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Washing Ni-rich layered materials with water is a simple and effective way to reduce gas evolution by eliminating the gas generation factors. However, the water-washing process itself degrades the electrochemical performances; hence additional treatments such as heating and coating are undertaken. Thus, most studies for the post-process mainly focus on the relationship between additional treatments and electrochemical performances, not paying much attention to the water-washing effect. Here, we focused on the effect of water-washing on the Ni-rich layered materials by studying bare and water-washed LiNi0.88Co0.054Mn0.066O2(NCM) cathodes. The results of synchrotron-based X-ray analysis indicate that the crystal and electronic structures are the same in the bulk aspect after the water-washing process, but differences occur in the surface environment. The amount of Li2CO3 decreases while NiO-like rock-salt phase increases on the surface of the water-washed NCM, and it deteriorates the rate performances by elevating the surface resistances. Furthermore, the surface layer reconstruction of water-washed NCM, which has lower capacity retention during 200 cycles, is much more severe than the bare NCM; this indicates that the water-washing process makes the surface of Ni-rich layered materials more vulnerable to the side reaction, facilitating the formation of NiO-like rock-salt phase by the reconstruction.

The demand for energy storage is exponentially increasing with growth of the human population, which is highly energy intensive. Batteries, supercapacitors, and hybrid capacitors are key energy sto...

As the importance of additional capacity beyond the theoretical limitation of lithium-ion batteries has been recognized, extensive research into effectively utilizing the extra lithium accommodation is being conducted. One of the most effective strategies to increase capacity is the use of catalytic materials well-known to promote electrochemical reactivity. Herein, we adopt platinum (Pt) metal as an electrode material to take advantage of dual charge storage properties: (i) the Li–Pt alloying reaction and (ii) additional Li storage reaction induced by catalytic properties. The prepared Pt electrode yields an initial capacity of ∼863 mA h g−1 during the 1st cycle and a reversible capacity of ∼600 mA h g−1, which is much larger compared to the previously reported capacity of 137 mA h g−1. Additionally, the complex Li-ion storage in Pt metal involving alloying reaction and catalytic effect induced charge storage reactions shows high reversibility, realizing a stable electrochemical performance upon cycling. This study holds great promise for understanding the origin of additional capacities from the catalytic effect of alloying type anodes and could be a trendsetter for designing high-capacity anode materials for next-generation lithium rechargeable batteries.

Sodium-ion batteries (SIBs) hold great potential for use in large-scale grid storage applications owing to their low energy cost compared to lithium analogs. The symmetrical SIBs employing Na

Developing high-energy lithium-ion batteries with long-term stability is critical for realizing sustainable energy applications; however, it remains highly challenging. Exploring multi-redox based electrode materials can help to achieve high capacity and high energy density in LIBs. Polyanion based monoclinic Li3V2(PO4)3 (LVP) cathodes have emerged as an interesting candidate for LIBs owing to their robust 3D structure, high theoretical capacity (∼197 mA h g−1), high working potential (>4.0 V), and high Li-ion diffusion coefficient. A vital challenge for the commercialization of LVP cathodes is their capacity fading behavior, originating when all three Li ions are removed (charging up to 4.8 V vs. Li/Li+). Understanding the phase transition and structural change during three Li-ion removal is indispensable to overcome the capacity fading in LVP cathodes. Herein, we explore for the first time the phase transition behavior responsible for severe capacity fading in LVP cathodes by combining synchrotron-based X-ray diffraction and GITT techniques. The study reveals the formation of a distorted Li-deficient Li1−xV2(PO4)3 phase upon third Li-ion removal which affects the consecutive Li-ion insertion, leading to a capacity loss. Furthermore, we reveal that the Li-ion insertion during discharge is a two-phase reaction, in contrast to the common understanding, which is a solid-solution reaction. This study emphasizes the importance of controlling distortion in polyanion frameworks to achieve high stability.

Sodium batteries have been recognized as a promising alternative to lithium-ion batteries. However, the liquid electrolyte used in these batteries has inherent safety problems. Polymer electrolytes have been considered as safer and more reliable electrolyte systems for rechargeable batteries. Herein, a thermoplastic polyurethane elastomer-based gel polymer electrolyte with high ionic conductivity and high elasticity was reported. It had an ambient-temperature ionic conductivity of 1.5 mS cm-1 and high stretchability, capable of withstanding 610 % strain. Coordination between Na+ ions and polymer chains increased the degree of salt dissociation in the gel polymer electrolyte compared with the liquid electrolyte. An Na/Na3 V2 (PO4 )3 cell assembled with gel polymer electrolyte exhibited good cycling performance in terms of discharge capacity, cycling stability, and rate capability, which was owing to the effective trapping ability of organic solvents in the polymer matrix and uniform flux of sodium ions through the gel polymer electrolyte.

Non-aqueous electrical double-layer capacitors (EDLCs) with high energy density and long cycle life are the key to meet future energy demands. The performance of such high-energy supercapacitors greatly depends on the textural properties of the porous carbon electrode. Ordered mesoporous carbon materials are always the prominent electrodes for capacitor applications and the roles of pore size and pore structure need to be investigated in a non-aqueous capacitor system to achieve high performance. Herein, a series of well-ordered mesoporous carbon materials (OMCs) with high specific surface areas and high pore volumes are synthesized utilizing mesoporous silica (SBA-15 and KIT-6) templates at different carbonization temperatures and studied for EDLCs with non-aqueous electrolytes. The performance of EDLCs greatly depends on the mesopore structure and mesoporous surface area, which is evident from the electrochemical performance. In particular, CMK-3 (prepared using SBA-15) shows a higher specific capacitance than CMK-8 (prepared using KIT-6), which may come from the long straight channels of CMK-3 leading to a lower internal resistance and larger number of ion-diffusion pathways. The mesopores provide not only larger pores for fast electrolyte ion transport but also a high surface area and high pore volume for ion storage during the charge–discharge processes. Increasing the carbonization temperature from 600 to 900 °C increases the mesoporous surface area, resulting in enhanced specific capacitance.

Sodium ion batteries (SIBs) are the promising candidate for large scale applications due to their high abundance and low cost.The symmetrical SIBs (similar cathode and anode configuration) are highly promising as they exhibit negligible volume changes during the charge/discharge process and making SIBs highly stable. Several NASICON (sodium superionic conductor) have high potential towards symmetrical SIBs due to presence of multi-redox reactions in both anodic and cathodic regions. Na3V2(PO4)3 (NVP) has been found to be appeal for symmetrical SIB systems due to presence of flat voltage profile, multi-redox with a single transition metal, and a large working voltage difference between anodic and cathodic regions can greatly improve the output of the NVP symmetrical cell. However, the phase transitions associated during the electrochemical reaction in the symmetrical NVP cells are not widely studied. The synchrotron X-ray studies in NVP symmetrical cells confirms the redox reaction involving ≈2 moles of Na+ reaction instead of 1 mole of Na+ reaction. The in-situ X-ray diffraction and X-ray absorption spectroscopy during the electrochemical cycling confirms the reversible formation of Na5V2(PO4)3 phase in the anode and NaV2(PO4)3 phase in the cathode. The charge storage process in NVP cathode region is through V3+/V4+ redox, and charge storage process in NVP anode region is through V3+/V2+ redox. The 2 moles sodium-ion storage process can make a discharge capacity of ≈99 mAh g−1, increasing the energy output of the symmetrical NVP.

Manganese oxide (MnO2) is a promising material for supercapacitor applications, with a theoretical ultra-high energy density of 308 Wh/kg. However, such ultra-high energy density has not been achieved experimentally in MnO2-based supercapacitors because of several practical issues, such as low electrical conductivity of MnO2, incomplete utilization of MnO2, and dissolution of MnO2. The present study investigates the potential of MnO2/reduced graphene oxide (rGO) hybrid nanoscroll (GMS) structures as electrode material for overcoming the difficulties and for developing ultra-high-energy storage systems. A hybrid supercapacitor, comprising MnO2/rGO nanoscrolls as anode material and activated carbon (AC) as a cathode, is fabricated. The GMS/AC hybrid supercapacitor exhibited enhanced energy density, superior rate performance, and promising Li storage capability that bridged the energy–density gap between conventional Li-ion batteries (LIBs) and supercapacitors. The fabricated GMS/AC hybrid supercapacitor demonstrates an ultra-high lithium discharge capacity of 2040 mAh/g. The GMS/AC cell delivered a maximum energy density of 105.3 Wh/kg and a corresponding power density of 308.1 W/kg. It also delivered an energy density of 42.77 Wh/kg at a power density as high as 30,800 W/kg. Our GMS/AC cell’s energy density values are very high compared with those of other reported values of graphene-based hybrid structures. The GMS structures offer significant potential as an electrode material for energy-storage systems and can also enhance the performance of the other electrode materials for LIBs and hybrid supercapacitors.

Development of supercapacitors with high energy density and long cycle life using sustainable materials for next-generation applications is of paramount importance. The ongoing challenge is to elevate the energy density of supercapacitors on par with batteries, while upholding the power and cyclability. In addition, attaining such superior performance with green and sustainable bio-mass derived compounds is very crucial to address the rising environmental concerns. Herein, we demonstrate the use of watermelon rind, a bio-waste from watermelons, towards high energy, and ultra-stable high temperature green supercapacitors with a high-voltage ionic liquid electrolyte. Supercapacitors assembled with ultra-high surface area, hierarchically porous carbon exhibits a remarkable performance both at room temperature and at high temperature (60 °C) with maximum energy densities of ∼174 Wh kg−1 (25 °C), and 177 Wh kg−1 (60 °C) – based on active mass of both electrodes. Furthermore, an ultra-high specific power of ∼20 kW kg−1 along with an ultra-stable cycling performance with 90% retention over 150,000 cycles has been achieved even at 60 °C, outperforming supercapacitors assembled with other carbon based materials. These results demonstrate the potential to develop high-performing, green energy storage devices using eco-friendly materials for next generation electric vehicles and other advanced energy storage systems.

Electrochemical energy storage (EES) devices with simultaneous high energy and high power output are critical in next-generation smart applications. Sodium hybrid capacitors (NHCs) are relatively new devices integrating the functions of batteries and capacitors. Research on capacitor-type carbon electrodes in NHCs is necessary to improve the energy-power behavior. Herein, we study ordered mesoporous carbon (OMC) materials synthesized at different temperatures (600 °C, 750 °C, and 900 °C) utilizing the KIT-6 silica template applied as adsorption cathodes for NHCs, paired with the superionic conductor Na3V2(PO4)3 as the anode material. Raman measurement indicates that the degree of graphitization is maximized at 750 °C. As a result, the OMC carbonized at 750 °C delivered the best performance among three OMCs, with a high energy density (54 W h kg−1), high power (2200 W kg−1) and superior stability (5000 cycles). The current research demonstrates a new platform for utilizing OMCs as adsorption electrodes in NHCs to realize a high-energy, high-power, and highly stable storage devices.

Correction for ‘Enhancing electrochemical performance by triggering a local structure distortion in lithium vanadium phosphate cathode for Li ion batteries’ by Hyunyoung Park et al., J. Mater. Chem. A, 2022, https://doi.org/10.1039/D2TA06837K.

Electrochemical ultracapacitors exhibiting high energy output and an ultra-long cycle life, utilizing green and sustainable materials, are of paramount importance for next-generation applications. Developing an ultracapacitor that has high output energy under high power conditions in a high-voltage non-aqueous electrolyte and maintaining a long cycle life is an ongoing challenge. Herein, we utilize watermelon seeds, a bio-waste from watermelons, for use in high-voltage, high-energy, and high-power ultracapacitors in a sodium ion-based non-aqueous electrolyte. The as-synthesized hierarchically porous, high surface area carbon is surface-engineered with a large quantity of nitrogen and sulfur heteroatoms to give a high specific capacitance of ∼252 F g−1 at 0.5 A g−1 and 90 F g−1 at 30 A g−1. An ultra-high stability of ∼90% even after 150 000 cycles (10 A g−1) with 100% coulombic efficiency is achieved at room temperature (25 °C), equivalent to an ultra-low energy loss of ∼0.0667% per 1000 cycles. Furthermore, the porous carbon demonstrates remarkable stability even at high temperature (55 °C) for 100 000 cycles (10 A g−1), ensuring the safety of the device and enabling it to outperform graphene-based materials. A maximum energy of ∼79 W h kg−1 and a maximum power of 22.5 kW kg−1 with an energy retention of ∼28.2 W h kg−1 was attained. The results provide new insights that will be of use in the development of high-performance, green ultracapacitors for advanced energy storage systems.

Sodium hybrid capacitors (NHCs) have tremendous potential to meet the simultaneous high energy–high power requirement of next-generation storage applications. But NHCs still face some obstacles due to poor sodium ion kinetics, low power, and poor cyclability while working with several inorganic sodium ion hosts. Additionally, developing high-performance NHCs that are sustainable and versatile is more crucial from the perspective of energy storage devices. Here, we report a conceptually new and high performance organic sodium hybrid capacitor (ONHC) system, developed by substituting a conventional toxic-metal-containing inorganic battery electrode of an NHC with a nano-structured, metal free, and renewable organic molecule – disodium rhodizonate – to host sodium ions. The sustainability of the ONHC is greatly enhanced by the simultaneous utilization of high surface area cardamom shell (as biomass)-derived porous carbon as a high-power capacitor electrode. The new system exhibits an outstanding performance, delivering a high energy density of ∼87 W h kg−1 along with a high specific power of 10 kW kg−1 (based on the mass in both electrodes), outperforming inorganic sodium hosts. High durability over 10 000 cycles (∼85% retention) with an ultra-low energy loss of ∼0.15% per 100 cycles is also demonstrated, indicating its emergence as a rival to conventional metal containing lithium and sodium hybrid capacitors. The current study provides new opportunities for developing greener and sustainable devices beyond conventional systems for next-generation storage applications.

Developing sodium based energy storage systems that retain high energy density at high power along with stable cycling is of paramount importance to meet the energy demands of next generation applications. This requires the development of electrodes beyond the conventional intercalation-based chemistry to overcome the sluggish diffusion-limited reaction kinetics and limited cycle life. Herein, we report a rationally designed hollow graphene nanosphere (HGS) cathode, which utilizes non-destructive, ultra-fast surface redox reactions at oxygen functional groups and delivers a discharge capacity of ∼155 mA h g−1 (0.1 A g−1) corresponding to a high energy of ∼415 W h kg−1 and retains ∼88 W h kg−1 of energy at a remarkable specific power of ∼84 kW kg−1 (40 A g−1), which are beyond the capabilities of intercalation-based electrodes. Moreover, the achieved cycling performance (86% capacity retention after 50 000 cycles at 10 A g−1) is the most stable cathode performance reported so far. The rationally designed sodium metal battery full cells with a sodium metal deposited aluminium current collector anode and the HGS cathode showed a similar sodium ion storage performance with high capacity, good rate capability, and stability. We certainly believe that the current research could direct the future research development towards transition metal-free, ultra-high power and super stable cathodes for sodium energy storage devices.

The abundance of sodium resources has recently motivated the investigation of sodium ion batteries (SIBs) as an alternative to commercial lithium ion batteries. However, the low power and low capacity of conventional sodium anodes hinder their practical realization. Although most research has concentrated on the development of high-capacity sodium anodes, anodes with a combination of high power and high capacity have not been widely realized. Herein, we present a simple microwave irradiation technique for obtaining few-layered, ultrathin two-dimensional SnS2 over graphene sheets in a few minutes. SnS2 possesses a large number of active surface sites and exhibits high-capacity, rapid sodium ion storage kinetics induced by quick, nondestructive pseudocapacitance. Enhanced sodium ion storage at a high current density (12 A g–1), accompanied by high reversibility and high stability, was demonstrated. Additionally, a rationally designed sodium ion full cell coupled with SnS2//Na3V2(PO4)3 exhibited exceptional ...

The development of hybrid capacitors (HCs) has become essential for meeting the rising demand for devices that simultaneously deliver high energy with high power. Although the challenge to develop high-performance HCs remains great, it is also simultaneously essential to develop an eco-friendly and cleaner energy storage system for sustainable future use. To date, hybrid capacitors utilize heavily toxic inorganic insertion electrodes and hazardous coke-derived porous carbon adsorption electrodes to host ions. Herein, we present a conceptually novel all-organic sodium hybrid capacitor (OHC), rationally designed by replacing the conventional electrodes with clean, green, and metal free organic molecules, to host ions. A high energy density of ∼95 Wh kg–1 and an ultrahigh power density of 7 kW kg–1 (based on active mass in both electrodes) are achieved with a low energy loss of ∼0.22% per 100 cycles (∼89% retention after 5000 cycles), outperforming conventional HCs. The outstanding energy–power behavior of O...

In Sodium-ion capacitors (SICs), employing high-capacity anodes based on alloying/conversion reactions can potentially alleviate the performance issues but are susceptible to rapid capacity fading due to consistent dissolution of the electrode surface by the electrolyte. Herein, we extend the “hybrid mixed electrolyte” strategy to ion capacitors for overcoming the rapid cycle decay issues in high-energy SICs: molybdenum disulphide (MoS2, MS) nanocrystals grown on carbon nitride (C3N4, CN), denoted as MS/CN, as anode exhibited remarkable performance in both sodium electrolyte and replaced with a hybrid mixed electrolyte comprising larger Na+ ions and smaller Li+ ions. Thus, constructed SICs exhibited a high energy density of 124 Wh Kg−1 with a mixed ion electrolyte, and low energy loss (71% retention after 40000 cycles) with a hybrid electrolyte (lower than conventional sodium-ion-based electrolyte: 37% retention after 15000 cycles). Systematic investigations, including X-ray photoelectron spectroscopy and electron probe microanalysis, revealed an advantageous formation of a stable interface for electrode and electrolyte.

We report a novel P2-type Na0.5Ni0.26Cu0.07Mn0.67O2 (NCM) mixed oxide obtained by conventional solid-state method as a prospective cathode for sodium-ion battery (SIB) applications. X-ray diffraction analysis shows that NCM exhibits a hexagonal structure with a P63/mmc (No. 194) space group, in which Na-ions are located in a prismatic environment. The introduction of Cu into the lattice enhances its structural stability, showing a capacity retention of 83% after 100 cycles, which is much better than its native compound. MgO encapsulation was performed to further improve the interfacial kinetics and suppress P2–O2 phase transition. MgO coating significantly improves the electrochemical activity at high cut-off voltages, for instance, highest capacity of 131 mA h g−1 was noted with superior rate performance of 83 and 51 mA h g−1 at 5 and 20C, respectively. As expected, dual modification by Cu-ion doping and MgO coating provides a novel strategy for designing high-rate SIB cathodes.

Lithium-ion hybrid capacitors (LICs) take the advantage of simultaneous high energy – power output, and become increasingly important for next generation applications. Developing a high performing LICs with high energy-power-cycle combination remains a significant challenge due to low capacity intercalation electrodes, and kinetically sluggish alloying type electrodes. A strategy employing fast pseudocapacitive lithium ion storage in high-capacity alloying type anode, rather than a bulk storage, can output kinetically superior LICs with high energy even at high power conditions. Herein, we demonstrate a highly interconnected 3-dimensional (3D) SiO2 nanospheres embedded Nitrogen-doped carbon shell with fast lithium ion storage kinetics as high performing anode for LICs. As a result, LIC with a high energy (139 Wh kg−1), high power density (42 kW kg−1), and super stability (20,000 cycles) is obtained, outperforming previously studied alloying type metal oxide and sulfide anodes. A flexible LICs is further demonstrated which shows good stability under different bending conditions. The current research promotes the practical utilization of earth-abundant material as a high capacity and high rate electrode for the next-generation flexible and wearable devices.

Sodium-ion batteries have gained an intense attention as a promising alternate for Li-ion batteries due to their low cost, and abundant availability. To meet high energy density requirements, developing a high voltage cathode with ultra-long cycle life is of great importance. Na3V2(PO4)2F3 (NVPF) features a high working voltage, fast sodium-ion diffusion channels, and small volume change during the cycling process. However, the practical performance of NVPF cathode is currently hindered by poor Na+ ion diffusion at high voltage, low cycle life, and limited rate behavior. Herein, we evaluate the effect of synthesis conditions in sol–gel technique, binders (PVDF, PAI and CMC), and electrolytes (ether, and ester based solvents) to overcome the diffusion limitation in high voltage NVPF cathode. Benefiting from the synergistic effect of CMC binder, and DEGME electrolyte, and reduced graphene oxide composite, NVPF effectively overcome the potential barrier during Na+ ion insertion/extraction at high voltage. NVPF with CMC binder and DEGDME electrolyte displayed a high Na+ ion diffusion kinetics, low cell resistance, and delivered an excellent electrochemical performance. NVPF delivered a high coulombic efficiency (92%), long cycle life (10,000 cycles), and an excellent rate performance (50 C), outperforming the conventional PVDF binder, and carbonate based electrolytes. Furthermore, the full-cell constructed by NVPF cathode, and Na3V2(PO4)3 anode delivered an capacity retention. The current study provides new insights for overcoming the kinetic barrier during sodium ion storage in high voltage cathode that could direct the research development towards high energy sodium-ion batteries.

Functional materials with high energy density – high rate capabilities have continued to gain importance, and are extensively studied for next-generation energy storage applications.[1] The ongoing challenge is to elevate the power density of batteries on par with capacitors, while holding the energy density and cycle life.[2] The sluggish intercalation kinetics, and continuous transition metal dissolution in conventional electrodes hampers the realization of high power, and highly stable devices.[3] To overcome the kinetic issues, we rationally designed graphene hollow nanospheres (GHNS) with dual heteroatoms (nitrogen and sulfur) as both anode and cathode for Na-ion based energy storage system. The self-assembly of 2D graphene into a highly connected 3D architecture facilitates facile Na-ion storage, while the nitrogen and sulfur hetero atoms infiltrated in the carbonaceous matrix elevates the kinetics of the GHNS. The full-cell based on GHNS electrodes displays a high operating voltage, high energy density (121 Wh kg−1 at 100 W kg−1), and high power density (51 kW kg-1). Further, the sodium-ion storage system can render remarkable cycling stability of ~85% retention after 10,000 cycles (~0.0015% decay per cycle). Development of such nanostructured functional materials could establish a trade‐off relationship between high energy and high power devices. References [1] J. R. Miller, P. Simon, Science 2008, 321, 651. [2] H. Jiang, P. S. Lee, C. Li, Energy Environ. Sci. 2013, 6, 41. [3] R. Thangavel, B. Moorthy, D.K. Kim, Y.-S. Lee, Adv. Energy Mater. 2017, 7, 1602654.

Manganese oxide (MnO2) is a promising material for supercapacitor applications, with a theoretical ultra-high energy density of 308 Wh/kg. However, such ultra-high energy density has not been achieved experimentally in MnO2-based supercapacitors because of several practical issues, such as low electrical conductivity of MnO2, incomplete utilization of MnO2, and dissolution of MnO2. The present study investigates the potential of MnO2/reduced graphene oxide (rGO) hybrid nanoscroll (GMS) structures as electrode material for overcoming the difficulties and for developing ultra-high-energy storage systems. A hybrid supercapacitor, comprising MnO2/rGO nanoscrolls as anode material and activated carbon (AC) as a cathode, is fabricated. The GMS/AC hybrid supercapacitor exhibited enhanced energy density, superior rate performance, and promising Li storage capability that bridged the energy&ndash, density gap between conventional Li-ion batteries (LIBs) and supercapacitors. The fabricated GMS/AC hybrid supercapacitor demonstrates an ultra-high lithium discharge capacity of 2040 mAh/g. The GMS/AC cell delivered a maximum energy density of 105.3 Wh/kg and a corresponding power density of 308.1 W/kg. It also delivered an energy density of 42.77 Wh/kg at a power density as high as 30,800 W/kg. Our GMS/AC cell&rsquo, s energy density values are very high compared with those of other reported values of graphene-based hybrid structures. The GMS structures offer significant potential as an electrode material for energy-storage systems and can also enhance the performance of the other electrode materials for LIBs and hybrid supercapacitors.

Present state-of-the-art graphene-based electrodes for supercapacitors remain far from commercial requirements in terms of high energy density. The realization of high energy supercapacitor electrodes remains challenging, because graphene-based electrode materials are synthesized by the chemical modification of graphene. The modified graphene electrodes have lower electrical conductivity than ideal graphene, and limited electrochemically active surface areas due to restacking, which hinders the access of electrolyte ions, resulting in a low energy density. In order to solve the issue of restacking and low electrical conductivity, we introduce thiol-functionalized, nitrogen-doped, reduced graphene oxide scrolls as the electrode materials for an electric double-layer supercapacitor. The fabricated supercapacitor exhibits a very high energy/power density of 206 Wh/kg (59.74 Wh/L)/496 W/kg at a current density of 0.25 A/g, and a high power/energy density of 32 kW/kg (9.8 kW/L)/9.58 Wh/kg at a current density of 50 A/g; it also operates in a voltage range of 0~4 V with excellent cyclic stability of more than 20,000 cycles. By suitably combining the scroll-based electrode and electrolyte material, this study presents a strategy for electrode design for next-generation energy storage devices with high energy density without compromising the power density.

Despite their high specific capacity, sodium layered oxides suffer from severe capacity fading when cycled at higher voltages. This key issue must be addressed in order to develop high-performance cathodes for sodium ion batteries (SIBs). Herein, we present a comprehensive study on the influence of Al doping of Mn sites on the structural and electrochemical properties of a P2–Na0.5Mn0.5–xAlxCo0.5O2 (x = 0, 0.02, or 0.05) cathode for SIBs. Detailed structural, morphological, and electrochemical investigations were carried out using X-ray diffraction, cyclic voltammetry, and galvanostatic charge–discharge measurements, and some new insights are proposed. Rietveld refinement confirmed that Al doping caused TMO6 octahedra (TM = transition metal) shrinkage, resulting in wider interlayer spacing. After optimizing the aluminum concentration, the cathode exhibited remarkable electrochemical performance, with better stability and improved rate performance. Electrochemical impedance spectroscopy (EIS) measurements ...

The low volumetric energy density of reduced graphene oxide (rGO)-based electrodes limits its application in commercial electrochemical energy storage devices that require high-performance energy storage capacities in small volumes. The volumetric energy density of rGO-based electrode materials is very low due to their low packing density. A supercapacitor with enhanced packing density and high volumetric energy density is fabricated using doped rGO scrolls (GFNSs) as the electrode material. The restacking of rGO sheets is successfully controlled through synthesizing the doped scroll structures while increasing the packing density. The fabricated cell exhibits an ultrahigh volumetric energy density of 49.66 Wh/L with excellent cycling stability (>10 000 cycles). This unique design strategy for the electrode material has significant potential for the future supercapacitors with high volumetric energy densities.

Electrochemical supercapacitors with high energy density are promising devices due to their simple construction and long-term cycling performance. The development of a supercapacitor based on electrical double-layer charge storage with high energy density that can preserve its cyclability at higher power presents an ongoing challenge. Herein, we provide insights to achieve a high energy density at high power with an ultrahigh stability in an electrical double-layer capacitor (EDLC) system by using carbon from a biomass precursor (cinnamon sticks) in a sodium ion-based organic electrolyte. Herein, we investigated the dependence of EDLC performance on structural, textural, and functional properties of porous carbon engineered by using various activation agents. The results demonstrate that the performance of EDLCs is not only dependent on their textural properties but also on their structural features and surface functionalities, as is evident from the electrochemical studies. The electrochemical results are highly promising and revealed that the porous carbon with poor textural properties has great potential to deliver high capacitance and outstanding stability over 300 000 cycles compared with porous carbon with good textural properties. A very low capacitance degradation of around 0.066 % per 1000 cycles, along with high energy density (≈71 Wh kg-1 ) and high power density, have been achieved. These results offer a new platform for the application of low-surface-area biomass-derived carbons in the design of highly stable high-energy supercapacitors.

With limited amounts of fossil fuels and increasing demand for efficient energy management, lithium-ion batteries (LIBs) have been a leading power source for hybrid electric vehicles and large-scale energy storage systems. However, rising price of lithium sources has become a significant concern, caused by increasing market demand for lithium and limited amounts of lithium resources. In this respect, sodium-based batteries have been considered an alternative to the LIBs due to the abundance of sodium resources in nature.1 Like LIBs, enhancing the battery safety is a significant concern, because use of highly flammable organic solvents may trigger safety problems. Gel polymer electrolytes present many potential advantages, including enhanced safety, good interfacial contact, easy processing to make thin film and flexibility in the battery design, as compared to conventional separators.2 In this study, we prepared polyurethane (PU)-based gel polymer electrolyte (GPE) composed of PU polymer matrix and sodium-ion liquid electrolyte, which exhibited good compatibility with liquid electrolyte and superior electrochemical properties. The PU GPE was employed to assemble the Na/Na3V2(PO4)3 cells. Electrochemical performance of the sodium cells was enhanced by employing the PU GPE. References M.D. Slater, D. Kim, E. Lee and C.S. Johnson, Adv. Funct. Mater., 23, 947-958 (2013). H. Gao, B. Guo, J. Song, K. Park and J.B. Goodenough, Adv. Energy Mater., 5, 1402235 (2015). Figure 1

Sodium ion batteries have been recently proved to be a cost-effective and promising alternative to lithium-ion batteries for next generation high-energy applications. However, the sluggish intercalation kinetics in batteries greatly forbid the efficient high power operation.[1] Recently, sodium hybrid capacitors (NHCs) emerged as a promising energy storage system to retain high specific energy at high power conditions. Benefiting from the simultaneous sodium intercalation/deintercalation in battery type electrode and anionic adsorption/desorption in capacitor type electrode, a fast kinetics in NHCs have been achieved. However, the poor sodium ion storage in battery electrode along with limited anionic adsorption in commercial electrode diminish the output performance of NHCs. The research on NHCs is still in a nascent stage and requires deep investigation to improve energy retention and cycle stability at high power. The kinetics in both battery and capacitor type electrodes must be synergistically improved to achieve a high energy.[2] In this work, we developed a high performing NHC with metal oxide nanoparticles embedded in graphene network as a battery electrode along with a highly mesoporous carbon derived from bio-mass precursor as a capacitor electrode. The highly favorable architecture in both the electrodes showed an enhanced capability towards ion storage (Shown in Ragone plot). A high energy retention at high power condition along with ultra-high stability have been achieved. The detailed results will be presented and discussed in detail. References [1] J. R. Miller, P. Simon, Science 2008, 321, 651. [2] R. Thangavel, B. Moorthy, D. K. Kim, Y.-S. Lee, Adv. Energy Mater. 2017, 1602654. Figure 1

Hybrid capacitors, especially sodium hybrid capacitors (NHCs), have continued to gain importance and are extensively studied based on their excellent potential to serve as advanced devices for fulfilling high energy and high power requirements at a low cost. To achieve remarkable performance in hybrid capacitors, the two electrodes employed must be superior with enhanced charge storage capability and fast kinetics. In this study, a new sodium hybrid capacitor system with a sodium super ionic conductor NaTi2(PO4)3 grown on graphene nanosheets as an intercalation electrode and 2D graphene nanosheets as an adsorption electrode is reported for the first time. This new system delivers a high energy density of ≈80 W h kg−1 and a high specific power of 8 kW kg−1. An ultralow performance fading of ≈0.13% per 1000 cycles (90%–75 000 cycles) outperforms previously reported sodium ion capacitors. The enhanced charge transfer kinetics and reduced interfacial resistance at high current rates deliver a high specific energy without compromising the high specific power along with high durability, and thereby bridge batteries and capacitors. This new research on kinetically enhanced NHCs can be a trendsetter for the development of advanced energy storage devices requiring high energy—high power.

Correction for ‘Cu-doped P2-Na0.5Ni0.33Mn0.67O2 encapsulated with MgO as a novel high voltage cathode with enhanced Na-storage properties’ by Hari Vignesh Ramasamy et al., J. Mater. Chem. A, 2017, DOI: 10.1039/c6ta10334k.

Since 1990 lithium-ion (Li-ion) batteries have been commercially available and currently remain as the technology of choice for applications where high energy densities are required. Sodium-ion (Na-ion) technology is similar in many ways to Li-ion technology, but is still in its initial stage. Current research trends are mostly based on Na-ion based technology due to several commercial advantages, including lower cost, greater sustainability and improved safety characteristics.1, 2 Among different types of cathode materials available, layered oxides such as NaxMO2 (M = transition metal) have shown great promise in terms of both cost and performance.3,4 According to Delmas et al, these layered oxides are classified into different structures, the most common of which are O3, P2 and P3.5 In these descriptions, the O and P refer to an octahedral (O), or prismatic (P), coordination of the Na-ions, and the number refers to the number of layers in the unit cell. P2-type Na-Ni-Mn-O has been considered as a suitable cathode material for the modern day requirement of high power and energy applications due to their low cost, easy synthesis and high theoretical capacity of greater than 250 mAhg-1. However this material has the serious problem of capacity fading due to structural instability. Cationic substitution and surface coating was an efficient strategy to enhance the electrochemical performance by improving the structural stability and preventing Mn3+ dissolution into electrolyte at higher voltages. In this work a novel P2-type Na0.5Ni0.33Cu0.07Mn0.67O2 was synthesized using the single step conventional solid state method and studied as cathode material for sodium ion batteries. The presence of Cu in the lattice structure enhanced the capacity retention to 83% after 100 cycles along with smooth voltage plateau in the high voltage region as shown in Figure 1. Surface coating with MgO increased the specific capacity of the material in the extended voltage window of 2.0 – 4.5V. The MgO coated material shows a smooth voltage plateau without any phase gliding in the higher voltage as in Figure 2. The capacity retention after 70 cycles is found to be 77.6% with enhanced performance. Hence the MgO coated Na0.5Ni0.26Cu0.07Mn0.67O2is studied as a novel cathode for room temperature Na-ion batteries. References: [1] V. Palomares, P. Serras, I. Villaluenga, K.B. Hueso, J. Carretero-Gonz, T. Rojo, Energy Environ. Sci. 5, 2012, 5884. [2] J. Barker, M.Y. Saidi, J. Swoyer, Electrochem. Solid St. 6, 2003, A1. [3] S.W. Kim, D.H. Seo, X. Ma, G. Ceder, K. Kang, Adv. Energy Mater. 2, 2012, 710. [4] M. Slater, D. Kim, E. Lee, C.S. Johnson, Adv. Func. Mater. 23, 2013, 947. [5] C. Delmas, C. Fouassier, P. Hagenmuller, Physica B+C , 99, 1980, 81. Figure 1(a). Cycle stability of Na0.5Ni0.26Cu0.07Mn0.66O2 at 0.25C from 2.0 - 4.25V. ( Inset figure shows the XRD pattern and unit cell diagram of metal substituted sample). (b) Cyclic stability of MgO coated Na0.5Ni0.26Cu0.07Mn0.66O2 in high voltage of 2-4.5V Figure 1

Sodium ion batteries are emerging candidate for next generation high energy application including electrical vehicles and grid storage.[1] Rather than the similar working principle, the wide availability and low cost of sodium made them a suitable and an interesting candidate for large energy applications. The research for sodium ion batteries is majorly on improving their poor kinetics due to their large ionic radii resulting in low energy and power density.[2]The possible solution could be designing a hybrid capacitor which greatly improves the energy density and power density simultaneously because of their fast kinetics. In this work, we have developed and fabricated a new high performing 3 V sodium hybrid capacitor (NHC) using NASICON structured Na3V2(PO4)3 – (NVP) and a carbon derived from bio resource in an organic electrolyte. Two reactions occurs simultaneously, (i) intecalaction / deintercalation of sodium ions in NVP which brings high energy density, (ii) adsorption/ desorption of anion in the bio carbon giving high power density. An energy density of 118 Wh kg−1 has been achieved at a specific power of 95 W kg−1, retaining 60 Wh kg−1 of energy at high specific power of 850 W kg−1. A superior and an extremly outstanding stability of 95% is achieved after 10,000 cycles. The obtained results are one of the highest ever reported and it outperforms the present lithium hybrid capacitor by all means (energy density, power density, stability). The results will be presented and discussed in detail. References: 1) N. Yabuuchi,M. Kajiyama, J. Iwatate, H. Nishikawa, S. Hitomi, R. Okuyama, R. Usui, Y. Yamada, S. Komaba, Nat.Mater. 2012, 11, 512. 2) V. Etacheri, R. Marom, R. Elazari, G. Salitra, D. Aurbach, Energy Environ. Sci. 2011, 4, 3243. Figure 1

A novel sodium hybrid capacitor (NHC) is constructed with an intercalation-type sodium material [carbon coated-Na3V2(PO4)3, C-NVP] and high surface area-activated carbon derived from an eco-friendly resource cinnamon sticks (CDCs) in an organic electrolyte. This novel NHC possesses a combination of high energy and high power density, along with remarkable electrochemical stability. In addition, the C-NVP/CDC system outperforms present, well-established lithium hybrid capacitor systems in all areas, and can thus be added to the list of candidates for future electric vehicles. A careful optimization of mass balance between electrode materials enables the C-NVP/CDC cell to exhibit extraordinary capacitance performance. This novel NHC produces an energy density of 118 Wh kg−1 at a specific power of 95 W kg−1 and retains an energy density of 60 Wh kg−1 with high specific power of 850 W kg−1. Furthermore, a discharge capacitance of 53 F g−1 is obtained from the C-NVP/CDC cell at a 1 mA cm−2 current density, along with 95% capacitance retention, even after 10 000 cycles. The sluggish kinetics of the Na ion battery system is successfully overcome by developing a stable, high-performing NHC system.

Development of cathode materials for lithium battery application like electric vehicle (EV) and plug-in hybrid electric vehicle (PHEV) requires high capacity materials[1]. At the same time, cost, environmental concerns and safety issues cannot be excluded. Recently, lithium transition-metal silicates such as Li2MSiO4 (M=Fe, Mn and Co) have been extensively studied as cathode materials for lithium ion batteries, due to high theoretical capacity and better thermal stability than lithium transition metal oxides such as LiCoO2. Among them, Li2MnSiO4 cathode could be a better choice as a high capacity( ~330 mAh/g) cathode for lithium ion batteries than Li2FeSiO4 cathode material. Due to Mn2+/Mn3+ and Mn3+/Mn4+ redox couples, extraction of two lithium ions can be achieved from Li2MnSiO4. However, due to defects such as structure change after the first charge and low electronic conductivity(~ < 10-14S/cm), this material has poor cycle performance and lower capacity than the theoretical prediction [2-3]. In this regard, the current work is aimed on the improvement of capacity and cycle stability of Li2MnSiO4 cathode active material by applying Cu doping and poly-aniline composites. The Li2Mn0.95Cu0.05SiO4were prepared using the sol-gel synthesis. PANI was synthesized by oxidative polymerization. XRD patterns as shown in Figure 1 exhibit that the Cu doping and PANI composite does not contribute to structure change of Li2MnSiO4. From the cycle performances as shown in Figure 2, the Li2Mn0.95Cu0.05SiO4/PANI cell shows a high discharge capacity, as well as improved cycle retention compared with pristine Li2MnSiO4 material. Synthesis methodology of Li2Mn0.95Cu0.05SiO4/PANI materials along with their physical, morphological and electrochemical characteristics will be discussed in detail. References : [1] R.J. Gummow, N.Sharma, V.K.Peterson, Y.He, J. solid state chem., 188 (2012) 32–37. [2] R. Dominko, M. Bele, A. Kokalj, M. Gaberscek, J. Jamnik , J. Power Sources., 174 (2007) 457–461. [3] D. M. Kempaiah, D. Rangappa, I. Honma, Chem. Commun.,48 (2012) 2698–2700.