Improved Electrochemical Performance of NASICON Type Na3V2-xCox(PO4)3/C (x = 0-0.15) Cathode for High Rate and Stable Sodium-Ion Batteries.

In recent years, the Na-ion SuperIonic CONductor (NASICON) based polyanionics are considered pertinent cathode materials in sodium-ion batteries due to their 3D open framework, which can accommodate a wide range of Na content and can offer high ionic conductivity with great structural stability. However, owing to the inferior electronic conductivity, these materials suffer from unappealing rate capability and cyclic stability for practical applications. Therefore, in this work we investigate the effect of Co substitution at the V site on the electrochemical performance and diffusion kinetics of Na3V2-xCox(PO4)3/C (x = 0-0.15) cathodes. All the samples are characterized through Rietveld refinement of the X-ray diffraction patterns, Raman spectroscopy, transmission electron microscopy, etc. We demonstrate improved electrochemical performance for the x = 0.05 electrode with a reversible capacity of 105 mAh g-1 at 0.1 C. Interestingly, the specific capacity of 80 mAh g-1 is achieved at 10 C with retention of about 92% after 500 cycles and 79.5% after 1500 cycles and having nearly 100% Coulombic efficiency. The extracted diffusion coefficient values through the galvanostatic intermittent titration technique and cyclic voltammetry are found to be in the range of 10-9 to 10-11 cm2 s-1. The post-mortem studies show excellent structural and morphological stability after testing for 500 cycles at 10 C. Our study reveals the role of optimal dopant of Co3+ ions at the V site in improving the cyclic stability at a high current rate.

Salt-Assisted Recovery of Sodium Metal Anodes for High-Rate Capability Sodium Batteries.

Rechargeable sodium metal batteries are considered to be one of the most promising high energy density and cost-effective electrochemical energy storage systems. However, their practicality is constrained by the high reactivity of sodium metal anodes that readily brings about excessive accumulation of inactive Na species on the surface, either by chemical reactions with oxygen and moisture during electrode handling or through electrochemical processes with electrolytes during battery operation. Herein, this paper reports on an alkali, salt-assisted, assembly-polymerization strategy to recover Na activity and to reinforce the solid-electrolyte interphase (SEI) of sodium metal anodes. To achieve this, an alkali-reactive coupling agent 3-glycidoxypropyltrimethoxysilane (GPTMS) is applied to convert inactive Na species into Si-O-Na coordination with a self-assembly GPTMS layer that consists of inner O-Si-O networks and outer hydrophobic epoxides. As a result, the electrochemical activity of Na metal anodes can be fully recovered and the robust GPTMS-derived SEI layer ensures high capacity and long-term cycling under an ultrahigh rate of 30 C (93.1 mAh g-1, 94.8% after 3000 cycles). This novel process provides surface engineering clues on designing high power density and cost-effective alkaline metal batteries.

Direct oral anticoagulants for stroke prevention in patients with device-detected atrial fibrillation: assessing net clinical benefit.

Subclinical, device-detected atrial fibrillation (AF) is frequently recorded by pacemakers and other implanted cardiac rhythm devices. Patients with device-detected AF have an elevated risk of stroke, but a lower risk of stroke than similar patients with clinical AF captured with surface electrocardiogram. Two randomized clinical trials (NOAH-AFNET 6 and ARTESiA) have tested a direct oral anticoagulant (DOAC) against aspirin or placebo. A study-level meta-analysis of the two trials found that treatment with a DOAC resulted in a 32% reduction in ischaemic stroke and a 62% increase in major bleeding; the results of the two trials were consistent. The annualized rate of stroke in the control arms was ∼1%. Several factors point towards overall net benefit from DOAC treatment for patients with device-detected AF. Strokes in ARTESiA were frequently fatal or disabling and bleeds were rarely lethal. The higher absolute rates of major bleeding compared with ischaemic stroke while on treatment with a DOAC in the two trials are consistent with the ratio of bleeds to strokes seen in the pivotal DOAC vs. warfarin trials in patients with clinical AF. Prior research has concluded that patients place a higher emphasis on stroke prevention than on bleeding. Further research is needed to identify the characteristics that will help identify patients with device-detected AF who will receive the greatest benefit from DOAC treatment.

Extending the π-Conjugation of A Donor-Acceptor Covalent Organic Framework for High-Rate and High-Capacity Lithium-Ion Batteries.

Realizing high-rate and high-capacity features of Lihium-organic batteries is essential for their practical use but remains a big challenge, which is due to the instrinsic poor conductivity, limited redox kinetics and low utility of organic electrode mateials. This work presents a well-designed donor-acceptor Covalent Organic Framework (COFs) with extended conjugation, mesoscale porosity, and dual redox-active centers to promote fast charge transfer and multi-electron processes. As anticipated, the prepared cathode with benzo [1,2-b:3,4-b':5,6-b''] trithiophene (BTT) as p-type and pyrene-4,5,9,10-tetraone (PTO) as n-type material (BTT-PTO-COF) delivers impressive specific capacity (218 mAh g-1 and 275 mAh g-1 at 0.2 A g-1 in ether-based and carbonate-based electrolyte respectively) and outstanding rate capability (79 mAh g-1 at 50 A g-1 in ether-based electrolyte and 124 mAh g-1 at 10 A g-1 in carbonate-based electrolyte). Moreover, the potential of BTT-PTO-COF electrode for prototype batteries has been demonstrated by full cells of dual-ion batteries, which attain comparable electrochemical performances to the half cells. Moreover, mechanism studies combining ex-situ characterization and theoratical calculations reveal the efficient dual-ion storage process and facile charge transfer of BTT-PTO-COF. This work not only expands the diversity of redox-active COFs but also provide concept of structure design for high-rate and high-capacity organic electrodes.

Enhancing Reversibility and Kinetics of Anionic Redox in O3-NaLi1/3Mn2/3O2 through Controlled P2 Intergrowth.

Anionic redox chemistry can surpass theoretical limits of conventional layered oxide cathodes in energy density. A recent model system of sodium-ion batteries, O3-NaLi1/3Mn2/3O2, demonstrated full anionic redox capacity but is limited in reversibility and kinetics due to irreversible structural rearrangement and oxygen loss. Solutions to these issues are missing due to the challenging synthesis. Here, we harness the unique structural richness of sodium layered oxides and realize a controlled ratio of P2 structural intergrowth in this model compound with the overall composition maintained. The resulted O3 with 27% P2 intergrowth structure delivers an excellent initial Coulombic efficiency of 87%, comparable to the state-of-the-art Li-rich NMCs. This improvement is attributed to the effective suppression of irreversible oxygen release and structural changes, evidenced by operando Differential Electrochemical Mass Spectroscopy and X-ray Diffraction. The as-prepared intergrowth material, based on the environmentally benign Mn, exhibits a reversible capacity of 226 mAh g-1 at C/20 rate with excellent cycling stability stemming from the redox reactions of oxygen and manganese. Our work isolates the role of P2 structural intergrowth and thereby introduces a novel strategy to enhance the reversibility and kinetics of anionic redox reactions in sodium layered cathodes without compromising capacity.

PVA-assisted spray deposited porous Li4Ti5O12 thin film as high-rate and long-cycle anode for lithium-ion thin-film batteries.

Spinel Li4Ti5O12 (LTO), a zero-strain material, is a promising anode material for solid-state thin-film lithium-ion batteries (TFB). However, the preparation of high-performance Li4Ti5O12 thin-film electrodes through facile methods remains a significant challenge. Herein, we present a novel approach to prepare a binder- and conductor-free porous Li4Ti5O12 (P-LTO) thin-film. This approach polyvinyl alcohol (PVA)-assisted spray deposition and does not require the use of complex or expensive methods. Adding PVA to the precursor solution effectively prevents thin-film cracking during high-temperature annealing, enhances adhesion, and forms a highly interconnected porous structure. This unique structure shortens the lithium-ion diffusion pathways and facilitates electron transport. Therefore, P-LTO thin film electrodes demonstrate exceptional rate capacity of 104.1 mAh/g at a current density of 100C. In addition, the electrodes exhibit ultra-long cycle stability, retaining 80.9 % capacity after 10,000 cycles at 10C. This work offers a novel approach for the preparation of high-performance thin-film electrodes for TFBs.

In-situ biological biogas upgrading using upflow anaerobic polyfoam bioreactor: Operational and biological aspects.

A high rate upflow anaerobic polyfoam-based bioreactor (UAPB) was developed for lab-scale in-situ biogas upgrading by H2 injection. The reactor, with a volume of 440 mL, was fed with synthetic wastewater at an organic loading rate (OLR) of 3.5 g COD/L·day and a hydraulic retention time (HRT) of 7.33 h. The use of a porous diffuser, alongside high gas recirculation, led to a higher H2 liquid mass transfer, and subsequently to a better uptake for high CH4 content of 56% (starting from 26%). Our attempts to optimize both operational parameters (H2 flow rate and gas recirculation ratio, which is the total flow rate of recirculated gas over the total outlet of gas flow rate) were not initially successful, however, at a very high recirculation ratio (32) and flow rate (54 mL/h), a significant improvement of the hydrogen consumption was achieved. These operational conditions have in turn driven the methanogenic community toward the dominance of Methanosaetaceae, which out-competed Methanosarcinaceae. Nevertheless, highly stable methane production rates of 1.4-1.9 L CH4/Lreactor.day were observed despite the methanogenic turnover. During the different applied operational conditions, the bacterial community was especially impacted, resulting in substantial shifts of taxonomic groups. Notably, Aeromonadaceae was the only bacterial group positively correlated with increasing hydrogen consumption rates. The capacity of Aeromonadaceae to extracellularly donate electrons suggests that direct interspecies electron transfer (DIET) enhanced biogas upgrading. Overall, the proposed innovative biological in-situ biogas upgrading technology using the UAPB configuration shows promising results for stable, simple, and effective biological biogas upgrading.

Ultrafast Dual-Shock Chemistry Synthesis of Ordered/Disordered Hybrid Carbon Anodes: High-Rate Performance of Li-Ion Batteries.

Graphite exhibits crystal anisotropy, which impedes the mass transfer of ion intercalation and extraction processes in Li-ion batteries. Herein, a dual-shock chemical strategy has been developed to synthesize the carbon anode. This approach comprised two key phases: (1) a thermal shock utilizing ultrahigh temperature (3228 K) can thermodynamically facilitate graphitization; (2) a mechanical shock (21.64 MPa) disrupting the π-π interactions in the aromatic chains of carbon can result in hybrid-structured carbon composed of crystalline and amorphous carbon. The optimized carbon (DSC-200-0.3) demonstrates a capacity of 208.61 mAh/g at a 10C rate, with a significant enhancement comparing with 15 mAh/g of the original graphite. Impressively, it maintains 81.06% capacity even after 3000 charge-discharge cycles. Dynamic process analysis reveals that this superior rate performance is attributed to a larger interlayer spacing facilitating ion transport comparing with the original graphite, disordered amorphous carbon for additional lithium storage sites, and crystallized carbon for enhanced charge transfer. The dual-shock chemical approach offers a cost-effective and efficient method to rapidly produce hybrid-structured carbon anodes, enabling 10C fast charging capabilities in lithium-ion batteries.

Outcomes of Device-detected Atrial High-rate Episodes in Patients with No Prior History of Atrial Fibrillation: A Systematic Review and Meta-analysis.

Background: Outcomes of device-detected AF remain unclear in individuals without a prior history of AF. Methods: A meta-analysis was conducted to evaluate outcomes in individuals with no prior history of AF who experienced device-detected AF. Outcomes assessed were clinical AF, thromboembolism and all-cause mortality. A fixed-effects model was used to calculate RRs with 95% CI. Results: Compared to individuals who did not experience device-detected AF, those who did had increased risks of clinical AF (RR 3.33, 95% CI [1.99.5.57]; p<0.0001) and thromboembolic events (RR 2.21; 95% CI [1.72.2.85]; p<0.0001). The risk of all-cause mortality was similar between both groups (RR 1.19; 95% CI [0.95.1.49]; p=0.13). Subgroup analysis revealed an increased risk of thromboembolic events among device-detected AF .24 hours (RR 12.34; 95% CI [2.70.56.36]). Conclusion: While there is an increased risk of clinical AF and thromboembolism in individuals with device-detected AF, mortality was insignificant.

Three-dimensional high-aspect-ratio microarray thick electrodes for high-rate hybrid supercapacitors.

Hybrid supercapacitors (HSCs) with facile integration and high process compatibility are considered ideal power sources for portable consumer electronics. However, as a crucial component for storing energy, traditional thin-film electrodes exhibit low energy density. Although increasing the thickness of thin films can enhance the energy density of the electrodes, it gives rise to issues such as poor mechanical stability and long electron/ion transport pathways. Constructing a stable three-dimensional (3D) ordered thick electrode is considered the key to addressing the aforementioned contradictions. In this work, a manufacturing process combining lithography and chemical deposition techniques is developed to produce large-area and high-aspect-ratio 3D nickel ordered cylindrical array (NiOCA) current collectors. Positive electrodes loaded with nickel-cobalt bimetallic hydroxide (NiOCA/NiCo-LDH) are constructed by electrodeposition, and HSCs are assembled with NiOCA/nitrogen-doped porous carbon (NiOCA/NPC) as negative electrodes. The HSCs exhibits 55% capacity retention with the current density ranging from 2 to 50 mA cm-2. Moreover, it maintains 98.2% of the initial capacity after long-term cycling of 15,000 cycles at a current density of 10 mA cm-2. The manufacturing process demonstrates customizability and favorable repeatability. It is anticipated to provide innovative concepts for the large-scale production of 3D microarray thick electrodes for high-performance energy storage system.

Exceptional Rate Performances of Li-Rich Mn-Based Cathodes Enabled by Boron-Based Additives-Driven Self-Optimized Interface.

Li-rich Mn-based cathode material (LRM), as a promising cathode for high energy density lithium batteries, suffers from severe side reactions in conventional lithium hexafluorophosphate (LiPF6)-based carbonate electrolytes, leading to unstable interfaces and poor rate performances. Herein, a boron-based additives-driven self-optimized interface strategy is presented to dissolve low ionic conductivity LiF nanoparticles at the outer cathode electrolyte interface, leading to the optimized interfacial components, as well as the enhanced Li ion migration rate in electrolytes. Being attributed to these superiorities, the LRM||Li battery delivers a high-capacity retention of 92.19% at 1C after 200 cycles and a low voltage decay of 1.08 mV/cycle. This work provides a new perspective on the rational selection of functional additives with an interfacial self-optimized characteristic to achieve a long lifespan LRM with exceptional rate performances.

Pilot-scale microalgae cultivation and wastewater treatment using high-rate ponds: a meta-analysis.

Microalgae cultivation in wastewater has been widely researched under laboratory conditions as per its potential to couple treatment with biomass production. Currently, only a limited number of published articles consider outdoor and long-term microalgae-bacteria cultivations in real wastewater environmental systems. The scope of this work is to describe microalgal cultivation steps towards high-rate algal pond (HRAP) scalability and identify key parameters that play a major role for biomass productivity under outdoor conditions and long-term cultivations. Reviewed pilot-scale HRAP literature is analysed using multivariate analysis to highlight key productivity parameters within environmental and operational factors. Wastewater treatment analysis indicated that HRAP can effectively remove 90% of NH4+, 70% of COD, and 50% of PO43-. Mean reference values of 210 W m-2 for irradiation, 18 °C for temperature, pH of 8.2, and HRT of 7.7 are derived from pilot-scale cultivations. Microalgae biomass productivity at a large scale is governed by solar radiation and NH4+ concentration, which are more important than retention time variations within investigated studies. Hence, selecting the correct type of location and a minimum of 70 mg L-1 of NH4+ in wastewater will have the greatest effect in microalgae productivity. A high nutrient wastewater content increases final biomass concentrations but not necessarily biomass productivity. Pilot-scale growth rates (~ 0.54 day-1) are half those observed in lab experiments, indicating a scaling-up bottleneck. Microalgae cultivation in wastewater enables a circular bioeconomy framework by unlocking microalgal biomass for the delivery of an array of products.

Dynamic pH regulation drives Nitrosomonas for high-rate stable acidic partial nitritation.

How to intensify the ammonia oxidation rate (AOR) is still a bottleneck impeding the technology development for the innovative acidic partial nitritation because the eosinophilic ammonia-oxidizing bacteria (AOB), such as Nitrosoglobus or Nitrosospira, were inhibited by the high-level free nitrous acid (FNA) accumulation in acidic environments. In this study, an innovative approach of dynamic acidic pH regulation control strategy was proposed to realize high-rate acidic partial nitritation driven by common AOB genus Nitrosomonas. The acidic partial nitrification process was carried out in a laboratory-scale sequencing batch moving bed biofilm reactor (SBMBBR) for long-term (700 days) to track the effect of dynamic acidic pH on nitrifying bacterial activity. The results indicated that the influent NH4+-N concentration was about 100 mg/L, the nitrite accumulation ratio was exceeding 90%, and the maximum AOR can reach 14.5 ± 2.6 mg N L-1h-1. Although the half-saturation inhibition constant of NOB (KI_FNA(AOB)) reached 0.37 ± 0.10 mg HNO2N/L and showed extreme adaptability in FNA, the inactivation effect of FNA (6.1 mg HNO2N/L) for NOB was much greater than that of AOB, with inactivation rates of 0.61 ± 0.08 h-1 and 0.06 ± 0.01 h-1, respectively. The effluent pH was gradually reduced to 4.5 by ammonia oxidation process and the periodic FNA concentration reached 6.5 mg HNO2N/L to inactivate nitrite-oxidizing bacteria (NOB) without negatively affecting Nitrosomonas during long-term operation. This result provides new insights for the future implementation of high-rate stabilized acidic partial nitritation by Nitrosomonas.

Closed loop stimulation reduces the incidence of atrial high-rate episodes compared with conventional rate-adaptive pacing in patients with sinus node dysfunctions.

AIMS: Subclinical atrial fibrillation (AF) is associated with increased risk of progression to clinical AF, stroke, and cardiovascular death. We hypothesized that in pacemaker patients requiring dual-chamber rate-adaptive (DDDR) pacing, closed loop stimulation (CLS) integrated into the circulatory control system through intra-cardiac impedance monitoring would reduce the occurrence of atrial high-rate episodes (AHREs) compared with conventional DDDR pacing. METHODS AND RESULTS: Patients with sinus node dysfunctions (SNDs) and an implanted pacemaker or defibrillator were randomly allocated to dual-chamber CLS (n = 612) or accelerometer-based DDDR pacing (n = 598) and followed for 3 years. The primary endpoint was time to the composite endpoint of the first AHRE lasting ≥6 min, stroke, or transient ischaemic attack (TIA). All AHREs were independently adjudicated using intra-cardiac electrograms. The incidence of the primary endpoint was lower in the CLS arm (50.6%) than in the DDDR arm (55.7%), primarily due to the reduction in AHREs lasting between 6 h and 7 days. Unadjusted site-stratified hazard ratio (HR) for CLS vs. DDDR was 0.84 [95% confidence interval (CI), 0.72-0.99; P = 0.035]. After adjusting for CHA2DS2-VASc score, the HR remained 0.84 (95% CI, 0.71-0.99; P = 0.033). In subgroup analyses of AHRE incidence, the incremental benefit of CLS was greatest in patients without atrioventricular block (HR, 0.77; P = 0.008) and in patients without AF history (HR, 0.73; P = 0.009). The contribution of stroke/TIA to the primary endpoint (1.3%) was low and not statistically different between study arms. CONCLUSION: Dual-chamber CLS in patients with SND is associated with a significantly lower AHRE incidence than conventional DDDR pacing.

Subclinical Atrial Fibrillation: To Anticoagulate or Not?

Atrial fibrillation (AF) carries a stroke risk, often necessitating anticoagulation, especially in patients with risk factors. With the advent of implantable and wearable heart monitors, episodes of short bouts of atrial arrhythmias called atrial high-rate episodes (AHREs) or subclinical AF (SCAF) are commonly identified. The necessity of anticoagulation in patients with SCAF is unclear. However, recent randomized controlled trials, the NOAH-AFNET 6 and ARTESIA, have offered insights into this matter. Furthermore, a study-level meta-analysis combining data from both these trials has provided more detailed information. Reviewing the information thus far, we can conclude that DOACs can result in a notable reduction in the risk of ischemic stroke and can potentially decrease the risk of debilitating stroke, albeit with an increased risk of major bleeding. Thus, informed, shared decision-making is essential, weighing the potential benefits of stroke prevention against the risk of major bleeding when considering anticoagulation in this patient population.

Atrial High-Rate Episodes in Elderly Patients: The Anticoagulation Therapy Dilemma.

Atrial fibrillation (AF) has been associated with higher morbidity and mortality rates, especially in older patients. Subclinical atrial fibrillation (SCAF) is defined as the presence of atrial high-rate episodes (AHREs) > 190 bpm for 10 consecutive beats > 6 min and <24 h, as detected by cardiac implanted electronic devices (CIEDs). The selection of eligible patients for anticoagulation therapy among elderly individuals with AHREs detected through CIEDs remains a contentious issue. The meta-analysis of ARTESiA and NOAH-AFNET 6 clinical trials revealed that taking Edoxaban or Apixaban as oral anticoagulation therapy can reduce the risk of stroke by approximately 32% while increasing the risk of major bleeding by approximately 62%. However, it is still unclear which are, among patients with SCAF, those who can take the highest net clinical benefit from anticoagulant therapy. The present review summarizes the current evidence on this intriguing issue and suggests strategies to try to better stratify the risk of stroke and systemic embolism in patients with AHREs. We propose incorporating some parameters including chronic kidney disease (CKD), obesity, enlarged left atrial volume, the efficacy in blood pressure management, and frailty into the traditional CHA2DS2-VASc score. Future trials will be needed to verify the clinical usefulness of the proposed prognostic score mainly in the view of a personalized therapeutic approach in patients with SCAF.

Management of atrial arrhythmias identified by cardiac devices.

Implantable cardiac devices have shown that atrial fibrillation (AF) is more frequent than previously assumed, with subclinical, asymptomatic, self-limiting manifestations called atrial high-rate events (AHREs) or subclinical AF. The clinical significance and correct therapeutic management of these episodes of subclinical AF is less well defined than in the case of clinically manifest AF. Two important randomized studies on the topic have recently been published, NOAH-AFNET 6 and ARTESIA, which, however, have not definitively clarified the topic. In patients with AHRE or subclinical AF, the average thrombo-embolic risk is lower than that in patients with clinically manifest AF and is ∼1%. For this reason, in these patients, the possibility that the benefit of anticoagulant therapy is overshadowed by the risk of bleeding is very high. Therefore, while waiting for new tools that allow a better stratification of low-risk patients, we must rely on individual clinical evaluation and overcome the qualitative dichotomy (AHRE yes vs. AHRE no), preferring instead an approach that is as quantitative as possible and takes into account the number of episodes, their duration, and the patient's CHADSVASC score, before deciding, in each individual case, whether or not to use anticoagulant therapy.

Enhancing environmental performance in biogas production from wastewater-grown microalgae: A life cycle assessment perspective.

The production of biogas from microalgae has gained attention due to their rapid growth, CO2 sequestration, and minimal land use. This study uses life cycle assessment to assess the environmental impacts of biogas production from wastewater-grown microalgae through anaerobic digestion within an optimized microalgae-based system. Using SimaPro® 9 software, 3 scenarios were modeled considering the ReCiPe v1.13 midpoint and endpoint methods for environmental impact assessment in different categories. In the baseline scenario (S1), a hypothetical system for biogas production was considered, consisting of a high rate algal pond (HRAP), a settling, an anaerobic digester, and a biogas upgrading unit. The second scenario (S2) included strategies to enhance biogas yield, namely co-digestion and thermal pre-treatment. The third scenario (S3), besides considering the strategies of S2, proposed the biogas upgrading in the HRAP and the digestate recovery as a biofertilizer. After normalization, human carcinogenic toxicity was the most positively affected category due to water use in the cultivation step, accounted as avoided product. However, this category was also the most negatively affected by the impacts of the digester heating energy. Anaerobic digestion was the most impactful step, constituting on average 60.37% of total impacts. Scenario S3 performed better environmentally, primarily due to the integration of biogas upgrading within the cultivation reactor and digestate use as a biofertilizer. Sensitivity analysis highlighted methane yield's importance, showing potential for an 11.28% reduction in ionizing radiation impacts with a 10% increase. Comparing S3 biogas with natural gas, the resource scarcity impact was reduced sixfold, but the human health impact was 23 times higher in S3.

High-capacity K+-pillared layered manganese dioxide as cathode material for high-rate aqueous zinc-ion battery.

Sluggish kinetics and severe structural instability of manganese-based cathode materials for rechargeable aqueous zinc-ion batteries (ZIBs) lead to low-rate capacity and poor cyclability, which hinder their practical applications. Pillaring manganese dioxide (MnO2) by pre-intercalation is an effective strategy to solve the above problems. However, increasing the pre-intercalation content to realize stable cycling of high capacity at large current densities is still challenging. Here, high-rate aqueous Zn2+ storage is realized by a high-capacity K+-pillared multi-nanochannel MnO2 cathode with 1 K per 4 Mn (δ-K0.25MnO2). The high content of the K+ pillar, in conjunction with the three-dimensional confinement effect and size effect, promotes the stability and electron transport of multi-nanochannel layered MnO2 in the ion insertion/removal process during cycling, accelerating and accommodating more Zn2+ diffusion. Multi-perspective in/ex-situ characterizations conclude that the energy storage mechanism is the Zn2+/H+ ions co-intercalating and phase transformation process. More specifically, the δ-K0.25MnO2 nanospheres cathode delivers an ultrahigh reversible capacity of 297 mAh g-1 at 1 A g-1 for 500 cycles, showing over 96 % utilization of the theoretical capacity of δ-MnO2. Even at 3 A g-1, it also delivered a 63 % utilization and 64 % capacity retention after 1000 cycles. This study introduces a highly efficient cathode material based on manganese oxide and a comprehensive analysis of its structural dynamics. These findings have the potential to improve energy storage capabilities in ZIBs significantly.

An Ultralight Composite Current Collector Enabling High-Energy-Density and High-Rate Anode-Free Lithium Metal Battery.

Anode-free lithium (Li) metal batteries are promising alternatives to current Li-ion batteries due to their advantages such as high energy density, low cost, and convenient production. However, the copper (Cu) current collector accounts for more than 25 wt% of the total weight of the anode-free battery without capacity contribution, which severely reduces the energy and power densities. Here, a new family of ultralight composite current collectors with a low areal density of 0.78 mg cm-2, representing significant weight reduction of 49%-91% compared with the Cu-based current collectors for high-energy Li batteries, is presented. Rational molecular engineering of the polyacylsemicarbazide substrate enables enhanced interfacial interaction with the sputtered Cu layer, which results in excellent interfacial stability, flexibility, and safety for the obtained anode-free batteries. The battery-level energy density has been significantly improved by 36%-61%, and a maximum rate capability reaches 5 C (10 mA cm-2) attributed to the homogeneous Li+ flux and smooth Li deposition on the nanostructured Cu layer. The results not only open a new avenue to improve the energy and power densities of anode-free batteries via composite current collector innovation but, in a broader context, provide a new paradigm to pursue high-performance, high-safety, and flexible batteries.