3D Printable Ceramic–Polymer Electrolytes for Flexible High‐Performance Li‐Ion Batteries with Enhanced Thermal Stability

Abstract

This study establishes an approach to 3D print Li‐ion battery electrolytes with controlled porosity using a dry phase inversion method. This ink formulation utilizes poly(vinyldene fluoride) in a mixture of N‐methyl‐2‐pyrrolidone (good solvent) and glycerol (weak nonsolvent) to generate porosity during a simple drying step. When a nanosized Al2O3 filler is included in the ink, uniform sub‐micrometer pore formation is attained. In other words, no additional processing steps such as coagulation baths, stretching, or etching are required for full functionality of the electrolyte, which makes it a viable candidate to enable completely additively manufactured Li‐ion batteries. Compared to commercial polyolefin separators, these electrolytes demonstrate comparable high rate electrochemical performance (e.g., 5 C), but possess better wetting characteristics and enhanced thermal stability. Additionally, this dry phase inversion method can be extended to printable composite electrodes, yielding enhanced flexibility and electrochemical performance over electrodes prepared with only good solvent. Finally, sequentially printing this electrolyte ink over a composite electrode via a direct write extrusion technique has been demonstrated while maintaining expected functionality in both layers. These ink formulations are an enabling step toward completely printed batteries and can allow direct integration of a flexible power source in restricted device areas or on nonplanar surfaces.

3D Printing of Freestanding MXene Architectures for Current‐Collector‐Free Supercapacitors

“…The wet 3D structures are subsequently freeze‐dried to give freestanding Ti 3 C 2 T x architectures without the necessity of any further thermal or chemical treatments as are normally required when using additives or GO . Freeze‐drying protects the internal integrity and the external shape of the structures with low shrinkage resulting in Ti 3 C 2 T x 3D architectures of well‐defined shapes ( Figure a–d) and filaments in the micrometer range.…”

Elevated‐Temperature 3D Printing of Hybrid Solid‐State Electrolyte for Li‐Ion Batteries

“…Besides electrode materials, 3D printing of solid‐state electrolytes have also been reported over the past few years. Blake et al demonstrated a porous polymer based separator with a good thermal stability and electrolyte wetting ability . McOwen et al reported Li 7 La 3 Zr 2 O 12 based inks with two binder systems that could be built into thin and intricate architectures after sintering .…”

“…Second, it is necessary to avoid shrinkage of the structure during solidification. Generally, solvent‐evaporation and solidification are achieved by postprocessing heat treatments, which would change the shape of the electrolyte layer, leading to its shrinkage and eventual distortion . This shrinkage could potentially be minimized by printing the electrolyte directly onto the electrode.…”

Additive Manufacturing of Batteries

“…e) Wettability testing for the electrolyte CPE–PI and Celgard 2325. f) Shrinkage of CPE–PI and Celgard 2325 as a function of temperature. Reproduced with permission . Copyright 2017, Wiley‐VCH.…”

“…However, it is challenging to fabricate a high‐performance membrane with a controlled pore size using the traditional methods. Recently, Blake et al developed a new method to 3D print high‐performance and flexible ceramic–polymer electrolytes (CPEs) . In their work, PVDF and glycerol were dissolved by NMP, and then mixed with a high loading of Al 2 O 3 .…”