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The aqueous zinc‐ion battery is promising as grid scale energy storage device, but hindered by the instable electrode/electrolyte interface. Herein, we report the lean‐water ionic liquid electrolyte for aqueous zinc metal batteries. The lean‐water ionic liquid electrolyte creates the hydrophobic tri‐layer interface assembled by first two layers of hydrophobic OTF− and EMIM+ and third layer of loosely attached water, beyond the classical Gouy–Chapman–Stern theory based electrochemical double layer. By taking advantage of the hydrophobic tri‐layer interface, the lean‐water ionic liquid electrolyte enables a wide electrochemical working window (2.93 V) with relatively high zinc ion conductivity (17.3 mS/cm). Furthermore, the anion crowding interface facilitates the OTF− decomposition chemistry to create the mechanically graded solid electrolyte interface layer to simultaneously suppress the dendrite formation and maintain the mechanical stability. In this way, the lean‐water based ionic liquid electrolyte realizes the ultralong cyclability of over 10000 cycles at 20 A/g and at practical condition of N/P ratio of 1.5, the cumulated areal capacity reach 1.8 Ah/cm2, which outperforms the state‐of‐the‐art zinc metal battery performance. Our work highlights the importance of the stable electrode/electrolyte interface stability, which would be practical for building high energy grid scale zinc‐ion battery. [ABSTRACT FROM AUTHOR]

Herein, non‐carbonized wood‐based electrodes and separators with well‐aligned channels and excellent mechanical properties are developed for supercapacitors. To enhance the conductivity and boost the capacitance, Ti3C2 (MXene) nanosheets with high electrical conductivity and excellent electrochemical activity are loaded into the wood cells via self‐assembly triggered by fast evaporating water in Ti3C2 suspension. By the assistance of positive charged polydopamine microspheres with large surface area, the self‐restacking of Ti3C2 nanosheets can be avoided and the high mass loading (50 wt%) can be achieved due to the extra driving force for Ti3C2 absorption. Benefiting from the conductive Ti3C2 nanosheets with massive active sites and the multiple well‐aligned channels in wood with efficient transportation pathways for charge carriers, the as‐designed free‐standing electrode shows a large areal capacitance of 1060 mF cm−2 at 0.5 mA cm−2 and high capacitance retention of 67% at 10 mA cm−2. Also, this electrode is highly size‐customizable, showing a good ability to be industrially processed into various shapes and dimensions. Furthermore, an all‐wood based supercapacitor with Ti3C2/wood composites as two layers of electrodes and a wood slice as the separator is fabricated, presenting a high energy density of 10.5 μW h cm−2 at 389.9 μW cm−2. [ABSTRACT FROM AUTHOR]

Ti 3 C 2 T x (a typical MXene) films can be used as free-standing electrodes due to their ultrahigh electrical conductivity, well flexibility and high electrochemical activity. However, inevitable self-restacking issue of Ti 3 C 2 T x nanosheets largely decreases exposed area and impedes the ion transport in Ti 3 C 2 T x film. Herein, hierarchically porous carbon (HPC) introduced into Ti 3 C 2 T x film can not only act as the pillar for adjacent Ti 3 C 2 T x nanosheets to prevent their typical self-restacking and further accelerate rapid ion transport in the transverse direction, but also ensure rapid ion transport in the longitudinal direction by introducing abundant macro/mesopores. By easily changing the amount of HPC (0–60%), the porosity of the film is well controlled, with adjustable specific surface area (SSA) from 8 m2 g−1 to 755 m2 g−1. The prepared quasi-solid-state supercapacitor fabricated by 60% HPC shows a good stability after different bending angles, high capacitance of 211 mF cm−2, energy density of 4.68 μW h cm−2 at 19.91 μW cm−2, and high capacitance retention of 86% after 10,000 charging-discharging cycles. This work will pave a facile route to alleviate the self-restacking phenomenon of Ti 3 C 2 T x film by constructing transverse and longitudinal channels for rapid ion transport. [Display omitted] • The porous structure can be easily adjusted in the MXene film. • Both transverse and longitudinal channels are constructed in the MXene film. • The supercapacitor has a good flexibility and a high areal specific capacitance. [ABSTRACT FROM AUTHOR]

Lignocellulose including cellulose, lignin, and hemicellulose could be extracted from wood, and has been used to prepare carbon electrode. However, complicated extraction greatly increases preparation cost. To achieve maximum utilization of lignocellulose and avoid complicated extraction, wood with porous structure and good mechanical strength is used as carbon precursor. Additionally, chemical activation is commonly used to create micropores to provide high capacitance, but it brings in natural structure destruction, and generation of wastewater during pickling. Moreover, to achieve desirable energy density, multi-step strategy with long duration is required for loading active materials on carbonized lignocellulose (CL). Herein, a one-step method is developed to prepare a free-standing hybrid CL electrode (CLE) by using Lewis acid in three aspects: (1) as structure protection agent, (2) as activating agent, (3) as active materials donor, which bypasses pickling and further avoids the generation of wastewater. Additionally, natural vessels in wood can not only provide large space for active materials loading, but also act as rapid ions diffusion way, simultaneously confining active materials detachment. Benefiting from the synergistic effect of porous structure and Lewis acid, this work not only makes full utilization of lignocellulose, but also makes CLE exhibit excellent performance in hybrid oxide supercapacitor. [ABSTRACT FROM AUTHOR]

The demerits of the carbonized eggshell membrane (EM), such as high cost, high brittleness, immutable shape and size, greatly limit its application in demanding supercapacitors as free-standing electrode. Herein, the reconstituted EM (REM) with good flexibility and excellent size-customizability is developed, which is due to their fibrous structure and abundant surface polar groups. Ti 3 C 2 nanosheet (a typical MXene) with ultra-high electrical conductivity and good electrochemical activity is then coated on REM surface, and undergoes a low-temperature carbonization (350 °C) to prepare CREM/T. Multi-functions of Ti 3 C 2 are exhibited: (1) constructing a conductive network on REM surface by randomly stacking to yield a high electrical conductivity of 78.1 S cm−1, (2) being as a protective mold to remain the inherent flexibility and porosity of REM during carbonization, (3) creating nanopores by inducing self-activation, and (4) yielding a large capacitance of 1729 mF cm−2 at 0.5 mA cm−2 and a high rate capability of 82 % after increasing the current density by 50 folds. Furthermore, an all-EM-based supercapacitor is fabricated with REM as the separator and CREM/T as the electrode. It delivers a high energy density of 16.1 μW h cm−2 at 1301 μW cm−2, and shows stable capacitive behaviors during bending. • The reconstitution strategy endows good size-customizability to eggshell membrane. • MXene remains the inherent structure of eggshell membrane during carbonization. • MXene induces a self-activation on eggshell membrane during carbonization. • An all eggshell-membrane-based supercapacitor is fabricated. [ABSTRACT FROM AUTHOR]

Conventional approaches for the production of copper-doped porous carbon microspheres from biomass involve a multi-step process, including spherical-shape development, carbonization, activation, and thermal treatment in the presence of a copper donor. In this work, a clean and industrially suitable approach is proposed to directly prepare copper-doped porous carbon microspheres from enzymatic hydrolysis lignin by utilizing cupric chloride dihydrate in four aspects: (1) as a microwave absorber to rapidly elevate the heating temperature, achieving an exceedingly short production duration of 8 min and a high carbon yield of 35.1%, (2) as a sphering agent to build a core-shell structure containing disordered carbon in the shell layer and copper-related particles in the core layer, limiting the volume changes of the copper-related particles and restraining their aggregation, (3) as a porogen to obtain a hierarchical porous structure with a high specific surface area of 1083 m2 g−1 and a mesopore ratio of 44.2%, and (4) as a copper donor to grow abundant copper-related particles, bypassing the purification process. The porous structure ensures the rapid ion transport for the copper-related particles which in turn provide a significant pseudo-capacitance. The resultant electrode achieves a remarkably high specific capacitance of 736 F g−1 at 1 A g−1. Moreover, the fabricated supercapacitor delivers an energy density of up to 43.9 W h kg−1 at 0.5 kW kg−1. This work demonstrates a clean and industrially applicable method to utilize biomass waste in high-value-added electrode materials with a low overall production cost. Image 1 • A very short production duration of 8 min and a high yield of 35.1% are achieved. • CuCl 2 acts as a microwave absorber, sphering agent, porogen, and Cu donor. • A novel core-shell and Cu-doped structure is constructed. • A remarkably high energy density of 43.9 W h kg−1 is achieved at 0.5 kW kg−1. [ABSTRACT FROM AUTHOR]