Development Of Flexible Lithium-ion Batteries Research Articles

Spider Silk-Inspired Binder Design for Flexible Lithium-Ion Battery with High Durability.

The development of flexible lithium-ion batteries (LIBs) imposes demands on energy density and high mechanical durability simultaneously. Due to the limited deformability of electrodes, as well as the flat and smooth surface of the metal current collectors, stable/durable/reliable contact between electrode materials and the current collectors remains a challenge, in particular, for electrodes with high loading mass and heavily deformed batteries. Binders play an essential role in binding particles of electrode materials and adhering them to current collectors. Herein, inspired by spider silk, a binder for flexible LIBs is developed, which equips a cross-linked supramolecular poly(urethane-urea) to the polyacrylic acid. The binder imparts super high elastic restorability originating from the meticulously engineered hydrogen-bonding segments as well as extraordinary adhesion. The developed binder provides excellent flexibility and intact electrode morphologies without disintegration even when the electrode is largely deformed, enabling a stable cycling and voltage output even when the batteries are put under tough dynamic deformation tests. The flexible LIBs exhibit a high energy density of 420WhL-1 , which is remarkably higher than reported numbers. The unique binder design is greatly promising and offers a valuable material solution for LIBs with high-loading mass and flexible designs.

Preparation of a SiO2 @Carbon Sphere/SiO2 -CNF Multilayer Self-standing Anode Prepared via an Alternate Electrospraying - Electrospinning Technique.

The development of flexible lithium-ion batteries (FLIBs) is restrained by traditional rigidity anodes. Carbon nanofiber (CNF) is a promising anode material owing to its high specific surface and superior ion transportation capability. However, the low amount of active material loaded on the CNFs and the poor stability during long cycling restrain their applications. Herein, a SiO2 @carbon sphere/SiO2 -CNF self-standing anode was prepared via alternate electrospraying-electrospinning. The SiO2 content of the anode was increased through the electrospraying SiO2 @carbon spheres layers, and the electrospun SiO2 -CNFs as robust layers enhanced the stability of the anode. The self-standing anode exhibited 633 mA h g-1 in the initial cycle and maintained a 70% Coulomb efficiency for 1000 cycles at a current density of 100 mA g-1 , which could be applied in FLIB and other electrochemical storage devices.

Ultrafast Kinetics in a PAN/MgFe2O4 Flexible Free-Standing Anode Induced by Heterojunction and Oxygen Vacancies.

Flexibility and power density are key factors restricting the development of flexible lithium-ion batteries (FLIBs). Interface and defect engineering can modify the intrinsic ion/electron kinetics by regulating the electronic structure. Herein, a polyacrylonitrile/MgFe2O4 (PAN-MFO) electrode with heterojunction and oxygen vacancies was first designed and synthesized as a flexible free-standing anode of FLIBs by electrostatic spinning technology. The PAN carbon nanofiber (PAN-CNF) as the skeleton structure provides fast conductive channels, buffers the volume expansion, and enhances the cycle stability. The heterostructure constructs the internal electric field, facilitates the Li+/charge transfer, intensifies the Li+ adsorption energy, and enhances the interfacial lithium storage. Oxygen vacancies improve the intrinsic conductivity, lower the Li+ diffusion barrier, weaken the Fe-O bonding, and facilitate the conversion reaction. Because of the synergistic effect of the multifunctional structure, the PAN-MFO shows superior cycle and rate performance with ultrafast kinetics. Flexible LiCoO2/PAN-MFO full pouch cells were also assembled that demonstrated a stable cycle performance and power supply in both the plain and bent states.

A novel all-fiber-based LiFePO4/Li4Ti5O12 battery with self-standing nanofiber membrane electrodes.

Electrodes with high conductivity and flexibility are crucial to the development of flexible lithium-ion batteries. In this study, three-dimensional (3D) LiFePO4 and Li4Ti5O12 fiber membrane materials were prepared through electrospinning and directly used as self-standing electrodes for lithium-ion batteries. The structure and morphology of the fibers, and the electrochemical performance of the electrodes and the full battery were characterized. The results show that the LiFePO4 and Li4Ti5O12 fiber membrane electrodes exhibit good rate and cycle performance. In particular, the all-fiber-based gel-state battery composed of LiFePO4 and Li4Ti5O12 fiber membrane electrodes can be charged/discharged for 800 cycles at 1C with a retention capacity of more than 100 mAh·g−1 and a coulombic efficiency close to 100%. The good electrochemical performance is attributed to the high electronic and ionic conductivity provided by the 3D network structure of the self-standing electrodes. This design and preparation method for all-fiber-based lithium-ion batteries provides a novel strategy for the development of high-performance flexible batteries.

Macroporous MoS2/carbon hybrid film with superior ion/electron conductivity for superhigh areal capacity Li-ion batteries

The development of flexible lithium-ion batteries (LIBs) with very high areal capacity becomes extremely important in achieving precision medicine due to the limited area of the involved LIB devices. However, the improvement of areal capacity using well-known conventional strategies unavoidably engenders serious polarization and gravimetric specific capacity fading. Herein, we report an entirely new insight into constructing superhigh areal-specific-capacity LIBs by designing an electron/ion dual-conductive macroporous MoS2/C hybrid film. A four-film stacked electrode even with a high mass loading of ∼12.0 mg cm−2 can deliver an unprecedented high areal specific capacity of 7.21 mA h cm−2, almost double that of best material reported to date (4 mA h cm−2). Such film electrode unexpectedly shows a positive linear increase of areal specific capacity versus layer number, but no gravimetric capacity (high value of ∼600 mA h g−1) change. The electrode kinetics studies reveal that such superhigh areal-specific-capacity lithium storage is mainly attributed to excellent ion transport (10−8–10−9 cm2 s−1) and electron transfer (21.3 S cm−1) of three-dimensional macroporous MoS2/C hybrid film. This work demonstrates a new concept of dual-conductive film electrode for the development and application of LIBs with tailorable areal specific capacity.

Issues and Challenges Facing Flexible Lithium‐Ion Batteries for Practical Application

With the advent of flexible electronics, lithium-ion batteries have become a key component of high performance energy storage systems. Thus, considerable effort is made to keep up with the development of flexible lithium-ion batteries. To date, many researchers have studied newly designed batteries with flexibility, however, there are several significant challenges that need to be overcome, such as degradation of electrodes under external load, poor battery performance, and complicated cell preparation procedures. In addition, an in-depth understanding of the current challenges for flexible batteries is rarely addressed in a systematical and practical way. Herein, recent progress and current issues of flexible lithium-ion batteries in terms of battery materials and cell designs are reviewed. A critical overview of important issues and challenges for the practical application of flexible lithium-ion batteries is also provided. Finally, the strategies are discussed to overcome current limitations of the practical use of flexible lithium-based batteries, providing a direction for future research.

Understanding the Effects of Electrode Formulation on the Mechanical Strength of Composite Electrodes for Flexible Batteries.

Flexible lithium-ion batteries are necessary for powering the next generation of wearable electronic devices. In most designs, the mechanical flexibility of the battery is improved by reducing the thickness of the active layers, which in turn reduces the areal capacity and energy density of the battery. The performance of a battery depends on the electrode composition, and in most flexible batteries, standard electrode formulation is used, which is not suitable for flexing. Even with considerable efforts made toward the development of flexible lithium-ion batteries, the formulation of the electrodes has received very little attention. In this study, we investigate the relation between the electrode formulation and the mechanical strength of the electrodes. Peel and drag tests are used to compare the adhesion and cohesion strength of the electrodes. The strength of an electrode is sensitive to the particle size and the choice of polymeric binder. By optimizing the electrode composition, we were able to fabricate a high areal capacity (∼2 mAh/cm2) flexible lithium-ion battery with conventional metal-based current collectors that shows superior electrochemical and mechanical performance in comparison to that of batteries with standard composition.

Recent progress on flexible lithium rechargeable batteries

Flexible lithium ion batteries (LIBs) have received considerable attention as a key component to enable future flexible electronic devices. A number of designs for flexible LIBs have been reported in recent years; in this article, we review recent progress. We focus on how flexibility can be introduced into each component of the LIB, including the active materials, electrolytes, separators, and current collectors. Approaches to integrating each component into a single device are described and the corresponding changes in the electrochemical and mechanical properties are discussed. Finally, the key challenges in the development of flexible LIBs are summarized.