Hydrogel‐Based Additive Manufacturing of Lithium Cobalt Oxide

Abstract

3D multicomponent metal oxides with complex architectures can enable previously impossible energy storage devices, particularly lithium‐ion battery (LIB) electrodes with fully controllable form factors. Existing additive manufacturing approaches for fabricating 3D multicomponent metal oxides rely on particle‐based or organic–inorganic binders, which are limited in their resolution and chemical composition, respectively. In this work, aqueous metal salt solutions are used as metal precursors to circumvent these limitations, and provide a platform for 3D printing multicomponent metal oxides. As a proof‐of‐concept, architected lithium cobalt oxide (LCO) structures are fabricated by first synthesizing a homogenous lithium and cobalt nitrate aqueous photoresin, and then using it with digital light processing printing to obtain lithium and cobalt ion containing hydrogels. The 3D hydrogels are calcined to obtain micro‐porous self‐similar LCO architectures with a resolution of ≈100 µm. These free‐standing, binder‐ and conductive additive‐free LCO structures are integrated as cathodes into LIBs, and exhibit electrochemical capacity retention of 76% over 100 cycles at C/10. This facile approach to fabricating 3D LCO structures can be extended to other materials by tailoring the identity and stoichiometry of the metal salt solutions used, providing a versatile method for the fabrication of multicomponent metal oxides with complex 3D architectures.

Three‐dimensional chemical reactors: in situ materials synthesis to advance vat photopolymerization

“…Yee et al fabricated metal oxides using metal-nitrate-containing aqueous photoresins, in a process that combined solution combustion synthesis (SCS) with VP. 215 The use of aqueous metal nitrate solutions as metal oxide precursors allowed for compositional versatility, and also compatibility with high-resolution VP techniques. This was demonstrated in the fabrication of piezoelectric zinc oxide microstructures with TPL using a zinc nitrate aqueous photoresin (Fig.…”

“…217 Copyright 2020, Springer Nature. 215 SCS is a highly facile and versatile technique for the fabrication of metal oxide materials but is characterized by the rapid formation of a large amount of gases due to the oxidizing nature of the metal nitrates. 222 As a result, the LCO structures were macroporous despite the slow calcination process used.…”

Toward High Resolution 3D Printing of Shape-Conformable Batteries via Vat Photopolymerization: Review and Perspective

“…Among the expected challenges are: determining suitable precursor compounds and stoichiometries, obtaining rheological properties of the precursor resin that allow 3D printing of self-standing structures, and finding appropriate thermal post-processing conditions for the synthesis of battery materials and the elimination of non-electroactive components. Specifically focused on LIB, Yee et al [65] reported the synthesis of LiCoO2 via projection VPP. In this case, an aqueous PEGDA-based resin was loaded with Co(NO3)2.6H2O and LiNO3 in stoichiometric ratios, from which a hydrogel was printed and calcinated at 700 ºC (Fig.…”

“…In contrast, 3D printed electrodes require a certain micro-porosity, so that adequate electrolyte impregnation is allowed. To address this issue, Yee et al [65] worked on the tuning ratio of PEGDA-to-LiCoO2, and found that by increasing the lithium precursor, it was possible to increase the micro-porosity without excessively increasing the Ohmic impedance. Two other methods to promote micro-porosity are also mentioned.…”

“…Surprisingly, the structure presented promising first discharge capacity of 310 mAh/g at C/20 and a retention of 80% after 100 cycles when tested in half-cell configuration versus lithium. It is worth noting that these pioneering studies [65,66], cycled independent 3D electrodes against a lithium foil (planar structure), resulting in 2.5D batteries [67], as the lithium-ion diffusion is relegated only to two dimensions. In all, these promising efforts demonstrated that VPP of precursor UVcurable resins for battery applications is achievable and highlighted the potential to manufacture 3D designs that were previously thought impossible.…”