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Silicon is a promising high-capacity anode material for lithium-ion batteries yet attaining long cycle life remains a significant challenge due to pulverization of the silicon and unstable solid-electrolyte interphase (SEI) formation during the electrochemical cycles. Despite significant advances in nanostructured Si electrodes, challenges including short cycle life and scalability hinder its widespread implementation. To address these challenges, we engineered an empty space between Si nanoparticles by encapsulating them in hollow carbon tubes. The synthesis process used low-cost Si nanoparticles and electrospinning methods, both of which can be easily scaled. The empty space around the Si nanoparticles allowed the electrode to successfully overcome these problems Our anode demonstrated a high gravimetric capacity (∼1000 mAh/g based on the total mass) and long cycle life (200 cycles with 90% capacity retention).

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Transparent devices have recently attracted substantial attention. Various applications have been demonstrated, including displays, touch screens, and solar cells; however, transparent batteries, a key component in fully integrated transparent devices, have not yet been reported. As battery electrode materials are not transparent and have to be thick enough to store energy, the traditional approach of using thin films for transparent devices is not suitable. Here we demonstrate a grid-structured electrode to solve this dilemma, which is fabricated by a microfluidics-assisted method. The feature dimension in the electrode is below the resolution limit of human eyes, and, thus, the electrode appears transparent. Moreover, by aligning multiple electrodes together, the amount of energy stored increases readily without sacrificing the transparency. This results in a battery with energy density of 10 Wh∕L at a transparency of 60%. The device is also flexible, further broadening their potential applications. The transparent device configuration also allows in situ Raman study of fundamental electrochemical reactions in batteries.energy storage | flexible electronics | self-assembly | transparent electronics T ransparent electronics is an emerging and promising technology for the next generation of optoelectronic devices. Transparent devices have been fabricated for various applications, including transistors (1-6), optical circuits (7), displays (8-10), touch screens (11), and solar cells (12)(13)(14). However, the battery, a key component in portable electronics, has not been demonstrated as a transparent device. Consequently, fully integrated and transparent devices cannot be realized because the battery occupies a considerable footprint area and volume in these devices (e.g., cell phones and tablet computers). Typically, a battery is composed of electrode materials, current collectors, electrolyte, separators, and packaging (15). None of them are transparent except for the electrolyte. Furthermore, as these components are in series, all of them must be clear to make the whole device transparent. A widely used method for making transparent devices is to reduce the thickness of active materials down to much less than their optical absorption length, as demonstrated in carbon nanotubes (5, 7), graphene (11), and organic semiconductors (12,14). However, this approach is not suitable for batteries, because, to our knowledge, no battery material has an absorption length long enough in the full voltage window. For example, LiCoO 2 and graphite, the most common cathode and anode in Li-ion batteries, are good absorbers even with a thickness less than 1 μm. Moreover, black conductive carbon additive is always required in electrodes, which occupies at least 10% of the total volume (16). In contrast, to power common portable electronics, the total thickness of electrode material needs to be on the order of 100 μm-1 mm, much longer than the absorption length of electrode materials. This dilemma comes from the fact that the trans...

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We designed and fabricated binder-free, 3D porous silicon nanostructures for Li-ion battery anodes, where Si nanoparticles electrically contact current collectors via vertically grown silicon nanowires. When compared with a Si nanowire anode, the areal capacity was increased by a factor of 4 without having to use long, high temperature steps under vacuum that vapour-liquid-solid Si nanowire growth entails.

The development of the world economy and the consequent increase in traffic means that increasing numbers of heavy fuel-powered vehicles are appearing on our roads, resulting in greater pollution of the environment. Electric vehicles (EVs) are a new, developing trend in the world automotive industry, and an important tool for reducing CO 2 emissions and protecting the environment. EVs must first and foremost be safe and reliable, and must operate with acceptable costs. Unfortunately, thus far, few kinds of batteries can meet all the requirements for EVs. [1][2][3][4][5][6][7][8] In the case of lithium-ion batteries, their use in EVs is still handicapped by significant safety problems, although their other performance attributes are often satisfactory. The main problem is that they use flammable organic electrolytes, which cannot withstand improper use, such as overcharging or short-circuiting, although much effort has been expended in this direction. [4] The development of new types of "green" battery materials and safer, less-expensive rechargeable systems is therefore necessary.In the mid 1990s, a new type of rechargeable lithium-ion battery with an aqueous electrolyte was reported. [9,10] This battery uses lithium-intercalation compounds such as LiMn 2 O 4 , LiNi 0.81 Co 0.19 O 2 , and VO 2 as the electrode material and an alkaline or neutral aqueous electrolyte, [9][10][11] and can overcome the disadvantages of nonaqueous lithium-ion batteries, such as high cost and safety problems. However, since its cycling was reported to be very poor it failed to attract strong interest from researchers.Here we report that an aqueous rechargeable lithium battery (ARLB) with LiCoO 2 as the positive electrode, LiV 3 O 8 as the negative electrode, and saturated LiNO 3 solution as the electrolyte shows good cycling and therefore shows promise as a power source for safe EVs.The cyclic voltammograms of LiV 3 O 8 and LiCoO 2 in saturated LiNO 3 aqueous electrolyte are shown in Figure 1. In the case of LiV 3 O 8 , there is one pair of redox peaks located at À0.19 (red. 1) and 0.098 V (ox. 1) versus a saturated calomel electrode (SCE), which is evidently due to the intercalation and deintercalation reaction accompanying gain and loss of an electron. The average redox potential is À0.046 V (versus SCE). Since hydrogen evolution was observed at a more negative potential due to overpotential (ca. À1.0 V versus SCE), it is clear that LiV 3 O 8 is very stable in this aqueous electrolyte and can be used as a negative electrode material without significant hydrogen evolution. LiCoO 2 also exhibits one pair of Li + intercalation and deintercalation peaks at 0.8 (red. 2) and 1.35 V (ox. 2) versus SCE, respectively (average redox potential of 1.075 V versus SCE). These voltages are also lower than that for oxygen evolution, which is at approximately 1.8 V versus SCE. This illustrates that the positive electrode is also stable in this aqueous solution.The charge and discharge curves of LiV 3 O 8 //LiCoO 2 cells in the first cycle in organic ...