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A microgrid-patterned silicon (MPS) electrode is presented as an electroactive Li host, which enables stepwise sequential Si lithiation/delithiation and Li plating/stripping reactions for a high-energy-density Li–metal full cell.

A biphasic liquid electrolyte based on the kosmotropic effect is presented to fulfill the requirements of anodes and cathodes. Kosmotropic anions enable demixing of aqueous and nonaqueous electrolytes, improving redox kinetics at cathodes and Zn2+ cyclability at anodes.

To dramatically improve the performance of non-precious catalyst-based anion exchange membrane fuel cells (AEMFCs), a conceptual change in the structure of conventional electrocatalysts is needed. Here we report a novel work function tailoring of graphene via adopting a graphene shell-encapsulated Co nanoarchitecture to efficiently activate the graphitic carbon shell as an exclusive and main active site for the oxygen reduction reaction (ORR). Theoretical calculations and electrochemical analysis suggest that the charge transfer from core Co nanoparticles to the outer graphene shell results in a significant change in the electronic structure of the graphene shell and reduces its work function. The present catalyst shows high ORR catalytic activity but exceptionally enhanced durability compared to a Pt catalyst in alkaline media, which is attributed mainly to the reduced work function of the outer graphene shell and the 3D nanographene structure providing a large number of active carbon sites. The single cell using the graphene shell-encapsulated Co nanoparticles as a cathode catalyst produces a high maximum power density of 412 mW cm−2, making this among the best non-precious catalysts for the ORR reported so far. Therefore, our results demonstrate a promising strategy to rationally design inexpensive and durable oxygen reduction catalysts, and this hybrid concept will provide a new perspective for catalyst structures which can practically be used in AEMFCs.

Traditional single-phase electrolytes, which are widely used in current state-of-the-art rechargeable batteries, have difficulties simultaneously fulfilling different chemical/electrochemical requirements of anodes and cathodes. Here, we demonstrate a new class of monolithic heterojunction quasi-solid-state electrolytes (MH-QEs) based on thermodynamically immiscible dual phases. As a proof-of-concept of the MH-QEs, their application to lithium–sulfur batteries is explored. Driven by combined effects of structural uniqueness and thermodynamic immiscibility, the electrode-customized MH-QEs provide exceptional electrochemical performance that lies far beyond those accessible with conventional battery electrolytes.

Lithium–sulfur (Li–S) batteries have attracted considerable attention as a promising alternative to current state-of-the-art lithium-ion batteries (LIBs), however, their practical use remains elusive, which becomes more serious upon application to flexible/wearable electronics. Here, we demonstrate a new class of nanomat Li–S batteries based on all-fibrous cathode–separator assemblies and conductive nonwoven-reinforced Li metal anodes as an unprecedented strategy toward ultrahigh energy density and mechanical flexibility. Sulfur cathodes, which are fibrous mixtures of sulfur-deposited multi-walled carbon nanotubes and single-walled carbon nanotubes, are monolithically integrated with bi-layered (pristine cellulose nanofiber (CNF)–anionic CNF) paper separators, resulting in metallic foil current collector-free, all-fibrous cathode–separator assemblies. The cathode–separator assemblies, driven by their all-fibrous structure (contributing to three-dimensional bi-continuous electron/ion conduction pathways) and anionic CNFs (suppressing the shuttle effect via electrostatic repulsion), improve redox kinetics, cyclability and flexibility. Nickel-/copper-plated conductive poly(ethylene terephthalate) nonwovens are physically embedded into Li foils to fabricate reinforced Li metal anodes with dimensional/electrochemical superiority. Driven by the structural uniqueness and chemical functionalities, the nanomat Li–S cells provide exceptional improvements in electrochemical performance (the (cell-based) gravimetric/volumetric energy density = 457 W h kgcell−1/565 W h Lcell−1 and the cycling performance (over 500 cycles) under 110% capacity excess of the Li metal anode) and mechanical deformability (they even can be crumpled).

Bipolar all-solid-state lithium-ion batteries (LIBs) have attracted considerable attention as a promising approach to address the ever-increasing demand for high energy and safety. However, the use of (sulfide- or oxide-based) inorganic solid electrolytes, which have been the most extensively investigated electrolytes in LIBs, causes problems with respect to mechanical flexibility and form factors in addition to their longstanding issues such as chemical/electrochemical instability, interfacial contact resistance and manufacturing processability. Here, we develop a new class of flexible/shape-versatile bipolar all-solid-state LIBs via ultraviolet (UV) curing-assisted multistage printing, which does not require the high-pressure/high-temperature sintering processes adopted for typical inorganic electrolyte-based all-solid-state LIBs. Instead of inorganic electrolytes, a flexible/nonflammable gel electrolyte consisting of a sebaconitrile-based electrolyte and a semi-interpenetrating polymer network skeleton is used as a core element in the printed electrodes and gel composite electrolytes (GCEs, acting as an ion-conducting separator membrane). Rheology tuning (toward thixotropic fluid behavior) of the electrode and GCE pastes, in conjunction with solvent-drying-free multistage printing, enables the monolithic integration of in-series/in-plane bipolar-stacked cells onto complex-shaped objects. Because of the aforementioned material and process novelties, the printed bipolar LIBs show exceptional flexibility, form factors, charge/discharge behavior and abuse tolerance (nonflammability) that far exceed those achievable with inorganic-electrolyte-based conventional bipolar cell technologies.

The combination of energy generation and energy storage systems is the ultimate solution to meet the ever-increasing demand for high-energy-density power sources. Here, we demonstrate a new class of monolithically integrated, photo-rechargeable portable power sources based on miniaturized crystalline Si photovoltaics (c-Si PVs) and printed solid-state lithium-ion batteries (LIBs). A solid-state LIB with a bipolar cell configuration is fabricated directly on the aluminium electrode of a c-Si PV module through an in-series printing process, which enables the seamless architectural/electrical connection of the two different energy systems. The single-unit PV–LIB device shows exceptional electrochemical performance that lies far beyond those achievable by conventional PVs or LIBs alone: it displays fast, low-light-intensity and high-temperature photo-charging; a photo-electric conversion/storage efficiency of 7.61%; a sustainable cycling performance; and continuous discharging at an extremely high current density of 28C under sunlight illumination. This study opens a facile and scalable route for the development of single-unit, photo-rechargeable mobile high-performance batteries that are required for the future era of ubiquitous electronics.

The forthcoming ubiquitous innovations driven by flexible/wearable electronics and Internet of Things (IoT) have inspired the relentless pursuit of advanced power sources with versatile aesthetics. Here, we demonstrate a new class of solid-state flexible power sources that are fabricated directly on conventional A4 paper using a commercial desktop inkjet printer. A salient feature of the inkjet-printed power sources is their monolithic integration with paper, i.e., they look like inkjet-printed letters or figures that are commonly found in office documents. A supercapacitor (SC), which is composed of activated carbon/carbon nanotubes (CNTs) and an ionic liquid/ultraviolet-cured triacrylate polymer-based solid-state electrolyte, is chosen as a model power source to explore the feasibility of the proposed concept. Cellulose nanofibril-mediated nanoporous mats are inkjet-printed on top of paper as a primer layer to enable high-resolution images. In addition, CNT-assisted photonic interwelded Ag nanowires are introduced onto the electrodes to further improve the electrical conductivity of the electrodes. The inkjet-printed SCs can be easily connected in series or parallel, leading to user-customized control of cell voltage and capacitance. Notably, a variety of all-inkjet-printed SCs featuring computer-designed artistic patterns/letters are aesthetically unitized with other inkjet-printed images and smart glass cups, underscoring their potential applicability as unprecedented object-tailored power sources.

The unending demand for portable, flexible, and even wearable electronic devices that have an aesthetic appeal and unique functionality stimulates the development of advanced power sources that have excellent electrochemical performance and, more importantly, shape versatility. The challenges in the fabrication of next-generation flexible power sources mainly arise from their limited form factors, which prevent their facile integration into differently shaped electronic devices, and from the lack of reliable electrochemical materials that exhibit optimized attributes and suitable processability. This review describes the technological innovations and challenges associated with flexible energy storage and conversion systems such as lithium-ion batteries and supercapacitors, along with an overview of the progress in flexible proton exchange membrane fuel cells (PEMFCs) and solar cells. In particular, recently highlighted cable-type flexible batteries with extreme omni-directional flexibility are comprehensively discussed.

A facile approach to fabricate a highly bendable plastic crystal composite electrolyte (PCCE) for use in shape conformable all-solid-state lithium-ion batteries is demonstrated. This strategy is based on integration of a semi-interpenetrating polymer network (semi-IPN) matrix with a plastic crystal electrolyte (PCE, 1 M lithium bis-trifluoromethanesulfonimide in succinonitrile). In comparison to conventional carbonate-based electrolytes, salient benefits of the PCE are the thermal stability and nonflammability, which show promising potential as a safer electrolyte. The semi-IPN matrix in the PCCE is composed of a UV (ultraviolet)-crosslinked ethoxylated trimethylolpropane triacrylate polymer network and polyvinylidene fluoride-co-hexafluoropropylene (as a linear polymer). Solid electrolyte properties of the PCCE are investigated in terms of plastic crystal behavior, mechanical bendability, and ionic transport. Owing to the presence of the anomalous semi-IPN matrix, the PCCE exhibits unprecedented improvement in bendability, along with affording high ionic conductivity. Based on this understanding of the PCCE characteristics, feasibility of applying the PCCE to solid electrolytes for lithium-ion batteries is explored. The facile ionic transport of the PCCE, in conjunction with suppressed growth of cell impedance during cycling, plays a crucial role in providing excellence in cell performance. These advantageous features of the PCCE are further discussed with an in-depth consideration of the semi-IPN matrix architecture and its specific interaction with the PCE.

A facile approach to the surface modification of spinel LiNi0.5Mn1.5O4 (LNMO) cathode active materials for high-voltage lithium ion batteries is demonstrated. This strategy is based on nanoarchitectured polyimide (PI) gel polymer electrolyte (GPE) coating. The PI coating layer successfully wrapped a large area of the LNMO surface via thermal imidization of 4-component (pyromellitic dianhydride/biphenyl dianhydride/phenylenediamine/oxydianiline) polyamic acid. In comparison to conventional metal oxide-based coatings, distinctive features of the unusual PI wrapping layer are the highly continuous surface coverage with nanometre thickness (∼10 nm) and the provision of facile ion transport. The nanostructure-tuned PI wrapping layer served as an ion-conductive protection skin to suppress the undesired interfacial side reactions, effectively preventing the direct exposure of the LNMO surface to liquid electrolyte. As a result, the PI wrapping layer played a crucial role in improving the high-voltage cell performance and alleviating the interfacial exothermic reaction between charged LNMO and liquid electrolyte. Notably, the superior cycle performance (at 55 °C) of the PI-wrapped LNMO (PI-LNMO) was elucidated in great detail by quantitatively analyzing manganese (Mn) dissolution, cell impedance, and chemical composition (specifically, lithium fluoride (LiF)) of byproducts formed on the LNMO surface.