Binders play an important role in electrode processing for energy storage systems. While conventional binders often require hazardous and costly organic solvents, there has been increasing development toward greener and less expensive binders, with a focus on those that can be processed in aqueous conditions. Due to their functional groups, many of these aqueous binders offer further beneficial properties, such as higher adhesion to withstand the large volume changes of several high-capacity electrode materials. In this review, we first discuss the roles of binders in the construction of electrodes, particularly for energy storage systems, summarize typical binder characterization techniques, and then highlight the recent advances on aqueous binder systems, aiming to provide a stepping stone for the development of polymer binders with better sustainability and improved functionalities.

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In this work the potential of employing electrophoretic deposition (EPD) for fabricating Li-ion battery electrodes without using binders and in particular eliminating volatile and toxic organic solvents such as n-methyl 2-pyrrolidone (NMP) is demonstrated. The paper in particular describes the successful application of the EPD method to fabrication of thick (>20 μm) nano-TiO 2 /carbon Li-ion intercalation anodes. The EPD system involves deposition of commercial P25 TiO 2 nanoparticles and carbon black on aluminum foil from an isopropanol bath without making use of charging agents or other additives. Hetero-coagulation of TiO 2 and C particles in the isopropanol medium enabled their 80 V DC cathodic deposition into a well-adhered film with effective intermixing of active and conductive components. Electrochemical testing of the newly binder-free EPD-built electrodes revealed comparable film conductivity, polarization and charge storage capacity properties with the standard binder-based PVDF/NMP electrodes. Most importantly, the charge storage, cycling, and rate properties of the EPD-built electrodes were greatly enhanced by post-EPD sintering of the film at 450 • C. The combined EPD-sintering route resulted in a superior conductive percolating network by promoting nanoscale film composition uniformity, inter-particle necking, and favorable porous structure for enhanced interfacing with the liquid electrolyte. The sintered EPD-built electrode exhibited almost 50% higher capacity retention than that of the standard binder-based electrode upon cycling. EPD with its inherent self-assembling functionality and its overall operational simplicity provides an advantageous and green Li-ion electrode fabrication alternative. Lithium ion batteries (LIBs) are by far the most advanced electrochemical energy storage cells that are presently powering at an ever increasing pace not only mobile electronics but also electric transportation and renewable energy installations. [1][2][3][4] There is tremendous R&D effort in progress to develop increasingly higher performance electrode (anode and cathode) materials and electrolytes 5 to meet the new range of LIB applications, as is the case of electric vehicles. 6 However in this effort equally important is the selection of materials and fabrication technologies that not only lead to high energy and power density LIBs but also are governed by sustainability and affordability principles. It is in this context that the present work seeks to develop a green Li-ion fabrication technology featuring electrophoretic deposition and non-toxic abundant chemicals and materials.Present state-of-the-art electrode fabrication for lithium-ion batteries involves mixing the active powder material (anode or cathode), conductive carbon, and the binder (poly(vinilydene) fluoride, PVDF) by typically dispersing them in a solvent, then tape casting the slurry onto a current collector substrate, and finally followed by drying (at 120• C) and calendaring/pressing. 7 The high cost of PVDF binder and the require...

Due to its formidably high theoretical capacity (3590 mAh/g at room temperature), silicon (Si) is expected to replace graphite as the dominant anode for higher energy density lithium (Li)-ion batteries. However, stability issues stemming from silicon's significant volume expansion (∼300%) upon lithiation have slowed down commercialization. Herein, we report the design of a scalable process to engineer core−shell structures capable of buffering this volume expansion, which utilize a core made up of a poly(ethylene oxide)−carboxymethyl cellulose hydrogel and silicon protected by a crumpled graphene shell. The volume expansion of the hydrogel upon exposure to water creates a void space between the Si−Si and Si− rGO interfaces within the core when the gel dries. Unlike sacrificial spacers, the dehydrated hydrogel remains in the core and acts as an elastic Li-ion conductor, which improves the stability and high rate performance. The optimized composite electrodes retain ∼81.7% of their initial capacity (1055 mAh/(g rGO+gel+Si )) after 320 cycles when an active material loading of 1 mg/cm 2 is used. At more practical mass loadings (2.5 mg/cm 2 ), the electrodes achieve 2.04 mAh/cm 2 and retain 79% of this capacity after 200 cycles against a lithium half-cell. Full cells assembled using a lithium ion phosphate cathode lose only 6.7% of their initial capacity over 100 cycles, demonstrating the potential of this nanocomposite anode for use in next-generation Li-ion batteries.

In this paper, electrophoretic deposition (EPD) is shown to promote nanoscale assembling of graphene oxide (GO) enabling the fabrication of highly homogeneous, robust, and capacity fade resistant composite titanium niobate...

Silicon anodes have a theoretical capacity of 3590 mAh g À 1 (for Li 15 Si 4 , at room temperature), which is tenfold higher than the graphite anodes used in current Li-ion batteries. This, and silicon's natural abundance, makes it one of the most promising materials for next-generation batteries. Encapsulating silicon nanoparticles (Si NPs) in a crumpled graphene shell by spray drying or spray pyrolysis are promising and scalable methods to produce core-shell structures, which buffer the extreme volume change (> 300 vol %) caused by (de)lithiaton of silicon. However, capillary forces cause the graphene-based materials to tightly wrap around Si NP clusters, and there is little control over the void space required to further improve cycle life.Herein, a simple strategy is developed to engineer void-space within the core by incorporating varying amounts of similarly sized polystyrene (PS) nanospheres in the spray drier feed mixture. The PS completely decomposes during thermal reduction of the graphene oxide shell and results in Si cores of varying porosity. The best performance is achieved at a 1 : 1 ratio (PS/Si), leading to high capacities of 1638, 1468, and 1179 mAh g À 1Si + rGO at 0.1, 1, and 4 A g À 1 , respectively. Moreover, at 1 A g À 1 , the capacity retention is 80.6 % after 200 cycles. At a practical active material loading of 2.4 mg cm À 2 , the electrodes achieve an areal capacity of 2.26 mAh cm À 2 at 1 A g À 1 .