Flexible Solid-state Electrolyte Research Articles

Slurry Casted Ultrathin Li3Zr2Si2PO12 Electrolyte Film for Solid-State Lithium Metal Batteries.

Thin and flexible solid-state electrolyte (SSE) films with high ionic conductivity and low interfacial resistance are urgently required for lithium metal batteries (LMBs). However, it's still challenging to reduce the film thickness to <20µm, especially for those with high ceramic contents. Herein, a facile slurry casting method is developed to prepare the ultra-thin (14µm) Li3Zr2Si2PO12 (LZSP) films with ceramic content up to 91% using a composite polymer binder, polyvinylidene fluoride (PVDF), and polyethylene oxide (PEO). It shows that PEO not only enhanced the film flexibility but also makes it be easily peeled off to form a freestanding membrane, PLN. To promote the interfacial ion transport, PEO/lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) is introduced to the film surface, and the resultant tri-layer film, PPLN, shows a satisfying room temperature ionic conductivity of 0.116mScm-1, high Li+ transference number of 0.79, and good compatibility with metal lithium. As a result, LMBs using LiFePO4 cathode and PPLN electrolyte exhibit excellent safety as well as electrochemical performances in the wide temperature range between room temperature (RT) and 100°C.

Reinforced flexible solid-state electrolyte membrane by polyurethane polymer of intrinsic microporosity for high-energy-density lithium metal battery

Poly (ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) are restricted in commercial applications due to the low ionic conductivity at ambient temperature and fragile mechanical properties. Polyurethanes (PUs) are unique materials coupled with superior rigidity and flexibility. Herein, we designed a novel polyurethane polymer of intrinsic microporosity (PPU), which was incorporated with PEO-based polymer electrolyte to prepare composite polymer electrolyte (CPE). The physicochemical and electrochemical properties of CPE membranes were explored. The high ionic conductivity (1.82 × 10−3 S cm−1 at 50 °C) and superior interfacial stability with the lithium anode was obtained. Furthermore, the rate performances and the cycling properties of CPE in LiFePO4 (LFP) batteries were extensively studied. The CPE-15% PPU film showed the excellent electrochemical stability of 84.3% capacity retention after 890 cycles at 0.5 C and 82.4% capacity retention after 500 cycles at 1.0 C at 50 °C. Especially, the CPE matched with high-voltage LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode delivered long-term stable cycling performances. The novel polymer electrolyte acquired could open up a new horizon to achieve high stable lithium metal batteries.

A flexible solid-state electrolyte based on comb-like PEG-functionalized covalent organic frameworks for lithium metal batteries

A composite polymer solid electrolyte was prepared with a fast highway for Li+ conduction based on the robust network of covalent organic framework, which shows good stability and superior electrochemistry performance.

Multilayer composite nanofibrous film accelerates the Li+ diffusion for quasi-solid-state lithium-ion batteries

The rational design of dense and flexible solid-state electrolytes (SSEs) with interface compatibility is still challenging. Here, we report a three-layer dense 3D nanofibrous matrix (PCOF) by constructing a nanofiber framework combining polyacrylonitrile (PAN) and fast Li-ion conductor covalent organic frameworks (COFs) by electrospinning method. PCOF film can maintain an extraordinary electrolyte/electrode interface and an interconnected ion-conduction pathway, accelerating Li+ diffusion. The PCOF quasi-solid-state electrolyte (QSSE) has high oxidative stability (4.70 V, versus Li+/Li) and ion conductivity of 2.94×10−4 S cm−1 at room temperature. Lithium-ion battery based on PCOF QSSE with LiFPO4 (LFP) cathode exhibits outstanding rate characteristics and cycling stability. This multi-layer composite strategy will start a new area of QSSEs lithium-ion electrolytic devices, and simultaneously accelerate the design of electrolytes featuring a wide range of properties.

Thin, Flexible, and High-Performance Solid-State Polymer Electrolyte Membranes for Li–O2 Batteries

A solid-state lithium–oxygen battery (SSLOB) has become more attractive as a next-generation energy storage device, with the expectation of long-term safe and wide applications with superior energy density. However, the development of a thin and flexible solid-state electrolyte having good interfacial and chemical stability toward lithium metal and/or oxygen has been a big challenge. Accordingly, a solid-state composite electrolyte membrane has been prepared by impregnating polyethylene glycol (PEG) and succinonitrile plastic crystals (SNPCs) along with lithium bromide redox mediator into a porous polytetrafluoroethylene (PTFE) substrate for application in a SSLOB. The prepared thin electrolyte membrane (23 μm) displays a high ionic conductivity of 1.03 mS cm–1, a tensile strength of 46.5 MPa, and elongation at a break of 100% with excellent flexibility. It also exhibits a wide electrochemical stability window (∼4.9 V) and low interfacial resistance of 80 Ω cm2. The SSLOB cell assembled with the synthesized XPEG/SNPC@PTFE electrolyte membrane shows excellent electrochemical stability during 277 cycles, maintaining a 1000 mAh g–1 discharge capacity. The low terminal voltage difference between the charge and discharge processes of these polymer electrolyte membranes (∼0.65 V) compared to those of liquid or other polymer electrolytes (∼1.4 V) is also an advantageous characteristic for their application in high-performance SSLOBs.

Gel Polymer-Based Composite Solid-State Electrolyte for Long-Cycle-Life Rechargeable Zinc–Air Batteries

Developing high-performance, safe, and flexible solid-state electrolytes (SSEs) for rechargeable solid-state zinc–air batteries (ZABs) is becoming increasingly crucial but remains fraught with tremendous challenges. Herein, a novel multinetwork cross-linked composite gel electrolyte (PVAA-Cellulose) was constructed by introducing poly(acrylic acid) (PAA) and ultrafine cellulose to the poly(vinyl alcohol) (PVA) gel electrolyte. By virtue of the extensive porous network and hydrogen bonding, the PVAA-Cellulose SSEs achieve optimal water retention, thermal stability, and high ionic conductivity of 123 mS cm–1 compared with PVAA (mixture of PVA and PAA). The investigation of the effects of different SSEs on zinc anodes after ZAB cycling reveals that PVAA-Cellulose SSE can effectively inhibit dendrite growth and oxidation byproduct generation on zinc anodes, which contributes to the long-term cycling stability of ZABs. As a result, solid-state ZABs assembled with PVAA-Cellulose SSEs possess a high power density of 74 mW cm–2, a specific capacity of 724 mAh gZn–1, and a long cycle stability of 54 h as well as the outstanding flexibility exhibited by the flexible ZAB devices.

Prospects of Sulfide-Based Solid-State Electrolytes Modified by Organic Thin Films

Lithium-ion batteries are key to tackling today’s energy crisis. In recent years, compared with the research on other components of lithium-ion batteries, the research on solid-state electrolytes is particularly hot. Among various solid-state electrolyte modification measures, we found that the material design of organic/inorganic composite flexible solid-state electrolytes can achieve the best all-solid-state battery cycling performance. Based on the study of sulfide-based organic/inorganic composite solid-state electrolytes, this article firstly introduces the classification of inorganic solid electrolytes and the advantages and disadvantages of each type of materials. At the same time, the research progress of various oxide solid electrolyte materials and sulfide solid electrolyte materials in recent years is introduced as well as the advantages of organic/inorganic composite solid-state electrolyte materials. Then the influencing factors that affect the performance of solid-state electrolytes, such as material lattice, lattice defects, electrolyte interface problems, and electrolyte microcracks, are introduced. Finally, the superiority of the industrial electrochemical performance of the organic/inorganic composite solid electrolyte material and its future prospects are introduced.

Large-scale preparation of ultrathin composite polymer electrolytes with excellent mechanical properties and high thermal stability for solid-state lithium-metal batteries

Large-scale preparation of ultrathin flexible solid-state electrolytes with high performance and low cost is critical for the commercialization of solid-state lithium-metal batteries. Herein, through a rational combination of the typical scraping and hot-pressing processes to impregnate polyethylene oxide (PEO)/Li-salt (LiTFSI) electrolyte into porous poly(tetrafluoroethylene) (PTFE) matrix, an ultrathin, highly dense composite polymer electrolyte (PLP-HP) has been successfully achieved. The hot-pressing process at appropriate temperature guarantees the densely impregnating of the PEO/LiTFSI conductive networks, and the enhancement effect of PTFE matrix ensures the excellent mechanical properties and the high thermal stability of the composite electrolyte with a thickness of 14.5 μm or even lower to 6 μm. As a result, the Li//Li symmetrical cell with the 14.5 μm thick electrolyte shows a stable cycling time of more than 900 h at 60°C without growth of Li dendrites and its LiFePO4//Li full cell can stably cycle more than 500 cycles with a superhigh average coulombic efficiency of over 99.9 % at 0.5 C and 60°C. Furthermore, the full cell with the 6 μm thick electrolyte even demonstrates more superior rate performance due to its much shorter Li+ diffusion distance, which enables the battery to operate at 30°C with a reversible capacity of around 135 mAh g−1 at 0.2 C. This study offers a guidance for the large-scale and low-cost preparation of high performance ultrathin composite polymer electrolytes.

Acceleration of selective lithium ion transport of PAES-g-2PEG self-assembled flexible solid-state electrolytes for lithium secondary batteries

The solid-state lithium secondary battery (LiB) is a promising alternative to resolve the drawbacks of conventional LiB, but it still suffers from low ionic conductivity and mechanical instability. Accordingly, the flexible self-assembled solid electrolytes (SEMs) based on poly(arylene ether sulfone) (PAES) grafted with double poly(ethylene glycol) (PEG) (PAES-g-2PEG) is prepared to maximize the ion conductivity by creation of large PEG conducting domains without thermal and mechanical failure via reinforcement of PAES matrix. The addition of ionic liquid (IL) along with ethylene carbonate (EC) results in a significant improvement in a selective lithium ion conductivity because of the improved molecular mobility of PEG segments and formation of [Li+(EC)x, (x = 1–5)] complexes for feasible single-ion transport. Consequently, the PAES-g-2PEG membranes containing IL-EC mixture (7:3, v/v) achieve the ionic conductivity of 1.15 × 10−3 S cm−1 and Li-ion transference number of 0.51 at room temperature. The PAES-g-2PEG membranes exhibit excellent mechanical flexibility and thermal stability with the onset degradation temperature of 250 °C. Due to the significant suppression of polysulfide permeation as well as high conductivity, the Li/SEM/S cell assembled with PAES-g-2PEG membranes delivers the discharge capacity of 987 mAh g−1 with 98.6% of coulombic efficiency, retaining 94.7% after 200 cycles at 0.2 C-rate.

Lithium-Rich Anti-perovskite Li2OHBr-Based Polymer Electrolytes Enabling an Improved Interfacial Stability with a Three-Dimensional-Structured Lithium Metal Anode in All-Solid-State Batteries.

All-solid-state lithium-metal batteries, with their high energy density and high-level safety, are promising next-generation energy storage devices. Their current performance is however compromised by lithium dendrite formation. Although using 3D-structured metal-based electrode materials as hosts to store lithium metal has the potential to suppress the lithium dendrite growth by providing a high surface area with lithiophilic sites, their rigid and ragged interface with solid-state electrolytes is detrimental to the battery performance. Herein, we show that Li2OHBr-containing poly(ethylene oxide) (PEO) polymer electrolytes can be used as a flexible solid-state electrolyte to mitigate the interfacial issues of 3D-structured metal-based electrodes and suppress the lithium dendrite formation. The presence of Li2OHBr in a PEO matrix can simultaneously improve the mechanical strength and lithium ion conductivity of the polymer electrolyte. It is confirmed that Li2OHBr does not only induce the PEO transformation of a crystalline phase to an amorphous phase but also serves as an anti-perovskite superionic conductor providing additional lithium ion transport pathways and hence improves the lithium ion conductivity. The good interfacial contact and high lithium ion conductivity provide sufficient lithium deposition sites and uniform lithium ion flux to regulate the lithium deposition without the formation of lithium dendrites. Consequently, the Li2OHBr-containing PEO polymer electrolyte in a lithium-metal battery with a 3D-structured lithium/copper mesh composite anode is able to improve the cycle stability and rate performance. The results of this study provide the experimental proof of the beneficial effects of the Li2OHBr-containing PEO polymer electrolyte on the 3D-structured lithium metal anode.

Transport Properties of Flexible Composite Electrolytes Composed of Li1.5Al0.5Ti1.5(PO4)3 and a Poly(vinylidene fluoride-co-hexafluoropropylene) Gel Containing a Highly Concentrated Li[N(SO2CF3)2]/Sulfolane Electrolyte.

Flexible solid-state electrolyte membranes are beneficial for feasible construction of solid-state batteries. In this study, a flexible composite electrolyte was prepared by combining a Li+-ion-conducting solid electrolyte Li1.5Al0.5Ti1.5(PO4)3 (LATP) and a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF–HFP) gel containing a highly concentrated electrolyte of Li[N(SO2CF3)2] (LiTFSA)/sulfolane using a solution casting method. We successfully demonstrated the operation of Li/LiCoO2 cells with the composite electrolyte; however, the rate capability of the cell degraded with increasing LATP content. We investigated the Li-ion transport properties of the composite electrolyte and found that the gel formed a continuous phase in the composite electrolyte and Li-ion conduction mainly occurred in the gel phase. Solid-state 6Li magic-angle spinning NMR measurements for LATP treated with the 6LiTFSA/sulfolane electrolyte suggested that the Li+-ion exchange occurred at the interface between LATP and 6LiTFSA/sulfolane. However, the kinetics of Li+ transfer at the interface between LATP and the PVDF–HFP gel was relatively slow. The interfacial resistance of LATP/gel was evaluated to be 67 Ω·cm2 at 30 °C, and the activation energy for interfacial Li+ transfer was 39 kJ mol–1. The large interfacial resistance caused the less contribution of LATP particles to the Li-ion conduction in the composite electrolyte.

Modification and regulation of electrode/electrolyte interface for high specific energy and long life lithium ion batteries

<p indent="0mm">In recent years, with the rapid developments of high-technology industries such as information technology and electric vehicles, there are urgent need to develop new generations of lithium-ion batteries with higher energy density, longer cycle life and improved safety. In addition to the development of high specific energy cathode and high specific capacity anode materials, regulating the stability of the electrode/electrolyte interface is critical to achieve and balance various performances of the batteries and finally realize their commercial application widely. However, the traditional carbonate electrolytes not only suffer from severe oxidation decomposition when the charging voltage is higher than 4.3 V (vs. Li/Li⁺), but also show poor compatibility with high-capacity silicon or silicon-carbon (Si-C) composite anodes and lithium metal anodes. Moreover, the traditional carbonate electrolytes are flammable, which is still a big safety concern to address for lithium ion battery. Therefore, rational design of electrolytes that match the high voltage cathode, high specific capacity Si-C abode or lithium metal anode, and has better safety property and especially under harsh conditions, has become a decisive factor for the rapid developments of high specific energy lithium-ion batteries. The present work reviews different kinds of liquid electrolytes with functional additives and utilization of solid state electrolytes which are explored by our group in the past 15 years. The design strategies and systematic investigations of the electrolytes recipes include: (1) Developing anti-oxidation solvent systems, for example, applications of new high-voltage nitriles or fluorinated solvents for high-voltage cathodes, such as suberonitrile (SUN), fluoroethylene carbonate (FEC) and ethyl-(2,2,2-trifluoroethyl) carbonate (ETFEC); (2) exploiting some novel multifunctional solvents or additives which contain flame retardant groups or can be used as film-forming agents for high-voltage cathodes. For example, some P-containing compounds such as <italic>N</italic>,<italic>N</italic>-diallyl-diethoxy phosphoramide (DADEPA), phenoxy cyclophosphazene (PFPN), and ionic liquid such as N-methyl-N-butylpyrrolidinium bis(trifluoromethylsulfonyl)imide (Py14TFSI), etc. In addition, we have also investigated a series of solid electrolytes such as Garnet-type electrolytes, gel polymer or composite polymer electrolyte with inorganic additives, which could greatly reduce the safety risk of batteries. These works include measurements of the activation energy and ion transport mechanism of oxide solid electrolyte with solid NMR techniques, interface modification of sulfide-type solid state battery with ionic liquids, and interface passivation mechanism of PEO-based polymer electrolyte, etc. Finally, some discussions and future perspectives in developing high-voltage and highly-safe liquid electrolyte and flexible solid-state electrolytes for all solid state batteries are presented. Although the commonly used high-voltage electrolytes are mainly composed of lithium salts, anti-oxidation solvents and functional additives such as nitriles, sulfones, fluoro-ethers or fluoro-carbonates, However, the acting mechanisms of those high-voltage electrolytes, especially solvents, salts and additives, are still not clear, especially the composition, structure and evolution of the electrochemical interfaces are lack of quantitative understanding. Therefore, combining theoretical calculation and advanced in-/ex-situ interface characterization techniques, fully understanding the working mechanism of the additives in high-voltage systems and the effective components of interface film, and designing novel functional electrolyte additives are crucial for the development of a new generation of high-specific energy lithium batteries. In addition, applications of flame-retardant solvents or additives to develop flame-retardant liquid-type electrolytes and developing new solid state electrolytes are both important strategies to reduce the potential safety hazards of lithium ion batteries. The future research should focus on how to improve the compatibility between flame-retardant solvents/additives and the cathode/anode interfaces in liquid electrolytes, minimize the negative impact on battery performance (cycle performance, rate performance, etc.), enhance the ionic conductivity and mechanical flexibilities of the solid electrolytes, optimize the electrolyte phase structure/mechanical properties, and regulate the stability of interfaces to ensure the long-term cycling stability of lithium metal anodes and metal oxide cathodes.

Reversible phase switching between antiferromagnetic SrCoO2.5 and ferromagnetic SrCoO3−δ by a flexible solid-state electrolyte gate

Manipulation of oxygen vacancies (VO) in transition metal oxides (TMOs) can largely alter their physical and chemical properties, such as electrical conductivity, magnetic state, optical band-gap, and electrocatalytic reactivity. Many experimental and theoretical works have been conducted to study the formation/annihilation of VO and its corresponding effect on the properties in TMOs. In this paper, a solid-state approach to modulate the oxygen stoichiometry in high quality SrCoOx epitaxial thin films was demonstrated. Dependence of the magnetic and electrical conducting properties on VO was investigated. Room temperature reversible phase switching between brownmillerite antiferromagnetic insulating SrCoO2.5 and perovskite ferromagnetic metallic SrCoO3−δ was achieved by electric-field induced oxygen non-stoichiometry. This room temperature reversible phase switching indicates that SrCoOx thin films are a promising candidate for practical applications in resistive random access memory and spintronic devices.

Flexible Solid-State Electrolyte with Aligned Nanostructures Derived from Wood

Solid-state Li-batteries (SSLiBs) with solid-state electrolytes (SSEs) can potentially block Li dendrite penetration, enabling the application of metallic lithium anodes to achieve high energy dens...

Suppressing Reactivity of Sulfides in Solution Processing Enables Scalable Manufacturing of Thin, Flexible Solid-State Electrolytes

All solid-state batteries (ASSBs) have the potential to deliver higher energy densities, wider operating temperature range and improved safety compared with today’s liquid electrolyte-based batteries. However, they still face challenges that limit their commercialization resulting from thick solid-state electrolytes (SSEs), and poor processability due to their unstable chemistries. Existing studies on solvent-binder based casting methods to reduce SSE thickness and improve processability still lack crucial fundamental understanding of the behavior and selection criteria for different SSE-binder-solvent systems. In this work, we attempt to isolate various SSE-binder-solvent system behaviors and study their chemical and electrochemical compatibilities using both bulk and surface sensitive characterization tools. With these findings, we introduce a novel binder-solvent combination that significantly reduces SSE thickness and improves processability of ASSBs while maintaining high ionic conductivity. The resulting organic/inorganic composite SSE was found to be stable against lithium metal by plating and stripping over extended cycles. This study suggests the importance of understanding fundamental SSE-binder-solvent interactions and provides a potential design strategy for scalable production of ASSBs.

Ceramic-Polymer Interaction in Solid-State Composite Electrolytes of Lithium Ion Batteries

Based on three dimensional (3D) pervoskite-type Li0.33La0.557TiO3 nanofibers and polymer, a composite solid state electrolyte has been fabricated. Our study shows that the ceramic-polymer interface has significant effect on the ionic conductivity of composite electrolytes and the cyclic performance of symmetric half cells. After a buffer later has been incorporated between the ceramic fibers and polymer matrix, the flexible solid-state electrolyte composite membrane exhibits high ionic conductivity at room temperature, a large electrochemical stability window and good mechanical stability in symmetric Li|electrolyte|Li cell.

One-Pot Synthesis of Co3 O4 /Ag Nanoparticles Supported on N-Doped Graphene as Efficient Bifunctional Oxygen Catalysts for Flexible Rechargeable Zinc-Air Batteries.

Flexible rechargeable zinc-air batteries are considered as one of the most promising power supplies for the emerging flexible and wearable electronic devices. However, the development of flexible zinc-air batteries is stagnant due to the lack of efficient bifunctional catalysts with high oxygen catalytic activity and flexible solid-state electrolytes with high mechanical stability and ionic conductivity. In this work, Co3 O4 /Ag@NrGO composite was synthesized by a facile one-pot method, and the catalyst shows remarkable oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) bifunctional catalytic activity and good long-term stability. In particular, the OER overpotential of Co3 O4 /Ag@NrGO reaches 437 mV, outperforming that of the commercial IrO2 catalyst. This can be attributed to the combined effects of Co3 O4 , Ag, and N-rGO. Furthermore, PAA (polyacrylic acid) and PVA (polyvinyl alcohol) based gel-electrolytes have been developed as flexible solid-state electrolytes for zinc-air batteries. The results show that PAA-based electrolyte is more favorable to the flexible zinc-air battery with a high power density due to its relatively high ionic conductivity. The maximum power density of flexible zinc-air batteries with Co3 O4 /Ag@NrGO catalyst and PAA-based electrolyte can reach 108 mW cm-2 , which is almost the highest value reached in recent reports. This work will provide valuable guidance for the development of flexible rechargeable zinc-air batteries with high power density and stability.

Solid-State Lithium Lanthanum Titanate-Polymer Composite Electrolyte for Lithium Ion Batteries

Three dimensional (3D) pervoskite-type Li0.33La0.557TiO3 nanofibers have been incorporated with a polymer matrix to form a solid-state composite electrolyte. This flexible solid-state electrolyte composite membrane exhibits high ionic conductivity at room temperature, a large electrochemical stability window and good mechanical stability in symmetric Li|electrolyte|Li cell.

Flexible, Solid-State, Ion-Conducting Membrane with 3D Garnet Nanofiber Networks for Lithium Batteries

Beyond state-of-the-art lithium-ion battery (LIB) technology with metallic lithium anodes to replace conventional ion intercalation anode materials is highly desirable because of lithium’s highest specific capacity (3,860 mA/g) and lowest negative electrochemical potential (∼3.040 V vs. the standard hydrogen electrode). In this work, we report for the first time, to our knowledge, a 3D lithium-ion–conducting ceramic network based on garnet-type Li6.4La3Zr2Al0.2O12 (LLZO) lithium-ion conductor to provide continuous Li+ transfer channels in a polyethylene oxide (PEO)-based composite. This composite structure further provides structural reinforcement to enhance the mechanical properties of the polymer matrix. The flexible solid-state electrolyte composite membrane exhibited an ionic conductivity of 2.5 × 10−4 S/cm at room temperature. The membrane can effectively block dendrites in a symmetric Li | electrolyte | Li cell during repeated lithium stripping/plating at room temperature, with a current density of 0.2 mA/cm2 for around 500 h and a current density of 0.5 mA/cm2 for over 300 h. The presentation will focus on our recent development of 3D garnet nano structured solid-state electrolyte membrane for Li metal batteries. Figure 1

A review of flexible lithium-sulfur and analogous alkali metal-chalcogen rechargeable batteries.

Flexible energy storage systems are imperative for emerging flexible devices that are revolutionizing our life. Lithium-ion batteries, the current main power sources, are gradually approaching their theoretical limitation in terms of energy density. Therefore, alternative battery chemistries are urgently required for next-generation flexible power sources with high energy densities, low cost, and inherent safety. Flexible lithium-sulfur (Li-S) batteries and analogous flexible alkali metal-chalcogen batteries are of paramount interest owing to their high energy densities endowed by multielectron chemistry. In this review, we summarized the recent progress of flexible Li-S and analogous batteries. A brief introduction to flexible energy storage systems and general Li-S batteries has been provided first. Progress in flexible materials for flexible Li-S batteries are reviewed subsequently, with a detailed classification of flexible sulfur cathodes as those based on carbonaceous (e.g., carbon nanotubes, graphene, and carbonized polymers) and composite (polymers and inorganics) materials and an overview of flexible lithium anodes and flexible solid-state electrolytes. Advancements in other flexible alkali metal-chalcogen batteries are then introduced. In the next part, we emphasize the importance of cell packaging and flexibility evaluation, and two special flexible battery prototypes of foldable and cable-type Li-S batteries are highlighted. In the end, existing challenges and future development of flexible Li-S and analogous alkali metal-chalcogen batteries are summarized and prospected.