The growing demand for wearable electronics and smart textiles has intensified research into flexible, miniaturized, high-performance, and safe energy storage devices. Lithium-sulfur (Li-S) batteries, with their high theoretical energy density supported by sulfur's multielectron chemistry and cost-effectiveness, are highly promising, yet they face critical bottlenecks. These challenges include low long-cycle capacity retention and inadequate cycling durability during bending. Conventional materials such as graphene and conductive polymers fall short in interface stability or scalable synthesis, failing to balance electrical conductivity with mechanical strength simultaneously. MXene emerges as a breakthrough, offering metal-grade conductivity, tunable surface chemistry, abundant functional groups, and exceptional mechanical resilience. Its layered structure not only anchors polysulfides but also withstands repeated deformations. This review systematically examines the design strategies for Li-S batteries that integrate flexibility, high energy density, and cycling stability. Firstly, synthesis, structure, properties, and analysis of advantages of MXene used in Li-S batteries are summarized. Subsequently, computational and simulation approaches are employed to analyze MXene's role in addressing shuttle effects and lithium dendrite growth. Applications of MXene-based materials in various components of flexible Li-S batteries are then discussed. Finally, insights are provided on challenges and future developments for MXene-based flexible Li-S batteries.

Three-dimensional (3D) carbonaceous hosts are ideal for lithium metal anodes (LMAs) owing to their lightweight architecture and high conductivity. However, spatial inhomogeneities in Li+ concentration and electric fields induce detrimental "top-growth" lithium deposition and dendrite formation. To overcome this challenge, a vertically graded 3D carbon fiber framework with functionally stratified silver nanoparticles (Ag NPs) layers (VGCF-Ag) is engineered. It comprises three functional layers: a bottom induction layer enriched with ultrathin Ag NPs to guide downward Li+ diffusion and enable preferential nucleation; a middle growth layer with fully exposed Ag NPs to ensure uniform Li deposition; a top lithiophobic layer with reduced fiber diameter to facilitate the downward migration of Li+ while serving as a buffer for Li growth. Characterization and simulations confirm that VGCF-Ag enables controlled "bottom-up" deposition by regulating Li+ kinetics and electrochemical deposition behavior. Electrochemical tests demonstrate exceptional performance, including stable cycling for 600 cycles in half-cells, over 2000 h in symmetric cells at 1 mA cm-2, and 92.2% capacity retention in full-cells after 800 cycles at 3C. Even at a low N/P ratio, it still shows remarkable performance. This vertically graded multifunctional layer design effectively suppresses dendrites, offering a scalable paradigm for high-energy-density batteries.

This study employed an ultrasound-assisted citric acid–sodium thiosulfate methodology aimed at reclaiming target metals from discarded lithium-ion batteries. By systematically investigating parameters such as the levels of citric acid and sodium thiosulfate, the solid-to-liquid ratio, temperature and reaction time under optimal recovery conditions, recovery rates of Li, Ni, Co and Mn exceeding 94% were achieved. The cathode material LiNi0.8Co0.1Mn0.1O2, hereafter referred to as NCM811, was subsequently synthesized and modified via aluminum oxide coating. It was found that the optimal application rate is 2% by weight. The resulting 2A@NCM composite exhibited the best electrochemical performance, retaining 95.24% of its original capacity when cycled within a voltage window of 2.8–4.3 V at 0.5 C upon 100 cycles. This study provides new insights into the recycling and recovery of used lithium-ion batteries.

Composite solid electrolytes hold the promise of merging complementary merits of solid polymer electrolytes and ceramic fillers to achieve solid batteries with comprehensive performance. Especially, three-dimensional inorganic electrolyte frameworks, such as Li7La3Zr2O12, with fast and continuous lithium ion migration channels demonstrate great promise in composite solid electrolytes. Nevertheless, brittle ceramic conductor skeletons are incapable of providing sufficient mechanical adaptability, which restricts their practical application. Herein, a flexible, ion-conducting network which integrates Li7La3Zr2O12 nanoparticles in polyacrylonitrile nanofibers is fabricated through electrospinning method. Subsequently, a composite electrolyte with three-dimensional continuous structure is achieved via in situ polymerizing of 1,3-dioxolane within the ionic conduction framework. The highly conductive Li7La3Zr2O12 reinforced polymer nanofibers are not only available to promote transportation of lithium ion, but also provide structural flexibility and mechanical robustness for composite electrolyte. Accordingly, the obtained composite electrolyte combines enhanced room temperature ionic conductivity (4.38 x 10-4 Scm-1) with structural flexibility and mechanical robustness, supported by exceptional interfacial compatibility with lithium metal, enabling ultra-stable lithium symmetric battery operation (3000 h at 0.1 mAcm-2). Furthermore, as-prepared LiFePO4 and LiCoO2/lithium solid-state batteries deliver high capacity retention of 96% after 350 cycles and capacity retention of 82% after 600 cycles at room temperature. This work provides a new avenue in design of advancing composite solid electrolytes.

The proliferation of portable electronics has intensified the demand for high-energy-density, safe electronic devices. Lithium-sulfur batteries (LSBs) have emerged as a promising solution due to their high theoretical energy density (2600 Wh kg−1), abundant sulfur resources, and cost-effectiveness. However, several challenges, including the inherent low electrical conductivity of sulfur, sluggish reaction kinetics of lithium polysulfides (LiPSs), and the severe shuttle effect, hinder the commercialization of LSBs. MXene-based materials, known for their high conductivity, strong lithophilicity, and mechanical strength, offer potential solutions to these issues. This review summarizes recent advancements in the application of MXene materials in LSB components, including methods for synthesizing and modifying MXene surfaces. The impact of these modifications on the electrochemical performance of LSBs is discussed, with particular emphasis on how MXene composites can enhance the performance of both electrodes and separators. Additionally, the application of MXene in lithium sulfide (Li2S) cathodes is explored, highlighting both opportunities and challenges. By integrating MXene into LSB systems, this review contributes to advancing the development of high-performance, sustainable energy storage solutions.

Parasitic shuttle effects and sluggish kinetics severely limit the practical applications of lithium-sulfur (Li-S) batteries. Developing conducting catalysts with high catalytic activity is effective strategy to address such issues. Electronic engineering as tuning strategy can optimize the electronic structure and enhance the redox reaction kinetics. Herein, NiSe2-CoSe2 hollow microspheres with abundant heterogeneous interfaces were synthesized as sulfur cathode catalysts. DFT calculations show that heterostructure can promote electron redistribution and form built-in electric field (BIEF), which causes the directional transfer of electrons. Additionally, NiSe2-CoSe2 has optimized adsorption energy, which can effectively suppress shuttle effect. Meanwhile, electrochemical tests further confirmed bidirectional catalytic ability. Benefiting the merits, S/NiSe2-CoSe2-GO-CNF (S/NiCo-GN) achieved an initial discharge specific capacity of 1353.35 mAh g- 1 at 0.2C and stable 1000 cycles at 1C with a capacity decay rate of only 0.044 % per cycle. Moreover, S/NiCo-GN also achieved high areal capacity of 1.688 mAh cm-2 at 0.5C under high loading (-2.5 mg cm- 2) and lean electrolyte (-10 mu L mg- 1) conditions. The flexible pouch cell further demonstrated its high safety, good thermal stability, and robust mechanical stability. This work provides guiding methods for the design of efficient catalysts, which can contribute to the realisation of high-performance Li-S batteries.

Sodium-based dual-ion batteries (SDIBs) have received widespread attention due to their high voltage, low cost, safety, and eco-friendliness. Nevertheless, the irregular spherical graphite cathodes are limited by the mass transfer non-uniformity and sluggish reaction kinetics due to uneven anion migration through the highly tortuous pathways and the inductive anisotropic electric fields. Herein, we report a facile dissolutionprecipitation-carbonation optimized modification strategy to synthesize a series of nano-Li2TiO3/C-modified graphite flake (GF-LTx, x = 1, 2.5, and 5) as cathode for SDIBs. The Li2TiO3-C-Cathode Electrolyte Interphase (Li2TiO3-C-CEI) trinity layer by in situ reactions shows good cycling performance. The intrinsic mechanism of Li2TiO3-C-CEI was further explored by DFT molecular orbital theory and distribution relaxation time (DRT) analysis. Notably, the GF-LT2.5 achieves 10,000 stable cycles at 3-5.2 V (vs. Na/Na+) with a initial capacity of 91.1 mAh g-1 and a decay rate of only 0.00217 % per cycle. Furthermore, GF-LT2.5 demonstrates an ultra-high rate performance of 100C with only 30 s for a single charge and 86 % capacity for low current density. Infrared thermography confirms the good thermal stability and safety of the gel-based flexible pouch cells. This work provides new insights into the design of high-rate performance, long-cycle stability, and high-safety energy storage systems.

The practical application of high-energy density lithium-oxygen (Li-O-2) batteries is severely impeded by the notorious cycling stability and safety, which mainly comes from slow kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at cathodes, causing inferior redox overpotentials and reactive lithium metal in flammable liquid electrolyte. Herein, a bifunctional electrode, a safe gel polymer electrolyte (GPE), and a robust lithium anode are proposed to alleviate above problems. The bifunctional electrode is composed of N-doped carbon nanotubes (N-CNTs) and Co4N by in situ chemical vapor deposition self-catalyzed growth on carbon cloth (N-CNTs@Co4N@CC). The self-supporting, binder-free N-CNTs@Co4N@CC electrode has a strong and stable three-dimensional (3D) interconnected conductive structure, which provides interconnectivity between the active sites and the electrode to promote the transfer of electrons. Furthermore, the N-CNT-intertwined Co4N ensures efficient catalytic activity. Hence, the electrode demonstrates improved electrochemical properties even under a large current density (2000 mA g(-1)) and long cycling operation (250 cycles). Moreover, a highly safe and flexible rechargeable cell using the 3D N-CNTs@Co4N@CC electrode, GPE, and robust lithium anode design has been explored. The open circuit voltage is stable at similar to 3.0 V even after 9800 cycles, which proves the mechanical durability of the integrated GPE cell. The stable cable-type Li-air battery was demonstrated to stably drive the light-emitting diodes (LEDs), highlighting the reliability for practical use.

Lithium-sulfur (Li-S) batteries are considered as promising candidates for next-generation energy storage systems. However, the commercial applications are severely limited by the sluggish kinetics and shuttling effect. Herein, we have designed an integrated free-standing functional CoSe-CNF-GO-MXene (CCGM) sulfur host with a "point-line-plane" 3D porous structure for Li-S batteries. The two-dimensional (2D) graphene, MXene and onedimensional (1D) nanocellulose fibers combined with zero-dimensional (0D) transition metal selenide (CoSe) shows good electrical conductivity and enhanced catalytic performance, respectively. Additionally, the rationally designed porous structure (from 0D to 3D) demonstrates well-connected ion/electron transport channels, conferring the good kinetic performance. Electrochemical tests show that CoSe catalytic materials with moderate adsorption energies can catalyse both precipitation and dissolution processes of Li2S, enabling fast conversion kinetics. The density functional theory (DFT) calculations show that the synergistic effect of CoSe, Ti3C2Tx, and graphene can improve the chemisorption and catalytic performance. As a result, the 3D porous S@CCGM cathode exhibits a high initial discharge capacity of 1205.1 mAh g- 1 at 0.2C and good long-term cycling performance with a low decay rate of 0.055 % per cycle at 1C. Furthermore, the gel electrolyte Li-S pouch cell successfully passes the 0-180 degrees bending test, nailing test, and cutting test. Such design offers a new perspective for the commercialization of safe and flexible electrochemical energy-storage devices especially in Li-S batteries.

Studies of graphite carbon anodes due to their well-defined voltage plateaus at low potentials (0.2 V vs Li/Li+) and relatively high initial Coulombic Efficiency (CE) for lithium-ion batteries (LIBs) are an active area of research. However, the sluggish kinetics of lithium intercalation into conventional graphite anodes leads to metallic lithium plating phenomenon. Herein, the semi-graphitic nitrogen-doped carbon (SGNC) via one-step catalytic carbonization of cocoon silk was proposed to address the above challenges. By doping spiral semi-graphitic carbon materials with nitrogen, the SGNC exhibits an insertion peak of graphite carbon below 0.2 V, as well as an adsorption peak for lithium storage between 0.2 and 3.0V in hard carbon. The optimized nitrogen-doped spiral-like carbon shows an absorption-insertion lithium storage mechanism. As a result, the SGNC anode demonstrates high initial capacity (782 mAh g-1 at 500 mA g-1 and maintained 915 mAh g-1 even after 1200 cycles) and good rate performance. The combined N-doping and nanopore defects in the spiral semi-graphitic carbon can significantly enhance the binding ability for Li-ions, charge transfer ability, and thereby improve the charge transport kinetics of the SGNC, resulting in improved rate capability.

Porous metallic materials are widely used for lithium-ion battery (LIB) electrodes because of their low density, efficient ionic/electron pathways, and high specific surface area. In this study, we fabricate nanoporous Cu using chemical and electrochemical dealloying methods based on a Cu-Ga alloy. The effects of the dealloying conditions on the derived microstructure of the nanoporous metal and its evolution mechanisms are discussed. Analysis and control of the electrochemical dealloying process reveal that the sample morphology can be adjusted and the phase component can be controlled. Accordingly, a 3D CuGa2 electrode with a nanoporous structure is controllably synthesized, and it exhibits a higher specific capacity and cyclic stability than a 2D CuGa2 electrode when used as a LIB anode.

Ga-based materials have emerged as novel self-healing anodes that can spontaneously repair cracks during cycling. However, Ga-based alloying is limited by an unstable solid-electrolyte interphase (SEI) and severe aggregation resulting from the fluidity of Ga. In this study, Ga2O3 nanoparticles of similar to 20 nm were synthe-sized. By confining and separating the Ga2O3 nanoparticles using doped carbon shells, Ga2O3@C with a pomegranate-like structure was successfully fabricated and used as an anode for ultra-long-life lithium-ion batteries. The carbon shell prevents aggregation of the lithium storage reaction product (Ga), provides better electrical conductivity, and forms a more stable SEI. The obtained Ga2O3@C anode exhibits a mixed lithium storage mechanism consisting of both diffusion-controlled and capacitive-controlled processes, with a pseudocapacitive contribution of up to 75.0 % at 1.0 mV s-1. The accelerated electrochemical reaction kinetics and high pseudocapacitive contribution of Ga2O3@C help deliver excellent cycling stability and rate properties. The Ga2O3@C anode can retain a capacity of similar to 297.4 mAh g-1 within 3000 cycles at a high current density of 2 A g-1.(c) 2022 Published by Elsevier B.V.

Co3O4 is considered as one of the most promising candidates in lithium-ion batteries (LIBs) anodes due to its lowcost, abundant availability, and high theoretical capacity. However, problems of heavy aggregation, and volume change of Co3O4 hinder its practical applicability. Based on above challenges, we successfully designed and prepared an electrode by adding carbon nanotubes (CNTs) and carbon nanofiber (CNF) via directional freezedrying. The as-prepared Co3O4/N-CNTs-CNF anode exhibits three-dimensional (3D) network structure to alleviate the volume expansion of Co3O4 and short the electron/ion transport paths. CNTs form a continuous conductive network that provides electron migration paths and prevents agglomeration of Co3O4, while CNF enhances the mechanical strength granting better flexibility. Density functional theory (DFT) calculations reveal that the N-CNTs/Co3O4 interface resulted in an electric field of the heterointerface, which facilitated charge transport. Moreover, the heterointerface possesses good electronic conductivity since more electronic states across the Fermi level. Based on these advantages, Co3O4/N-CNTs-CNF anode demonstrates an initial discharge capacity of 1176 mAh g-1 at a current density of 0.2C, high discharge specific capacity of 545 mAh g-1 at a current density of 5C, only 17.5% capacity loss over 824 cycles at 5C rate. Owing to its good electrochemical performance and flexibility, such design has great potential for applications of portable electronics.

Rechargeable lithium-oxygen (Li-O2) batteries are considered as one of the most ideal energy storage devices because of their high theoretical energy density. However, the practical application of Li-O2 batteries is hindered by their slow reaction kinetics and various notorious side reactions, which causing inferior redox over -potentials. Herein, Co4N nanoparticles electrode with low agglomeration by using a urea-glass route at moderate temperatures is proposed to address the above challenges. It shows high electron conductivity since it retained metallic cobalt crystal structure. In addition, the efficiently catalytic activity of Co4N can effectively suppress side reactions by reducing the charging polarization and expand the reaction kinetics. The DFT results demonstrate that the electronic structure change of Co4N crystal plays an important role in improving ORR activity. The overpotential for ORR increases in Co4N/N-CNTs is much easier to implement within the applied potential, and thus leading to a better catalytic performance toward ORR. Meanwhile, coupling with nitrogen can effectively optimize the electronic structure of Co4N sites in N-CNTs, thereby reducing the energy barrier of reaction intermediates to promote the reversible ORR kinetics process. Benefiting from the above advantages, the Co4N/N-CNTs delivers improved long-term cycling stability (80 cycles under O2 atmosphere) under the capacity limited at 500 mAh g-1 and current density at 200 mA g-1. This work suggests an effective pathway to fabricate the metal nitrides with efficiently catalytic activity.

Lithium-rich layered oxides (LLOs) are concerned as promising cathode materials for next-generation lithium-ion batteries due to their high reversible capacities (larger than 250 mA h g(-1)). However, LLOs suffer from critical drawbacks, such as irreversible oxygen release, structural degradation, and poor reaction kinetics, which hinder their commercialization. Herein, the local electronic structure is tuned to improve the capacity energy density retention and rate performance of LLOs via gradient Ta5+ doping. As a result, the capacity retention elevates from 73% to above 93%, and the energy density rises from 65% to above 87% for LLO with modification at 1 C after 200 cycles. Besides, the discharge capacity for the Ta5+ doped LLO at 5 C is 155 mA h g(-1), while it is only 122 mA h g(-1) for bare LLO. Theoretical calculations reveal that Ta5+ doping can effectively increase oxygen vacancy formation energy, thus guaranteeing the structure stability during the electrochemical process, and the density of states results indicate that the electronic conductivity of the LLOs can be boosted significantly at the same time. This strategy of gradient doping provides a new avenue to improve the electrochemical performance of the LLOs by modulating the local structure at the surface.

Cobalt phosphide (CoP) is considered as one of the most promising candidates for anode in lithium-ion batteries (LIBs) owing to its low-cost, abundant availability, and high theoretical capacity. However, problems of low conductivity, heavy aggregation, and volume change of CoP, hinder its practical applicability. In this study, a binder-free electrode is successfully prepared by growing CoP nanosheets arrays directly on a carbon cloth (CC) via a facile one-step electrodeposition followed by an in situ phosphorization strategy. The CoP@CC anode exhibits good interfacial bonding between the CoP and CC, which can improve the conductivity of the integrated electrode. More importantly, the 3D network structure composed of CoP nanosheets and CC provides sufficient space to alleviate the volume expansion of CoP and shorten the electron/ion transport paths. Moreover, the support of CC effectively prevents the agglomeration of CoP. Based on these advantages, when CoP@CC is paired with the NCM523 cathode, the full cell delivers a high discharge capacity 919.6 mAh g-1 (2.1 mAh cm-2 ) after 200 cycles at 0.5 A g-1 . The feasibility and safety of producing pouch cells are also explored, which show good flexibility and safety despite rigorous strikes (mechanical damage and severe deformations), implying a great potential for practical applications.

Gallium-based liquid metals are considered as potential anode materials for lithium-ion batteries owing to their self-healing, non-poisonous advantages, as well as high theoretical capacity. However, due to the alloying/ dealloying reaction mechanism to store lithium, Gallium-based alloys face huge volume change resulted in poor cycle life. Furthermore, the poor wettability of liquid metals on many kinds of substrates (carbon materials, stainless steel, etc.) and their strong ability to form alloys with many metallic current collectors (Cu, Al foil) make them hard to be designed into electrode with excellent electrochemical performance. One objective of this paper is to investigate Young's modulus of Ga discharged to different cut-off potentials, in order to gain a further understanding of mechanical property attenuation of Ga in the process of lithiation. Moreover, a threedimensional (3D) free-standing electrode is fabricated by confining Ga-based liquid metal, EGaIn, in the matrix of carbon nanofibers/carbon nanotubes paper (CNF/CNT@EGaIn NPs). The network structure provides effective pathways for electrons and ions, as well as enough space to contain the volume expansion of EGaIn. The dense CNT layer plays a further role on preventing EGaIn from shedding of the conductive substrates. Obtained CNF/CNT@EGaIn NPs exhibits a good ionic/electronic conductivity and mechanical stability, delivers capacity of 351 mAh g-1 at 1.6 A g-1 and remains a reversible capacity of ~420 mAh g-1 after 100 cycles at 800 mA g-1. This work could provide valuable insights into the development of Ga-based liquid metal anodes.

The development of lithium-sulfur (Li-S) batteries with high-energy density, flexibility, and safety is very appealing for emerging implantable devices, biomonitoring, and roll-up displays. Nevertheless, the poor cycling stability and flexibility of the existing sulfur cathodes, flammable liquid electrolytes, and extremely reactive lithium anodes raise serious battery performance degradation and safety issues. Herein, a metallic 1T MoS2 and rich oxygen vacancies TinO2n-1/MXene hierarchical bifunctional catalyst (Mo-Ti/Mx) anchored on a reduced graphene oxide-cellulose nanofiber (GN) host (Mo-Ti/Mx-GN) was proposed to address the above challenges. By applying a directional freezing process, the hierarchical architecture of a flexible GN scaffold composed of waved multiarch morphology with long-range alignment is achieved. The synergetic effects of 1T MoS2 and TinO2n-1/MXene are beneficial to suppress the shuttling behavior of lithium polysulfides (LiPSs), expedite the redox kinetics of sulfur species, and promote the electrocatalytic reduction of LiPSs to Li2S. The electrode demonstrates improved electrochemical properties with high sulfur-mass loading (8.4 mgs cm-2) and lean electrolyte (7.6 μL mgs-1) operation. We also explored the feasibility of producing pouch cells with such flexible electrodes, gel polymer electrolytes, and a robust lithium anode, which exhibited reversible energy storage and output, wide temperature adaptability, and good safety against rigorous strikes, implying the potential for practical applications.

Cobalt oxide (Co3O4) is currently suitable in energy storage applications because of its high capacity based on the conversion reaction mechanism. However, unmodified Co3O4 suffers from distinctly inferior rate capability and poor cycling stability. On the basis of the aforementioned considerations and density functional theory (DFT) simulations, the three-dimensional hierarchical porous structure (HPS) ultrasmall Co3O4 anchored into ionic liquid (IL) modified graphene oxide (GO) has been successfully prepared (ultrasmall/Co3O4-GA-IL). The ultrasmall/Co3O4-GA-IL consists of Co3O4 co-assembled with IL modified GO to generate the HPS which can facilitate ion transfer channels through reduction of the electron and ion transportation path and transmission impedance. In addition, N-doping graphene can enhance the inherent electrical conductivity of Co3O4, which is proved by the DFT calculations. By virtue of the novel superstructure, the ultrasmall/Co3O4-GA-IL electrode demonstrates a high reversible capacity of 1,304 mAh·g−1, an enhanced high-rate capability (715 mAh·g−1 at 5 C), and a capacity retention of 98.4% even after 500 cycles at 5 C rate, which corresponds to 0.0003% capacity loss per cycle. Pouch cells based on the cathode are further fabricated and demonstrate excellent mechanical and electrochemical properties under bent and folded state, highlighting the practical application of our deliberately designed electrode in wearable electronics.