The development of pseudocapacitive materials for energy-oriented applications has stimulated considerable interest in recent years due to their high energy-storing capacity with high power outputs. Nevertheless, the utilization of nanosized active materials in batteries leads to fast redox kinetics due to the improved surface area and short diffusion pathways, which shifts their electrochemical signatures from battery-like to the pseudocapacitive-like behavior. As a result, it becomes challenging to distinguish "pseudocapacitive" and "battery" materials. Such misconceptions have further impacted on the final device configurations. This Review is an earnest effort to clarify the confusion between the battery and pseudocapacitive materials by providing their true meanings and correct performance metrics. A method to distinguish battery-type and pseudocapacitive materials using the electrochemical signatures and quantitative kinetics analysis is outlined. Taking solid-state supercapacitors (SSCs, only polymer gel electrolytes) as an example, the distinction between asymmetric and hybrid supercapacitors is discussed. The state-of-the-art progress in the engineering of active materials is summarized, which will guide for the development of real-pseudocapacitive energy storage systems.

True Meaning of Pseudocapacitors and Their Performance Metrics: Asymmetric versus Hybrid Supercapacitors

Fundamentals, advances and challenges of transition metal compounds-based supercapacitors

Recent progress on porous carbon and its derivatives from plants as advanced electrode materials for supercapacitors

A review status on characterization and electrochemical behaviour of biomass derived carbon materials for energy storage supercapacitors

We demonstrate a facile efficient way to fabricate activated carbon nanosheets (ACNSs) consisting of hierarchical porous carbon materials. Simply heating banana leaves with K2 CO3 produce ACNSs having a unique combination of macro-, meso- and micropores with a high specific surface area of ∼1459 m2  g-1 . The effects of different electrolytes on the electrochemical supercapacitor performance and stability of the ACNSs are tested using a two-electrode system. The specific capacitance (Csp ) values are 55, 114, and 190 F g-1 in aqueous 0.5 M sodium sulfate, organic 1 M tetraethylammonium tetrafluoroborate in acetonitrile, and pure ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6 ]) electrolytes, respectively. The ACNSs also shows the largest potential window of 3.0 V, the highest specific energy (59 Wh kg-1 ) and specific power (750 W kg-1 ) in [BMIM][PF6 ]. A mini-prototype device is prepared to demonstrate the practicality of the ACNSs.

Preparation of Hierarchical Porous Activated Carbon from Banana Leaves for High-performance Supercapacitor: Effect of Type of Electrolytes on Performance

3D porous carbonaceous materials were prepared by combining pre-carbonization and KOH activation with sakura petals as raw materials. The prepared porous sakura carbon (SAC-4) exhibits a high specific surface area, a suitable pore size distribution, a low proportion of oxygen-rich groups and N functional groups, and a partially graphitized phase, which are very beneficial for the electrochemical performance of the material as a supercapacitor electrode. In the activation step, when the mass ratio of KOH to sakura carbon (SC) is 4, a supercapacitor is prepared. A maximal specific capacitance of 265.8 F g−1 is obtained when the current density is 0.2 A g−1. When the current density is 1 A g−1, after 2000 cycles in succession, the capacitance retention rate is excellent and the cycling stability can reach as high as 90.2%. The obtained results indicate that porous carbon prepared with sakura blossom as the raw material is an effective and environmentally friendly electrode material for energy storage.

https://pubs.rsc.org/en/content/articlepdf/2019/ra/c8ra09685f

Sakura-based activated carbon preparation and its performance in supercapacitor applications

Based on the complexes formed by the original Cr(III) in chrome-tanned leather shavings and the carboxyl groups in collagen as raw materials, a chromium oxide-carbon composite material was formed by the high-temperature carbonization of chromium-tanned leather shavings, followed by the leaching of chrome oxide and activation by KOH. By this method, the hierarchical porous carbon with a high surface area doped with oxygen and nitrogen was prepared. The forming process of the hierarchical porous structure is discussed in detail. Through adjusting the mass ratio of KOH to carbon during the activation process, with a mass ratio of 2, the chromium-tanned leather shavings-based hierarchical porous carbon (called CTSHPC-2) was prepared with an optimal specific surface area (3211 m2 g−1) and a large volume ratio of mesopores to macropores (61.9%) as well as abundant oxygen (13.92 at%) and nitrogen (3.58 at%) functional groups. The results showed that CTSHPC-2 obtained a high specific capacitance of 335.5 F g−1 at a current density of 0.5 A g−1. In addition, it had higher rate performance, low resistance, and better cycle stability. Even when the current density is 10 A g−1 over 5000 cycles, the specific capacity retention rate is 93.5%. Therefore, CTSHPC-2 is a promising electrode material for supercapacitors.

/pdf/preparation-of-chrome-tanned-leather-shaving-based-21pabb764d.pdf

Preparation of chrome-tanned leather shaving-based hierarchical porous carbon and its capacitance properties

The invention discloses a multifunctional comfortable running shoe with a shoe pad and shoe sole integrated structure. The multifunctional comfortable running shoe with the shoe pad and shoe sole integrated structure comprises a shoe upper, a shoe sole and a shoe pad, wherein the shoe upper comprises an elastic lace, a surface upper and elastic inner upper; the elastic inner upper is in contact with a foot; the surface upper is arranged on the outer surface of the elastic inner upper; the elastic lace is fixed to the surface upper and is used for adjusting the degree of tightness of a shoe cavity; the shoe sole comprises a shoe outsole, a shoe midsole, an inner bottom ring and the shoe pad; the inner bottom ring is bonded to the shoe midsole and is sewn on the inner upper foot of the upper; a plurality of shock absorption blocks are arranged on the shoe pad and the shoe outsole; and massage airbags are also arranged on the shoe pad. Due to adoption of the structure, compared with the prior art, the multifunctional comfortable running shoe with the shoe pad and shoe sole integrated structure has the advantages that a technology of removing the bonding of the shoe insole realizes theembedded assembly of the shoe pad and the shoe midsole, the performances of the shoe sole are fully exerted, the upper has a relatively good wrapping property, and the comfortableness of the whole shoe is improved.

Ma Fei

Papers

Sakura-based activated carbon preparation and its performance in supercapacitor applications

Preparation of chrome-tanned leather shaving-based hierarchical porous carbon and its capacitance properties

Multifunctional comfortable running shoe with shoe pad and shoe sole integrated structure