Binder-Free Electrodes and Their Application for Li-Ion Batteries

Abstract

Lithium-ion batteries (LIB) as energy supply and storage systems have been widely used in electronics, electric vehicles, and utility grids. However, there is an increasing demand to enhance the energy density of LIB. Therefore, the development of new electrode materials with high energy density becomes significant. Although many novel materials have been discovered, issues remain as (1) the weak interaction and interface problem between the binder and the active material (metal oxide, Si, Li, S, etc.), (2) large volume change, (3) low ion/electron conductivity, and (4) selfaggregation of active materials during charge and discharge processes. Currently, the binder-free electrode serves as a promising candidate to address the issues above. Firstly, the interface problem of the binder and active materials can be solved by fixing the active material directly to the conductive substrate. Secondly, the large volume expansion of active materials can be accommodated by the porosity of the binder-free electrode. Thirdly, the ion and electron conductivity can be enhanced by the close contact between the conductive substrate and the active material. Therefore, the binderfree electrode generally exhibits excellent electrochemical performances. The traditional manufacture process contains electrochemically inactive binders and conductive materials, which reduces the specific capacity and energy density of the active materials. When the binder and the conductive material are eliminated, the energy density of the battery can be largely improved. This review presents the preparation, application, and outlook of binder-free electrodes. First, different conductive substrates are introduced, which serve as carriers for the active materials. It is followed by the binderfree electrode fabrication method from the perspectives of chemistry, physics, and electricity. Subsequently, the application of the binder-free electrode in the field of the flexible battery is presented. Finally, the outlook in terms of these processing methods and the applications are provided.

Recent Progress in Binder‐Free Electrodes Synthesis for Electrochemical Energy Storage Application

“…Compared with the traditional slurry system, the binder‐free electrode has better electrochemical performance. Guarantees the active materials are uniformly anchored on the support material to prevent the agglomeration and reduce the volume expansion during cycles [53] . However, it is still a challenge to assemble a binder‐free energy storage device with high energy density, excellent stability and high mass load (>10 mg cm −2 for commercial applications).…”

“…Through vacuum filtration method, 2D materials can be easily assembled into flexible self‐standing paper‐like materials, which can be directly used as flexible binder‐free electrodes in energy storage devices [53] . Transition metal dichalcogenides (TMDCs) such as MoS 2 , MoSe 2 , WS 2 , as new class of 2D materials, attractive applications in electronics and energy storage devices [54] .…”

Solid Polymer Electrolytes with High Conductivity and Transference Number of Li Ions for Li‐Based Rechargeable Batteries

“…[ 33 ] Flexible devices even work when bent, folded, twisted, and stretched, and so their batteries have to as well. [ 34 ] SPEs have a tremendous advantage over other technologies since the polymeric backbone of a SPE offers mechanical flexibility needed for such batteries. [ 35 ]…”

“…[ 35 ] SPEs are currently the ideal electrolytes to use in high‐performance flexible batteries, because their flexible polymer backbones are able to accommodate reversible stretching and bending without failures. [ 34 ] Although the traditional battery and the flexible battery have similar working principles, traditional battery architectures contain liquid electrolytes and almost unstretchable separators ( Figure a). [ 231 ] When deformed, the electrolyte might become unevenly distributed/squeezed, and the separator might not recover its original shape.…”

Towards a More Sustainable Lithium‐Ion Battery Future: Recycling LIBs from Electric Vehicles

“…A mention should also be made to the efforts to develop binder‐free LIBs. These promise to bring about significant performance improvements through overcoming the “interface problem” between the binder and active materials in LIBs and improving ion and electron conductivity through close contact [51] . However, as preparation of a binder‐free electrode involves embedding the active electrode materials directly into the current collector – this, if anything, drives us further away from a circular economy.…”