayer pores on desolvation and PMUPD by insights from thermodynamics, kinetics, and experimental analyses. By manipulating the cutoff voltage to utilize partial PMUPD, a novel synergistic mechanism of co‐intercalation and PMUPD is revealed. A remarkable initial coulombic efficiency of 92% and a 65% capacity retention at 30C (80 mAh g−1) are realized in crystalline carbon anode. This work provides a new insight into the potassium storage mechanism of carbon anode and contributes to further research and application of the UPD behavior in other alkaline metal ion batteries. [ABSTRACT FROM AUTHOR]

Despite the extensive research on MnO2 as a pseudocapacitor electrode material, there has been no report on heterostructures of multiple phase MnO2. Here we report the combination of two high-capacitance phases of MnO2, namely, α-MnO2 nanowires and δ-MnO2 ultrathin nanoflakes, to form a core-branch heterostructure nanoarray. This material and structure design not only increases the mass loading of active materials (from 1.86 to 3.37 mg cm2), but also results in evident pseudocapacitance enhancement (from 28 F g-1 for pure nanowires to 178 F g-1 for heterostructures at 5 mV s-1). The areal capacitance is up to 783 mF cm-2 at 1 mV s-1. Upon 20 000 cycles, the heterostructure array electrode still delivers a reversible capacitance above 100 F g-1 at 4.5 A g-1. Kinetic analysis reveals that capacitances due to both capacitive and diffusion controlled processes have been enlarged for the self-branched heterostructure array. This work presents a new route to improve the electrochemical performance of MnO2 as a binder-free supercapacitor electrode.