Investigation of LiOH decomposition in nonaqueous electrolytes not only expands the fundamental understanding of four-electron oxygen evolution reactions in aprotic media but also is crucial to the ...development of high-performance lithium-air batteries involving the formation/decomposition of LiOH. In this work, we have shown that the decomposition of LiOH by ruthenium metal catalysts in a wet DMSO electrolyte occurs at the catalyst-electrolyte interface, initiated via a potential-triggered dissolution/reprecipitation process. The
UV-vis methodology devised herein provides direct experimental evidence that the hydroxyl radical is a common reaction intermediate formed in several nonaqueous electrolytes; this method is applicable to study other battery systems. Our results highlight that the reactivity of the hydroxyl radical toward nonaqueous electrolyte represents a major factor limiting O
evolution during LiOH decomposition. Coupling catalysts restraining hydroxyl reactivity with electrolytes more resistant to hydroxyl radical attack could help improve the reversibility of this reaction.
Transition‐metal selenides are considered as one of the promising anode materials for potassium ion batteries (PIBs) due to their high theoretical capacities. However, addressing the issue of ...irreversibility caused by the large volume changes during potassiation/depotassiation, especially at high rates, remains a major challenge. This challenge is tackled by constructing nickel‐iron selenide (NFS) with a unique hierarchically porous donut‐like morphology using a simple template‐free solvothermal strategy. With the bimetallic strategy and well‐designed architecture, the donut‐like NFS displays outstanding potassium storage performance, exhibiting a high reversible capacity (458 mAh g−1 even after 100 cycles at a slow rate of 0.1 A g−1), an impressive rate capability up to 10 A g−1 (≈10 mA cm−2), and an excellent capacity retention over 1000 cycles at 2 A g−1. By combining theoretical and experimental techniques, a two‐stage intercalation‐conversion reaction mechanism is put forward. This work provides an effective approach to develop bimetallic selenides electrode materials for applications in PIBs and potentially for other energy storage devices.
In order to control volume expansion of metal selenide during potassiation/depotassiation and improve their performance, donut‐like NFS are synthesized by using a template‐free strategy. The as synthesized donut‐like NFS electrode displays superior rate performance, which opens up a new way for the rational design of anode materials.
Abstract Transition‐metal selenides are considered as one of the promising anode materials for potassium ion batteries (PIBs) due to their high theoretical capacities. However, addressing the issue ...of irreversibility caused by the large volume changes during potassiation/depotassiation, especially at high rates, remains a major challenge. This challenge is tackled by constructing nickel‐iron selenide (NFS) with a unique hierarchically porous donut‐like morphology using a simple template‐free solvothermal strategy. With the bimetallic strategy and well‐designed architecture, the donut‐like NFS displays outstanding potassium storage performance, exhibiting a high reversible capacity (458 mAh g −1 even after 100 cycles at a slow rate of 0.1 A g −1 ), an impressive rate capability up to 10 A g −1 (≈10 mA cm −2 ), and an excellent capacity retention over 1000 cycles at 2 A g −1 . By combining theoretical and experimental techniques, a two‐stage intercalation‐conversion reaction mechanism is put forward. This work provides an effective approach to develop bimetallic selenides electrode materials for applications in PIBs and potentially for other energy storage devices.
Potassium-doped Na3V2(PO4)2F3@CNT(NVPF@CNT) is employed as a promising cathode for sodium-ion batteries via a simple sol-gel method in order to improve the intrinsic electronic conductivity and ion ...diffusion rate. The effects of K substitution on the crystal structure and electrochemical performance of NVPF are discussed. It is found that by introducing a moderate amount of K to replace the Na sites in the NVPF crystal structure, the ion diffusion path is effectively broadened, so the electrochemical performance is greatly improved. Excellent cyclic performance with a high specific capacity of 120 mAh g−1 is achieved at a low rate of 1C. After 1600 cycles at a discharge rate of 10C, the discharge capacity can still achieve values higher than 90 mAh g−1. Even at a high rate of 50C, the capacity retention ofNKVPF@CNTcould still remain as high as 90% after nearly 6000 cycles. In order to obtain a better understanding of the relationship between the ion doping and kinetic properties, a Rietveld refinement analysis and Randles-Sevcik equation-based theory are proposed in this research. This is the first time that potassium ion substitution has been used to improve the performance of NVPF and is proved to be an effective way to modify the lattice structure. Such work aids in the progression of sodium-based batteries.
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•Potassium-doped Na3V2(PO4)2F3@CNT is prepared as a high voltage cathode.•Na+ diffusion path is effectively broadened by K+ doping.•Excellent cyclic performance with a high specific capacity is achieved.•Simulation and experiment are combined to expound a new strategy for modification of electrode materials.
Na4Fe3(PO4)2P2O7 is considered to be a practical cathode material due to the wide source and low price of raw materials. However, the inherent isolation properties of the PO43− group result in low ...electronic conductivity and, subsequently, a low discharge capacity and poor cycling stability. Herein, polyvinylpyrrolidone assisted electrospinning method is used to synthesize Na4Fe3(PO4)2P2O7 nanoparticles embedded in carbon nanoribbons. The network structure of active materials wrapped in crosslinked carbon nanoribbons not only enables the ultra-fast transfer of electrons on the three-dimensional “highway” between the nanoparticles but also inhibits the aggregation of nanoparticles. These nanoribbons exhibit remarkable electrochemical performance, resulting from their exceptional electronic and ionic conductivity: high capacity of 128.6 mAh g−1 at 0.1C (1 C = 128.9 mAh g−1), extra-high rate capability (61.2 mAh g−1 at 50 C), and ultra-long cycle (72% capacity retention after 5000 cycles at 50 C). Meanwhile, Na4Fe3(PO4)2P2O7 nanoribbon also shows excellent low temperature properties. At −15 °C, the nanoribbon delivers 84.5 mAh g−1 of discharge capacity at 0.05C and displays long-term cycle performance (80.8% capacity retention after 700 cycles at 0.5C). Therefore, the Na4Fe3(PO4)2P2O7 nanoribbon with excellent electrochemical performance can be considered an attractive cathode electrode for the commercialization of sodium-ion battery.
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•Ultra-small Na4Fe3(PO4)2(P2O7) embedded in carbon nanoribbons is synthesized.•Ultra-small nanoparticles and thin nanoribbons enhance the reaction kinetics.•The nanoribbons can supply 3D electronic “superhighways".•The nanoribbons supply fast charge-discharge capability and ultra-long cycle life.•The electrode has strong resistance to low and variable temperatures.
The Mn-based mixed polyanion is expected to be a promising cathode material for sodium-ion batteries applied to large-scale smart grid energy storage systems due to its stable three-dimensional ...crystal structure, low cost, and high energy density. Herein, a novel carbon nanotube (CNT)-modified mixed-polyanion material (Na4Mn2Co(PO4)2P2O7) with a high voltage of 3.86 V is synthesized by a facile spray-drying method. The well-designed Na4Mn2Co(PO4)2P2O7/C-CNTs microsphere has excellent electronic and ionic conductivity by virtue of the carbon nanotube conductive skeleton. The as-prepared Na4Mn2Co(PO4)2P2O7/C-CNTs composite exhibits a reversible initial discharge capacity of 96.1 mA h g–1 and an energy density of 371 Wh kg–1 at 0.1 C. Furthermore, Na4Mn2Co(PO4)2P2O7/C-CNTs and hard carbon are assembled into a full battery, which delivers an initial discharge capacity of 88.8 mA h g–1, a working voltage of 3.85 V, and a promising energy density of 249.9 Wh kg–1 at 0.1 C. Therefore, the outstanding performance makes the Na4Mn2Co(PO4)2P2O7/C-CNTs material a potential candidate for large-scale applications of sodium-ion batteries.
Symmetric sodium ion full batteries with high energy density are expected to become promising storage devices. Na7V4(P2O7)4(PO4)/C can be assembled into a high energy density symmetric full battery ...due to 3.85 V operating voltage as a cathode and 0.94 V operating voltage as an anode. Here, the as-prepared Na7V4(P2O7)4(PO4)/C-GA (graphene aerogel) displays excellent electrochemical behavior as both cathode and anode. As the cathode, it can deliver a reversible capacity of 91.4 mA h g−1 at 1C (1C = 92.8 mA h g−1) and even shows 74 mA h g−1 capacity at 100C. Meanwhile, an ultra-long cycling property is obtained (77.2% capacity retention after 5000 cycles at 20C). As the anode, it can output 92.4 mA h g−1 at 25 mA g−1 and has a 79.2% capacity retention after 300 cycles at 50 mA g−1. Interestingly, the symmetric full battery assembled with NVPP/C-GA outputs an initial 81.9 mA h g−1 capacity, a high 2.84 V working voltage, and 232.6 Wh kg−1 energy density at 25 mA g−1. Therefore, our work shows potential application prospects of the symmetric full battery with Na7V4(P2O7)4(PO4)/C-GA in energy storage systems.
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•The Na7V4(P2O7)4(PO4)/C-GA has high ion diffusion coefficients (DNa+).•The 3D GA framework can improve the electronic conductivity of material.•The Na7V4(P2O7)4(PO4)/C-GA as cathode and anode shows excellent performance.•The symmetric sodium-ion full battery outputs high energy density.
Na2+2xFe2-x (SO4)3 is considered a promising cathode material for advanced sodium ion batteries with higher energy density due to its advantage of high-voltage, earth-abundant elements material and ...low-cost. However, strongly impeded by its fatal environmental sensitivity and low electronic conductivity, the NFS usually shows unsatisfactory electrochemical performance. Herein, a facile synthesis of microspherical NFS@reduced graphene oxide composites are synthesized through spray-drying method. The well-designed microspherical NFS@rGO with confined NFS nanocrystal in the three-dimensional graphene framework exhibits superb electronic and ionic conductivity as well as structural stability. The NFS@rGO composites show outstanding electrochemical properties: high sodium storage capacity (99 mAh g−1 at 0.1 C), superior rate performance (78 mAh g−1 at 60 C and even up to 72 mAh g−1 at 80 C), ultralong cycling stability (80.8% capacity retention after 2000 cycles at 30 C). The excellent performance makes the NFS@rGO material a prospective electrode candidate for large-scale SIBs.
Investigation of LiOH decomposition in nonaqueous electrolytes not only expands the fundamental understanding of four-electron oxygen evolution reactions in aprotic media but also is crucial to the ...development of high-performance lithium–air batteries involving the formation/decomposition of LiOH. In this work, we have shown that the decomposition of LiOH by ruthenium metal catalysts in a wet DMSO electrolyte occurs at the catalyst–electrolyte interface, initiated via a potential-triggered dissolution/reprecipitation process. The in situ UV–vis methodology devised herein provides direct experimental evidence that the hydroxyl radical is a common reaction intermediate formed in several nonaqueous electrolytes; this method is applicable to study other battery systems. Our results highlight that the reactivity of the hydroxyl radical toward nonaqueous electrolyte represents a major factor limiting O2 evolution during LiOH decomposition. Coupling catalysts restraining hydroxyl reactivity with electrolytes more resistant to hydroxyl radical attack could help improve the reversibility of this reaction.
Geopolitical conflicts, trade barriers, and other factors pose great risks to the stable supply of bulk commodities; however, cross-country and inter-temporal assessments and comparisons of various ...bulk commodity supply risks from the physical trade perspective are still lacking. This gap hinders a holistic understanding of global resource security and further appropriate policy formulation. Based on the Net Positive Import share, the Worldwide Governance Indicator (WGI), and the Bilateral Relationship Indicator which was innovatively quantified using the Global Database of Events, Language, and Tone (GDELT) this study evaluated 32 bulk commodity supply risks (including agricultural products, metals, and energy fuels) in China, Japan, and the USA for the period 1992–2019. We found that the three countries have experienced different supply risk evolutions related to their diverse domestic resource endowments and socioeconomic developmental stages. During the study period, China had increasing supply risks for 20 of the 32 bulk commodities compared to 10 for Japan and the USA. The overall bulk commodity supply risk increased substantially for China, remained high for Japan, and remained relatively low for the USA. Under increasing global trade system uncertainty, in addition to the supply diversification strategy, we advise net importer countries to utilise news media data such as GDELT to monitor and analyse geopolitical changes, especially for major suppliers, which would help improve resilience to supply disruptions.
•We assessed and compared 32 bulk commodity supply risks in China, Japan, and the USA for the period 1992–2019.•The Global Database of Events, Language, and Tone (GDELT) was used to quantify the bilateral relationship directly, which affects the supply risk.•The three countries have experienced different supply risk evolutions related to their diverse domestic resource endowments and socioeconomic developmental stages.•The overall bulk commodity supply risk increased substantially for China, remained high for Japan, and remained relatively low for the USA.•The GDELT provides an effective approach to monitoring geopolitical change, which helps improve the resilience to supply disruption.
