Flexible Li-ion Batteries Research Articles

Face-Centered-Cubic Lithium Crystals Formed in Mesopores of Carbon Nanofiber Electrodes

In the foreseeable future, there will be a sharp increase in the demand for flexible Li-ion batteries. One of the most important components of such batteries will be a freestanding electrode, because the traditional electrodes are easily damaged by repeated deformations. The mechanical sustainability of carbon-based freestanding electrodes subjected to repeated electrochemical reactions with Li ions is investigated via nanotensile tests of individual hollow carbon nanofibers (HCNFs). Surprisingly, the mechanical properties of such electrodes are improved by repeated electrochemical reactions with Li ions, which is contrary to the conventional wisdom that the mechanical sustainability of carbon-based electrodes should be degraded by repeated electrochemical reactions. Microscopic studies reveal a reinforcing mechanism behind this improvement, namely, that inserted Li ions form irreversible face-centered-cubic (FCC) crystals within HCNF cavities, which can reinforce the carbonaceous matrix as strong second-phase particles. These FCC Li crystals formed within the carbon matrix create tremendous potential for HCNFs as freestanding electrodes for flexible batteries, but they also contribute to the irreversible (and thus low) capacity of HCNFs.

Single-paper flexible Li-ion battery cells through a paper-making process based on nano-fibrillated cellulose

Recently, a need for mechanically flexible and strong batteries has arisen to power technical solutions such as active RFID tags and bendable reading devices. In this work, a method for making flex ...

Flexible and Conducting Metal-Fabric Composites Using the Flame Spray Process for the Production of Li-Ion Batteries

The wire flame spray process was used to produce electrically conductive and flexible Al coatings onto diverse textile fabrics. The investigation studied the influence of the spraying parameters and fabric materials on the electrical conductivity of the metal-fabric composites. Furthermore, this study showed that the production of flexible Li-ion batteries having good electrical properties based on the use of such flame-sprayed aluminium cathode current collectors is viable. Results show that a coating quantity threshold of about 20 mg/cm2 exists to obtain a sufficient electrical surface conductivity for a commercial use of the produced metal-fabric composites. An excellent electrical surface conductivity of the composites (about 500 SA) could be achieved through an adequate optimization of the spraying parameters. This conductivity increase enabled a reduction of the coating quantity and thus the flexibility of the fabric materials is better conserved, rendering the use of such composites for flexible batteries even more interesting. This study showed that the production of electrically conductive and flexible metal-fabric composites having sufficient electrical conductivity for the manufacture of flexible Li ions batteries is possible. This new method of producing such batteries represents an alternative to other chemically based processes which are hazardous to the environment because of their chemical nature.

Flexible Free-Standing Graphene/SnO2 Nanocomposites Paper for Li-Ion Battery

A flexible free-standing graphene/SnO₂ nanocomposites paper (GSP) was prepared by coupling a simple filtration method and a thermal reduction together for the first time. Compared with the pure SnO₂ nanoparticles, the GSP exhibited a better cycling stability, because the graphene with high mechanical strength and elasticity can work as a buffer to prevent the volume expansion and contraction of SnO₂ nanoparticles during the Li⁺ insertion/extraction process. Meanwhile, compared with single graphene paper, the GSP showed a higher capacity because of the hybridizing with higher capacity SnO₂ nanoparticles. The excellent electrochemical performance of the GSP as an anode material in Li-ion battery was obtained. The as-prepared GSP shows a great potential for flexible Li-ion batteries.

Aqueous processing of cellulose based paper-anodes for flexible Li-ion batteries

Cellulose fibers were used as novel bio-sourced binder to manufacture flexible cellulose/graphite paper-anodes for Li-ion batteries by means of a simple water-based filtration process easily up-scalable capitalizing conventional papermaking technologies. Paper-anodes showed excellent tensile properties with Young moduli ranging between 60 and 450 MPa, discharge capacity values up to 300/350 mA h g-1 and cycling performances comparable with conventional polymer-bonded graphite anodes.

Free-standing single-walled carbon nanotube/SnO 2 anode paper for flexible lithium-ion batteries

Free-standing single-walled carbon nanotube/SnO 2 (SWCNT/SnO 2) anode paper was prepared by vacuum filtration of SWCNT/SnO 2 hybrid material which was synthesized by the polyol method. From field emission scanning electron microscopy and transmission electron microscopy, the CNTs form a three-dimensional nanoporous network, in which ultra-fine SnO 2 nanoparticles, which had crystallite sizes of less than 5 nm, were distributed, predominately as groups of nanoparticles on the surfaces of single walled CNT bundles. Electrochemical measurements demonstrated that the anode paper with 34 wt.% SnO 2 had excellent cyclic retention, with the high specific capacity of 454 mAh g −1 beyond 100 cycles at a current density of 25 mA g −1, much higher than that of the corresponding pristine CNT paper. The SWCNTs could act as a flexible mechanical support for strain release, offering an efficient electrically conducting channel, while the nanosized SnO 2 provides the high capacity. The SWCNT/SnO 2 flexible electrodes can be bent to extremely small radii of curvature and still function well, despite a marginal decrease in the conductivity of the cell. The electrochemical response is maintained in the initial and further cycling process. Such capabilities demonstrate that this model hold great promise for applications requiring flexible and bendable Li-ion batteries.

Thin, Flexible Secondary Li-Ion Paper Batteries

There is a strong interest in thin, flexible energy storage devices to meet modern society needs for applications such as interactive packaging, radio frequency sensing, and consumer products. In this article, we report a new structure of thin, flexible Li-ion batteries using paper as separators and free-standing carbon nanotube thin films as both current collectors. The current collectors and Li-ion battery materials are integrated onto a single sheet of paper through a lamination process. The paper functions as both a mechanical substrate and separator membrane with lower impedance than commercial separators. The CNT film functions as a current collector for both the anode and the cathode with a low sheet resistance (∼5 Ohm/sq), lightweight (∼0.2 mg/cm(2)), and excellent flexibility. After packaging, the rechargeable Li-ion paper battery, despite being thin (∼300 μm), exhibits robust mechanical flexibility (capable of bending down to <6 mm) and a high energy density (108 mWh/g).

Microfibrillated cellulose–graphite nanocomposites for highly flexible paper-like Li-ion battery electrodes

Microfibrillated cellulose nanoparticles were used as binders for the aqueous processing of flexible electrodes for Li-ion batteries. Microfibrillated cellulose formed a nanostructured web-like network around graphite platelets conferring to the graphite anode a highly porous structure, excellent flexibility and good cycling performances.