Search

Developing high‐voltage and environmentally friendly aqueous electrolytes have become a significant trend in supercapacitors (SCs). However, achieving this goal usually requires the use of "water‐in‐salt" (WIS) electrolytes, inevitably increasing manufacturing costs and sometimes posing problems such as environmental pollution. Here, we developed a water/organic solvent hybrid electrolyte (8 m NaClO4‐20 % H2O‐30 % ACN‐50 % PEG‐200) with low cost and high‐voltage capacity using the water‐miscible polymer polyethylene glycol (PEG) as a crowding agent to suppress water activity, and acetonitrile (ACN) as a co‐solvent to improve the ion transport properties. The synergistic advantages of the two co‐solvents allow SCs using this electrolyte to have a high operative voltage window of up to 2.6 V, currently the highest operating voltage for aqueous carbon‐based SCs, excellent capacity retention (over 11000 cycles) and high energy densities (31.2 Wh kg−1). This work provides a promising method for developing green and inexpensive high‐voltage window aqueous electrolytes. [ABSTRACT FROM AUTHOR]

Owing to their unique nanosize effect and surface effect, pseudocapacitive quantum dots (QDs) hold considerable potential for high‐efficiency supercapacitors (SCs). However, their pseudocapacitive behavior is exploited in aqueous electrolytes with narrow potential windows, thereby leading to a low energy density of the SCs. Here, a film electrode based on dual‐confined FeOOH QDs (FQDs) with superior pseudocapacitive behavior in a high‐voltage ionic liquid (IL) electrolyte is put forward. In such a film electrode, FQDs are steadily dual‐confined in a 2D heterogeneous nanospace supported by graphite carbon nitride (g‐C3N4) and Ti‐MXene (Ti3C2). Probing of potential‐driven ion accumulation elucidates that strong adsorption occurs between the IL cation and the electrode surface with abundant active sites, providing sufficient redox reaction of FQDs in the film electrode. Furthermore, porous g‐C3N4 and conductive Ti3C2 act as ion‐accessible channels and charge‐transfer pathways, respectively, endowing the FQDs‐based film electrode with favorable electrochemical kinetics in the IL electrolyte. A high‐voltage flexible SC (FSC) based on an ionogel electrolyte is fabricated, exhibiting a high energy density (77.12 mWh cm−3), a high power density, a remarkable rate capability, and long‐term durability. Such an FSC can also be charged by harvesting sustainable energy and can effectively power various wearable and portable electronics. [ABSTRACT FROM AUTHOR]

Developing aqueous electrolyte with wide electrochemical stability window (ESW) is one of the key technologies to boosting the energy density of aqueous electrochemical double-layer capacitors (EDLCs). However, expanding the ESW using super-concentrated electrolytes comes at the expense of cost, ionic conductivity and the mass density of the device. Herein, we selected a cost-effective and environmentally friendly molecular crowding agent, polyethylene glycol dimethyl ether (PEGDME-250), as the electrolyte additive designed to achieve high ESW at low salt concentrations. First, PEGDME can reduces the activity of water and increases the ESW of the electrolyte by forming hydrogen bonds with free water molecule. In addition, PEGDME does not have the interaction between terminal groups compared to conventional polyethylene glycols (PEG), which helps to reduce the viscosity and improve the ionic conductivity of the electrolyte. By adjusting the composition of the electrolyte, the optimal electrolyte with a high ESW of 2.96 V was achieved with the formula of 3 m NaClO 4 -25 % H 2 O-75 % PEGDME. The EDLCs assembled with this diluted aqueous electrolyte and YP-50 F electrodes presents a high operational voltage window of 2.4 V and outstanding cycle stability (>10000 cycles), and maintains excellent rate performance in a temperature range of −10–35 ℃. • The addition of PEGDME reduces the activity of free water molecules. • Low concentration aqueous electrolyte realized electrochemical stabilization window of 2.96 V. • The EDLCs with optimized electrolyte and YP-50 F activated carbon were assembled. • The EDLCs were able to cycle 10,000 cycles at an operating voltage of 2.4 V. • The EDLCs were capable to maintain 72.3 % capacity when the current density increasing from 1 A g−1 to 10 A g−1. [ABSTRACT FROM AUTHOR]

[Display omitted] • The [DMP]BF 4 Pyrrolidine-based additive inhibit Zn dendrites and side reactions. • The battery with [DMP]BF 4 additive revealed excellent electrochemical performance. • Provide insights for other high performance ionic liquids to stabilize Zn anode. Despite aqueous zinc ion batteries (AZIBs) holding promising prospects owing to their affordability, cornucopian resources and intrinsic security, the poor reversibility and low coulomb efficiency of Zinc (Zn) anodes significantly shorten the lifespan of AZIBs, thus promoting the continuous exploration of novel high performance electrolyte additives that can stabilize Zn anodes. Herein, a commonly used pyrrolidine-based ionic liquid, N, N-dimethylpyrrolidinium tetrafluoroborate ([DMP]BF 4), was introduced into a typical ZnSO 4 aqueous electrolyte as an additive to strengthen the Zn anode stability. By a comprehensive series of electrochemical tests, structural characterizations, and theoretical calculations, the mechanism by which the [DMP]BF 4 additive enhances the stability of Zn anode was elucidated: can modulate the solvation structure of Zn2+, facilitate its transfer, de-solvation and deposition kinetics; can be preferentially adsorbed onto Zn anode surface, inducing Zn2+ epitaxial deposition along (0 0 2) crystal plane, regulating uniform nucleation, thereby mitigating Zn dendrite growth; can construct a self-healing zincophilic hydrophobic in-situ solid electrolyte interface (SEI) layer onto the Zn electrode surface, effectively isolating the direct contact between H 2 O and Zn anode, thus inhibiting parasitic side reactions. Consequently, Zn-Zn symmetrical cells assembled using [DMP]BF 4 showed a long and stable cycle life under diverse current densities and deposition areal capacities (approximately 2900 h under 1 mA cm−2, 1 mAh cm−2 as well as over 1400 h under 5 mA cm−2, 2.5 mAh cm−2). Furthermore, the full battery, utilizing Na 2 V 6 O 16 ·1.63H 2 O (NVO-H) nanowires as the cathode material, exhibited an extended cycle life of 500 cycles under 1 A/g and 2800 cycles under 3 A/g. This study establishes a reliable experimental foundation for the advancement of other high-performance ionic liquid additives. [ABSTRACT FROM AUTHOR]

[Display omitted] • A low-cost NaClO 4 -based water-in-salt electrolyte enabled the controllable EC exfoliation of graphite. • The structure of NaClO 4 -based solutions studied by Raman spectroscopy and DFT-MD simulations. • The amount of free water determines the EC exfoliation behaviors of graphite. Development of aqueous electrolytes in anodic electrochemical (EC) exfoliation is regarded as the preferred choice to prepare single or few layered graphene. Generally, in diluted aqueous electrolytes, however, the uncontrollable decomposition of water often provides excess driving forces, leading to the low ratio of single/few layered graphene nanosheets. Here, we employed a low-cost sodium perchlorate (NaClO 4)-based water-in-salt electrolyte (WIS) for the controllable EC exfoliation of graphite. Benefiting from the high salt-to-water ratio of the electrolyte, their thickness and oxidation extent of the resultant graphene nanosheets were able to be effectively controllable. Moreover, density-functional-theory-based molecular dynamics (DFT-MD) simulations exhibit a revolution from free water to bound water in WIS electrolytes as the salt-to-water ratio increases. Combined with the deconvolution peaks of the Raman spectra, the results further disclose that only at high concentration, free water molecules can be effectively restricted in WIS electrolyte, and they need to overcome more hindrance to arrive at the electrode surface for EC exfoliation than that in dilute electrolytes, therefore, the reaction rate of EC exfoliation can be controlled easily by reducing the amount of free water. Overall, this work demonstrated that controllable graphite exfoliation by changing the decomposition activity of water molecules. [ABSTRACT FROM AUTHOR]

Aqueous zinc ion chemistry is the hot topic of new energy storage technologies nowadays for its high intrinsic safety as well as its advantages in terms of environmental protection and price. However, the freezing of water at low temperatures limits the practical application to a broad range of temperatures. Herein, in view of the disturbing effect of Mg(ClO 4) 2 on hydrogen bond of water molecules, a novel anti-freezing electrolyte (0.4 m ZnSO 4 + 2.7 m Mg(ClO 4) 2) is developed, which features ultra-low freezing point (<−80 °C) and superior conductivity (7.50 mS cm−1 at −60 °C). Consequently, this organics-free hybrid electrolyte renders the as-built aqueous zinc ion hybrid capacitors (AZHCs) available to operate even at −60 °C with a high potential window of 2.4 V. Moreover, at −30 °C, such AZHC devices exhibit the highest specific capacity (123 mA h g−1), the maximum energy density (126 Wh kg−1 at 1050 W kg−1), an excellent rate performance (75.8 Wh kg−1 at 10495.4 W kg−1) and a stable working life over 32 000 cycles. This research points to a feasible strategy to improve the cryogenic performance of AZHCs with high energy density. • The addition of Mg(ClO 4) 2 can break the hydrogen bonding between water molecules. • The organics-free aqueous hybrid electrolyte possesses an ultra low freezing point. • The AZHCs exhibit excellent electrochemical performance at low temperatures. • The AZHCs possess a wider ESW at low temperatures. • Provide insights for other AZHCs to have superior low temperature performance. [ABSTRACT FROM AUTHOR]