Excellent Low-temperature Performance Research Articles

Catalytic effect of micro/nano-Ni on dehydrogenation performance of Mg90Al10 during air exposure

Air stability is one of the key challenges to be solved in practical application of Mg-based hydrogen storage materials. The dehydrogenation properties and microstructures of air-exposed Mg-Al-based hydrides with micro/nano-Ni added were systematically studied. In a surprise finding, Mg90Al10 with nano-Ni added can maintain excellent low-temperature dehydrogenation performance after air exposure for about 13 days, while the dehydrogenation performance of Mg90Al10 with micro-Ni added gradually deteriorates with the increase of air exposure time. Compared with micro-Ni, nano-Ni particles have smaller size, more uniform dispersion and higher chemical activity, which can effectively promote the desorption of hydrogen. Almost no oxide layer can be found on the surface of nano-Ni particles in the air exposed sample, indicating that it can still maintain excellent chemical activity after air exposure. Furthermore, nano-Ni can evenly coat on the surface of MgH2 through mechanical milling, which play a key role in inhibiting the adsorption of water and prevent MgH2 from being excessively oxidized during air exposure. This finding has an important value for the development of highly active and air stable hydrogen storage materials.

S-doped graphene nano-capsules toward excellent low-temperature performance in Li-ion capacitors

The electrochemical properties of LICs are greatly decreased at a low-temperature condition due to the sluggish Li-ion storage kinetics coupled with poor structural stability. Herein, S-doped graphene nano-capsules (SGCs) with good dispersibility is rational designed and serves as both the anode and cathode in symmetric LICs. At room temperature, all the half-cells of SGCs exhibit excellent high capacity, outstanding rate performance and ultra-long cycling stability. Furthermore, the assembled SGCs//SGCs LICs shows a high gravimetric energy density of 249.9 W h kg−1 at 2116.7 W kg−1 and high volumetric energy density of 172.4 W h L−1 at 1460.5 W L−1 coupled with 95.4% capacity retention for 10000 cycles. Even at −30 °C, It still displays 179.6 W h kg−1 at 1658.2 W kg−1 and 68.8 W h kg−1 at 4755.7 W kg−1 coupled with 84.3% capacity retention for 10000 cycles. Furthermore, a fabricated density functional theory (DFT) further demonstrates that the doped S atom plays a key role in enhancing the electronic conductivity and Li+ storage capability. Our results offer a promising application reserve force for the next generation energy storage devices in LICs.

Low-temperature and high-voltage lithium-ion battery enabled by localized high-concentration carboxylate electrolytes

Using localized high-concentration electrolytes (LHCEs), which have high oxidation resistance and low viscosity, in high-voltage lithium-ion batteries can facilitate the low-temperature operation of the batteries. In this study, a new short-chain fluorinated diluent 1,1,2,2-tetrafluoroethyl methyl ether is used to prepare a methyl acetate-based LHCE that shows good stability against a LiNi0.5Mn1.5O4 (LNMO) cathode. Furthermore, an LNMO||Li battery (3–4.9 V vs. Li/Li+) with the LHCE shows good cycling stability at room temperature at 1C. Owing to the excellent low-temperature performance of the LHCE, the battery can discharge 80.85% of its room temperature capacity at 0.2C at the temperature of −50 °C and show reversible charge/discharge behavior at 0.1C at the temperature of −40 °C. In this study, LHCEs are successfully used to realize a high-voltage battery that could operate with a relatively high current density (≥0.1C) at a low temperature (-50 °C).

One-pot synthesis of anti-freezing carrageenan/polyacrylamide double-network hydrogel electrolyte for low-temperature flexible supercapacitors

Stretchable carrageenan (CG) based double-network (DN) hydrogel has great potential in flexible energy storage devices. To achieve high conductivity at sub-zero temperatures, one-pot synthesis method is adopted for the fabrication of CG/polyacrylamide DN hydrogel with high LiCl concentration (termed CG/PAAm-xLi). In this method, a high temperature above 90 °C is required to fully melt CG network in the presence of high-concentration LiCl and to add the monomers of the second polymer network. Furthermore, by incorporation of small amounts of KCl, the obtained CG/PAAm-7Li/K DN hydrogel shows strong tensile properties with tensile elongation of 567.7%, and fracture energy of 967.3 kJ/m2. In addition, the conductivity of the CG/PAAm-7Li/K DN hydrogel achieves 1.9 S/m at − 40 °C. The flexible supercapacitor prepared by using CG/PAAm-7Li/K hydrogel electrolyte exhibits excellent low-temperature electrochemical properties (specific capacitance of 73.4 F/g, and capacitance retention of 95.6% after 20,000 cycles at − 40 °C). This high-temperature strategy may be extended to construct other ionic polysaccharide-based hydrogel electrolytes with high mechanical property and excellent low-temperature electrochemical performance, showing a broad prospect in the field of flexible electronics.

Enhanced Zn2+ transfer dynamics via a 3D bird nest-like VO2/MXene heterojunction for ultrahigh-rate aqueous zinc-ion batteries

With the increasing demand of the large-scale storage equipment, more scholars are involved in the research of aqueous zinc-ion batteries (AZIBs) owing to their cost-effectiveness, good safety and environment-friendly. Herein, we demonstrate a three-dimensional (3D) bird nest-like VO 2 /MXene heterojunction using a facile ultrasonication method combined with freeze-drying. The particular heterostructure of cathode material not only effectively suppresses the volume changes of electrodes, but also prominently improves the kinetics of active materials upon cycling, thus results in remarkably enhanced electrochemical performance. It delivers a specific capacity of 445 mAh g −1 at 0.1 A g −1 and exhibits unexceptionable high-rate capacities of 244.5 and 225.0 mAh g −1 at 20.0 (over 2600 cycles) and 30.0 (over 4000 cycles) A g −1 , respectively. Moreover, a high specific capacity of 247.2 mAh g −1 is achieved at 5.0 A g −1 at −20 °C, and almost no capacity loss is observed even after 2500 cycles. Moreover, the further research on ex-situ XPS and XRD measurements are carried out for VO 2 /MXene material in hope of better understanding its Zn 2+ storage mechanism. The proposed interfacial engineering approach combining metal oxides and MXene in this work opens up a novel way for cathode in AZIBs. • VO 2 /MXene was obtained by ultrasonication combined with freeze drying. • VO 2 /MXene exhibited ultrahigh-rate and excellent low-temperature performance. • Interface engineering boosted the electrochemical kinetics of VO 2 /MXene.

Mn-doped Na4Fe3(PO4)2(P2O7) facilitating Na+ migration at low temperature as a high performance cathode material of sodium ion batteries

Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 (NFPP) is known as a cathode material with great potential for sodium ion batteries (SIBs) due to its thermodynamic stability, considerable theoretical capacity and small volume change. However, its inherent poor conductivity leads to low discharge capacity and poor cycle stability, which greatly limits its widespread and practical application. In this work, a Mn 2+ doped NFPP together with the graphene modification, is proposed. It is found that the optimal Na 4 Fe 2.7 Mn 0.3 (PO 4 ) 2 P 2 O 7 /rGO(Mn0.3-NFPP/rGO) can provide an initial discharge capacity of 131.5 mAh g −1 at 0.1C, (1C = 129mAh g −1 ) also an excellent rate performance (70.2 mAh g −1 at 50C) and good long cycle stability (97.2% capacity retention after 2000 cycles at 10C) can be obtained. Impressively, the as-prepared Mn0.3-NFPP/rGO also shows excellent low-temperature performance, at −20 °C, it demonstrates a discharge capacity of 85.3 mAh g −1 at 0.2C and good rate performance. Density functional theory (DFT) calculation shows that Mn 2+ doping reduces the Na + migration energy barrier, and also narrows the bandgap of the NFPP lattice, which is beneficial to improve the Na + diffusion kinetics and conductivity. In addition, the doping of Mn 2+ can further help to improve its structural stability during the long cycling process. • Mn-doped Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) together with graphene modification is proposed. • Mn 2+ doping reduces the Na + migration energy barrier. • Mn 2+ doping narrows the bandgap of Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ). • The Na + migration is facilitated by Mn 2+ doping, particularly at low temperature.

One-pot synthesis and multifunctional surface modification of lithium-rich manganese-based cathode for enhanced structural stability and low-temperature performance

High-energy–density lithium-rich Li1.2Ni0.13Co0.13Mn0.54O2 is regarded as one of the most promising cathode materials for lithium-ion batteries. However, its practical application is restricted by critical kinetics drawbacks and poor low-temperature electrochemical performances. In this research, Li1.2Ni0.13Co0.13Mn0.54O2 submicron particles coated by a Li7La3Zr2O12 (LLZO) layer and co-doped by La/Zr cations has been fabricated via a facile one-pot sol–gel technique and subsequent heat treatment. The coating LLZO layer with a few nanometers is able to build a rapid lithium-ion transport channel for adjacent particles and suppress severe side reactions between active material and the electrolyte. Moreover, large-radius La/Zr cations co-doping can broaden the diffusion paths of lithium ions, hinder the detrimental structural transformation, and improve the electrochemical structure stability of the cathode during repeated cycles. Owing to numerous merits from this multifunctional surface modification strategy, the modified Li1.2Ni0.13Co0.13Mn0.54O2 composite exhibits the significantly decreased interface impedance, enhanced Li+ diffusion kinetics and mitigated phase transformation, as well as excellent low-temperature electrochemical performance. It can contribute ultrahigh capacities of 173.8 mAh g−1 at −10 ℃ and 134.1 mAh g−1 at −20 ℃, respectively, displaying great application prospects of Li-rich cathode materials.

Elaborately Designed S-Doped Graphene Nano-Capsules Toward Excellent Low-Temperature Performance in Li-Ion Capacitors

Elaborately Designed S-Doped Graphene Nano-Capsules Toward Excellent Low-Temperature Performance in Li-Ion Capacitors

Shape-Shifting, Conductive, Reprocessable Acrylate Polysiloxane with Excellent Low-Temperature and Oil-Resistance Performance

Shape-Shifting, Conductive, Reprocessable Acrylate Polysiloxane with Excellent Low-Temperature and Oil-Resistance Performance

Use of the active-phase Cu3Si alloy as superior catalyst to direct synthesis of trichlorosilane via silicon hydrochlorination

Here we report the first synthesis of nearly pure-phase Cu3Si alloy that can be a highly efficient catalyst in the hydrochlorination of silicon reaction. This material was prepared by a high-temperature (1050 ​°C) calcination method in which copper and silicon powders were used as the reactants. The X-ray photoelectron spectroscopy (XPS) study revealed that the Cu and Si atoms in the Cu3Si alloy carried part of positive and negative charge, respectively. When employed as the catalyst in the silicon hydrochlorination to SiHCl3 (TCS) for the production of Si polycrystals for Solar cell, the sample Cu3Si exhibited excellent low-temperature catalytic performance: the Si conversion and TCS selectivity respectively achieved 41.1% and 96.1% at 250 ​°C. Notably, its TCS yield at 250 ​°C was 1.2 times higher than that of the industrial catalyst-free system at 350 ​°C. Detailed analysis of the reaction process showed that the positively charged Cu atoms and negatively charged Si atoms in Cu3Si alloy could cleave the H–Cl bond in the reactant HCl and make the combination of H and Cl atom with Si atoms easier. Meanwhile, the reaction between the remaining Cu atom and Si was accelerated, leading to the generation of more active Cu6.69Si and ultimately superior catalytic performance. This work deepens the fundamental understanding of the hydrochlorination of silicon reaction, and provides an avenue for the synthesis of Si-based alloy catalysts.

Multilayered graphene endowing superior dispersibility for excellent low temperature performance in lithium-ion capacitor as both anode and cathode

Constructing all-graphene symmetric Lithium-ion capacitor (LIC) with high energy and power density has recently gained widespread attention. Here, O-doping multilayered porous graphene (OMG) with micron-size served as both cathode and anode for LIC was prepared via a simple and easily large-scale air thermal treatment method. By rational controlling the reaction temperature and time in the air, the obtained OMG nano-sheets possess high specific surface areas, abundant nano-pores channels, enlarged graphene-interlayers spacing, good conductivity and superior dispersibility. As anode, OMG delivered high average capacity (247 mA h g−1 at 1.0 A g−1), excellent rate capability (138 mA h g−1 at 10 A g−1) and long-term cycling performance (83% capacity retention for 10,000 cycles). As cathode, OMG showed large average capacity (196 mA h g−1 at 1.0 A g−1), superior rate performance (155 mA h g−1 at 10 A g−1) and outstanding cyclic stability (increasing capacity for 7000 cycles). The assembled all-graphene symmetric OMG//OMG LIC exhibited an excellent rate capability (70.7%), high energy density of 131.6 W h kg−1 at 2272 W kg−1 and high energy density of 87.3 W h kg−1 even at a higher power density of 21660 W kg−1 coupled with ultralong cycling stability (96.8% capacity retention for 5000 cycles). More importantly, OMG//OMG still exhibit excellent low-temperature electrochemical properties (98.5 W h kg−1 at 1130 W kg−1 and 94.2% capacity retention under −30 °C), indicating a great application prospect in the next generation energy storage devices for LIC.

Flexible and anti-freezing zinc-ion batteries using a guar-gum/sodium-alginate/ethylene-glycol hydrogel electrolyte

Natural polymer hydrogels are promising candidates for solid-state electrolytes in zinc-ion batteries. They are safe, biocompatible, and mechanically robust. However, the ionic conductivity of most natural polymer-based hydrogels is unsatisfactory, and they are particularly problematic at sub-zero temperatures because freezing severely limits their functionality. In this study, we fabricate composite hydrogels with high ionic conductivity (25.37 mS cm−1). This is done by blending two kinds of natural polymers, guar gum (GG) and sodium alginate (SA). The zinc-ion batteries with GG/SA hydrogel electrolytes show a superior electrochemical performance (354.9 mAh g−1 at 0.15 A g−1, 137.0 mAh g−1 at 6 A g−1 and capacity retention of 91.52% over 1000 cycles) than the zinc-ion batteries with the pure GG hydrogel electrolyte. In addition, to extend the application range of GG/SA hydrogels into the sub-zero temperature region, we introduce ethylene glycol (EG) into GG/SA to form GG/SA/EG anti-freeze hydrogel. Below -20 °C, the GG/SA/EG hydrogel maintains a high ionic-conductivity (6.19 mS cm−1), and the zinc-ion batteries, which were made of GG/SA/EG hydrogel electrolyte, showed an excellent low-temperature discharge performance, for a specific capacity of 181.5 mAh g−1 at 0.1 A g−1. This study describes a new approach for the development of natural polymer-based hydrogel electrolytes with high ionic-conductivity and good anti-freeze capability.

Enzyme-catalyzed synthesis and properties of polyol ester biolubricant produced from Rhodotorula glutinis lipid

Biolubricants do not cause the environmental pollution resulting from the manufacturing and use of mineral-based lubricants, but the commonly adopted chemical method of preparing biolubricants using expensive vegetable oils as raw materials is still environmentally and economically unsatisfactory. In this study, R. glutinis lipid with a high oleic-acid content was esterified with trimethylolpropane (TMP) by using the Candida sp. 99–125 enzyme in a solvent-free system, and the effect of the microbial oil with the high oleic-acid content on the performance of resulting biolubricants was investigated. The purpose of this study was to solve the problems of pollution caused by the chemical synthesis of biolubricants and of the uneconomical use of vegetable oils as raw materials. Further, this study aimed to improve the performance of biolubricants by using the microbial lipid with a high oleic-acid content. As a result of optimization of the reaction conditions, the yield of trimethylolpropane fatty acid triester (TFAT) reached 89.5%. The synthesized biolubricants had excellent low-temperature lubrication performance (pour point=−45 °C), and the physicochemical performance reached the ISOVG-46 grade. The results of the high-frequency reciprocating friction test (HRFT) show that the products have better tribological properties than mineral-based lubricants of the same viscosity grade (friction coefficient=0.085; average wear scar diameter=187 µm).

Novel Low-Temperature Electrolyte Using Isoxazole as the Main Solvent for Lithium-Ion Batteries.

A novel electrolyte system with an excellent low-temperature performance for lithium-ion batteries (LIBs) has been developed and studied. It was discovered for the first time, in this work, that when isoxazole (IZ) was used as the main solvent, the ionic conductivity of the electrolyte for LIBs is more than doubled in a temperature range between -20 and 20 °C compared to the baseline electrolyte using ethylene carbonate-ethyl methyl carbonate as solvents. To solve the problem of solvent co-intercalation into the graphite anode and/or electrolyte decomposition, the lithium difluoro(oxalato)borate (LiDFOB) salt and fluoroethylene carbonate (FEC) additive were used to form a stable solid electrolyte interphase on the surface of the graphite anode. Benefitting from the high ionic conductivity at low temperature, cells using a new electrolyte with 1 M LiDFOB in FEC/IZ (1:10, vol %) solvents demonstrated a very high reversible capacity of 187.5 mAh g-1 at -20 °C, while the baseline electrolyte only delivered a reversible capacity of 23.1 mAh g-1.

A Comprehensive Solution for Ni-Rich Cathodes by Lithium Silicate Coating

Ni-rich materials are among the most promising cathode materials for use in the electric vehicle industry with high energy density, excellent low temperature performance and rate performance. However, with the increase of Ni content, many problems emerge in Ni-rich materials, such as residual alkali and the side reactions at the electrode surface. In this work, we find that part of the residual lithium at the surface of the Li[Ni0.8Co0.1Mn0.1]O2 material can be converted into lithium silicate as a lithium-ion conductor, through the surface treatment of tetraethyl orthosilicate, thereby solving the above problems. Specifically, at a rate of 3C, the material with a coating amount of 2 wt% showed a capacity retention rate of 83.33% after 300 cycles, with the pristine material at only 64.60%. Furthermore, under the protection of the coating layer, the dissolution of the transition metal and side reactions on the cathode electrode surface were effectively suppressed. Experimental results proved that this method is reliable and easy to implement and can serve as a comprehensive solution for common problems of Ni-rich materials.

Concentrated hydrogel electrolyte for integrated supercapacitor with high capacitance at subzero temperature

Hydrogel electrolytes with anti-freezing properties are crucial for flexible quasi-solid-state supercapacitors operating at low temperatures. However, the electrolyte freezing and sluggish ion migration caused by the cold temperature inevitably damage the flexibility and electrochemical properties of supercapacitors. Herein, we introduce the concentrated electrolyte into a freeze-casted poly(vinyl alcohol) hydrogel film not only reducing the freezing point of the electrolyte (−51.14 °C) in gels for ensuring the flexibility, but also improving the ionic conductivity of the hydrogel electrolyte (5.92 mS cm−1 at −40 °C) at low temperatures. As a proof, an all-in-one supercapacitor, synthesized by the one-step polymerization method, exhibits a good specific capacitance of 278.6 mF cm−2 at −40 °C (accounting for 93.8% of the capacitance at room temperature), high rate performance (50% retention under the 100-fold increase in current densities), and long cycle life (88.9% retention after 8,000 cycles at −40 °C), representing an excellent low-temperature performance. Our results provide a fresh insight into the hydrogel electrolyte design for flexible energy storage devices operating in the wide range of temperature and open up an exciting direction for improving all-in-one supercapacitors.

Ta and Mo oxides supported on CeO2-TiO2 for the selective catalytic reduction of NOx with NH3 at low temperature

The SCR of NOx with NH3 is the most efficient technology to reduce the emission of nitrogen oxides from mobile and stationary sources. Ta and Mo catalysts supported on ceria-titania (molar ratio 40:100) were prepared via sol-gel (SG) and wet impregnation (WI) methods and tested for low-temperature NH3-SCR. The preparation methods led to bulk or core-shell catalysts and the effect of these features on performance was investigated in detail. The catalysts were systematically characterized using methods such as ICP-OES, N2 physisorption (BET), XRD, H2-TPR, NH3-TPD, XPS, Raman, in situ EPR, and in situ DRIFT spectroscopy. Among all the catalysts, Mo5/Ce40/Ti100 (SG) achieved the highest NOx conversion (80-95%) and N2 selectivity (>97%) over a wide temperature range of 175-400 °C. This material outperforms other reported Ce-Ti-based catalysts especially at low temperature. Highly dispersed active species, large BET surface area, high fractions of Ce3+ and enough chemisorbed oxygen species, Lewis acid sites, and good reducibility of the catalyst contribute to the excellent low-temperature DeNOx performance of this catalyst. The effect of H2O and SO2 in feed on the activity was investigated.

Improvement of short-term aging resistance of styrene-butadiene rubber modified asphalt by Sasobit and epoxidized soybean oil

Styrene-butadiene rubber modified asphalt (SBRMA) possesses the excellent low-temperature performance. Nevertheless, SBR copolymer is vulnerable to being decomposed when exposed to high-temperature and oxygen-rich environment during asphalt mixture mixing and compaction processes, which seriously compromises the improving effects of styrene-butadiene rubber (SBR) on thermal cracking resistance of asphalt binder. Therefore, reducing preparation temperatures of SBRMA mixture is a preferable way which can effectively enhance the performance of short-term aged SBRMA. In this research, in order to reduce the temperature during SBRMA mixture fabrication, three additives including Sasobit, epoxidized soybean oil (ESO) and Sasobit/ESO composite were chosen, and the effects of additives on physical, rheological properties of SBRMA, the chemical interactions between SBRMA and additives and their mixture preparation temperatures were evaluated. In addition, the effects of reduced short-term aging temperature by additives on performance of SBRMA and its mixture were investigated through physical, rheological, morphological and mechanical analyses. The results indicate that compared with Sasobit and ESO, Sasobit/ESO composite not only shows the better lowering effect on mixture preparation temperatures, but also can compensate for the adverse effects when Sasobit or ESO is added separately and enhance the high- and low-temperature performance of SBRMA concurrently. The reduced short-term aging temperature by Sasobit/ESO is beneficial to mitigating the adverse impacts of aging on performance of SBRMA. Moreover, adding Sasobit/ESO composite can enhance the thermal cracking resistance of SBRMA mixture.

Improve the low-temperature electrochemical performance of Li4Ti5O12 anode materials by ion doping

We adopt the strategy of doping ions of Mg2+, Cr3+, and F− into Li4Ti5O12 (LTO) to substitute Li, Ti, and O, respectively (called the corresponding sample Mg-LTO, Cr-LTO, and F-LTO, respectively), and investigated its influences on the low-temperature electrochemical performance of LTO. After doping, the electrical conductivity of Mg-LTO, Cr-LTO, and F-LTO increased from less than < 10− 13 S cm− 1 to 3.07 × 10− 7 S cm− 1, 5.57 × 10− 7 S cm− 1, and 7.04 × 10− 7 S cm− 1, respectively. Structural refinement shows that doping has little effect on the radius of the crystal diffusion sites. Further research shows that the main reason for the improvement of low-temperature electrochemical performance is that doping affects the electrical conductivity, micromorphology, and phase composition of LTO. At −20 °C/10 C (1C corresponding to 175 mAh g− 1), the discharge capacities of Mg-LTO, Cr-LTO and, F-LTO are 113 mAh g− 1, 123 mAh g− 1, and 128 mAh g− 1, respectively. As a contrast, there is no discharge capacity for Pure LTO at the same conditions. After 600 cycles at −20 °C/5C, the discharge capacities of the sample of Pure LTO, Mg-LTO, Cr-LTO, and F-LTO are 69.7 mAh g− 1, 107.5 mAh g− 1, 142.3 mAh g− 1, and 133.2 mAh g− 1, respectively. Mg-LTO, Cr-LTO, and F-LTO exhibit excellent low-temperature rate performance and cycling stability. The related electrochemical factors and materials structure mechanisms involved were discussed in detail.

Low-Temperature pseudocapacitive energy storage in Ti3C2Tx MXene

The use of pseudocapacitive electrode materials can enable devices to store more energy than electrical double-layer capacitors (EDLCs). However, only a few pseudocapacitive materials can maintain excellent performance at low temperatures, which limits their application in harsh climate conditions. Here we demonstrate that a pseudocapacitor with two-dimensional transition metal carbide (MXene) electrode can exhibit excellent low-temperature performance like EDLC. The MXene electrodes contain electrolyte between 2D sheets, and the electrolyte ions can unimpededly reach redox-active sites and interact with surface oxygen groups rapidly, even at low temperatures. With a combination of 40 wt.% sulfuric acid solution as the electrolyte, the working temperature of the MXene electrode extends to -60 °C. The electrode exhibits temperature-insensitive performance at a low scan rate, and the capacity of MXene (88 mAh g−1 at 5 mV s−1) stays almost constant when the temperature decreases from 20 to -50 °C. Moreover, at -50 °C, MXene electrodes show a high capacity retention of > 75% at 100 mV s−1, indicating good low-temperature rate performance. Interestingly, a broad working potential window of 1.5 V is achieved at -60 °C. Such an excellent low-temperature performance demonstrates that MXene is a promising electrode candidate for low-temperature pseudocapacitive energy storage applications.