Three-dimensional (3D)-printed membranes via stereolithography (SLA) are promising in oil−water separation, which is the key in the purification of industrial oily wastewater. To achieve gravity-driven oil−water separation, the membrane material needs to be simultaneously hydrophilic/oleophobic. However, most of the state-of-the-art materials for SLA do not meet the requirement. While wateradsorbing hydrogel is simultaneously hydrophilic/oleophobic and there have been reports on 3D printing of hydrogels in biomedical applications, the hydrogel is too soft for membrane application. Here, we report a simple approach to tackle the issue: a hydrogel coating on SLA-based plastic membranes. The coating is fabricated, using [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide as the zwitterionic monomer and acrylamide as the comonomer, via in situ polymerization on SLA-based plastic membranes. The contact angle tests and Fourier transform infrared spectrum show that such a membrane readily adsorbs water and becomes simultaneously hydrophilic/oleophobic. The oil−water separation tests indicate that the water-adsorbed membrane is highly efficient in gravitydriven oil−water separation in 31 repeating cycles. Our results indicate the great potential of 3D-printed membranes in oil−water separation.

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Owing to the rapid development of flexible/wearable devices in soft electronics, electronic textile, healthcare, and aeronautics, flexible lithium metal batteries (FLMBs) have gained great attentions as one of the most promising power sources. [1][2][3][4] Lithium (Li) metal is an ideal anode material due to its ultrahigh theoretical-specific capacity (3860 mAh g −1 ) and the lowest electrochemical potential (−3.04 V vs standard hydrogen electrode). [5][6][7][8][9][10][11][12][13] Despite these obvious superiorities, its practical application in flexible devices is mainly impeded by the limited flexibility, uncontrolled Li dendrites growth, and severe volume change upon cycling. [14,15] Employing a flexible self-standing threedimensional (3D) substrate in Li metal anode (LMA) is an effective strategy to tackle abovementioned issues. [9,[16][17][18][19] Large specific surface area and sufficient space of 3D substrate show immense promise for mitigating the volume change and Li dendrites' growth. Currently, metal-based and carbon-based 3D substrates are the two main categories in this regard. [20][21][22] Metal-based 3D substrates, such as nickel foam, copper foam, and TiO 2 nanotube arrays, improve the mechanical property and electrochemical performance of LMA. However, the heavy metallic components reduce the overall specific capacity and energy density of full batteries. Additionally, the expensive metal-based substrates increase the cost of industrial production. In contrast, carbonaceous substrates, such as carbon cloth and carbonized-polymer fiber/foam, are low-density, inexpensive, and sustainable. Guo and co-workers used graphitized carbon fibers as LMA substrate and achieved a high specific capacity of 1254 mAh g −1 based on the whole electrode at 0.5 mA cm −2 . [23] Although high specific capacity of LMA is achievable when employing a pristine carbon substrate, the growth of Li dendrites appears to be unavoidable, especially at high current density (>5 mA cm −2 ). This is likely due to its low lithiophilicity, unsmooth surface, and insufficient specific surface area, resulting in instability, high local current density, and uneven Li-ion concentration/electric field in the anode. Strategies of surface modification and structural remodeling are proposed to improve the performance of carbon substrates. For instance, Pan and co-workers obtained porous powder carbon with very high specific surface area by carbonizing metal-organic framework. [24] However, similar strategies are not suitable for self-standing 3D carbon substrates. As a result, unadorned 3D carbon substrates were historically adopted in the construction of flexible self-standing electrodes. [25][26][27][28][29] In addition to the application as LMA material, carbon substrate is also an excellent candidate for flexible cathodes. Therefore, A universal strategy to prepare flexible 3D carbon-based substrates suitable for both anode and cathode is highly desirable to achieve high-performance FLMBs.

Developing flexible electrodes with high active materials loading and excellent mechanical stability is of importance to flexible electronics, yet remains challenging. Herein, robust flexible electrodes with an encapsulated core-multishell structure are developed via a spraying-hydrothermal process. The multilayer electrode possesses an architecture of substrate/reduced graphene oxide (rGO)/bimetallic complex/rGO/bimetallic complex/rGO from the inside to the outside, where the cellulosic fibers serve as the substrate, namely, the core; and the multiple layers of rGO and bimetallic complex, are used as active materials, namely, the shells. The inner two rGO interlayers function as the cement that chemically bind to two adjacent layers, while the two outer rGO layers encapsulate the inside structure effectively protecting the electrode from materials detachment or electrolyte corrosion. The electrodes with a unique core-multishell structure exhibit excellent cycle stability and exceptional temperature tolerance (−25 to 40°C) for lithium and sodium storage. A combination of experimental and theoretical investigations are carried out to gain insights into the synergetic effects of cobalt-molybdenum-sulfide (CMS) materials (the bimetallic complex), which will provide guidance for future exploration of bimetallic sulfides. This strategy is further demonstrated in other substrates, showing general applicability and great potential in the development of flexible energy storage devices.

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