A novel multifunctional binder (P-ppCMC) with cross-linked and porous structure is simply prepared through partially protonation and template methods for silicon anodes to accommodate the large ...volume change of silicon and to enhance the lithium-ion diffusion during the charge/discharge process. In this binder, the cross-linked structure, formed through the carboxyl and hydroxyl groups in partially protonated carboxymethyl cellulose, increases the adhesion and mechanical property of binder, buffering the volume variation of silicon during repeated cycles. The porous structure, generated via template approach, enhances the lithium-ion diffusion and tolerates the volume variation of silicon. Therefore, the P-ppCMC binder significantly improves the cycling stability and rate performance of silicon anodes. The silicon anode with P-ppCMC displays a reversible capacity of 1835 mA h g−1 after 200 cycles at a current density of 0.5 A g−1, and a rate capability of 1707 mA h g−1 at 5 A g−1. The P-ppCMC binder also effectively increases the cycling stability of tin anodes.
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•A high ion-conductive and LiF-rich interlayer is formed on the surface of Li anode through the pre-treatment of PVDF-HFP/CuF2.•The simple modification can suppress the formation and ...growth of Li dendrites, and achieve dendrites elimination to some extent.•The dendrites suppression effectively reduces the parasitic side reaction between PEO-based electrolyte and Li anode, leading to high coulombic efficiency for all-solid-state batteries.
Polyethylene oxide (PEO)-based composite electrolytes are considered as competent candidates to achieve high energy density all-solid-state lithium batteries (ASSLBs) due to good flexibility, which can effectively solve the problem of large interfacial resistance with electrodes. However, poor mechanical strength and low Li+ transference number can’t restrain the formation and growth of Li dendrites, leading to parasitic reaction between electrolyte and Li anode and unsatisfied coulombic efficiency. Herein, Li metal is pre-treated by poly(vinylidene-co-hexafluoropropylene) (PVDF-HFP)/CuF2 composite to form a stable interlayer on the anode. In-situ reaction of CuF2 with Li greatly improves the contact between PVDF-HFP layer and Li anode, forming a LiF-rich modified layer. The interlayer with high mechanical strength and ionic conductivity can not only suppress the formation of Li dendrites, but also achieve the growth restriction and elimination of dendrites. Moreover, excellent elasticity and strong adhesion with Li anode can ensure the structure stability of modified layer during dynamic plating/stripping of Li. Applied in ASSLBs with PEO-based electrolyte, PVDF-HFP/CuF2 modified symmetrical Li cells demonstrate increased critical current density and extended cycle life than that of bare Li or single CuF2 treated Li. Furtherly, the ASSLBs with LiFePO4 cathode show excellent cycle stability and high coulombic efficiency over 1000 cycles at 1 C.
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In this work, we fabricated the free-standing porous silicon/MXene-2:1 composite film (pSi/MXene-2:1 film) as anodes for LIBs by facile vacuum filtration method. The pSi/MXene-2:1 film possesses ...excellent mechanical flexibility and the voids in the structure can well accommodate the volume expansion during cycling. Accordingly the film anodes shows steady cycling performance and rate performance.
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•Free-standing and binder-free pSi/MXene films were synthesized by vacuum filtration.•The porous structure accommodates volume expansion of pSi.•Thin thickness of pSi flakes provides superior reation kinetics.•The layer-by-layer structure ensures adequate electrical contact of pSi with MXene.•Both of half and full cell exhibit superior electrochemical performance.
Silicon is an ideal anode candidate for next-generation lithium-ion batteries (LIBs) due to its high specific capacity, low working potential and abundant sources. However, its practical application is seriously hindered by its huge volume expansion, which leads to the destruction of the electrode structure and the short cycle life. Herein, we fabricated flexible self-supporting binder-free porous silicon/MXene-2:1 composite film (pSi/MXene-2:1 film) as anode for LIBs by vacuum filtration. The pSi possesses sheet-shape resulting from layered montmorillonite, which is beneficial to shorten ion transport length. Furthermore, the pSi/MXene-2:1 film possesses excellent mechanical flexibility and the voids in the structure can well accommodate the volume expansion during cycling. Benefitting from these advantages, the pSi/MXene-2:1 film anode shows steady cycling performance with 1039.3 mAh/g at 500 mA g−1 after 200 cycles and excellent rate performance with 840.3 mAh/g at 5 A/g. Furthermore, a high reversible capacity of 1201 mAh/g can be obtained at 1 A/g for pSi/MXene-2:1||LiFePO4 full cell. This work provides a strategy to fabricate high-capacity and long-cycle self-supporting silicon-based anodes for flexible LIBs.
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In this work, a new effective and low-cost binder applied in porous silicon anode is designed through blending of low-cost poly(acrylic acid) (PAA) and poly(ethylene-co-vinyl acetate) (EVA) latex ...(PAA/EVA) to avoid pulverization of electrodes and loss of electronic contact because of huge volume changes during repeated charge/discharge cycles. PAA with a large number of carboxyl groups offers strong binding strength among porous silicon particles. EVA with high elastic property enhances the ductility of the PAA/EVA binder. The high-ductility PAA/EVA binder tolerates the huge silicon volume variations and keeps the electrode integrity during the charge/discharge cycle process. EVA colloids acting as host materials for electrolytes increase the electrolyte uptake of electrodes. The porous silicon electrode with the PAA/EVA binder exhibits a reversible capacity of 2120 mA h g–1 at 500 mA g–1 after 140 cycles because of the excellent ductility and lithium-ion transport properties of the PAA/EVA binder.
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Silicon (Si) is regarded as a promising negative material for Li-ion batteries (LIBs), but the poor cyclic performance limits its practical applications. Herein, we used several different ...carbonaceous materials as carbon sources to form Si/C composites, which was formed by etched Fe–Si alloys followed by mechanical ball mill mixing with carbon. It is found that the artificial graphite as the carbonaceous material can form a well-distributed mixture during the ball milling, and then uniformly coated with amorphous carbon pyrolyzed by the phenolic resin. The pore structure of Si particles can provide rapid diffusion for lithium ions, resulting in improving the electrochemical properties. The well-coated carbon layer promotes the formation of stable SEI layer on the composites surface, which is advantageous for the long cycle performance. The carbonaceous materials (artificial graphite, flake graphite and soft carbon) have remarkable influence on the electrochemical performance of Si/C composites. The silicon/graphite-artificial graphite (Si/C-AG) exhibits the best performance among these three Si/C composites. It delivers a specific capacity of 445 mAh g-1 at 0.5 A g−1 with a retention of 94% after 200 cycles. This work would be helpful with choosing suitable carbonaceous materials for the Si/C composites.
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•The various synthesis and delamination strategies of MXenes are briefly described.•The composition, morphology and a series of properties of MXene sediment are highlighted.•The ...applications of MXene sediment in various fields are comprehensively summarized.•The perspectives for the future development of MXene sediment are proposed.
In the past decade, MXenes have undergone rapid development in their synthesis, delamination and application. Specifically, the continuous optimization of the delamination methods has led to a great increase in the yield of single-/few-layered MXene nanosheets, but it is still far from 100%. Therefore, there always exists some MXene sediment that is difficult to be further exfoliated and generally discarded as trash in the early stage, leading to significant economic losses. Since 2020, researchers have discovered that MXene sediment possesses a series of outstanding properties, opening the door to turning MXene sediment trash to treasure. Related reports of MXene sediment have continuously increased in the past four years, but a systematic review on this topic has not been reported yet. Herein, the latest advances of MXene sediment are comprehensively summarized. Firstly, the various synthesis and delamination strategies of MXenes are briefly introduced. Subsequently, the composition and morphology, large interlayer spacing, superior rheological, electrical and mechanical properties of MXene sediment are discussed. Furthermore, the applications of MXene sediment in supercapacitors, lithium-ion batteries, electromagnetic interference shielding, electrothermal and photothermal conversion as well as sensors have been carefully summarized. Finally, some perspectives for the future development of MXene sediment are proposed. This review aims to arouse the scientific interest of researchers in MXene sediment, further boosting the comprehensive development of MXenes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The low initial Coulombic efficiency (ICE) greatly hinders the practical application of MXenes in sodium-ion batteries. Herein, theoretical calculations confirm that −F and −OH terminations as well ...as the tetramethylammonium ion (TMA+) intercalator in sediment Ti3C2T x (s-Ti3C2T x ) MXene possess strong interaction with Na+, which impedes Na+ desorption during the charging process and results in low ICE. Consequently, Na+-intercalated sediment Ti3C2T x (Na-s-Ti3C2T x ) is constructed through Na2S·9H2O treatment of s-Ti3C2T x . Specifically, Na+ can first exchange with TMA+ of s-Ti3C2T x and then combine with −F and −OH terminations, thus leading to the elimination of TMA+ and preshielding of −F and −OH. As expected, the resulting Na-s-Ti3C2T x anode delivers considerably boosted ICE values of around 71% in carbonate-based electrolytes relative to s-Ti3C2T x . Furthermore, electrolyte optimization is employed to improve ICE, and the results demonstrate that an ultrahigh ICE value of 94.0% is obtained for Na-s-Ti3C2T x in the NaPF6-diglyme electrolyte. More importantly, Na-s-Ti3C2T x exhibits a lower Na+ migration barrier and higher electronic conductivity compared with s-Ti3C2T x based on theoretical calculations. In addition, the cyclic stability and rate performance of the Na-s-Ti3C2T x anode in various electrolytes are comprehensively explored. The presented simple strategy in boosting ICE significantly enhances the commercialization prospect of MXenes in advanced batteries.
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•MXene/metal sodiophilic hosts are constructed via Lewis acidic etching.•Uniform Na nucleation and deposition are afforded for MXene/metal hosts.•The hosts deliver superior ...asymmetric, symmetric and full cell performance.•The Ti3C2/Zn host exhibits superior cyclic stability upon a high cutoff potential.
Although MXene-based 3D scaffolds have boosted the cyclability of Na metal, the complex and harsh synthetic process deteriorates their practical application. Herein, a series of MXene/metal sodiophilic frameworks are constructed through one-step Lewis acidic etching, and metal nanoparticles are uniformly distributed on the surface or intercalated into the large interlayer gaps of MXenes. Notably, MXenes with superior Na+/electron transport kinetics and mechanical flexibility remarkably reduce the local current density, homogenize Na+ flux and cushion huge volume change of Na metal. Moreover, sodiophilic species including MXenes and metals effectively induce Na uniform nucleation and smooth deposition among the 3D matrixes, leading to dendrite-free morphology. Consequently, MXene/metal hosts exhibit stable Na plating/stripping process for 900 cycles with high average Coulombic efficiencies of 99.9% (2 mA cm−2, 1 mAh cm−2). The MXene/metal-Na symmetric cells achieve low overpotentials of less than 15 mV and stable cycling for 2200 h (2 mA cm−2, 4 mAh cm−2). When paired with Na3V2(PO4)3 cathode, the full cells with a low N/P ratio (around 2) demonstrate high discharge capacity and excellent long-term cyclic performance over 600 cycles. The presented universal, safe and one-step approach in fabricating MXene/metal scaffolds shows bright prospects and may promote the development of alkali metal-based batteries.
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A simple, safe and in-situ growth strategy has been proposed for the fabrication of Ti3C2Tx@CoSe2 heterostructure via Lewis acidic etching route. With Ti3C2Tx@CoSe2 heterostructure coated separators ...for lithium-sulfur batteries, the shuttle effects have been effectively suppressed, promoting the conversion of lithium polysulfides and ultimately resulting in enhanced performance.
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•Ti3C2Tx@CoSe2 was prepared by Lewis acidic etching and subsequent selenization.•The heterostructure exhibits strong confinement and accelerates redox conversion of polysulfides.•The heterostructure modified separator enables significant improvement in the Li-S battery.•Ti3C2Tx@CoSy heterostructure was also prepared as a validation of the universality of our strategy.
Lithium-sulfur (Li-S) batteries are considered the desirable candidate for the next generation energy storage system, owing to their significant advantages in high theoretical energy density (2600 Wh kg−1) and environmental friendliness. Nevertheless, the notorious shuttle effect and sluggish conversion kinetics of lithium polysulfides (LiPSs) limit the application of Li-S batteries. Herein, heterostructure with CoSe2 nanoparticles strongly anchored on Ti3C2Tx substrate are prepared by a universal, simple, and non-hazardous preparation method, with Lewis acidic molten salt etching and subsequent in-situ selenization processes. The fabricated Ti3C2Tx@CoSe2 heterostructure exhibits high electrical conductivity and acts as electrocatalyst to facilitate the fast conversion of LiPSs. With Ti3C2Tx@CoSe2 heterostructure coated separator, the assembled Li-S cells deliver high initial capacity of 1183 mAh/g and well maintain at 788 mAh/g after 100 cycles at 0.5C. Besides, excellent rate performance (713 mAh/g at 3C) and long-term cycling performance (capacity fading rate of 0.059% per cycle at 0.5C and 0.041% per cycle at 1C) are achieved. The cells exhibited impressive performances even under the condition of lean electrolyte, high sulfur loading and practical shape (pouch cell). Additionally, Co atom was proved to serve as the catalytic site in the redox reaction of LiPSs by ex-situ XPS. Consequently, this work provides a new insight for the regulation of polysulfides conversion in Li-S batteries.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
