A protocol for gradient coating design zinc anodes for stable zinc ion batteries.

In this protocol, we present a modified gradient coating strategy for zinc anodes. We describe steps for synthesizing electrodes, measuring electrochemistry, and assembling and testing batteries. The protocol can be applied for broadening design ideas of functional interface coating. For complete details on the use and execution of this protocol, please refer to Chen et al. (2023).1.

Co-Doping of Al3+ and Ti4+ and Electrochemical Properties of LiNiO2 Cathode Materials for Lithium-Ion Batteries.

LiNiO2 cathode material for lithium-ion batteries has the advantages of high specific capacity, abundant resources, and low cost, but it suffers from difficulties in preparation, structural instability, and serious capacity decay. In this work, highly pure and layered structural LiNi0.95 Ala Ti0.05-a O2 (a=0, 0.025, 0.05) cathode materials were synthesized by a simply sol-gel method. The cation mixing of Ni2+ and Li+ , structural deterioration, irreversible conversion between H2 and H3 phases and unstable surface and CEI (Cathode-electrolyte interface) film can be effectively suppressed by co-doping with Al3+ and Ti4+ . A preferred LiNi0.95 Al0.025 Ti0.025 O2 sample provides a discharge specific capacity of 223 mAh g-1 at 0.1 C and 148.32 mAh g-1 at 5 C, a capacity retention of 72.7 % after 300 cycles at 1 C and a Li+ diffusion coefficient of about 2.0×10-9 cm2 s-1 .

Filling Selenium into Sulfur Vacancies in Ultrathin Tungsten Sulfide Nanosheets for Superior Potassium Storage.

The development of WS2 as an anode for potassium-ion batteries (PIBs) is severely confined by the low K+ storage capacity and poor intrinsic electrical conductivity. Our previous study demonstrated that the creation of sulfur vacancies (VS) in WS2 can enhance its K+ storage capability. However, it is a big challenge to keep the stability of VS while reserving the excellent activity. Herein, we design Se-filled WS2 nanosheets with VS (VS-WS2-Se NS) for PIBs. The Se heteroatom filling into the VS can not only stabilize and activate them, rendering more active sites to adsorb K+, but also further enhance the electrical conductivity. Consequently, the VS-WS2-Se NS anode presents significantly promoted storage capacity and reaction kinetics, superior to the pristine WS2 and WS2 with only VS. Remarkably, the VS-WS2-Se NS anode exhibits the highest specific capacity of 363.9 mA h g-1 at 0.05 A g-1. Simultaneously, a high reversible capacity of 144.2 mA h g-1 after 100 cycles at 2.0 A g-1 is shown. Ex situ analyses demonstrated that the potassium storage mechanism involves the intercalation and conversion reaction between WS2 and K+. Moreover, DFT calculations revealed that the Se filling into VS can further enhance the electrical conductivity and reduce the K-insertion energy barriers of WS2 and thus account for the outstanding electrochemical performance. This study demonstrates that engineering the vacancies by the heteroatom filling strategy offers a novel and feasible route for designing high-performance electrode materials in various energy-storage systems.

Mesoporous vanadium nitride as anion storage electrode for reverse dual-ion hybrid supercapacitor.

In traditional dual-ion systems, the cathode usually is employed as anion-storage materials. Herein, we propose a new dual-ion hybrid supercapacitor with reverse anion/cation-storage mechanism, consisting of a mesoporous (MPs) VN anode as a pivotal anion-storage material and K2-xMn8O16 nanosheet arrays grown on carbon cloth (NSs/CC) as (K-storage) cathode. During charge/discharge, the anode and cathode reversibly store/release OH- ions and K+ ions, respectively. Herein, the MPs VN as anion-storage electrode can operate in an alkaline condition and deliver a high capacitance of 251 mF cm-2 with desired low-voltage plateau. More importantly, benefiting from unique reverse dual-ion mechanism, the (MPs VN-K2-xMn8O16 NSs/CC) hybrid device displays excellent rate performance and satisfying area capacitance along with good durability of 92.2% after 10,000 cycles at a scan rate of 100 mV s-1. It offers new ideas to expand the range of anion-storage materials in dual-ion hybrid supercapacitors.

Multifunctional integrated VN/V2O5 heterostructure sulfur hosts for advanced lithium-sulfur batteries.

Lithium-sulfur (Li-S) batteries show great potential in future electric transportation and large-scale grid storage applications because of their attractive theoretical energy density (2600 W h kg-1) and relatively abundant sulfur reserves. However, the rapid capacity decay and unsatisfactory sulfur loading caused by the lithium polysulphide (LiPS) dissolution and low electrical conductivity of sulfur are the most urgent issues plaguing its practical applications. Herein, we report a multifunctional nanoporous (NP) VN/V2O5 binary host that can efficiently resolve the above conflicts by the synergy between the functions of two materials. The inner V2O5 facilitates rapid trapping of numerous LiPSs while the outer porous VN with abundant NP channels offers high conductivity and mild chemisorption, thereby improving the localization and catalytic conversion ability of LiPSs. Accordingly, the designed cathodes with 1.87 mg cm-2 sulfur content achieve an acceptable areal specific capacity (2.72 mA h cm-2), excellent rate capability (963 mA h g-1 at 5.0C), and cycling stability. Remarkably, the cathodes with ultrahigh sulfur loading of 9.02 mg cm-2 deliver a satisfactory areal specific capacity (12.12 mA h cm-2) and still maintain excellent durability.

A new potassium dual-ion hybrid supercapacitor based on battery-type Ni(OH)2 nanotube arrays and pseudocapacitor-type V2O5-anchored carbon nanotubes electrodes.

Hybrid supercapacitors (HSCs) with the characteristics of high energy density, long cycle life and without altering their power density need to be developed urgently. Herein, a novel dual-ion hybrid supercapacitors (DHSCs) with Ni(OH)2 nanotube arrays (NTAs) as positive electrode and V2O5 directly grown on freestanding carbon nanotubes (CNTs) as negative electrode is assembled. In charging mechanism of DHSCs, K+ are inserted into the V2O5 negative while OH- react with Ni(OH)2 positive; during discharge, the K+ and OH- are released from V2O5 negative and Ni(OH)2 positive, respectively, and return back to the electrolyte, which is quite different from traditional metal ion or alkaline supercapacitors. Because of the merits combining dual-ion mechanism and HSCs, the DHSC displays excellent capacity retention of âˆ¼ 81.4% after 10,000 cycles, high energy density of âˆ¼ 25.4 µWh cm-2 and high power density of âˆ¼ 4.66 mW cm-2, indicating the potential applications in the further on flexible wearable electronics.

Semi-coherent cation-rich Mn-Cu oxides heterostructures as cathode for novel aqueous potassium dual-ion energy storage devices.

In this work, combining both advantages of aqueous energy storage systems (ESS) and conventional dual-ion ESS, a novel aqueous dual-ion ESS is developed based on K+ and OH- electrochemistry by employing semi-coherent K1.33Mn8O16-CuO (sc-Mn-Cu) cathode. Profting from the elaborate design, the electrolyte and cathode simultaneously act as source of cations. In the novel aqueous dual-ion ESS configuration, the dependence of the performance on the electrolyte salt concentration is reduced and the sc-Mn-Cu cathode can host OH- with lower working potentials by conversion mechanism. Furthermore, based on the sc-Mn-Cu cathode and freestanding V2O3-VC (fs-V2O3-VC) anode, we developed a flexible quasi-solid-state device. Remarkably, it exhibits an ultrahigh energy density of ~39.9 µW h cm-2 together with high power density of carbon-based devices, which outperforms most previously reported flexible storage devices to our knowledge. These results indicating that the unique mechanism of the sc-Mn-Cu cathode opens up a promising direction for low-cost and high-performance novel aqueous ESS.

Novel 3D Nanoporous Zn-Cu Alloy as Long-Life Anode toward High-Voltage Double Electrolyte Aqueous Zinc-Ion Batteries.

The recharge ability of zinc metal-based aqueous batteries is greatly limited by the zinc anode. The poor cycling durability of Zn anodes is attributed to the dendrite growth, shape change and passivation, but this issue has been ignored by using an excessive amount of Zn in the past. Herein, a 3D nanoporous (3D NP) Zn-Cu alloy is fabricated by a sample electrochemical-assisted annealing thermal method combined, which can be used directly as self-supported electrodes applied for renewable zinc-ion devices. The 3D NP architectures electrode offers high electron and ion transport paths and increased material loading per unit substrate area, which can uniformly deposit/strip Zn and improve charge storage ability. Benefiting from the intrinsic materials and architectures features, the 3D NP Zn-Cu alloy anode exhibits high areal capacity and excellent cycling stability. Further, the fabricated high-voltage double electrolyte aqueous Zn-Br2 battery can deliver maximum areal specific capacity of ≈1.56 mAh cm-2 , which is close to the level of typical commercial Li-ion batteries. The excellent performance makes it an ideal candidate for next-generation aqueous zinc-ion batteries.

Extraordinary pseudocapacitive energy storage triggered by phase transformation in hierarchical vanadium oxides.

Pseudocapacitance holds great promise for improving energy densities of electrochemical supercapacitors, but state-of-the-art pseudocapacitive materials show capacitances far below their theoretical values and deliver much lower levels of electrical power than carbon-based materials due to poor cation accessibility and/or long-range electron transferability. Here we show that in situ corundum-to-rutile phase transformation in electron-correlated vanadium sesquioxide can yield nonstoichiometric rutile vanadium dioxide layers that are composed of highly sodium ion accessible oxygen-deficiency quasi-hexagonal tunnels sandwiched between conductive rutile slabs. This unique structure serves to boost redox and intercalation kinetics for extraordinary pseudocapacitive energy storage in hierarchical isomeric vanadium oxides, leading to a high specific capacitance of ~1856 F g-1 (almost sixfold that of the pristine vanadium sesquioxide and dioxide) and a bipolar charge/discharge capability at ultrafast rates in aqueous electrolyte. Symmetric wide voltage window pseudocapacitors of vanadium oxides deliver a power density of ~280 W cm-3 together with an exceptionally high volumetric energy density of ~110 mWh cm-3 as well as long-term cycling stability.

Ultrahigh-Power Pseudocapacitors Based on Ordered Porous Heterostructures of Electron-Correlated Oxides.

Nanostructured transition-metal oxides can store high-density energy in fast surface redox reactions, but their poor conductivity causes remarkable reductions in the energy storage of most pseudocapacitors at high power delivery (fast charge/discharge rates). Here it is shown that electron-correlated oxide hybrid electrodes made of nanocrystalline vanadium sesquioxide and manganese dioxide with 3D and bicontinuous nanoporous architecture (NP V2O3/MnO2) have enhanced conductivity because of metallization of electron-correlated V2O3 skeleton via insulator-to-metal transition. The conductive V2O3 skeleton at ambient temperature enables fast electron and ion transports in the entire electrode and facilitates charge transfer at abundant V2O3/MnO2 interface. These merits significantly improve the pseudocapacitive behavior and rate capability of the constituent MnO2. Symmetric pseudocapacitors assembled with binder-free NP V2O3/MnO2 electrodes deliver ultrahigh electrical powers (up to ≈422 W cm23) while maintaining the high volumetric energy of thin-film lithium battery with excellent stability.