Patent Application
20180241081
The present disclosure relates to an electrolyte, a flexible electrode and a flexible electronic device, and more particularly, to an electrolyte including a lithium-containing quasi-ionic liquid and a gel, and a flexible electrode and a flexible electronic device using the electrolyte as a conductive medium.
Lightweight, wearable and flexible supercapacitors (SCs) have generated acute interest for energy storage use due to their potential applications in wearable/roll-up display, electronic paper, mobile phone, sensor networks, hand-held portable devices and artificial electronic skin. SCs provide energy density greater than that of a conventional capacitor, with faster charge/discharge rates and a cycle life longer than that of batteries. A free-standing and binder-free electrode with robust mechanical strength and large capacitance is a vital factor for flexible SCs. As some of the most promising devices for energy storage, solid-state SCs have attracted intensive research interest because of their outstanding properties such as great safety, great flexibility, ultrathin profile, high power density, light weight, and reduced environmental footprint, all of which offers great promise in the field of lightweight, portable and roll-up electronics. Solid-state SCs enable an entire device to be flexible, lightweight, thin, and compact, but, to fill the increasing energy demands for the next-generation portable electronic devices, the energy density of solid-state SCs must be further improved within confined areas or spaces. Conductive paper electrodes have attracted much interest for the development of planar wearable SCs. Cellulose paper is a general type of cheap and abundant material having outstanding flexibility. The porous and natural rough surfaces of paper are perfect for energy-storage devices, in which high surface roughness is advantageous for the handling of ions and electrons. Paper is an insulator, however, which presents limitations. To improve the conductivity of paper, carbon nanotubes can be coated on the surface of the paper with a solution-based method, but such method requires environmentally destructive chemicals and complicated processes, and carbon nanotubes remain prohibitively expensive.
This Discussion of the Background section is provided for background information only. The statements in this Discussion of the Background are not an admission that the subject matter disclosed in this Discussion of the Background section constitutes prior art to the present disclosure, and no conductive paper electrodes, electrochemical capacitors or manufacturing methods described in this Discussion of the Background section may be used as an admission that any conductive paper electrode, electrochemical capacitor or manufacturing method of this application, including the conductive paper electrode, electrochemical capacitor and manufacturing method described in this Discussion of the Background section, constitutes prior art to the present disclosure.
One aspect of the present disclosure provides an electrolyte, a flexible electrode and a flexible electronic device.
An electrolyte according to some embodiments of the present disclosure includes a lithium-containing quasi-ionic liquid and a gel. The lithium-containing quasi-ionic liquid includes an organic compound having at least one acylamino group, and also includes a lithium salt.
In some embodiments, the lithium salt is characterized as LiX, where X includes ClO4−, SCN−, PF6−, B(C2O4)2−, N(SO2CF3)2−, CF3SO3−, or a combination thereof.
In some embodiments, the gel includes polyvinyl alcohol (PVA).
In some embodiments, the gel has a network structure, and the lithium-containing quasi-ionic liquid is sealed in the network structure.
In some embodiments, a weight ratio of the lithium-containing quasi-ionic liquid to the gel is between about 1:4.5 and about 4:1.
In some embodiments, the electrolyte is transparent.
In some embodiments, the electrolyte is flexible.
A flexible electrode according to some embodiments of the present disclosure includes a lithium-containing quasi-ionic liquid and a gel. The lithium-containing quasi-ionic liquid includes an organic compound having at least one acylamino group, and a lithium salt. The gel has a network structure, wherein the lithium-containing quasi-ionic liquid is sealed in the network structure.
In some embodiments, the lithium salt is characterized as LiX, where X includes ClO4−, SCN−, PF6−, B(C2O4)2−, N(SO2CF3)2−, CF3SO3−, or a combination thereof.
In some embodiments, the organic compound comprises acetamide, urea, methylurea (NMU), 2-oxazolidinone (OZO), ethyleneurea, 1,3-dimethylurea DMU, or a combination thereof.
In some embodiments, the gel includes polyvinyl alcohol (PVA).
In some embodiments, a weight ratio of the lithium-containing quasi-ionic liquid to the gel is between about 1:4.5 and about 4:1.
In some embodiments, the flexible electrode is transparent.
A flexible electronic device according to some embodiments of the present disclosure includes a flexible electronic component, and a flexible electrode electrically connected to the flexible electronic component. The flexible electrode includes a lithium-containing quasi-ionic liquid and a gel. The lithium-containing quasi-ionic liquid includes an organic compound having at least one acylamino group, and a lithium salt. The gel has a network structure, wherein the lithium-containing quasi-ionic liquid is sealed in the network structure.
In some embodiments, the lithium salt is characterized as LiX, where X includes ClO4−, SCN−, PF6−, B(C2O4)2−, N(SO2CF3)2−, CF3SO3−, or a combination thereof.
In some embodiments, the organic compound includes acetamide, urea, methylurea (NMU), 2-oxazolidinone (OZO), ethyleneurea, 1,3-dimethylurea DMU, or a combination thereof.
In some embodiments, the gel includes polyvinyl alcohol (PVA).
In some embodiments, the flexible electrode is transparent.
In some embodiments, a weight ratio of the lithium-containing quasi-ionic liquid to the gel is between about 1:4.5 and about 4:1.
The foregoing has outlined rather broadly the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter, and form the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes as those of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the disclosure as set forth in the appended claims.
A more complete understanding of the present disclosure may be derived by referring to the detailed description and claims when considered in connection with the Figures, where like reference numbers refer to similar elements throughout the Figures, and:
The following description of the disclosure accompanies drawings, which are incorporated in and constitute an electrolyte, a flexible electrode, and a flexible electronic device of this specification, and illustrate embodiments of the disclosure, but the disclosure is not limited to the embodiments. In addition, the following embodiments can be properly integrated to complete another embodiment.
References to “one embodiment,” “an embodiment,” “exemplary embodiment,” “some embodiments,” “other embodiments,” “another embodiment,” etc. indicate that the embodiment(s) of the disclosure so described may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Further, repeated use of the phrase “in the embodiment” does not necessarily refer to the same embodiment, although it may.
The present disclosure is directed to an electrolyte including a mixture of a lithium-containing quasi-ionic liquid and a gel. The lithium-containing quasi-ionic liquid is located in the space of a network structure formed from the flexible gel, and thus can provide conductivity in a flexible state. The present disclosure is further directed to a flexible electrode formed from the above electrolyte, which exhibits high flexibility. The following description is also directed to a flexible electronic device including a flexible electronic component and the above flexible electrode, as discussed below.
In order to make the present disclosure completely comprehensible, detailed steps and structures are provided in the following description. Obviously, implementation of the present disclosure does not limit special details known by persons skilled in the art. In addition, known structures and steps are not described in detail, so as not to limit the present disclosure unnecessarily. Preferred embodiments of the present disclosure will be described below in detail. However, in addition to the detailed description, the present disclosure may also be widely implemented in other embodiments. The scope of the present disclosure is not limited to the detailed description, and is defined by the claims.
As shown in
The lithium salt in some embodiments is characterized as LiX, where Li is lithium, and X includes ClO4−, SCN−, PF6−, B(C2O4)2−, N(SO2CF3)2−, CF3SO3−, the like, or a combination thereof. LiN(SO2CF3)2 is also known as lithium bis(trifluoromethylsulfonyl)imide (LiTFSI). In some embodiments, examples of the ranges of molar ratios (ratio of lithium salt to the organic compound) of the lithium-containing quasi-ionic liquid are listed in Table 1.
In some embodiments, the gel 14 includes a water-soluble gel such as polyvinyl alcohol (PVA) or the like.
In an exemplary embodiment, the lithium-containing quasi-ionic liquid includes urea-LiClO4 ionic liquid, and the gel includes PVA. An example of preparation for the electrolyte 1 is illustrated as follows: Urea-LiClO4 ionic liquid with molar ratio 4:1 is prepared from urea (Acros Inc., 95+%) and LiClO4 (Acros Inc., AP). Next, the PVA/urea-LiClO4 quasi-ionic liquid gel is prepared by mixing urea-LiClO4 ionic liquid (5 g) and polyvinyl alcohol gel (PVA, 5 g) and heated at 110° C. for 1 hour under vigorous stirring until a homogeneous sticky solution is formed. The solution is cooled at room temperature, and the solution becomes a clear and transparent gel. The organic compound, the lithium salt and the gel are stable at room temperature and are not sensitive to water and light, and thus the electrolyte 1 can be prepared at room temperature and in a water-containing environment.
The lithium-containing quasi-ionic liquid 12 including the organic compound and the lithium salt is conductive and configured as electrolyte. The gel 14 such as PVA gel has a network structure, and the lithium-containing quasi-ionic liquid 12 is sealed in the network structure, which allows the lithium-containing quasi-ionic liquid 12 to travel in the space of the network structure and provides conductivity. The electrolyte 1 can have a range of properties, and the physical properties of the gel 14 can be modified by, for example, adjusting the ratio of the gel 14 to the lithium-containing quasi-ionic liquid 12. When the ratio of the gel 14 to the lithium-containing quasi-ionic liquid 12 is higher, the electrolyte 1 is softer and more flexible; when the ratio of the gel to the lithium-containing quasi-ionic liquid is lower, the electrolyte 1 is harder. In some embodiments, the weight ratio of the lithium-containing quasi-ionic liquid 12 to the gel 14 is, but not limited to be, in a range of from about 1:4.5 to about 4:1. Consequently, the form of the electrolyte 1 can be modified by, for example, adjusting the ratio of the gel to the lithium-containing quasi-ionic liquid.
In the description, all electrochemical tests were measured with the AUTOLAB workstation. The specific capacitance of cycle voltammetry (CV) and charge/discharge cycle is calculated as follows:
Csp=Qm/ΔV (1)
Csp=IΔt/ΔVw (2)
in which Qm is the specific voltammetric charge (based on Mn oxide mass) integrated from CV, ΔV is the scanning range (i.e., 0.8V×2), I is applied current density (2 A/g), w is Mn oxide mass, and Δt is duration of discharge cycling. With charge-discharge curves based on two electrode systems, Csp is specific capacitance of symmetric supercapacitor, and energy density (E) and power density (P) are calculated from chronopotentiometric curves according to equations (3) and (4):
E=½CspΔV2 (3)
P=E/Δt (4)
Where Δt is time to discharge, and ΔV is cell voltage (i.e., 2.0V).
The electrochemical properties of a three electrode cell are studied in Na2SO4 aqueous (0.5 M), urea-LiClO4 ionic liquid electrolyte and urea-LiClO4/PVA quasi-ionic liquid electrolyte, respectively. The conductivity data of urea-LiClO4/PVA (10 mS/cm) are greater than those of urea-LiClO4/PVA (0.1 mS/cm) at 27° C. Urea-LiClO4 and PVA can form a complex system.
The calculated capacitances of the MNNGP in urea-LiClO4/PVA, Na2SO4, and urea-LiClO4 are 960 F/g, 600 F/g, and 220 F/g, respectively. Csp of MNNGP electrodes in urea-LiClO4/PVA is also much greater than those of MnO2 nanobar (625 F/g), MnO2 hierarchical tubular (315 F/g), amorphous porous Mn3O4 (432 F/g), and graphite/PEDOT/MnO2 composites (264 F/g).
Galvanostatic charging/discharging curves of MNNGP electrodes in urea-LiClO4/PVA at varied current density are shown in
To illustrate the oxidation-state change of MNNGP electrode in urea-LiClO4/PVA and the energy storage mechanism at varied operating temperatures during charge/discharge cycles, the chemical state change with different applied potentials by in situ Mn K-edge XAS is investigated. Experimental results show XANES spectra of MNNGP electrode in urea-LiClO4/PVA at 90° C. recorded at applied potentials varied in this sequence: +0V, then +0.8V, and finally returning to +0V. A rising edge of Mn K-edge spectra of MNNGP altered to increasing energy with enhanced potential, and came back almost to the original state as the potential was reversed. An absorption threshold energy (E0), which is obtained from the first inflection point of the edge, is associated with transition-metal oxidation states. On the basis of E0 derived from XANES in
The above electrolyte is proven to have good conductivity, and can be individually configured as a flexible electrode.
In conclusion, the electrolyte, the flexible electrode and the flexible electronic device are advantageous due to light weight, flexibility, high conductivity, and sustainability. The electrolyte is stable at room temperature and is not sensitive to water, and thus can be prepared at room temperature and in a water-containing environment, which reduces manufacturing costs and simplifies processes. The electrolyte/electrode system can be assembled to a quasi-ionic liquid electrolyte and hybrid paper electrode system, which will be prospective for many flexible and wearable applications such as batteries, fuel cells, wearable/roll-up displays, electronic papers, touch devices, mobile phones, sensor networks, hand-held portable devices and artificial electronic skin.
As used herein, the terms “approximately,” “substantially,” “substantial” and “about” are used to describe and account for small variations. When used in conjunction with an event or circumstance, the terms can refer to instances in which the event or circumstance occurs precisely as well as instances in which the event or circumstance occurs to a close approximation. For example, when used in conjunction with a numerical value, the terms can refer to a range of variation of less than or equal to ±10% of that numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. For example, two numerical values can be deemed to be “substantially” the same or equal if a difference between the values is less than or equal to ±10% of an average of the values, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. For example, “substantially” parallel can refer to a range of angular variation relative to 0° that is less than or equal to ±10°, such as less than or equal to ±5°, less than or equal to ±4°, less than or equal to ±3°, less than or equal to ±2°, less than or equal to ±1°, less than or equal to ±0.5°, less than or equal to ±0.1°, or less than or equal to ∓0.05°. For example, “substantially” perpendicular can refer to a range of angular variation relative to 90° that is less than or equal to ±10°, such as less than or equal to ±5°, less than or equal to ±4°, less than or equal to ±3°, less than or equal to ±2°, less than or equal to ±1°, less than or equal to ±0.5°, less than or equal to ±0.1°, or less than or equal to ±0.05°.
Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims. For example, many of the processes discussed above can be implemented in different methodologies and replaced by other processes, or a combination thereof.
Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
