All-solid-state batteries (ASSBs) are gaining prominence for their ability to overcome the intrinsic drawbacks of conventional liquid-based counterparts, such as electrolyte leakage, flammability, and limited voltage window. Nevertheless, ASSBs have so far been mainly investigated using lab-scale dry mixing processes and therefore suffer from limitation of scalability and agglomeration of active particles in the composite electrodes. Here, we report a systematic investigation on ASSBs fabricated by a solution-based casting process. By screening a wide range of binders and solvents, acrylonitrile butadiene rubber and para-xylene were a suitable binder and solvent, respectively, compatible with sulfide glass-ceramic solid electrolyte. This binder-solvent combination facilitates homogeneous dispersion of the solid electrolyte in the slurry and electrolyte layer, offering high adhesion between electrode materials and comparable lithium ionic conductivity to that of the dry mixing-based counterpart. When solution-based casting processes were adopted for both electrolyte and composite cathode (containing LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) layers, the solution-processed cell exhibits decent performance in rate capability and cyclability due to higher homogeneity of the electrode components, originating from the appropriate combination of solvent and binder.

Recent studies of all-solid-state batteries (ASSBs) have identified sulfide-based electrolytes with comparable ionic conductivities as those of liquid counterparts. Nevertheless, solution-based manufacturing is unestablished, since it is challenging to find adhesive polymeric binders that can be dispersed in common solvents with sulfide electrolytes. Currently available binders exhibit insufficient electrode adhesion due to their low polarity and are compromised by the chemical stability of a slurry. Here, we report a thiol−ene click reaction used to graft styrene−butadiene-blockcopolymer with carboxylic acid at an optimal concentration. With polarity tuning, the click binder results in a uniform electrode slurry without ruining the structure of the sulfide electrolytes, while enabling electrode adhesion 1.4 times as high as that of commercial lithium-ion battery electrodes. The click binder also allows ASSBs to deliver decent electrochemical performance, implying that fine polarity tuning of functional binders can constitute an important step forward in advancing ASSBs to a real scalable technology.

Sulfide‐based all‐solid‐state batteries (ASSBs) have been featured as promising alternatives to the current lithium‐ion batteries (LIBs) mainly owing to their superior safety. Nevertheless, a solution‐based scalable manufacturing scheme has not yet been established because of the incompatible polarity of the binder, solvent, and sulfide electrolyte during slurry preparation. This dilemma is overcome by subjecting the acrylate (co)polymeric binders to protection−deprotection chemistry. Protection by the tert‐butyl group allows for homogeneous dispersion of the binder in the slurry based on a relatively less polar solvent, with subsequent heat‐treatment during the drying process to cleave the tert‐butyl group. This exposes the polar carboxylic acid groups, which are then able to engage in hydrogen bonding with the active cathode material, high‐nickel layered oxide. Deprotection strengthens the electrode adhesion such that the strength equals that of commercial LIB electrodes, and the key electrochemical performance parameters are improved markedly in both half‐cell and full‐cell settings. The present study highlights the potential of sulfide‐based ASSBs for scalable manufacturing and also provides insights that protection−deprotection chemistry can generally be used for various battery cells that suffer from polarity incompatibility among multiple electrode components.

can deliver superior rate performance despite its inherently low electric conductivity. Especially, modifications of the intrinsic phase via doping [17] with aliovalent elements and incorporating off-stoichiometry [18] improved the rate performance remarkably. Also, the formation of metastable structures that allows the nucleation of a second phase to bypass was revealed [19,20] as the origin of the exceptional rate capability of LFP.Besides the tuning of active material, various polymeric binders were lately investigated [21][22][23][24][25] for LFP electrodes in both organic and aqueous media. Aqueous binders were particularly highlighted because of their conspicuous advantages, including low cost and easy disposal of waste solvents after processing. [21,22,24,26] In spite of these advantages, currently, LFP electrodes are mostly manufactured via N-methyl-2pyrrolidone (NMP)-based slurry process because the use of aqueous media causes Li ion extraction from active powder and corrosion of aluminum (Al) current collector. [27][28][29] As in most LIB cathodes, polyvinylidene difluoride (PVDF) dispersed in NMP has been mainly used for LFP electrodes, to take advantages of the properties of PVDF, such as high electrochemical stability, high specific dielectric constant, and decent Li ion conductivity. However, PVDF binders operate mainly based on van der Waals interaction, leading to weak adhesion of the electrode to the current collector. Also, PVDF used for most commercial LIBs has high molecular weights (MWs) of around 1 000 000 and therefore often suffers from binder aggregation during slurry preparation as well as in the final electrode film. Herein, we introduce an unconventional binder, namely spandex, with relatively low molecular weight of around 300 000. Compared to the commercial PVDF binders with both high and low MWs, the spandex binder exhibited superiority in uniformness of electrode morphology, adhesion of electrode to an Al current collector, conservation of solvent during slurry preparation, and rate capability in battery operation. Furthermore, the enhanced adhesion of electrode renders the spandex binder suitable for 3D porous electrodes that are considered for future flexible battery applications. Moreover, we can take advantage of the long research and industrial experience of spandex; spandex is usually produced by step-growth polymerization and used for various applications, including clothes, daily supplies, biomedical devices, etc. [30,31] This investigation conveys a useful lesson that although occupying a small content in the electrode, binder can considerably improve the performance of established commercial LIB electrodes, and unexplored polymers can be good candidates for such opportunities. Figure 1 schematically illustrates the electrode morphologies when high MW PVDF (H-PVDF) and low MW spandex (L-spandex) are adopted as binders. H-PVDF often causes Lithium-ion batteries (LIBs) have been successfully developed as power sources for mobile information technology (IT) devices and hybrid...

Wearable rechargeable batteries require electrode platforms that can withstand various physical motions, such as bending, folding, and twisting. To this end, conductive textiles and paper have been highlighted, as their porous structures can accommodate the stress built during various physical motions. However, fabrics with plain weaves or knit structures have been mostly adopted without exploration of nonwoven counterparts. Also, the integration of conductive materials, such as carbon or metal nanomaterials, to achieve sufficient conductivity as current collectors is not well-aligned with large-scale processing in terms of cost and quality control. Here, the superiority of nonwoven fabrics is reported in electrochemical performance and bending capability compared to currently dominant woven counterparts, due to smooth morphology near the fiber intersections and the homogeneous distribution of fibers. Moreover, solution-processed electroless deposition of aluminum and nickel-copper composite is adopted for cathodes and anodes, respectively, demonstrating the large-scale feasibility of conductive nonwoven platforms for wearable rechargeable batteries.