Design of Electrode Architecture for Deformable Energy Storage Devices

INTRODUCTION

B ACKGROUND

However, flexible electronics face limitations for advanced applications such as wearable devices that withstand the complex physical stress of the human body and fabric (> 30% and > 100% of skin and joint stress, respectively) [9-11]. In general, the main approaches for fabricating stretchable electronics have been proposed, such as (ⅰ) bent configuration and (ⅱ) island bridge arrangement.

Figure 1-1. The development of stretchable electronics.

D EFORMABLE BATTERIES

D EFORMABLE ELECTRODES

Before stretching, the 2D distribution patterns of the conductive fillers (CB, CNT, and hybrid carbon) of the composites were found to have isotropic structural orientations (Figure S11). The relationship between resistance and strain also depends on the thickness of the Janus electrode.

Figure 1-5. Various fabrication methods of stretchable electrode such as wave structure, island structure, and textile structure [35, 36, 48]

R EFERENCE

FOLDABLE ELECTRODE ARCHITECTURES BASED ON SILVER-NANOWIRE-

I NTRODUCTION
E XPERIMENTAL
R ESULTS AND DISCUSSION
C ONCLUSION
R EFERENCE

The morphologies of CNTs and CBs were determined by transmission electron microscopy (TEM) (Figure S1, Supporting Information). In the last stage of the process, the resulting polymer composite was thermally cured in an oven. The surface morphology of the HCP composite produced by the BF method was observed using line electron microscopy (SEM).

This result shows that the resistance of the polymer composite sheet decreased with the increase in the amount of conductive fillers. Finally, a metallic zinc was electrodeposited on one side of the Ag/SBS composite (the opposite side was protected with polyimide (PI) tape). The cyclic voltammetry (CV) test of the Janus face electrode appears as shown in Fig.

Figure 2-1. LTO-loaded AgNW$MF. AgNW : MF : LTO = 1 : 1.1 : 5 in weight. Loading density of LTO = 5 mg LTO cm -2

JABUTICABA-INSPIRED HYBRID CARBON FILLER/POLYMER ELECTRODE

I NTRODUCTION

Conductive polymer composites consisting of conductive fillers and elastic polymer matrices are considered promising for the production of stretchable electrodes due to their advantageous characteristics, such as easy to produce, low cost, and scalable production process. Carbon nanotubes (CNT), which are widely used as conductive fillers, are exemplary polymer composite materials due to their excellent mechanical properties, high aspect ratios, and high electrical conductivity. However, its application to stretchable composites is limited for two reasons: (i) the agglomeration of CNT during composite preparation results in low electrical conductivity, [14] and (ii) the percolation network between the CNT is blocked when a composite containing it contains, is stretched. Recently, Kyrylyuk et al. It is not easy to analyze the behavior of fillers during stretching processes, but a clear understanding of this phenomenon is critical for the design and evaluation of the electrical properties of stretchable electrodes.

Lithium-ion batteries (LIBs) are frequently used to power electronic devices due to their many advantages such as high energy density and long-term cycle life.[18,19] The LIBs are mainly based on flammable and toxic organic electrolytes. The risk of them exploding and catching fire due to the reactivity of their electrolytes and active materials during repeated mechanical deformation processes makes them undesirable proposals for stretchable electronic devices.[20] Furthermore, organic electrolytes are expensive to produce and they exhibit low power densities due to their intrinsically low Li-ion transport capacities.[21] A promising alternative power source for stretchable electronics is an aqueous rechargeable lithium-ion battery (ARLB); it is based on highly safe aqueous electrolytes that have high Li-ionic conductivity (relative to their power density).[22]. To confirm the suitability of the polymer composite for use as a stretchable electrode in practical applications, we used it together with a stretchable ARLB in a deformable electronic device.

E XPERIMENTAL

The microstructure of LMO@CNT was investigated using an X-ray diffractometer (XRD, Bruker D8-Advance), which was run at 3 kW using Cu Kα radiation. The morphologies of nanocomposite and active materials were investigated using a field emission scanning electron microscopy (FE-SEM, Hitachi S-4800). The change in R-value with stretching was measured using a multimeter at a stretch ranging from 0 to 200%.

The samples were left perpendicular to the beam direction and stretched in the vertical direction at a constant stretching speed of 20 µm/s. The stretchable electrode, which was composed of active materials (LMO@CNT and PI@AC), conductive carbon (super P) and polymer binder (PVDF) in a mass ratio of 8:1:1, was fabricated by the spraying method. on the hob at 150 oC. The electrochemical properties of half and full cells were investigated using an electrochemical tester (Biologic scientific instrument, VSP) with 1 M aqueous electrolyte Li2SO4.

R ESULTS AND DISCUSSION

By applying a strain of 200%, we found that the normalized resistance of CNT/polymer, CB/polymer and HCP. As the strain increased, the 2D distribution patterns of the CNT/polymer composite and HCP became more stretched, which indicated that the CNT. This result indicated that the fillers were denser in the strain direction, especially in the composites containing CNTs.

However, we found that the orientation factor of the HCP composite did not decrease but remained close to that of the CNT/polymer composite. However, a significant increase in Lp value was found in the HCP composite at the cross-sectional plane, which indicated that the number of connections increased as the strain increased. The LMO@CNT and PI@AC electrodes were fabricated by spraying the active materials onto the HCP composite.

Figure 3-1. Steps for the fabrication and morphological characterization of the carbon/polymer composite

C ONCLUSION

R EFERENCE

The schematic illustration of the Janus face electrode fabrication procedures is shown in Fig. To investigate the structural characterizations of the Janus-faced electrode, we performed scanning electron microscopy analysis. At a strain of 0%, the Ag/SBS composite patterns are isotropic dispersion structure, indicating that the Ag NPs are randomly distributed in the polymer matrix.

The electrochemical performance of the batteries shows excellent long-term cyclability and a very stable capacity even at 200% load. We also performed the durability test of electrical conductivity of the GAP multilayer conductors under loads of 20%, 30% and 40% (Figure 3e). In contrast, AuPU nanocomposite films showed a butterfly-like pattern upon stretching, due to the non-affine relative displacements of the Au NPs in the polymer matrix under strain.

DESIGN OF JANUS-FACED ELECTRODE FOR HIGHLY STRETCHABLE ZINC-

I NTRODUCTION

Among the zinc-based batteries, the zinc-silver batteries are the most mature batteries because they have already been used in small devices and large-scale applications[12]. For these reasons, the zinc-silver batteries are a plausible answer to the deformable power source for the portable devices. Various approaches have been proposed for the design of stretchable zinc-silver batteries, especially using concepts of tattoo-based batteries, fully printed batteries and cable-type batteries so far[13-18].

Here we present stretchable rechargeable zinc-silver batteries based on a Janus electrode, consisting of a cathode and an anode on one electrode. This unique configuration guarantees long-term cycling of zinc-silver batteries thanks to zinc dendrite suppression. Furthermore, the Janus-oriented electrode exhibits mechanical robustness as well as stable electrical conductivity under large voltage.

E XPERIMENTAL

The tips and the middle region of the electrode, which act as tab and electrolyte contact region, were each masked and the rest was spray coated with 10 mL of SBS solution (4 wt% in toluene). After the electrode was spray-coated with 4 wt% SBS solution, the surface was completely covered with SBS block copolymers and was easily functionalized by O2 plasma treatment. Thicker PDMS film (2.4 cm × 2.2 cm × 720 μm) with void center was used for a spacer and provided sufficient space for electrolyte injection.

Both the outer and inner PDMS films were treated with O2 plasma (CUTE, Femto Science, Korea) for one minute at 100 W. An electrode area which was fully covered with SBS block copolymers was treated with O2 plasma and attached for spacer PDMS.

R ESULTS AND DISCUSSION

Figure 3a presents the evolution of the changes in the two-dimensional (2D) SAXS patterns for the bare SBS film and the Ag/SBS composite during stretching and relaxation under a strain of 200%. The electrochemical properties of stretchable zinc-silver batteries were tested in an aqueous electrolyte using a beaker cell with 1 M KOH. The electrochemical performance of zinc-silver solid batteries operating at a voltage window between 1.2 V and 1.8 V and the corresponding charge and discharge profiles at different current densities of 0.5, 1 and 2 mA cm-2 are presented in Fig.

In Fig.4x, the cycling performance of the batteries showed a highly stable capacity of 1.1 mA h cm-2, corresponding to an outstanding capacity retention of 88%. To gain additional insights into this concept, we performed electrochemical plating stripping cycles and performed SEM analysis of the surface of cathode side after cycling (Supporting Information Fig. SX). This increased surface capacitance under voltage is due to a new surface of the electrode exposed to electrolyte by stretching.

Figure 4-1 | Fabrication and characterization. a, Schematic illustration showing the fabrication process of Janus-faced electrode

C ONCLUSION

R EFERENCE

GRADIENT ASSEMBLED POLYURETHANE-BASED STRETCHABLE

I NTRODUCTION
E XPERIMENTAL
R ESULTS AND DISCUSSION
CONCLUSION
REFERENCE

Most uniquely, this GAP stretchable multilayer conductor demonstrates not only top surface conductive structure with superior mechanical stretch even over 300% strain in the case of high gradient architecture, but also whole plane conductor from top surface to end of the conductor by increasing the number of interlayers in the case of low-gradient architecture. High GAP conductors showed superior stretch above 300%, compared to that of low GAP conductors as strain below 100% (Figure 3a). The electrical conductivity of all GAP multilayer conductors showed a similar change in resistance regardless of the number of interlayers and gradient assembly, because the top conductive composite layer is identical to 90 wt% in the AuPU nanocomposite (Figure 3d).

Therefore, the vertically oriented conductivity in low-GAP conductors was theoretically calculated to demonstrate the conduction path through the stretchable layer as a function of the number of interlayers (Figure S9). We considered the contact layer between the conductive layer and the stretchable layer, which resulted in a slight decrease in the stretchable layer thickness (i.e., resistance) with the increase in the number of interlayers shown in the SEM images (Figure 2) because the number of mixed contact layers increased. . To validate the use of the stretchable GAP multilayer as a current collector electrode for practical applications, the electrochemical performance of an aqueous rechargeable lithium-ion battery (ARLB) as a promising energy source was investigated.