There are significant challenges in developing deformable devices at the system level that contain integrated, deformable energy storage devices. Here we demonstrate an origami lithium-ion battery that can be deformed at an unprecedented high level, including folding, bending and twisting. Deformability at the system level is enabled using rigid origami, which prescribes a crease pattern such that the materials making the origami pattern do not experience large strain. The origami battery is fabricated through slurry coating of electrodes onto paper current collectors and packaging in standard materials, followed by folding using the Miura pattern. The resulting origami battery achieves significant linear and areal deformability, large twistability and bendability. The strategy described here represents the fusion of the art of origami, materials science and functional energy storage devices, and could provide a paradigm shift for architecture and design of flexible and curvilinear electronics with exceptional mechanical characteristics and functionalities.

We have produced stretchable lithium-ion batteries (LIBs) using the concept of kirigami, i.e., a combination of folding and cutting. The designated kirigami patterns have been discovered and implemented to achieve great stretchability (over 150%) to LIBs that are produced by standardized battery manufacturing. It is shown that fracture due to cutting and folding is suppressed by plastic rolling, which provides kirigami LIBs excellent electrochemical and mechanical characteristics. The kirigami LIBs have demonstrated the capability to be integrated and power a smart watch, which may disruptively impact the field of wearable electronics by offering extra physical and functionality design spaces.

Paper folding techniques are used in order to compact a Li-ion battery and increase its energy per footprint area. Full cells were prepared using Li4Ti5O12 and LiCoO2 powders deposited onto current collectors consisting of paper coated with carbon nanotubes. Folded cells showed higher areal capacities compared to the planar versions with a 5 × 5 cell folded using the Miura-ori pattern displaying a ~14× increase in areal energy density.

Density-controlled ZnO nanorod arrays (ZNAs) were prepared on pre-treatment substrates by a hydrothermal approach under different conditions. The effect of substrate pre-treatment conditions on controlling the density of ZNAs was systematically studied by scanning electron microscopy and x-ray diffraction. It is demonstrated that the substrate pre-treatment conditions such as the concentration of the ZnO colloid, spin coating times, and substrate annealing treatment have their respective influence on controlling the density of the ZNAs. The introduction of a ZnO nanoparticle layer on the substrate not only helps to control the nanorod density but also has a strong impact on the orientation of the nanorod arrays. Although controlling the spin coating process has a similar mechanism to controlling the concentration of colloid, it offers a convenient method to prepare a series of ZNAs with variable density. An annealing treatment of the substrate can influence the microstructure of the ZnO seed layer and then influence the density of the ZNAs.

There is a great deal of interest in developing next-generation lithium ion (Li-ion) batteries with higher energy capacity and longer cycle life for a diverse range of applications such as portable electronic devices, satellites, and next-generation electric vehicles. Silicon (Si) is an attractive anode material that is being closely scrutinized for use in Li-ion batteries because of its highest-known theoretical charge capacity of 4200 mAh g −1 .[1] The development of Si-anode Li-ion batteries has been hindered, however, mostly because of the large volumetric changes (up to 400%) that occur upon insertion and extraction of Li ions, and in turn the large electrochemically related stress, which results in electrode pulverization, loss of electrical contact, and early capacity fading of battery cells. [2][3][4][5] Despite this challenge, the extraordinarily high energy capacity of Si in its own right has motivated researchers to develop new techniques that reduce the limitations of Si as a practical anode material. Ultrathin Si films down to 50 nm in thickness have been reported for successful antipulverization and capacity nondegradation over two thousand charge/discharge cycles on roughened current collectors. [6] This result, together with a surge of work on improving the capacity retention of Si anodes such as nanoparticles [7,8] and/or composites, [9][10][11][12] nanowires, [13][14][15] or nanotubes [16,17] have shown improved performances, where the nanoforms of materials can offer expansion spaces during lithium insertion/extraction ( Figure 1A). However, some degree of capacity fading still exists due to the limited space for accommodating the facile strain expansion as well as decreased accessibility of the electrolyte to the solid -electrolyte interphase (SEI) between the silicon nanostructures and electrolyte. Here, we present a new strategy of stress relaxation for Si films using an elastomeric substrate that will establish an alternative route for new electrode design. In addition, the design of the anodes offers more efficient ion and electron transport than the reported work that uses nanoparticles, nanowires, or nanotubes.The general concept of stress relaxation can be understood using an eigen strain analogy. It is well-known that the eigen deformation of a free-standing material does not lead to mechanical stress, but only to self-compatible deformations, and eigen-strain-induced stresses are generated when the eigen strain is constrained. Consequently, the stress can be released by removing these constraints (e.g., stainless steel [13] and rough substrates [6] ). Herein, we report an approach in which the rigid substrates (e.g., current collectors) that constrain the "free" expansion/contraction of the Si anodes during charge/ discharge are replaced by soft substrates. The mechanism for stress relaxation is that the volumetric strain in Si that is induced by charge/discharge cycling can buckle the flat Si thin films when they are on soft substrates ( Figure 1B), which in turn releases the stress ...

We report a strain sensing approach that utilizes wrinkled patterns on poly (dimethylsiloxane) (PDMS) as an optical grating to measure thermally-induced strain of different materials. The mechanism for the strain sensing and the effect of PDMS grating on strain sensing are discussed. By bonding the PDMS grating onto a copper or silicon substrate, the coefficient of thermal expansion (CTE) of the substrates can be deduced by measuring the diffraction angle change due to the change in PDMS grating periodicity when thermal strain is introduced. The measured CTEs agree well with the known reference values.

Metal-organic frameworks (MOFs) have risen as a kind of porous materials consisting of organic ligands and metal centers or clusters, providing compelling potential for various fields. Recently, MOF-based materials have...

No abstract