Zn2+ Pre‐Intercalation Stabilizes the Tunnel Structure of MnO2 Nanowires and Enables Zinc‐Ion Hybrid Supercapacitor of Battery‐Level Energy DensityChen, Qiang; Jin, Jialun; Kou, Zongkui; Liao, Cong; Liu, Ziang; Zhou, Liang; Wang, John; Mai, Liqiang
doi: 10.1002/smll.202000091pmid: 32174015
Although there has been tremendous progress in exploring new configurations of zinc‐ion hybrid supercapacitors (Zn‐HSCs) recently, the much lower energy density, especially the much lower areal energy density compared with that of the rechargeable battery, is still the bottleneck, which is impeding their wide applications in wearable devices. Herein, the pre‐intercalation of Zn2+ which gives rise to a highly stable tunnel structure of ZnxMnO2 in nanowire form that are grown on flexible carbon cloth with a disruptively large mass loading of 12 mg cm−2 is reported. More interestingly, the ZnxMnO2 nanowires of tunnel structure enable an ultrahigh areal energy density and power density, when they are employed as the cathode in Zn‐HSCs. The achieved areal capacitance of up to 1745.8 mF cm−2 at 2 mA cm−2, and the remarkable areal energy density of 969.9 µWh cm−2 are comparable favorably with those of Zn‐ion batteries. When integrated into a quasi‐solid‐state device, they also endow outstanding mechanical flexibility. The truly battery‐level Zn‐HSCs are timely in filling up of the battery‐supercapacitor gap, and promise applications in the new generation flexible and wearable devices.
Self‐Assembly Behavior of Oppositely Charged Inverse Bipatchy MicrocolloidsNaderi Mehr, Fatemeh; Grigoriev, Dmitry; Heaton, Rebecca; Baptiste, Joshua; Stace, Anthony J.; Puretskiy, Nikolay; Besley, Elena; Böker, Alexander
doi: 10.1002/smll.202000442pmid: 32181972
A directed attractive interaction between predefined “patchy” sites on the surfaces of anisotropic microcolloids can provide them with the ability to self‐assemble in a controlled manner to build target structures of increased complexity. An important step toward the controlled formation of a desired superstructure is to identify reversible electrostatic interactions between patches which allow them to align with one another. The formation of bipatchy particles with two oppositely charged patches fabricated using sandwich microcontact printing is reported. These particles spontaneously self‐aggregate in solution, where a diversity of short and long chains of bipatchy particles with different shapes, such as branched, bent, and linear, are formed. Calculations show that chain formation is driven by a combination of attractive electrostatic interactions between oppositely charged patches and the charge‐induced polarization of interacting particles.
Enhanced Peltier Effect in Wrinkled Graphene Constriction by Nano‐Bubble EngineeringHu, Xudong; Gong, Xue; Zhang, Miao; Lu, Huihui; Xue, Zhongying; Mei, Yongfeng; Chu, Paul K.; An, Zhenghua; Di, Zengfeng
doi: 10.1002/smll.201907170pmid: 32105406
Inspired by the promising applications in thermopower generation from waste heat and active on‐chip cooling, the thermoelectric and electrothermal properties of graphene have been extensively pursued by seeking ingeniously designed structures with thermoelectric conversion capability. The graphene wrinkle is a ubiquitous structure formed inevitably during the synthesis of large‐scale graphene films but the corresponding properties for thermoelectric and electrothermal applications are rarely investigated. Here, the electrothermal Peltier effect from the graphene wrinkle fabricated on a germanium substrate is reported. Peltier cooling and heating across the wrinkle are visualized unambiguously with polarities consistent with p‐type doping and in accordance with the wrinkle spatial distribution. By direct patterning of the nano‐bubble structure, the current density across the wrinkle can be boosted by current crowding to enhance the Peltier effect. The observed Peltier effect can be attributed to the nonequilibrium charge transport by interlayer tunneling across the van der Waals barrier of the graphene wrinkle. The graphene wrinkle in combination with nano‐bubble engineering constitutes an innovative and agile platform to design graphene and other more general two‐dimensional (2D) thermoelectrics and opens the possibility for realizing active on‐chip cooling for 2D nanoelectronics with van der Waals junctions.
Overcoming the Interfacial Limitations Imposed by the Solid–Solid Interface in Solid‐State Batteries Using Ionic Liquid‐Based InterlayersPervez, Syed Atif; Kim, Guktae; Vinayan, Bhaghavathi P.; Cambaz, Musa A.; Kuenzel, Matthias; Hekmatfar, Maral; Fichtner, Maximilian; Passerini, Stefano
doi: 10.1002/smll.202000279pmid: 32105407
Li‐garnets are promising inorganic ceramic solid electrolytes for lithium metal batteries, showing good electrochemical stability with Li anode. However, their brittle and stiff nature restricts their intimate contact with both the electrodes, hence presenting high interfacial resistance to the ionic mobility. To address this issue, a strategy employing ionic liquid electrolyte (ILE) thin interlayers at the electrodes/electrolyte interfaces is adopted, which helps overcome the barrier for ion transport. The chemically stable ILE improves the electrodes‐solid electrolyte contact, significantly reducing the interfacial resistance at both the positive and negative electrodes interfaces. This results in the more homogeneous deposition of metallic lithium at the negative electrode, suppressing the dendrite growth across the solid electrolyte even at high current densities of 0.3 mA cm−2. Further, the improved interface Li/electrolyte interface results in decreasing the overpotential of symmetric Li/Li cells from 1.35 to 0.35 V. The ILE modified Li/LLZO/LFP cells stacked either in monopolar or bipolar configurations show excellent electrochemical performance. In particular, the bipolar cell operates at a high voltage (≈8 V) and delivers specific capacity as high as 145 mAh g−1 with a coulombic efficiency greater than 99%.