Zheng-Ze Pan

Breathable and Wearable Energy Storage Based on Highly Flexible Paper Electrodes.

Breathable and wearable energy storage is achieved based on an innovative design solution. Carbon nanotube/MnO2 -decorated air-laid paper electrodes, with outstanding flexibility and good electrochemical performances, are prepared. They are then assembled into solid-state supercapacitors. By making through-holes on the supercapacitors, breathable and flexible supercapacitors are successfully fabricated.

Fabrication of an MOF-derived heteroatom-doped Co/CoO/carbon hybrid with superior sodium storage performance for sodium-ion batteries

Metal–organic frameworks (MOFs) have gained significant attention as precursors for the fabrication of porous hybrid materials due to their highly controllable composition, structure and pore size. However, at present, MOF-derived materials have rarely been investigated as anode materials for sodium-ion batteries. In this work, we report the fabrication of a Ni-doped Co/CoO/N-doped carbon (NC) hybrid using bimetallic Ni–Co-ZIF as the starting precursor. The resulting Ni-doped Co/CoO/NC hybrid is highly microporous with a high specific surface area of 552 m2 g−1. When employed as an anode material for sodium-ion batteries, the Ni-doped Co/CoO/NC hybrid exhibited both good rate performance with a high discharge capacity of 218 mA h g−1 at a high current density of 500 mA g−1 and good cycling stability, as a high discharge capacity of 218.7 mA h g−1 can be retained after 100 cycles at 500 mA g−1, corresponding to a high capacity retention of 87.5%. The excellent electrochemical performance of the Ni-doped Co/CoO/NC hybrid for SIBs may be attributed to the synergistic effects of various factors, including: (i) the presence of a carbon matrix which provides protection against aggregation and pulverization during sodiation/desodiation; (ii) the highly microporous nature along with the presence of a few mesopores which facilitates better insertion/de-insertion of Na+ ions; (iii) the Ni-doping which introduces defect sites into the atomic structure of CoO via partial substitution, thus enhancing the conductivity of the cobalt oxide (CoO) component and hence, the overall hybrid material, and (iv) the N-doping which promotes a faster migration speed of sodium ions (Na+) across the carbon layer by creating defect sites, thereby improving the conductivity of the carbon frameworks in the hybrid material.

Cellulose Nanofiber as a Distinct Structure-Directing Agent for Xylem-like Microhoneycomb Monoliths by Unidirectional Freeze-Drying

Honeycomb structures have been attracting attention from researchers mainly for their high strength-to-weight ratio. As one type of structure, honeycomb monoliths having microscopically dimensioned channels have recently gained many achievements since their emergence. Inspired by the microhoneycomb structure that occurs in natural tree xylems, we have been focusing on the assembly of such a structure by using the major component in tree xylem, cellulose, as the starting material. Through the path that finally led us to the successful reconstruction of tree xylems by the unidirectional freeze-drying (UDF) approach, we verified the function of cellulose nanofibers, toward forming xylem-like monoliths (XMs). The strong tendency of cellulose nanofibers to form XMs through the UDF approach was extensively confirmed with surface grafting or a combination of a variety of second components (or even a third component). The resulting composite XMs were thus imparted with extra properties, which extends the versatility of this kind of material. Particularly, we demonstrated in this paper that XMs containing reduced graphene oxide (denoted as XM/rGO) could be used as strain sensors, taking advantage of their penetrating microchannels and the bulk elasticity property. Our methodology is flexible in its processing and could be utilized to prepare various functional composite XMs.

Stacking up layers of polyaniline/carbon nanotube networks inside papers as highly flexible electrodes with large areal capacitance and superior rate capability

Developing high-performance flexible film-like electrodes is still a primary task for the practical applications of wearable/portable planar supercapacitors. In this work, a facile and effective approach, i.e., stacking up layers of polyaniline (PANI)/carbon nanotube (CNT) composite networks inside air-laid papers, is proposed to fabricate highly flexible paper electrodes with large areal capacitance and superior rate capability. The layer-by-layer deposition of PANI/CNT networks endows the fabricated paper electrodes with high loading and uniform distribution of PANI; meanwhile, the good electrical conductivity and porous structure of these introduced PANI/CNT networks guarantee sufficient paths for electron movement and ion transportation in the electrodes. Consequently, when 4 layers of PANI/CNT networks (with optimal PANI content) are stacked inside papers, the areal capacitance of the prepared electrode is as high as 1506 mF cm−2 at a charge/discharge current of 10 mA cm−2 and 1298 mF cm−2 at 100 mA cm−2; the electrode also exhibits high flexibility and good cycling stability (with 82% capacitance retention after 11 500 charge/discharge cycles). These merits make our PANI/CNT/papers promising candidates for flexible planar supercapacitor electrodes. Besides, this work is believed to provide a new thought for producing high-loading and high-energy wearable/portable energy storage devices.

A hollow spherical carbon derived from the spray drying of corncob lignin for high-rate-performance supercapacitors

Controlling the microstructure of biomass-derived carbon is of essential importance for directing its use. Herein, a hollow spherical carbon (HSC) was prepared from corncob lignin through spray drying and subsequent heat treatment. The HSC, which is characterized by its hierarchically porous structure, delivers high rate capability when it is directly used as electrode material for supercapacitors. This strategy that uses lignin as the precursor avoids the intrinsic difficulty in tuning the microstructure of the biomass-derived carbons and is suitable for mass production for practical use.

A Dual-Function Na2SO4 Template Directed Formation of Cathode Materials with a High Content of Sulfur Nanodots for Lithium–Sulfur Batteries

The sulfur content in carbon-sulfur hybrid using the melt-diffusion method is normally lower than 70 wt%, which greatly decreases the energy density of the cathode in lithium-sulfur (Li-S) batteries. Here, a scalable method inspired by the commercialized production of Na2 S is used to prepare a hierarchical porous carbon-sulfur hybrid (denoted HPC-S) with high sulfur content (≈85 wt%). The HPC-S is characterized by the structure of sulfur nanodots naturally embedded in a 3D carbon network. The strategy uses Na2 SO4 as the starting material, which serves not only as the sulfur precursor but also as a salt template for the formation of the 3D carbon network. The HPC-S cathode with such a high sulfur content shows excellent rate performance and cycling stability in Li-S batteries because of the sulfur nanoparticles, the unique carbon framework, and the strong interaction between them. The production method can also be readily scaled up and used in practical Li-S battery applications.

Microhoneycomb Monoliths Prepared by the Unidirectional Freeze-drying of Cellulose Nanofiber Based Sols: Method and Extensions

Monolithic honeycomb structures have been attractive to multidisciplinary fields due to their high strength-to-weight ratio. Particularly, microhoneycomb monoliths (MHMs) with micrometer-scale channels are expected as efficient platforms for reactions and separations because of their large surface areas. Up to now, MHMs have been prepared by a unidirectional freeze-drying (UDF) method only from very limited precursors. Herein, we report a protocol from which a series of MHMs consisting of different components can be obtained. Recently, we found that cellulose nanofibers function as a distinct structure-directing agent towards the formation of MHMs through the UDF process. By mixing the cellulose nanofibers with water soluble substances which do not yield MHMs, a variety of composite MHMs can be prepared. This significantly enriches the chemical constitution of MHMs towards versatile applications.

A Nacre-Like Carbon Nanotube Sheet for High Performance Li-Polysulfide Batteries with High Sulfur Loading

Abstract Lithium‐sulfur (Li‐S) batteries are considered as one of the most promising energy storage systems for next‐generation electric vehicles because of their high‐energy density. However, the poor cyclic stability, especially at a high sulfur loading, is the major obstacles retarding their practical use. Inspired by the nacre structure of an abalone, a similar configuration consisting of layered carbon nanotube (CNT) matrix and compactly embedded sulfur is designed as the cathode for Li‐S batteries, which are realized by a well‐designed unidirectional freeze‐drying approach. The compact and lamellar configuration with closely contacted neighboring CNT layers and the strong interaction between the highly conductive network and polysulfides have realized a high sulfur loading with significantly restrained polysulfide shuttling, resulting in a superior cyclic stability and an excellent rate performance for the produced Li‐S batteries. Typically, with a sulfur loading of 5 mg cm−2, the assembled batteries demonstrate discharge capacities of 1236 mAh g−1 at 0.1 C, 498 mAh g−1 at 2 C and moreover, when the sulfur loading is further increased to 10 mg cm−2 coupling with a carbon‐coated separator, a superhigh areal capacity of 11.0 mAh cm−2 is achieved.