Fragmented Carbon Nanotube Macrofilms as Adhesive Conductors for Lithium-Ion Batteries

Polymer binders such as poly(vinylidene fluoride) (PVDF) and conductive additives such as carbon black (CB) are indispensable components for manufacturing battery electrodes in addition to active materials. The concept of adhesive conductors employing fragmented carbon nanotube macrofilms (FCNTs) is demonstrated by constructing composite electrodes with a typical active material, LiMn₂O₄. The adhesive FCNT conductors provide not only a high electrical conductivity but also a strong adhesive force, functioning simultaneously as both the conductive additives and the binder materials for lithium-ion batteries. Such composite electrodes exhibit superior high-rate and retention capabilities compared to the electrodes using a conventional binder (PVDF) and a conductive additive (CB). An <i>in situ</i> tribology method combining wear track imaging and force measurement is employed to evaluate the adhesion strength of the adhesive FCNT conductors. The adhesive FCNT conductors exhibit higher adhesion strength than PVDF. It has further been confirmed that the adhesive FCNT conductor can be used in both cathodes and anodes and is proved to be a competent substitute for polymer binders to maintain mechanical integrity and at the same time to provide electrical connectivity of active materials in the composite electrodes. The organic-solvent-free electrode manufacturing offers a promising strategy for the battery industry

Dynamic and Galvanic Stability of Stretchable Supercapacitors

Stretchable electronics are emerging as a new technological advancement, since they can be reversibly stretched while maintaining functionality. To power stretchable electronics, rechargeable and stretchable energy storage devices become a necessity. Here, we demonstrate a facile and scalable fabrication of full stretchable supercapacitor, using buckled single-walled carbon nanotube macrofilms as the electrodes, an electrospun membrane of elastomeric polyurethane as the separator, and an organic electrolyte. We examine the electrochemical performance of the fully stretchable supercapacitors under dynamic stretching/releasing modes in different stretching strain rates, which reveal the true performance of the stretchable cells, compared to the conventional method of testing the cells under a statically stretched state. In addition, the self-discharge of the supercapacitor and the electrochemical behavior under bending mode are also examined. The stretchable supercapacitors show excellent cyclic stability under electrochemical charge/discharge during in situ dynamic stretching/releasing

Bidirectional Correlation between Mechanics and Electrochemistry of Poly(vinyl alcohol)-Based Gel Polymer Electrolytes

The electrochemical–mechanical coupling property of solid electrolyte membranes is critical to improving the performance of solid-state energy storage devices. A new phenomenon was observed in which the electrochemical charge–discharge process induced aligned wrinkles on the edge of poly­(vinyl alcohol)-H₂SO₄ gel polymer electrolytes (GPEs), which is attributed to the deformation of polymer chains under electrochemical stimulation according to multiscale simulations. In the reverse direction, by means of modeling and testing, it was proved that the ionic conductivity of GPEs can be tuned by mediating the mechanical properties of GPEs via tailoring the polymer at the nanoscale. This bidirectional correlation reveals the coupling mechanisms between mechanical and electrochemical properties of GPEs and provides an insightful understanding of the origin and regulation of the ionic conductivity of GPEs, which is fundamental to improving the performance of GPEs

Dynamic and Galvanic Stability of Stretchable Supercapacitors

Stretchable electronics are emerging as a new technological advancement, since they can be reversibly stretched while maintaining functionality. To power stretchable electronics, rechargeable and stretchable energy storage devices become a necessity. Here, we demonstrate a facile and scalable fabrication of full stretchable supercapacitor, using buckled single-walled carbon nanotube macrofilms as the electrodes, an electrospun membrane of elastomeric polyurethane as the separator, and an organic electrolyte. We examine the electrochemical performance of the fully stretchable supercapacitors under dynamic stretching/releasing modes in different stretching strain rates, which reveal the true performance of the stretchable cells, compared to the conventional method of testing the cells under a statically stretched state. In addition, the self-discharge of the supercapacitor and the electrochemical behavior under bending mode are also examined. The stretchable supercapacitors show excellent cyclic stability under electrochemical charge/discharge during in situ dynamic stretching/releasing

Dynamic and Galvanic Stability of Stretchable Supercapacitors

Stretchable electronics are emerging as a new technological advancement, since they can be reversibly stretched while maintaining functionality. To power stretchable electronics, rechargeable and stretchable energy storage devices become a necessity. Here, we demonstrate a facile and scalable fabrication of full stretchable supercapacitor, using buckled single-walled carbon nanotube macrofilms as the electrodes, an electrospun membrane of elastomeric polyurethane as the separator, and an organic electrolyte. We examine the electrochemical performance of the fully stretchable supercapacitors under dynamic stretching/releasing modes in different stretching strain rates, which reveal the true performance of the stretchable cells, compared to the conventional method of testing the cells under a statically stretched state. In addition, the self-discharge of the supercapacitor and the electrochemical behavior under bending mode are also examined. The stretchable supercapacitors show excellent cyclic stability under electrochemical charge/discharge during in situ dynamic stretching/releasing

Bidirectional Correlation between Mechanics and Electrochemistry of Poly(vinyl alcohol)-Based Gel Polymer Electrolytes

The electrochemical–mechanical coupling property of solid electrolyte membranes is critical to improving the performance of solid-state energy storage devices. A new phenomenon was observed in which the electrochemical charge–discharge process induced aligned wrinkles on the edge of poly­(vinyl alcohol)-H₂SO₄ gel polymer electrolytes (GPEs), which is attributed to the deformation of polymer chains under electrochemical stimulation according to multiscale simulations. In the reverse direction, by means of modeling and testing, it was proved that the ionic conductivity of GPEs can be tuned by mediating the mechanical properties of GPEs via tailoring the polymer at the nanoscale. This bidirectional correlation reveals the coupling mechanisms between mechanical and electrochemical properties of GPEs and provides an insightful understanding of the origin and regulation of the ionic conductivity of GPEs, which is fundamental to improving the performance of GPEs

Dynamic and Galvanic Stability of Stretchable Supercapacitors

Stretchable electronics are emerging as a new technological advancement, since they can be reversibly stretched while maintaining functionality. To power stretchable electronics, rechargeable and stretchable energy storage devices become a necessity. Here, we demonstrate a facile and scalable fabrication of full stretchable supercapacitor, using buckled single-walled carbon nanotube macrofilms as the electrodes, an electrospun membrane of elastomeric polyurethane as the separator, and an organic electrolyte. We examine the electrochemical performance of the fully stretchable supercapacitors under dynamic stretching/releasing modes in different stretching strain rates, which reveal the true performance of the stretchable cells, compared to the conventional method of testing the cells under a statically stretched state. In addition, the self-discharge of the supercapacitor and the electrochemical behavior under bending mode are also examined. The stretchable supercapacitors show excellent cyclic stability under electrochemical charge/discharge during in situ dynamic stretching/releasing

Antimony-Coated Carbon Nanocomposites as High-Performance Anode Materials for High-Temperature Sodium–Metal Batteries

Metallic sodium (Na) possesses several advantageous characteristics, including a high theoretical specific capacity, low electrode potential, and availability in abundance, making it an ideal anode material for sodium–metal batteries (SMBs). However, the practical use of Na metal anodes is severely impeded due to the uncontrolled formation of dendrites due to the slow electrochemical kinetics and chemical instability of the formed solid-electrolyte interphase (SEI) layer. This situation can worsen considerably under high-temperature (HT) conditions (>55 °C). To overcome this issue, we have fabricated a thermally stable antimony (Sb)-coated carbon (Sb@C) nanocomposite as a sodium host material, where Sb nanoparticles are encapsulated within the carbon layers. This unique nanostructure controls vaporization during the plating-stripping process and dendrite formation and provides acceptor sites for Na+ ions. The Sb@C electrode exhibits an extended life span of symmetrical cycles (2400 h at 1 mA cm–2) due to the abundant nucleation sites. It maintains a low nucleation overpotential (∼15 mV), enhancing its performance and long cycle stability. Moreover, the in situ formed Na–Sb synergistically offers durable ionic/electronic diffusion paths and chemically interacts with Na, forming abundant Na nucleation sites. Therefore, in this study, we emphasize the importance of the rational design of highly stable alloys and present an effective strategy for achieving high-performance sodium–metal anodes

Multiscale Interfacial Strategy to Engineer Mixed Metal-Oxide Anodes toward Enhanced Cycling Efficiency

Interconnected macro/mesoporous structures of mixed metal oxide (MMO) are developed on nickel foam as freestanding anodes for Li-ion batteries. The sustainable production is realized via a wet chemical etching process with bio-friendly chemicals. By means of divalent iron doping during an in situ recrystallization process, the as-developed MMO anodes exhibit enhanced levels of cycling efficiency. Furthermore, this atomic-scale modification coherently synergizes with the encapsulation layer across a micrometer scale. During this step, we develop a quasi-gel-state tri-copolymer, i.e., F127–resorcinol–melamine, as the N-doped carbon source to regulate the interfacial chemistry of the MMO electrodes. Electrochemical tests of the modified Fe<i>_x</i>Ni_1–<i>x</i>O@NC–NiF anode in both half-cell and full-cell configurations unravel the favorable suppression of the irreversible capacity loss and satisfactory cyclability at the high rates. This study highlights a proof-of-concept modification strategy across multiple scales to govern the interfacial chemical process of the electrodes toward better reversibility

Fluorinated, Sulfur-Rich, Covalent Triazine Frameworks for Enhanced Confinement of Polysulfides in Lithium–Sulfur Batteries

Lithium–sulfur battery represents a promising class of energy storage technology owing to its high theoretical energy density and low cost. However, the insulating nature, shuttling of soluble polysulfides and volumetric expansion of sulfur electrodes seriously give rise to the rapid capacity fading and low utilization. In this work, these issues are significantly alleviated by both physically and chemically restricting sulfur species in fluorinated porous triazine-based frameworks (FCTF-S). One-step trimerization of perfluorinated aromatic nitrile monomers with elemental sulfur allows the simultaneous formation of fluorinated triazine-based frameworks, covalent attachment of sulfur and its homogeneous distribution within the pores. The incorporation of electronegative fluorine in frameworks provides a strong anchoring effect to suppress the dissolution and accelerate the conversion of polysulfides. Together with covalent chemical binding and physical nanopore-confinement effects, the FCTF-S demonstrates superior electrochemical performances, as compared to those of the sulfur-rich covalent triazine-based framework without fluorine (CTF-S) and porous carbon delivering only physical confinement. Our approach demonstrates the potential of regulating lithium–sulfur battery performances at a molecular scale promoted by the porous organic polymers with a flexible design