All-inkjet-printed, solid-state flexible supercapacitors (SCs) on paper are demonstrated as a new class of power sources with exceptionally versatile aesthetics. The inkjet-printed SCs look like inkjet-printed letters or figures commonly found in office documents and are aesthetically unitized with other printed images on paper.

The rapidly approaching smart/wearable energy era necessitates advanced rechargeable power sources with reliable electrochemical properties and versatile form factors. Here, as a unique and promising energy storage system to address this issue, we demonstrate a new class of heterolayered, one-dimensional (1D) nanobuilding block mat (h-nanomat) battery based on unitized separator/electrode assembly (SEA) architecture. The unitized SEAs consist of wood cellulose nanofibril (CNF) separator membranes and metallic current collector-/polymeric binder-free electrodes comprising solely single-walled carbon nanotube (SWNT)-netted electrode active materials (LiFePO4 (cathode) and Li4Ti5O12 (anode) powders are chosen as model systems to explore the proof of concept for h-nanomat batteries). The nanoporous CNF separator plays a critical role in securing the tightly interlocked electrode-separator interface. The SWNTs in the SEAs exhibit multifunctional roles as electron conductive additives, binders, current collectors and also non-Faradaic active materials. This structural/physicochemical uniqueness of the SEAs allows significant improvements in the mass loading of electrode active materials, electron transport pathways, electrolyte accessibility and misalignment-proof of separator/electrode interface. As a result, the h-nanomat batteries, which are easily fabricated by stacking anode SEA and cathode SEA, provide unprecedented advances in the electrochemical performance, shape flexibility and safety tolerance far beyond those achievable with conventional battery technologies. We anticipate that the h-nanomat batteries will open 1D nanobuilding block-driven new architectural design/opportunity for development of next-generation energy storage systems.

Reactive oxygen species or superoxide (O 2 − ), which damages or ages biological cells, is generated during metabolic pathways using oxygen as an electron acceptor in biological systems. Superoxide dismutase (SOD) protects cells from superoxide-triggered apoptosis by converting superoxide to oxygen and peroxide. Lithium−oxygen battery (LOB) cells have the same aging problems caused by superoxide-triggered side reactions. We transplanted the function of SOD of biological systems into LOB cells. Malonic acid-decorated fullerene (MA-C 60 ) was used as a superoxide disproportionation chemocatalyst mimicking the function of SOD. As expected, MA-C 60 as the superoxide scavenger improved capacity retention along charge/discharge cycles successfully. A LOB cell that failed to provide a meaningful capacity just after several cycles at high current (0.5 mA cm −2 ) with 0.5 mAh cm −2 cutoff survived up to 50 cycles after MA-C 60 was introduced to the electrolyte. Moreover, the SOD-mimetic catalyst increased capacity, e.g., more than a 6-fold increase at 0.2 mA cm −2 . The experimentally observed toroidal morphology of the final discharge product of oxygen reduction (Li 2 O 2 ) and density functional theory calculation confirmed that the solution mechanism of Li 2 O 2 formation, more beneficial than the surface mechanism from the capacity-gain standpoint, was preferred in the presence of MA-C 60 .

Redox-active organic electrode materials have garnered considerable interest as an emerging alternative to currently widespread inorganic-(or metal)-based counterparts in lithium-ion batteries (LIBs). Practical use of these materials, however, has posed a challenge due to their electrically insulating nature, limited specific capacity, and poor electrochemical durability. Here, a new class of multiwalled-carbon-nanotube-(MWCNT)-cored, meso-tetrakis(4-carboxyphenyl) porphyrinato cobalt (CoTCPP) is demonstrated as a 1D nanohybrid (denoted as CC-nanohybrid) strategy to develop an advanced LIB anode. CoTCPP, which is one of the metalloporphyrins having multielectron redox activities, shows strong noncovalent interactions with MWCNTs due to its conjugated π-bonds, resulting in successful formation of the CC-nanohybrids. The structural uniqueness of the CC-nanohybrid facilitates electron transport and electrolyte accessibility, thereby improving their redox kinetics. Inspired by the 1D structure of the CC-nanohybrid, all-fibrous nanomat anode sheets are fabricated through concurrent electrospraying/electrospinning processes. The resulting nanomat anode sheets, driven by their 3D bicontinuous ion/electron conduction pathways, provide fast lithiation/delithiation kinetics, eventually realizing the well-distinguishable lithiation behavior of CoTCPP. Notably, the nanomat anode sheets exhibit exceptional electrochemical performance (≈226 mAh g sheet −1 and >1500 cycles at 5 C) and mechanical flexibility that lie far beyond those achievable with conventional LIB anode technologies.

Lithium-sulfur (Li-S) batteries have garnered considerable interest as a promising alternative to current state-of-the-art Li-ion batteries. However, the shuttle effect poses a formidable challenge to development of Li-S batteries. Considering that all ions in electrolytes move through separators between electrodes, significant attention should be paid to separators to prevent the shuttle effect. Here, a new class of spiderweb-mimicking, anion-exchanging separators based on polyionic liquids ("spiderweb separators") is demonstrated to address the aforementioned issue. The spiderweb separator consists of sandwich-type functional nanomats (top/bottom layers = multi-walled carbon nanotube-wrapped polyetherimide nanomats, middle layer = poly(1ethyl-3-methylimidazolium) bis(trifluoromethanesulfonyl)imide (PVIm[TFSI], polyionic liquid)/poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) nanomat) on polyethylene separator. The middle nanomat layer enables (discharge voltage-dependent) reversible trap/release of polysulfides via an anion exchange reaction between TFSI−anions (from PVIm[TFSI]) and polysulfides. The top/bottom nanomat layers respectively act as an upper current collector and a blocking layer to prevent crossover of polysulfides to Li anodes. Driven by its unique morphology and chemical functionalities, the spiderweb separator prevents the shuttle effect while ensuring facile ion transport, leading to exceptional improvement in the electrochemical performance (capacity = 819 mAh g −1 and cycling retention = 72% (at 2.0 C/2.0 C) after 300 cycles) of Li-S batteries. The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201801422.outperform current state-of-the-art Li-ion batteries. Li-S batteries show a high theoretical capacity (1672 mAh g −1 ), low cost, natural abundance, and use of environmentally benign sulfur active materials. Despite such remarkable advantages, the practical use of Li-S batteries is challenging due to the electrically inert nature of sulfur, the volume change of sulfur cathodes, and the shuttle effect of lithium polysulfides (Li 2 S x ). [9,[11][12][13] In particular, the shuttle effect and consequent accumulation of electrically irreversible low-order lithium polysulfides (including Li 2 S 2 and Li 2 S) on electrodes are considered formidable obstacles to the long-term cycling performance of Li-S batteries.Enormous research efforts have been undertaken to resolve these problems, [14][15][16][17][18][19] with a focus on conductive, scaffold-based, nanostructured sulfur cathodes, functional electrolytes/additives, and conductive interlayers. Meanwhile, considering that all ions (including polysulfides) in electrolytes move through electrolyte-soaked separators between the sulfur cathodes and Li metal anodes, separators should not be underestimated in research activities on preventing the shuttle effect. Recently, the modification of separators with carbon-based conductive layers [20][21][22][23][24][25][26][27][28] a...