Exploring 2D Energy Storage Materials: Advances in Structure, Synthesis, Optimization Strategies, and Applications for Monovalent and Multivalent Metal‐Ion Hybrid Capacitors

Abstract

utilization of environmentally friendly renewable energy sources, such as solar energy, wind energy, and tidal energy. However, these renewable energy sources are intermittent in nature, which makes them unable to provide a stable energy supply. Therefore, energy storage devices play an integral role in setting up renewable energy systems. [1] At present, electrochemical energy storage (EES) technologies are the most commonly used due to high energy conversion efficiency, wide range of energy and power densities, relatively long lifetime, and low maintenance costs, among which lithium-ion batteries (LIBs) and supercapacitors (SCs) are considered to be the promising two. [2,3] LIBs, which have occupied half of the market of EES devices since their successful commercialization more than 30 years ago, have the advantages of high energy density, stable performance, and moderate cost, but their low power density and poor cycle performance are detrimental to fast and longterm energy storage. [4][5][6] By contrast, SCs, another excellent energy storage device, have the ability to store and release energy quickly and has an extremely long cycle life and good safety. The very limited energy density however greatly increases the number of equipment required to store the same energy, thus making SCs undesirable to meet the actual demand for high energy storage. [7][8][9] Consequently, in order to assist in realizing the vision of replacing nonrenewable fossil energy with environmentally friendly renewable energy, EES devices that can concurrently provide good energy density and high power performance are urgently needed.As a new type of EES device emerging after metal-ion batteries (MIBs) and SCs, metal-ion hybrid capacitors (MHCs) blessed with fabulous power performance, decent energy density, and remarkable cycle stability are considered to be one of the most prospective EES devices. [10] In 2001, the first MHC, using activated carbon (AC) as the cathode and nanostructured Li 4 Ti 5 O 12 (LTO) as the anode, was constructed by Amatucci et al., which possessed an energy density as high as 20 Wh kg −1 , about threefold than that of traditional SCs, showing promising rate capability in the meanwhile. [11] ThisThe design and development of advanced energy storage devices with good energy/power densities and remarkable cycle life has long been a research hotspot. Metal-ion hybrid capacitors (MHCs) are considered as emerging and highly prospective candidates deriving from the integrated merits of metal-ion batteries with high energy density and supercapacitors with excellent power output and cycling stability. The realization of high-performance MHCs needs to conquer the inevitable imbalance in reaction kinetics between anode and cathode with different energy storage mechanisms. Featured by large specific surface area, short ion diffusion distance, ameliorated in-plane charge transport kinetics, and tunable surface and/or interlayer structures, 2D nanomaterials provide a promising platform for manufacturing battery-type electrod...

Versatile carbon superstructures for energy storage

“…139–142 Carbon materials are the most widely applied supercapacitor electrodes due to their good conductivity, large surface area, and easy-adjustable pore environments. 143–145 For carbon-based supercapacitors, an ideal carbon electrode should feature an ordered morphology, rational pore-structure parameters, and heteroatomic functions to promote an enhancement of the charge-storage properties. 144,146…”

“…[139][140][141][142] Carbon materials are the most widely applied supercapacitor electrodes due to their good conductivity, large surface area, and easy-adjustable pore environments. [143][144][145] For carbon-based supercapacitors, an ideal carbon electrode should feature an ordered morphology, rational pore-structure parameters, and heteroatomic functions to promote an enhancement of the charge-storage properties. 144,146 Compared with the currently used porous carbons, carbon superstructures with well-dened geometries and exposed electroactive motifs enable them to serve as desirable platforms for exploring the ion-uptake/removal behaviors during supercapacitor electrochemistry.…”

A multifunctional paper-based supercapacitor with excellent temperature adaptability, plasticity, tensile strength, self-healing, and high thermoelectric effects

“…Energy and environmental issues have always been two key core issues that cannot be avoided in the development of human society. [1][2][3][4][5] Especially with the continuous reduction of petrochemical resources and outstanding environmental problems caused by them, researchers have been focussing on the research and development of new and sustainable green electrochemical energy sources. [6][7][8][9][10] Among them, supercapacitors, as electrochemical energy storage devices with high power density, long cycle life, good safety, and other advantages, have attracted extensive attention from researchers.…”

Exchanging Anion in CuCo─Carbonate Double Hydroxide for Faradaic Supercapacitors: A Case Study

“…17 In the MH family, similar to traditional layered double hydroxides (LDH), carbonate double hydroxide (CDH) has a general formula of M 2 CO 3 (OH) 2 , constituting divalent metal host cation connected with hydroxyl anions and intercalated carbonate anions in the lattice structure. 18,19 The CDH are distinguished from conventional lamellar-structured LDH by the nonappearance of X-ray diffraction planes (003) and (006). 20 In CDH, along with the influences of metal compositions in host layers, the anion also has a great impact on electrochemical activity, as anion exchanging ease flawless ion transport throughout the material and improved porous structure.…”