Stretchable Batteries Research Articles

Stretchable Energy Storage with Eutectic Gallium Indium Alloy

AbstractThe integration of electronics with the human body or wearables necessitates the evolution of energy storage devices capable of seamless adaptation to the conformability of the skin and textiles. This work focuses on developing an intrinsically stretchable electrode prepared by sedimenting the liquid metal particles in a conductive stretchable matrix. The liquid metal‐based electrode can be stretched to ≈900% strain, and its conductivity increases by extending to 250% and retaining its initial conductivity at 500% strain. Benefitting from these properties, the assembled all‐solid‐state energy storage device provides high stretchability of up to 150% strain and a capacity of 0.42 mAh cm−3 at a high coulombic efficiency of 90%. The charge storage mechanism is investigated by probing the electrode/electrolyte interface, uncovering the intricate gallium‐bis(trifluoromethane)sulfonimide (Ga‐TFSI) complexation during electrochemical cycling through in situ Raman spectroscopy, ex situ X‐ray photoelectron spectroscopy (XPS) analyses, and density functional theory (DFT) calculations. This work offers a promising avenue for the advancement of stretchable batteries.

Stretchable Coaxial Gel Polymer Electrolyte Based on a Styrene–Ethylene–Butylene–Styrene Block Copolymer Nanofiber for Stretchable Lithium-Ion Batteries

Stretchable Coaxial Gel Polymer Electrolyte Based on a Styrene–Ethylene–Butylene–Styrene Block Copolymer Nanofiber for Stretchable Lithium-Ion Batteries

Integration of deformable matrix and lithiophilic sites for stable and stretchable lithium metal batteries

In response to the growing interest in wearable devices, the demand for next-generation wearable devices that can endure various mechanical deformations such as folding and stretching is also increasing. As a result, the development of stretchable batteries, capable of operating under diverse conditions, is regarded as crucial for the advancement of these future wearable technologies. Many current studies on stretchable batteries suffer from limited energy density and complicated fabrication procedures. Thus, the development of batteries that meet both high stretchability and energy density remains challenging due to these factors. Herein, we propose a stretchable and lithiophilic matrix as a host for lithium (Li) metal anodes to realize stretchable Li metal batteries (LMBs), which consists of a polymer matrix embedded with silver nanoparticles (AgNPs). The lithiophilic AgNPs are incorporated both on the surface and within the elastic fiber matrix, providing facile Li nucleation kinetics and an electron-conductive network. Surface AgNPs serve as a primary electron pathway and offer numerous nucleation seeds to facilitate uniform Li electrodeposition. Meanwhile, AgNPs embedded in the matrix provide a sturdy conductive network even under mechanical deformation. Consequently, the structure-forming factors of stretchable lithiophilic Ag-incorporated matrix (SLiM) electrode contribute to enhanced electrochemical properties as a versatile Li metal host. As a proof of concept, the designed all-stretchable LMB with the SLiM electrode demonstrates minimal degradation of electrochemical performance in deformable conditions and confirms the feasibility of an LMB in stretchable application. This work provides insight into stretchable LMBs aimed at both highly deformable and high-energy-density wearable devices.

Self-Healing Stretchable Li-Ion Battery Based on a High-Voltage Hydrogel Electrolyte

Safe and deformable soft batteries are desirable for future wearable electronic devices. However, current Li-ion batteries on the commercial market are rigidly packaged and hermetically sealed to prevent moisture penetration and the leakage of toxic and flammable organic electrolytes. Since the modulus of elasticity and gas permeability of materials are inextricably linked, stretchable batteries often experience significant performance degradation over time in the ambient due to inevitable moisture penetration. Furthermore, the polymer-based flexible packaging materials can be easily damaged resulting in electrolyte leakage that poses significant safety concerns. Here we report a non-toxic, aqueous hydrogel electrolyte instead of its organic counterpart that is demonstrated to 1) enable highly safe operations due to its non-toxic and non-flammable nature; 2) alleviate the moisture penetration problem from the outside environment; (3) have a high-voltage working window of ~2.97V; and (4) allow the construction of stretchable batteries by using elastic polymer packaging materials instead of rigid hermetic seals. The prototype batteries have shown good stretchability (50% strain) and flexibility (radius of curvature < 2mm) to enable conformal attachments to a wide range of geometric surfaces. The prototype battery also shows outstanding cyclic stability, retaining ~90% of the original capacity after 100 cycles for over 2 months in the ambient environment without using any rigid hermetic sealing package. Finally, a prototype battery with a self-healing elastomer package remains functional after being punctured by a needle 5 times at different locations in the package. Furthermore, it can recover >90% of its capacity after being cut through by a razor blade and subsequently healed at 70 for 10 minutes. Such safe and highly stretchable batteries would be useful for several wearable electronic applications such as blood glucose monitoring, hearing rate monitoring, temperature monitoring, wireless charging, smart clothing, etc. Figure 1

Elastic Polymer Electrolytes Integrated with In Situ Polymerization-Transferred Electrodes toward Stretchable Batteries

Elastic Polymer Electrolytes Integrated with In Situ Polymerization-Transferred Electrodes toward Stretchable Batteries

Coaxially spinning stretchable zin-ion battery fiber with waterproof and scissorability

Wearable energy storage with super mechanic flexibility, stretchability and safety has been in pursuit for smart flexible textiles. Fiber batteries, though having their superiority in spinnability, knittability and adaptability for breathable textiles with comparison to planar batteries, were normally produced with complicated procedures. To simplify the production process, in this study we showed that stretchable and scissorable Zinc-ion battery fibers could be spun through a dual-core spinning head with double concentric sheathes, by combining a one-step coaxial wet-spinning process and an in-situ photo-polymerization process. The resultant fibers showed super stretchability up to 500 % strain. The presence of outer protection layer also offered super abrasion resistance and endurability to water and stress. Besides the spinnability and knittability into fabric, the battery fibers also maintained their functionality even after being cut into short segments. Thus, this study may not only offer a platform of one-step coaxial wet spinning process to produce battery fibers, but also offer an endurable energy-storage solution applicable in various wearable devices.

Stretchable and self-healable lithium-ion batteries with all-in-one configuration

Stretchable lithium-ion batteries (LIBs) are highly desirable to serve as the power sources of stretchable and wearable electronic devices. Furthermore, endowing stretchable LIBs with self-healability can prolong their life-time and enhance their reliability. However, previously reported self-healable LIBs were flexible rather than stretchable, while the stretchable LIBs were unable to self-heal. Herein, we present a novel strategy to fabricate stretchable and self-healable LIBs with all-in-one configuration, by exploiting dynamic covalent polymers as both the electrolyte and the binder of electrodes. The developed polymer electrolyte exhibits a room-temperature ionic conductivity as high as 3.6 × 10−4 S cm−1 and possesses an elongation-at-break of 250 ± 30 %. Moreover, the stretchable electrolyte is highly resilient and its ionic conductivity shows minimal changes at different strains. The electrolyte exhibits an autonomous self-healing property at room temperature, making the cut sample easily recover its original performance. Importantly, the electrolyte and electrodes can be fused together at the interface to construct a healable LIB with all-in-one configuration, through the exchange of the dynamic imine bonds that exist in both the electrolyte and electrodes. As a result, the as-developed LIB possesses an elongation-at-break of 220 ± 20 % and can supply power in the course of stretching and releasing. Furthermore, the cut and then healed LIB can still deliver an average discharge capacity of 126.4 mAh g−1 and steadily provide power for LED. This work offers a new avenue for the development of stretchable and self-healable LIBs for the stretchable and wearable electronic devices.

Stretchable Metal‐Air Batteries Through Sliding Electrodes

AbstractSoft robots and wearable technologies benefit significantly from stretchable batteries, yet the rigid nature of high‐capacity electrodes creates large trade‐offs in battery performance and stretchability. This study introduces a new approach for realizing stretchable batteries by allowing the electrodes to slide along a stretchable electrolyte. When the sliding‐electrodes battery is stretched, the forces are transmitted through the hydrogel electrolyte and elastomeric enclosure, while the rigid electrodes slide relative to the hydrogel to maintain interfacial contact. The sliding‐electrodes approach allows 100% of the unstretched battery area to be covered by thick electrodes so that the battery areal capacity and power are improved by up to 10X of prior stretchable designs. Three metal‐air batteries achieve areal capacities of up to 104 mWh cm−2. Further mechanical testing, electrochemical characterization, and integration into soft robotic systems demonstrate the potential of these stretchable batteries in practical applications. The sliding‐electrodes battery can stably power multiple servo motors and sensing circuits under stretching, twisting, bending, and after impact.

Recent Advances on Stretchable Aqueous Zinc-Ion Batteries for Wearable Electronics.

The rapid development of wearable electronics has stimulated the pursuit of advanced stretchable power sources. As a promising candidate, stretchable aqueous zinc-ion batteries (AZIBs), have attracted unprecedented attention owing to their intrinsic safety, low cost, environmental benignity, and high performance, and can be endowed with additional functionalities to broaden the applications of wearable electronics. Here, a comprehensive review on the latest advances of stretchable AZIBs is presented. The materials and methods for stretchable components in AZIBs are first summarized, covering current collectors, electrodes, electrolytes/separators, and encapsulating layers. Subsequently, the benefits of the coplanar, fiber-shaped, and sandwiched configurations for stretchable AZIBs are analyzed. Moreover, the additional features integrated into stretchable AZIBs are highlighted. Finally, the challenges and prospects of stretchable AZIBs for wearable applications in the future are proposed.

Stretchable and biodegradable plant-based redox-diffusion batteries.

The redox-diffusion (RD) battery concept introduces an environmentally friendly solution for stretchable batteries in autonomous wearable electronics. By utilising plant-based redox-active biomolecules and cellulose fibers for the electrode scaffold, separator membrane, and current collector, along with a biodegradable elastomer encapsulation, the battery design overcomes the reliance on unsustainable transition metal-based active materials and non-biodegradable elastomers used in existing stretchable batteries. Importantly, it addresses the drawback of limited attainable battery capacity, where increasing the active material loading often leads to thicker and stiffer electrodes with poor mechanical properties. The concept decouples the active material loading from the mechanical structure of the electrode, enabling high mass loadings, while retaining a skin-like young's modulus and stretchability. A stretchable ion-selective membrane facilitates the RD process, allowing two separate redox couples, while preventing crossovers. This results in a high-capacity battery cell that is both electrochemically and mechanically stable, engineered from sustainable plant-based materials. Notably, the battery components are biodegradable at the end of their life, addressing concerns of e-waste and resource depletion.

Hierarchically Interpenetrated and Reentrant Microcellular Frameworks for Stretchable Lithium Metal Batteries.

With the rapid development of human-friendly wearable devices, energy storage components are required to have skin-like stretchability or free-form to fit closer and more comfortably to the human body. This study introduces a hierarchically interpenetrated reentrant microcellular structure combined with 2D cellular graphene/MXene/carbon nanotubes (CNTs) and 3D cellular melamine foam. This composite structure works as a stretchable framework of lithium metal composite electrodes to provide stretchability for lithium metal electrodes, which are promising as next-generation energy storage systems. The interpenetrated but independent cellular structures successfully obtain stable structural deformability from the nonconductive and deformable melamine foam, while at the same time, high electrical conductivity, lithiophilicity, and mechanical stability of the graphene/CNT/MXene network serve as a lithium deposition support during the electrodeposition of lithium. The reentrant structure is fabricated by radial compressing the hierarchical cellular structures to take advantage of the structural stretchability of the accordion-like reentrant frameworks. The lithium-deposited composite electrodes exhibit much lower overpotential during Li stripping and plating than lithium metal foil anodes and show stable electrochemical performances under 30% of mechanical strain. The reentrant microcellular electrodes offer great potential for advanced designs of lithium metal electrodes for stretchable batteries with high energy density.

Liquid Metal–Elastomer Seals for Stretchable Organic Electrolyte‐Based Lithium‐Ion Batteries

AbstractRapid progresses concerning wearable electronics call for stretchable batteries. Owing to the merits of high energy density and wide operating voltage range, organic electrolyte‐based lithium‐ion batteries (LIBs) take a large proportion in the powering markets. Due to the high sensitivity to moisture and oxygen, it is difficult to obtain long‐term reliable stretchable organic electrolyte‐based LIBs when they are directly exposed to the air. Benefiting from the outstanding gas impermeability of liquid metal (LM) and relatively good barrier properties for reactive acid gas molecules by polyisobutylene (PIB), an LM‐PIB seal is demonstrated for organic electrolyte‐based LIBs. In the seal, LM can prevent the inward permeation of oxygen and water vapor, and PIB can block the outward permeation of hydrolysis acid generated from the side reactions during the operation of the organic electrolyte‐based LIBs, which helps prevent the detrimental interaction between the hydrolysis acid and LM. A specific capacity of over 120 mAh g−1 is achieved and the battery shows consistent electrochemical performances under multiple deformations. This study offers a different design approach for long‐term operation of stretchable organic electrolyte‐based LIBs.

Mechanically Rupturing Liquid Metal Oxide Induces Electrochemical Energy

AbstractLiquid metals, such as Gallium‐based alloys, have unique mechanical and electrical properties because they behave like liquid at room temperature. These properties make liquid metals favorable for soft electronics and stretchable conductors. In addition, these metals spontaneously form a thin oxide layer on their surface. Applications made possible by this delicate oxide skin include shape reconfigurable electronics, 3D‐printed structures, and unconventional actuators. This paper introduces a new approach where liquid metal oxide serves as an electrochemical energy source. By mechanically rupturing their surface oxide, liquid metals form a galvanic cell and convert their chemical energy to electrical energy. When dispersing liquid metals into an ionically‐conductive liquid to form emulsions, this composite material can provide ∼500 mV of open‐circuit voltage and up to ∼4 μW of power. Protected by the naturally occurring oxide skin, the passivating oxide layer of the liquid metal shields it from self‐discharge over time. The device is also stable in harsh environments, such as high temperature or aquatic conditions. Future applications of this device are demonstrated by designing a strain‐activated stretchable battery and a pressure‐sensitive self‐powered keypad. These findings may unlock new pathways to design stretchable batteries and harness their inherent energy for self‐powered robust devices.

Stretchable fabric-based lithium-ion battery

In many applications ranging from wearable devices to implantable biosensors, next-generation electronics are expected to be stretchable which necessitates a concomitant development of fully stretchable batteries. Stretchable lithium-ion batteries must provide stable performance while subjected to mechanical deformations such as stretching, bending, and twisting. Although there has been a noticeable progress in the development of flexible energy storage devices, stretchable lithium-ion batteries still face several persistent challenges. While in a prior work we successfully presented a proof-of-concept that rendered just the cathode to be stretchable, in this work we present the design, fabrication and characterization of a complete fully stretchable fabric-based lithium ion battery. The electrochemical and mechanical performances of the fabric-based battery are investigated and discussed. Solid polymer electrolyte stretchable fabric-based battery offers a more compatible and safer alternative to liquid based batteries, especially for the application of textile wearable devices that may involve intimate contact with human skin and organs. We demonstrate that our fabric-based battery can stretch up to 15% strain without a significant increase in its internal impedance.

Sandwich Configuration of Zinc Anode, Gel Electrolyte, and Radical Polymer Cathode for Fully Stretch‐Rechargeable Battery

AbstractOver the past decade, there is gradual development in fully stretchable semiconductors. However, to bring these devices to market, they require a reliable built‐in power source that can maintain stable output voltage, charge/discharge capabilities, and cycle life. Unfortunately, complex cell configurations have hindered the development of stretchable batteries. To overcome this, a fully stretch‐rechargeable battery with a sandwich configuration is fabricated. The cathode layer comprises electrically conductive poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and a redox‐active TEMPO‐substituted polymer, while the anode consists of a carbon nanotube layer deposited with zinc metal. By sandwiching a hydrogel between these two layers, a rechargeable battery is created that is attachable to human skin and &lt;40 µm thick. This thin device offers a promising voltage of 1.8 V and is robust against repeated stretching, liquid leakage, and self‐discharging reactions induced by oxygen. This study is expected to open up new horizons for e‐skin and stretchable electronic fields.

Stretchable high-capacity SiOx/carbon anode with good cycle stability enabled by a triblock copolymer elastomer

Stretchable lithium-ion batteries (LIBs) are key technologies for flexible/wearable electronics, yet low energy density and poor stability remain challenges. Here, we proposed a high-capacity stretchable SiOx/C anode with good stability, using triblock copolymer elastomer matrix poly(styrene-b-(n-butyl acrylate)-b-styrene) (SBAS) to provide stretchability (up to 1160%) and mechanical support. SBAS cross-links with SiOx to enhance interface adhesion. Single-walled carbon nanotubes (SWCNTs) were introduced to construct long-range conductive network and further improve mechanical strength. Besides, SBAS has strong π-π conjugation with SWCNTs, which keeps stability of the conductive network of integrated electrodes during stretching. When the deformation increases to 15%, resistance of the electrode only increases by 1.3 times. After 50 stretching-releasing cycles at 10% strain, it maintains a high capacity of 1442 mAh g−1 at 150 mA g−1. After 100 cycles, it achieves an excellent capacity retention of 91.6%. This work provides new insight into the development of high-capacity anodes for stretchable LIBs.

Ultrastretchable and Compact Zn-MnO2 Rechargeable Battery

The rise of stretchable electronics calls for deformable forms of rechargeable batteries as compatible power sources. The crumpled electrode design is a promising avenue for stretchable batteries by providing sufficient internal space to accommodate tensile deformations. Current electrodes typically have rough surfaces with visible corrugations, which present practical challenges in assembling compact cells for wearable systems. In this study, we report the design and preparation of ultrastretchable electrodes with microwrinkled surface textures. Crumpled electrodes are created in a transfer-printing process based on active materials deposited on metal film current collectors. A polymer membrane is introduced as a key mechanical support to effectively enhance the durability of these electrodes against large and repetitive tensile strains. A stretchable pouch cell of Zn-MnO2 rechargeable battery is constructed with a total thickness of ∼1 mm. The battery cell demonstrates a high specific capacity of 211 mAh g–1, stable charge–discharge cycling performances, and ultrahigh deformability of up to 525% strain. The compact design allows the battery to achieve conformal attachment to the skin and versatile integration with various deformable systems. The present work offers a generic approach to creating highly stretchable batteries with microwrinkled electrodes.

Liquid metal-based soft, hermetic, and wireless-communicable seals for stretchable systems.

Soft materials tend to be highly permeable to gases, making it difficult to create stretchable hermetic seals. With the integration of spacers, we demonstrate the use of liquid metals, which show both metallic and fluidic properties, as stretchable hermetic seals. Such soft seals are used in both a stretchable battery and a stretchable heat transfer system that involve volatile fluids, including water and organic fluids. The capacity retention of the battery was ~72.5% after 500 cycles, and the sealed heat transfer system showed an increased thermal conductivity of approximately 309 watts per meter-kelvin while strained and heated. Furthermore, with the incorporation of a signal transmission window, we demonstrated wireless communication through such seals. This work provides a route to create stretchable yet hermetic packaging design solutions for soft devices.

Sustainable stretchable batteries for next-generation wearables

Stretchable battery technology still faces several challenges to progress the development of next-generation wearables. This perspective will evaluate current strategies and provide a discussion on possible avenues for future research.

An intrinsically stretchable symmetric organic battery based on plant-derived redox molecules

A plant-based, stretchable organic battery was developed by formulating a quaternary biocomposite electrode that possesses high electrical and ionic conductivities, charge storage capacity of 6.8 mA h cm−3, and tensile stretchability over 300%.