Electrolyte Infiltration Research Articles

Spontaneously dissolved MnO: A better cathode material for rechargeable aqueous zinc-manganese batteries

Manganese-based oxides (MnOx) cathodes, with profuse crystal structures and valence states, have raised extensive research interstate for aqueous zinc-manganese batteries. However, the lack of a clear reaction mechanism and source of capacity presents significant challenges for the design and development of advanced manganese-based oxide cathodes. Herein, by exploring the electrochemical activation processes and reaction mechanisms of MnOx (including MnO2, Mn2O3, Mn3O4 and MnO), MnO is proved to hold superior potential for zinc-ion batteries cathode application compared to other MnOx owing to its exceptional spontaneous dissolution activation activity and the largest proportion of Mn. Further, to ulteriorly enhance the dissolution activation and poor electronic conductivity of MnO, a porous carbon matrix-encapsulated MnO nanocomposite (MnO@PC) is successfully synthesized. Moreover, the porous carbon matrix could facilitate electrolyte infiltration and promote adsorption towards Mn2+ and Zn2+ cations, leading to more Zn4SO4·(OH)6·xH2O (ZSH) deposition and greater stability of the reversible ZSH-assisted deposition/dissolution reaction. Therefore, MnO@PC can display improved capacity of 269 mAh g-1 (0.1 A g-1) with an exceptional capacity retention of 93% after 120 cycles in pure ZnSO4 electrolyte. And at 2.0 A g-1, the capacity could reach 75 mAh g-1 and be well maintained in 2000 cycles.

Boosting redox kinetics using rationally engineered cathodic interlayers comprising porous rGO–CNT framework microspheres with NiSe2-core@N-doped graphitic carbon shell nanocrystals for stable Li–S batteries

Here, we propose the synthesis of a three-dimensional (3D) nanostructure comprising NiSe2-core@N–doped graphitic carbon (NGC) shell nanocrystals securely implanted within a highly conductive and porous reduced graphene oxide–carbon nanotube (rGO–CNT) framework (3D P-NiSe2@NGC/rGO–CNT), using spray pyrolysis technique followed by selenization and utilized as multifunctional cathodic interlayers in lithium–sulfur (Li–S) cells. The uniformly distributed arrays of macropores (ϕ = 100 nm) were formed by thermal decomposition of polystyrene nanobeads (ϕ = 200 nm). The porous structure shortens the charge diffusion length, allowing rapid charge transport and efficient electrolyte percolation besides accommodating unwanted volume perturbations. The NGC shell surrounding the NiSe2 nanocrystals acted as the primary conduction conduit for electron transport, while the self-supporting rGO–CNT framework served as a secondary pathway for consecutive electron transfer besides enhancing the structural robustness. Further, the polar NiSe2 nanocrystals offered numerous chemisorption sites for effectively capturing polysulfides, thus minimizing the shuttling effect and increasing active material utilization. The Li–S cell exhibited improved rate performance (till 4.0C) and excellent cycling stability (1000 cycles at 2.0C, average capacity decay rate of 0.04% per cycle). Even at severe cell parameters (effective S content = 74%, S loading = 4.5 mg cm−2, and electrolyte/sulfur = 5.7 µL mg−1), the cells delivered a stable rate performance and long-term cycling (400 cycles at 0.1C, average decay rate of 0.10% per cycle). We believe the nanostructure design strategy that we developed for this study could spur the development of more enduring and practical Li–S battery technology.

Hollow multi-shelled spherical Co3O4/CNTs composite as a superior anode material for lithium-ion batteries

Hollow multi-shelled spherical Co3O4/CNTs composite was prepared by a facile MOF-assisted strategy by introducing carbon nanotubes (CNTs) directly into the precursor. The hierarchical porous structure of the obtained multi-shelled Co3O4 nanospheres can effectively alleviate volume change and facilitate the infiltration of electrolyte into the interior. The interconnected CNTs can reduce the electrochemical polarization by improving the conductivity of the body material. As an anode for lithium ion batteries, the as-synthesized Co3O4/CNTs composite exhibits superior lithium ion storage performance. A high reversible specific capacity of 653.1 mAh g−1 was obtained after 500 cycles at 1000 mA g−1, suggesting a significant inspiration for fabricating application for advanced electrochemical devices.

Mass Loading-Independent Lithium Storage of Transitional Metal Compounds Achieved by Multi-Dimensional Synergistic Nanoarchitecture.

Nanostructured transitional metal compounds (TMCs) have demonstrated extraordinary promise for high-efficient and rapid lithium storage. However, good performance is usually limited to electrodes with low mass loading (≤1.0 mg cm-2 ) and is difficult to realize at higher mass loading due to increased electrons/ions transport limitations in the thicker electrode. Herein, the multi-dimensional synergistic nanoarchitecture design of graphene-wrapped MnO@carbon microcapsules (capsule-like MnO@C-G) is reported, which demonstrates impressive mass loading-independent lithium storage properties. Highly porous MnO nanoclusters assembled by 0D nanocrystals facilitate sufficient electrolyte infiltration and shorten the solid-state ions transport path. 1D carbon shell, 2D graphene, and 3D continuous network with tight interconnection accelerate electrons transport inside the thick electrode. The capsule-like MnO@C-G delivers ultrahigh gravimetric capacity retention of 91.0% as the mass loading increases 4.3 times, while the areal capacities increase linearly with the mass loading at various current densities. Specifically, the capsule-like MnO@C electrode delivers a remarkable areal capacity of 2.0 mAh cm-2 at a mass loading of 3.0 mg cm-2 . Moreover, the capsule-like MnO@C also demonstrates excellent performance in full battery applications. This study demonstrates the effectiveness of multi-dimensional synergistic nanoarchitecture in achieving mass loading-independent performance, which can be extended to other TMCs for electrochemical energy storage.

Oxygen vacancy engineered electron structure of porous CexCo3−xO4 nanorods for wide spectrum photocatalytic hydrogen evolution

Development of high-performance semiconductors for photocatalytic hydrogen evolution is a promising solution to solve the current energy crisis. In this work, a porous and oxygen vacancy-enriched CexCo3−xO4-Vo nanorods (CexCo3−xO4-Vo NRs) with adjust electron structure were fabricated by Ce-doping for wide spectrum photocatalytic hydrogen evolution. Because Ce doping regulates the Co3+/Co2+ atomic ratio of Co3O4 nanorods (Co3O4 NRs), resulting in a reduction of oxygen vacancy formation energy and confirmed by electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy measurements (XPS) studies. The formation of oxygen vacancy leads to a modification in the positions of conduction band and valence band positions of CexCo3−xO4-Vo NRs. The ultraviolet photoelectron spectroscopy (UPS) spectra results indicate that the generation of oxygen vacancies leads to a more negative Fermi level in CexCo3−xO4-Vo NRs. This result directly results in an enhanced capacity for H+ reduction of CexCo3−xO4-Vo NRs. Density functional theory (DFT) calculations demonstrate that Ce0.15Co2.85O4-Vo NRs have faster electron transfer rates. In addition, the porous rod-like structure endows it abundant electron diffusion pathways, facilitates electrolyte infiltration, and establishes an ideal electrolyte/catalyst contact interface. Among them, Ce0.15Co2.85O4-Vo NRs have the best photocatalytic hydrogen evolution activity (3912.8 μmol g−1), which were 2.2 times more than that of Co3O4 NRs, and an excellent stability also obtained. This work provides a new idea for elements doping Co3O4 NRs to in situ-induced oxygen vacancies for enhanced photocatalytic hydrogen evolution.

Na4MnCr(PO4)3 with a Dual Conductive Network for Sodium‐Ion Batteries

AbstractNASICON (NAtrium Super Ionic CONductor)‐structured Na4MnCr(PO4)3 has attracted attention as a promising cathode for sodium‐ion batteries due to its high operating voltage and specific capacity contributed by multielectron reactions. Unfortunately, its intrinsic low electronic conductivity significantly hinders the release of specific capacity and rate capability, preventing its practical application. Herein, a carbon layer with dual conductive networks connected by chain‐like Ketjen black (KB) is built on the surface of Na4MnCr(PO4)3 material. This novel Na4MnCr(PO4)3/C@KB composite material exhibits improved rate capability of 61.2 mAh g−1 at 2 C compared to 19.5 mAh g−1 of Na4MnCr(PO4)3/C and high reversible capacity of 88.0 mAh g−1 at 1 C with 73% capacity retention after 100 cycles. The enhanced electrochemical performance can be ascribed to an increase of electronic conductivity enabled by the dual conductive 3D network construction and an adequate infiltration of electrolyte by substantial pores existence in carbon layer. A promising dual conductive network design strategy is demonstrated here for improving the performance of NASICON‐structured cathodes.

High specific surface area MXene/SWCNT/cellulose nanofiber aerogel film as an electrode for flexible supercapacitors

Transition metal carbonitrides (MXene) with two-dimensional layered structures are a recent research topic in the field of supercapacitors. However, because MXene can easily self-stack, its capacitance performance is affected. To this end, one-dimensional cellulose nanofibers (CNF) and carboxylic single-walled carbon nanotubes (SWCNT) were used to intercalate MXene to obtain well-dispersed MXene/SWCNT/CNF aqueous suspensions and their hybrid hydrogels, and to obtain hybrid aerogels through supercritical drying. CNF gives aerogel excellent porosity, a high specific surface area (301.03 m2 g−1), good electrolyte infiltration, and gentle mechanical flexibility, while SWCNT imparts high conductivity to aerogel film. We assembled a symmetrical all-solid-state flexible supercapacitor and interdigitated micro-supercapacitors using an aerogel film as a flexible electrode. The area specific capacity of the above electrode reaches 746.68 mF cm−2 and 244.50 mF cm−2, respectively. This study provides a fabrication method of polymer–inorganic hybrid nanocomposite aerogel film electrodes for flexible supercapacitors.

Thick‐Network Electrode: Enabling Dual Working Voltage Plateaus of Zn‐ion Micro‐Battery with Ultrahigh Areal Capacity

AbstractAqueous Zn‐ion micro‐batteries (AZMBs) have been recently shown to be promising integrated and safe micropower sources for portable electronics but with wide commercial adoption greatly constrained by their relatively low areal capacity. Although increasing the electrode thickness is proposed, the performance is compromised due to sluggish reaction kinetics, slow ion diffusion rate, and underutilization of active materials. Herein, the technique of utilizing a 3D thick‐network electrode, consisting of closely interweaved MnO2 nanowires (MnO2 NWs), silver nanowires (AgNWs), and carbon nanotubes (CNTs) is presented. The technique readily enables electrode realization up to a thickness of 351 µm, where the porous structure, high hydrophilicity, and fast electrolyte infiltration jointly contribute to fast kinetics. Matching with a Zn metal anode, the prototyped AZMBs acquire an ultra‐high areal capacity/power density of 809 µAh cm−2/1951 µW cm−2. Additionally, as MnO2 NWs and AgNWs collectively participate in the reaction as active substances, the AZMBs deliver dual voltage plateaus to further improve the areal energy density, realizing a maximum value of 896 µWh cm−2. The 3D thick‐network electrode supporting dual working voltage plateaus can provide a path forward for developing AZMBs with simultaneously ultra‐high areal capacity and energy density.

Carbon microspheres with gigapores for application as electrode-active material of sodium-ion batteries

Micro- and mesoporous carbons are known to be effective anode materials for sodium-ion (Na+) batteries (SIBs). In contrast, macroporous and gigaporous carbons have rarely been studied for this purpose, even though their porous structure may facilitate electrolyte infiltration to enhance cell performance. Here, a series of gigaporous carbon microspheres (GCS) was synthesized by carbonizing gigaporous polymeric microspheres at different temperatures (700–2500 °C) and adopted as anode-active material of SIBs. All GCS samples exhibited a particle size of 10–15 μm and an average pore size of 0.3–0.5 μm. Nevertheless, their specific surface areas decreased over a large range with increasing carbonization temperature from >400 m2 g−1 to <30 m2 g−1. The GCS samples fabricated at higher temperatures demonstrated better electronic conductivity and a larger contribution from Na + insertion/extraction instead of adsorption/desorption to the capacity of constructed cells during charge/discharge. GCS carbonized at 850–1000 °C resulted in cells with the best capacity performance (>300 mAh g−1). The reason is that GCS produced at lower temperatures had insufficient conductivity and underwent limited electrochemical reactions with Na+, leading to a low capacity. On the other hand, an excessively high carbonization temperature produced carbons having a small d-spacing and lacking the beneficial carbonyl groups, which hindered both Na+ insertion/extraction and adsorption/desorption and therefore also reduced the cell capacity.

Hierarchical Electrode Architecture Enabling Ultrahigh-Capacity LiFePO4 Cathodes with Low Tortuosity.

Thickening electrodes are expected to increase the energy density of batteries. Unfortunately, the manufacturing issues, sluggish electrolyte infiltration, and restrictions on electron/ion transport seriously hamper the development of thick electrodes. In this work, an ultrathick LiFePO4 (LFP) electrode with hierarchically vertical microchannels and porous structures (I-LFP) is rationally designed by combining the template method and the mechanical channel-making method. By using ultrasonic transmission mapping technology, it is proven that the open and vertical microchannels and interconnected pores can successfully overcome the electrolyte infiltration difficulty of conventional thick electrodes. Meanwhile, both the electrochemical and simulation characterizations reveal the fast ion transport kinetics and low tortuosity (1.44) in the I-LFP electrode. As a result, the I-LFP electrode delivers marked improvements in rate performance and cycling stability even under a high areal loading of 180 mg cm-2. Moreover, according to the results of operando optical fiber sensors, the stress accumulation in the I-LFP electrode is effectively alleviated, which further confirms the improvement of mechanical stability.

Tuning hierarchical structure of probiotics-derived porous carbon for potassium-ion batteries

Biomass derived carbon-based materials are considered as prospective anode candidates for potassium ion batteries (PIBs) because of their abundant resources, low cost, high specific surface area and abundant active sites. However, the practical application of carbon-based electrodes for PIBs is intrinsically hindered by the unsatisfactory reversible capacity caused by the huge volume expansion during the embedding of potassium ions. Herein, a three-dimensional (3D) probiotics-derived porous N doped carbon nanosheets aggregate with the highly branched carbon nanotube (denoted as 3D-PNC@CNTs) is designed as advanced anode for PIBs. The as-prepared 3D-PNC@CNTs possesses the 3D interconnected conductive framework composed of ultrathin carbon nanosheets, rich hierarchical pores, and high edge defects. These features facilitate the rapid electrons/ions transfer, provide enough space to accommodate the huge volume change, ensure easy electrolyte infiltration and provide many active sites for K+ storage. By virtue of these features, 3D-PNC@CNTs displays a high reversible capacity of 458 mAh g−1 at 100 mA g−1 and excellent cycling stability (143 mAh g−1 at 1000 mA g−1 after 500 cycles). This work provides important insights into biomass materials as promising anode materials for rechargeable PIBs.

Three-dimensional hierarchically porous micro sponge-ball comprising anatase TiO2 nanodots and nitrogen-doped graphitic carbon as anodes for ultra-stable lithium-ion batteries

Hierarchically porous three-dimensional micro sponge-balls comprising highly conductive nitrogen-doped graphitic carbon (NGC) and anatase-type TiO2 nanodots (TiO2@NGC MSB) are synthesized using spray pyrolysis technique followed by heat treatment. The as-sprayed powders obtained after spray pyrolysis consist of polystyrene (PS) nanobeads-derived macropores and anatase TiO2 nanodots embedded in an amorphous carbon (AC)-NGC carbon matrix (TiO2@NGC-AC MSB). The subsequent heat treatment of the as-sprayed powders at 300 °C resulted in the formation of additional micropores by selective removal of the AC into gaseous products to form TiO2@NGC MSB. The obtained hierarchically porous and highly conductive architecture guarantees effective electrolyte infiltration inside the electrode, enhanced Li-ion diffusion, and faster charge transfer during the redox reactions. Benefited from the structural merits, the TiO2@NGC MSB anode exhibits remarkable electrochemical performance compared to those of TiO2@NGC-AC MSB and filled-type TiO2 anodes. A reasonable discharge capacity of 105 mA h g−1 at a high current density of 10.0 A g−1 and exceptional cycling performance (219 mA h g−1 with 0.0006 % decay rate after 2000 cycles at 2.0 A g−1 and 160 mA h g−1 with 0.003 % decay rate after 5000 cycles at 3.0 A g−1) are obtained.

Decoupling the Effect of Electrolyte Infiltration on the Intercalation of Alkali Metal Ions in Highly Oriented Pyrolytic Graphite

Diffusion coefficients of ion in graphitic materials are responsible for high-rate batteries. However, the complex electrochemical response presented a challenge to accurately measure the diffusion coefficient of alkali-metal ions in graphitic materials. Here we design a method to identify the diffusion coefficients of Li+ and Na+ in highly oriented pyrolytic graphite (HOPG) with and without presence of liquid electrolyte infiltration. The results reveal inherent high diffusivity of Li+ in HOPG (∼10−7 cm2·s−1), as compared to HOPG with electrolyte infiltration (∼10−8 cm2·s−1), while Na+ has almost no interlayer diffusion without solvent infiltration. The presence of electrolyte has different effect on the interlayer diffusion of Li+ and Na+.

Low carrier recombination in polysiloxane gel electrolyte for high-performance DSSC

Previous research on quasi-solid-state DSSC (QSS-DSSC) that utilized polysiloxane-based polymer gel electrolytes (PGE) showed that the functional performance of the cells was highly affected by electrolyte infiltration into the TiO2 nano-porous layers. This study evaluated the efficiency enhancement in siloxane-based cells by introducing a TiCl4 pre-treatment process twice. We compared the impedance spectrum of PGE-based DSSC without (type-1 PGE) and with (type-2 PGE) with the addition of propylene carbonate, measured under dark and light illumination. The impedance spectra of both cells showed different characteristics at different condition measurements, especially in the high-frequency region. Unlike the type-2 PGE-based DSSC, the type-1 PGE-based DSSC did not show the transmission line characteristic, which indicated less charge carrier diffusion inside the TiO2 nano-porous layer. Under light illumination, the interfacial charge transfer between electrons inside TiO2 layers with the electrolyte (Rct), and the electron lifetime inside TiO2 layers before it is recombined (τ r), became smaller for type-2 PGE-based DSSC and larger for type-1 PGE-based DSSC. This indicated that the recombination rate increased as the PGE became more vicious. This result supports the photovoltaic characteristics that yield current density and efficiency values of 16 mA cm−2 and 5.37% for type-2 PGE-based DSSC, 13.4 mA cm−2, and 4.72% for type-1 PGE-based DSSC. The challenge for further improvement in DSSC that employs PGE is to elevate the wetting capability of the gel inside the TiO2 layer without additional solvent since additional solvent eventually can reduce ionic concentration and consequently increase the Rct value as shown in the analysis of the impedance spectrum of TiO2 layer without dye.

Alkali-Etched NiCoAl-LDH with Improved Electrochemical Performance for Asymmetric Supercapacitors

Hydrotalcite, first found in natural ores, has important applications in supercapacitors. NiCoAl-LDH, as a hydrotalcite-like compound with good crystallinity, is commonly synthesized by a hydrothermal method. Al3+ plays an important role in the crystallization of hydrotalcite and can provide stable trivalent cations, which is conducive to the formation of hydrotalcite. However, aluminum and its hydroxides are unstable in a strong alkaline electrolyte; therefore, a secondary alkali treatment is proposed in this work to produce cation vacancies. The hydrophilicity of the NiCoAl-OH surface with cation vacancy has been greatly improved, which is conducive to the wetting and infiltration of electrolyte in water-based supercapacitors. At the same time, cation vacancies generate a large number of defects as active sites for energy storage. As a result, the specific capacity of the NiCoAl-OH electrode after 10,000 cycles can be maintained at 94.1%, which is much better than the NiCoAl-LDH material of 74%.

Three-dimensional printed Li4Ti5O12@VSe2 composites as high-performance anode material in full 3D-printed lithium-ion batteries with three-dimensional -printed LiFePO4@AC/rGO cathode

Currently, the development of high-performance lithium-ion batteries (LIBs) with improved areal capacity is still challenging. The common strategy to improve areal capacity is to increase the thickness of electrode materials. However, the application of thick electrodes remains challenge due to poor mechanical properties, slow charge and ion transport, and poor electrolyte infiltration. In this study, thick electrodes are constructed by 3D printing a Li4Ti5O12@VSe2-based ink. The highly electrical conductor VSe2 on the Li4Ti5O12 surface improves the ion and charge transport and eases the internal resistance of the 3D-printed electrode during charge and discharge. As a result, LIBs employing these thick electrodes show a high-rate capability of 128.9 mAh/g at 10 C, improved areal capacities up to 6.2 mAh/cm2, and ultrastable cycling capability (84.5% of capacity retention after 1700 cycles). Moreover, full cells utilizing 3D-Li4Ti5O12@VSe2 as the anode and 3D-LiFePO4@AC/rGO as the cathode with 1.81 V potential yield a high specific capacity of 152.5 mAh/g at 0.1C, a high specific energy density of 276.025 Wh/kg, and a power density of 30.5 W/kg at 0.1C. This work paves the way to designing thick electrodes for high-performance LIBs.

Ni/Ni2P@C heterostructure loaded porous carbon microrods framework connected by N-doped carbon nanotubes for lithium-ion batteries

The caterpillar-like structure material (Ni/Ni2P@C-NCNTs) consisting of carbon microrods framework embedded with Ni/Ni2P nanoparticles coated by carbon layer (Ni/Ni2P@C) connected by interlaced N-doped carbon nanotubes is synthesized via a feasible method. The characteristic Ni/Ni2P@C core-shell structure effectively restrains the volume change and accelerates the infiltration of electrolyte. The Ni/Ni2P heterostructure is beneficial for the transfer of ions and electrons. Employing N-doped carbon nanotubes NCNTs into the composites successfully builds a conductive network and makes up for the poor electronic conductivity of transition-metal phosphides (TMPs). Consequently, Ni/Ni2P@C-NCNTs delivers a reversible capacity of 659.8 mAh g−1 at 100 mA g−1 after 170 cycles and an excellent rate performance of 330 mAh g−1 at 1000 mA g−1 as an anode material for lithium ion batteries (LIBs). The specific characteristics of Ni/Ni2P@C-NCNTs provide a novel design strategy of anode materials for LIBs and make it prospective for the application of TMPs in batteries.

N-Type Polyoxadiazole Conductive Polymer Binders Derived High-Performance Silicon Anodes Enabled by Crosslinking Metal Cations.

The dilemma of employing high-capacity battery materials and maintaining the electrodes' electrical and mechanical integrity requires a unique binder system design. Polyoxadiazole (POD) is an n-type conductive polymer with excellent electronic and ionic conductive properties, which has acted as a silicon binder to achieve high specific capacity and rate performance. However, due to its linear structure, it cannot effectively alleviate the enormous volume change of silicon during the process of lithiation/delithiation, resulting in poor cycle stability. This paper systematically studied metal ion (i.e., Li+, Na+, Mg2+, Ca2+, and Sr2+)-crosslinked PODs as silicon anode binders. The results show that the ionic radius and valence state remarkably influence the polymer's mechanical properties and the electrolyte's infiltration. Electrochemical methods have thoroughly explored the effects of different ion crosslinks on the ionic and electronic conductivity of POD in the intrinsic and n-doped states. Attributed to the excellent mechanical strength and good elasticity, Ca-POD can better maintain the overall integrity of the electrode structure and conductive network, significantly improving the cycling stability of the silicon anode. The cell with such binders still retains a capacity of 1770.1 mA h g-1 after 100 cycles at 0.2 C, which is ∼285% that of the cell with the PAALi binder (620.6 mA h g-1). This novel strategy using metal-ion crosslinking polymer binders and the unique experimental design provides a new pathway of high-performance binders for next-generation rechargeable batteries.

Enhanced Hydro-Actuation and Capacitance of Electrochemically Inner-Bundle-Activated Carbon Nanotube Yarns.

Recently, several attempts have been made to activate or functionalize macroscopic carbon nanotube (CNT) yarns to enhance their innate abilities. However, a more homogeneous and holistic activation approach that reflects the individual nanotubes constituting the yarns is crucial. Herein, a facile strategy is reported to maximize the intrinsic properties of CNTs assembled in yarns through an electrochemical inner-bundle activation (EIBA) process. The as-prepared neat CNT yarns are two-end tethered and subjected to an electrochemical voltage (vs Ag/AgCl) in aqueous electrolyte systems. Massive electrolyte infiltration during the EIBA causes swelling of the CNT interlayers owing to the tethering and subsequent yarn shrinkage after drying, suggesting activation of the entire yarn. The EIBA-treated CNT yarns functionalized with oxygen-containing groups exhibit enhanced wettability without significant loss of their physical properties. The EIBA effect of the CNTs is experimentally demonstrated by hydration-driven torsional actuation (∼986 revolutions/m) and a drastic capacitance improvement (approximately 25-fold).

Mussel stimulated modification of flexible Janus PAN/PVDF-HFP nanofiber hybrid membrane for advanced lithium-ion batteries separator

Bicomponent polyacrylonitrile/Poly(vinylidene fluoride-co-hexafluoropropylene) (PAN/PVDF-HFP) Janus nanofibers based hybrid membrane was successfully prepared by parallel electrospinning technology. Subsequently, modified PAN/PVDF-HFP hybrid membrane (M-PAN/PVDF-HFP) was further fabricated via mimicking the adhesive of mussel by coating dopamine alternative through polymerization of catechol and tetraethylenepentamine (TEPA) in weakly alkali solution. M-PAN/PVDF-HFP maintains the abundant pore structure of the electrospun hybrid membrane and further provides excellent electrolyte infiltration with high porosity (82.09%) and outstanding electrolyte retention (553.23%). Simultaneously, the mechanical strength of the separator was significantly improved (14.36 MPa). Electrochemical studies displayed that the M-PAN/PVDF-HFP composite membrane delivered superior ion conductivity (2.81 mS/cm) and wide electrochemical stability window (∼5.25 V). The cell assembled by M-PAN/PVDF-HFP separator presented outstanding rate capability with high specific capacity of 147 mAh/g at 1 C and excellent cycle stability with discharge capacity of 120 mAh/g at 1 C after 600 cycles. Furthermore, M-PAN/PVDF-HFP separator exhibited ultra-flexibility with remarkable electrochemical performance after repeated bending for 500 to 1000 time. This work provides new insights into polyamine modified hybrid membranes for the potential practical applications in lithium-ion batteries separator.