Specific energy

About: Specific energy is a research topic. Over the lifetime, 2282 publications have been published within this topic receiving 50908 citations. The topic is also known as: energy density & massic energy.

High-Capacity Cathode Material with High Voltage for Li-Ion Batteries

Abstract: Electrochemical energy storage devices with a high energy density are an important technology in modern society, especially for electric vehicles. The most effective approach to improve the energy density of batteries is to search for high-capacity electrode materials. According to the concept of energy quality, a high-voltage battery delivers a highly useful energy, thus providing a new insight to improve energy density. Based on this concept, a novel and successful strategy to increase the energy density and energy quality by increasing the discharge voltage of cathode materials and preserving high capacity is proposed. The proposal is realized in high-capacity Li-rich cathode materials. The average discharge voltage is increased from 3.5 to 3.8 V by increasing the nickel content and applying a simple after-treatment, and the specific energy is improved from 912 to 1033 Wh kg-1 . The current work provides an insightful universal principle for developing, designing, and screening electrode materials for high energy density and energy quality.

Review: carbon onions for electrochemical energy storage

Abstract: Carbon onions are a relatively new member of the carbon nanomaterials family. They consist of multiple concentric fullerene-like carbon shells which are highly defective and disordered. Due to their small size of typically below 10 nm, the large external surface area, and high conductivity they are used for supercapacitor applications. As electrode materials, carbon onions provide fast charge/discharge rates resulting in high specific power but present comparatively low specific energy. They improve the performance of activated carbon electrodes as conductive additives and show suitable properties as substrates for redox-active materials. This review provides a critical discussion of the electrochemical properties of different types of carbon onions as electrode materials. It also compares the general advantages and disadvantages of different carbon onion synthesis methods. The physical and chemical properties of carbon onions, in particular nanodiamond-derived carbon onions, are described with emphasis on those parameters especially important for electrochemical energy storage systems, including the structure, conductivity, and porosity. Although the primary focus of current research is on electrode materials for supercapacitors, the use of carbon onions as conductive additives and for redox-active species is also discussed.

Space-separated quantum cutting with silicon nanocrystals for photovoltaic applications

Abstract: For optimal energy conversion in photovoltaic devices (electricity to and from light) one important requirement is that the full energy of the photons is used. However, in solar cells, a single electron–hole pair of specific energy is generated when the incoming photon energy is above a certain threshold, with the excess energy being lost to heat. In the so-called quantum-cutting process, a high-energy photon can be divided into two, or more, photons of lower energy. Such manipulation of photon quantum size can then very effectively increase the overall efficiency of a device. In the current work, we demonstrate (space-separated) photon cutting by silicon nanocrystals, in which nearby Er3+ ions and neighbouring nanocrystals are used to detect this effect.

Non-encapsulation approach for high-performance Li–S batteries through controlled nucleation and growth

Abstract: High-surface-area, nanostructured carbon is widely used for encapsulating sulfur and improving the cyclic stability of Li–S batteries, but the high carbon content and low packing density limit the specific energy that can be achieved. Here we report an approach that does not rely on sulfur encapsulation. We used a low-surface-area, open carbon fibre architecture to control the nucleation and growth of the sulfur species by manipulating the carbon surface chemistry and the solvent properties, such as donor number and Li+ diffusivity. Our approach facilitates the formation of large open spheres and prevents the production of an undesired insulating sulfur-containing film on the carbon surface. This mechanism leads to ~100% sulfur utilization, almost no capacity fading, over 99% coulombic efficiency and high energy density (1,835 Wh kg−1 and 2,317 Wh l−1). This finding offers an alternative approach for designing high-energy and low-cost Li–S batteries through controlling sulfur reaction on low-surface-area carbon. Sulfur encapsulation with nanoporous carbon is a widely adopted approach for Li–S batteries, but this often results in low sulfur utilization and low volumetric energy density. Here the authors report a non-encapsulation approach for the growth of S-containing species with low-surface-area carbon and high energy.