Highly‐Safe and Ultra‐Stable All‐Flexible Gel Polymer Lithium Ion Batteries Aiming for Scalable Applications

Abstract

over other rechargeable battery technologies, including relatively high energy and power densities, long cycling life, little memory effect, and low self-discharge. [6][7][8] When used in flexible electronics, LIBs need to be flexible, thin, stretchable, and even foldable. [9][10][11] So far, flexible LIBs have been investigated for decades. Numerous strategies, such as fiber-shaped, [12] sponge-like, [13] spring-like stretchable, [14] and paper-like LIBs [15] have been reported, but none has been successful in real commercial applications. The reasons may be due to 1) low energy density, 2) poor mechanical flexibility, 3) poor safety, and 4) not being suitable for scalable applications. Presently, the development in the field of flexible LIBs is still at the early stage of research in laboratories, and most of the reports focus on flexible electrodes based on flexible current collectors. [13,[15][16][17][18] Conventional metal foils (aluminum [Al] and copper [Cu]) as current collectors to support active materials [19] are unfit for flexible batteries because the active materials (cathode and anode) are easily delaminated from their smooth surface when the flexible batteries are bent. In addition, the high-density characteristics of metal restrict the mass energy density of LIBs. Therefore, replacing the metal foils with a highly conductive, light-weight, thin, and flexible current collector could enhance both the mass energy density and mechanical flexibility.Recently, carbon-based materials featuring good electrical conductivity, high mechanical durability and low density are considered as the promising choice for current collectors in flexible LIBs. [20,21] The reported carbon based materials include carbon nanotubes (CNTs), [15,[22][23][24][25][26] carbon cloth, [27] carbon fibers, [28] graphene based film, [29] and foam. [30,31] Thanks to the tremendous research efforts devoted over the past decades, research on flexible LIBs has made substantial progress. However, from the perspective of scalable applications, the above-mentioned carbon based materials still have some insurmountable problems. First, due to the difficult dispersion of CNTs and other nanocarbon materials in solution, the major challenge is to fabricate CNT films with uniform thickness and mass. [26] Although flexible CNT films can also be prepared directly through the floating-catalyst chemical vapor deposition (CVD) method at the high-temperature zone of the chamber with robustness and high conductivity, the area of the obtained films is limited by the diameter of the reaction chamber. [32,33] Second, for carbon cloth, there are numerous With the development of flexible electronics, flexible lithium ion batteries (LIBs) have received great attention. Previously, almost all reported flexible components had shortcomings related to poor mechanical flexibility, low energy density, and poor safety, which led to the failure of scalable applications. This study demonstrates a fully flexible lithium ion battery using LiCoO 2 as the cathode, Li 4 Ti ...

Pathways of Developing High‐Energy‐Density Flexible Lithium Batteries

“…Therefore, several representative examples of GPEs, including poly(ethylene oxide) (PEO), poly(vinylidenefluoride)‐hexafluoropropylene (PVDF‐HFP), poly(ethoxylated trimethylolpropane triacrylate), and poly(vinylidene fluoride‐tri‐fluoroethylenechlorofluoroethylene) (PTC), will be discussed in details for achieving high‐safety FLBs in this section. [ 88–90 ]…”

“…The development of GPEs with high flame retardancy and high‐voltage stability is another feasible strategy to improve the safety of FLBs. [ 90 ] A novel GPE of GO‐doped PTC/PEO (GO‐GPE) was also developed by cross‐linking PTC, PEO, and GO via hydrogen bonding interactions (Figure 5c). [ 90 ] Due to the high dielectric constant of PTC, GO‐GPEs could effectively dissociate the lithium salts of LiPF 6 and generate a large quantity of charge carriers for rapid ion diffusion.…”

Benzodithiophene‐S,S‐tetraoxide (BDTT) as an Acceptor Towards Donor‐Acceptor (D‐A)‐Type Semiconducting Electropolymers

“…Recent developments in conducting polymers have enabled their use in diverse industrial applications such as lithium-ion batteries, [1] organic photovoltaics, [2] organic field-effect transistors (OFET), [3] and NIR polymer probes. [4,5] In part, the donoracceptor (D-A) design is an effective strategy to tune the optical band gap of a material.…”

Semi‐interpenetrating gel polymer electrolyte based on PVDF‐HFP for lithium ion batteries

“…The solvent acts as a plasticizer and its addition results in the swelling of the polymer matrix, which physical aspect changes from a solid to a gel. 13 Up to now, many kinds of polymeric hosts have been proposed, such as polyethylene oxide (PEO), [17][18][19] polymethyl methacrylate (PMMA), 20,21 polyacrylonitrile (PAN), 22,23 polyimide (PI), 24 polyvinylidene fluoride (PVDF), [25][26][27] PVDF-HFP, [28][29][30] and so on. However, these polymer matrices have some intrinsic defects, for example, PEO based GPEs exhibits lower ionic conductivity because of high crystalline at room temperature.…”