Initial Discharge Research Articles

A microwave discharge in high-velocity flows initiated by a half-wave antenna

A microwave discharge in high-velocity (150—250 m/s) air flows induced on a half-wave vibrator is studied. A cw magnetron microwave generator with a frequency of 2.45 GHz and an output power of up to 5 kW was used for initiation of the microwave discharge. The high-speed video imaging was used for studying the discharge structure, determining the diameter and length of the plasma channel as a function of flow velocity and pressure. Electron concentration and temperature, along with characteristic gas temperature, were determined based on the optical spectra. The possibility of using this microwave discharge for ignition of hydrocarbon–air mixtures in combustion chambers of ramjet engines is proved experimentally.

Effect of TaC content on microstructure and wear behavior of PRMMC Fe-TaC coating manufactured by electrospark deposition on AISI304 stainless steel

The Fe-TaC coatings on stainless steel by electrospark granule deposition in an anode mixture of iron granules and tantalum carbide powder were first obtained. The material deposition rate on the substrate increased with the TaC powder concentration growth in the anode mixture, facilitating the initiation of electrical discharges. X-ray analysis of deposited coatings shows the presence of the TaC, γFe, and αFe phases. The tantalum carbide concentration grows with an increase in the content of TaC powder in the anode mixture, from 2.4 to 14.8 vol%. The dependence of the wear rate of coatings on the concentration of tantalum carbide in the anode mixture had a parabola form, with a minimum of 5 vol%. However, with a further increase in the TaC concentration in the anode mixture, the wear rate of the coatings monotonically increased due to spalling of TaC grains due to a deficiency of the metal binder.

Degradation mechanism for epoxy resins under combined electric, thermal and compressive stresses

Epoxy resins are widely used in equipment such as ultra-high voltage dry-type bushings, which are subjected to severe electric, thermal, and compressive stresses. Some physical mechanisms have already been proposed to explain the degradations generated by these different stresses, however their effects have not yet been quantified.. The degradation characteristics of epoxy resin under combined stresses of 8 kV/mm, 40 °C-120 °C, and 0–60 MPa were investigated in experiments. The results showed that the degradation characteristics turned significantly with the increase of compressive stress. With the increase in compressive stress, initially the partial discharge initiation voltage, tree initiation voltage and time to breakdown increased, and fractal dimension decreased. While the compressive stress exceeded the turning point, the characteristics were reversed. It can be suggested that opposing mechanisms exist. The free volume and phase field theories dominate at lower and higher stresses, respectively. A novel degradation model of the epoxy resin was proposed based on the theories above. When the compressive stress was low, the reduction of free volume played a dominant role in slowing down the degradation. When the compressive stress was high, the partial energy density concentration accelerated the degradation and played a dominant role. The molecular dynamics and finite element simulation of degradation process stress was carried out and proved consistent with experiments. It confirmed the proposed degradation model reliable and valid.

Analysis of the Double Head Streamer Discharge Simulation under Different Pressures

In this research, the dynamics of double-head streamer discharge initiation, propagation, interaction and breakdown in the air under different pressure values were presented. The double-head streamer discharge dynamics were analysed within a plane-to-plane electrode configuration. That was done through many aspects proposed, such as electron density, electric field, space charge density and streamer propagation speed. The simulation performed using ‘COMSOL Multiphysics’ is based on the finite element method and was carried out with the fluid model. The fluid model describes the movement of particle concentrations using partial differential equations (PDEs) together with Poisson’s equation; Poisson's equation and charge concentrations determine the electric field distribution in space. According to the results, as the pressure increased from (1, 2 and 3atm), the evolution time of the streamer increased from (0.563 to16.29ns) with the same breakdown voltage of 19kV. This means that the double-head streamer discharge developed faster with the decrease in pressure.

Achieving Low Voltage Plasma Discharge in Aqueous Solution Using Lithographically Defined Electrodes and Metal/Dielectric Nanoparticles.

Because of the high dielectric strength of water, it is extremely difficult to discharge plasma in a controllable way in the aqueous phase. By using lithographically defined electrodes and metal/dielectric nanoparticles, we create electric field enhancement that enables plasma discharge in liquid electrolytes at significantly reduced applied voltages. Here, we use high voltage (10-30 kV) nanosecond pulse (20 ns) discharges to generate a transient plasma in the aqueous phase. An electrode geometry with a radius of curvature of approximately 10 μm, a gap distance of 300 μm, and an estimated field strength of 5 × 106 V/cm resulted in a reduction in the plasma discharge threshold from 28 to 23 kV. A second structure had a radius of curvature of around 5 μm and a gap distance of 100 μm had an estimated field strength of 9 × 106 V/cm but did not perform as well as the larger gap electrodes. Adding gold nanoparticles (20 nm diameter) in solution further reduced the threshold for plasma discharge to 17 kV due to the electric field enhancement at the water/gold interface, with an estimated E-field enhancement of 4×. Adding alumina nanoparticles decorated with Pt reduced the plasma discharge threshold to 14 kV. In this scenario, the emergence of a triple point at the juncture of alumina, Pt, and water results in the coexistence of three distinct dielectric constants at a singular location. This leads to a notable concentration of electric field, effectively aiding in the initiation of plasma discharge at a reduced voltage. To gain a more comprehensive and detailed understanding of the electric field enhancement mechanism, we performed rigorous numerical simulations. These simulations provide valuable insights into the intricate interplay between the lithographically defined electrodes, the nanoparticles, and the resulting electric field distribution, enabling us to extract crucial information and optimize the design parameters for enhanced performance.

Dynamic propagation velocity of a positive streamer in a 3 m air gap under lightning impulse voltage

Streamers represent an important stage in the initiation of gap discharge. In this work, we used an eight-frame intensified charge-coupled device camera to capture the streamer development process when a lightning impulse voltage of 95%–100% U 50% was applied in a 3 m rod–plate gap and the streamer velocity was analyzed. Analysis of the observations shows that streamer velocity can be defined by three stages: rapid velocity decline (stage 1), rapid velocity rise (stage 2) and slow velocity decline (stage 3). The effects of electrode shape, applied voltage and gap breakdown or withstanding on streamer velocity were analyzed. The electrode with a larger radius of curvature will result in a higher initial velocity, and a higher voltage amplitude will cause the streamer to propagate faster at stage 3. Gap withstanding or breakdown has no obvious effect on streamer velocity. In addition, the experimental results are compared with previous results and the statistical characteristics of the primary streamer discharge are discussed.

Outcomes After Initiation of Medications for Alcohol Use Disorder at Hospital Discharge

US Food and Drug Administration-approved medications for alcohol use disorder (MAUD) are significantly underused. Hospitalizations may provide an unmet opportunity to initiate MAUD, but few studies have examined clinical outcomes of patients who initiate these medications at hospital discharge. To investigate the association between discharge MAUD initiation and 30-day posthospitalization outcomes. This cohort study was conducted among patients with Medicare Part D who had alcohol-related hospitalizations in 2016. Data were analyzed from October 2022 to December 2023. Discharge MAUD initiation was defined as oral naltrexone, acamprosate, or disulfiram pharmacy fills within 2 days of discharge. The primary outcome was a composite of all-cause mortality or return to hospital (emergency department visits and hospital readmissions) within 30 days of discharge. Secondary outcomes included these components separately, return to hospital for alcohol-related diagnoses, and primary care or mental health follow-up within 30 days of discharge. Propensity score 3:1 matching and modified Poisson regressions were used to compare outcomes between patients who received and did not receive discharge MAUD. There were 6794 unique individuals representing 9834 alcohol-related hospitalizations (median [IQR] age, 54 [46-62] years; 3205 hospitalizations among females [32.6%]; 1754 hospitalizations among Black [17.8%], 712 hospitalizations among Hispanic [7.2%], and 7060 hospitalizations among White [71.8%] patients). Of these, 192 hospitalizations (2.0%) involved discharge MAUD initiation. After propensity matching, discharge MAUD initiation was associated with a 42% decreased incidence of the primary outcome (incident rate ratio, 0.58 [95% CI, 0.45 to 0.76]; absolute risk difference, -0.18 [95% CI, -0.26 to -0.11]). These findings were consistent among secondary outcomes (eg, incident rate ratio for all-cause return to hospital, 0.56 [95% CI, 0.43 to 0.73]) except for mortality, which was rare in both groups (incident rate ratio, 3.00 [95% CI, 0.42 to 21.22]). Discharge MAUD initiation was associated with a 51% decreased incidence of alcohol-related return to hospital (incident rate ratio, 0.49 [95% CI, 0.34 to 0.71]; absolute risk difference, -0.15 [95% CI, -0.22 to -0.09]). In this cohort study, discharge initiation of MAUD after alcohol-related hospitalization was associated with a large absolute reduction in return to hospital within 30 days. These findings support efforts to increase uptake of MAUD initiation at hospital discharge.

Avocado seed biomass-assisted synthesis of heterostructure bismuth vanadate nanomaterial by combustion method for the application of electrochemical lithium battery storage and supercapacitor

With the global demand for lithium-ion batteries (LIBs), research is focused on developing advanced energy storage materials with high energy and power densities. Hetero-structured nanomaterials have garnered significant interest in energy storage applications based on their unique architecture providing sites for improved electrochemical activity. This work reports a facile single-step combustion synthesis of bismuth vanadate nanoparticles (BVNPs) using avocado seed powder, an economical and eco-friendly fuel source. By optimizing the precursor-to-fuel ratio to 1:1, highly pure phase BVNPs were obtained as characterized via XRD, FT-IR, SEM-EDAX, TEM, UV-DRS, PL, BET, and DLS analyses. When assessed as an electrode material for LIBs, the BVNP1:1 delivered an exceptional initial discharge capacity of 2166 mAhg−1 and a retention of ∼53 mAhg−1 over 90 cycles with 99% Coulombic efficiency. The BVNP1:1 electrode exhibited a maximum specific capacitance of 545.65 mF/cm2 at 2 mA/cm2 current density as a supercapacitor. The combination of scalable green synthesis, excellent phase purity, and superior electrochemical performance makes these BVNPs a promising and sustainable electrode material for forthcoming energy storage technologies to meet the surging energy needs.

Pericapsular nerve group block and lateral femoral cutaneous nerve block versus fascia iliaca block for multimodal analgesia after total hip replacement surgery: A retrospective analysis.

Optimal pain control with limited muscle weakness is paramount for a swift initiation of physical therapy and early discharge. Fascia iliaca compartment block (FICB) has been recommended since it offers good pain control with a low risk of motor block. Pericapsular nerve group (PENG) block with lateral femoral cutaneous block (LFCN) has been proposed as an effective alternative to FICB that offers better pain control with a considerably lower risk of motor block. We aimed to compare the aforementioned blocks and determine which one yielded the lowest numeric rating scale (NRS) score. We designed a retrospective analysis of patients undergoing elective total hip arthroplasty. The primary outcome was the NRS score at 6, 12, and 24 hours. The secondary outcomes were total opioid consumption, time to first PRN opioid, and time to first postoperative ambulation. 52 patients were recruited, (13 PENG plus LFCN, 39 FICB). PENG plus LCFN resulted in a lower NRS at all three-time points (mean difference and 95%CI at 6 h 0.378 [-0.483; 1.240], at 12 h 0.336 [-0.378; 1.050], and at 24 h 0.464 [0.013; 0.914] P = 0.02). Moreover, less PRN opioids were requested in the PENG plus LCFN vs. FICB group (0 [0;7.5] vs 60 [15;80] milligrams of morphine equivalents, P = 0.001). No delay in the first ambulation or initiation of physical rehabilitation was reported in either group. PENG plus LCFN seems to offer better pain control and lead to less PRN opioids. Neither block hindered physical therapy nor ambulation. These results need to be confirmed with a larger prospective and randomized study.

Machine Learning Model for Readmission Prediction of Patients With Heart Failure Based on Electronic Health Records: Protocol for a Quasi-Experimental Study for Impact Assessment.

Care for patients with heart failure (HF) causes a substantial load on health care systems where a prominent challenge is the elevated rate of readmissions within 30 days following initial discharge. Clinical professionals face high levels of uncertainty and subjectivity in the decision-making process on the optimal timing of discharge. Unwanted hospital stays generate costs and cause stress to patients and potentially have an impact on care outcomes. Recent studies have aimed to mitigate the uncertainty by developing and testing risk assessment tools and predictive models to identify patients at risk of readmission, often using novel methods such as machine learning (ML). This study aims to investigate how a developed clinical decision support (CDS) tool alters the decision-making processes of health care professionals in the specific context of discharging patients with HF, and if so, in which ways. Additionally, the aim is to capture the experiences of health care practitioners as they engage with the system's outputs to analyze usability aspects and obtain insights related to future implementation. A quasi-experimental design with randomized crossover assessment will be conducted with health care professionals on HF patients' scenarios in a region located in the South of Sweden. In total, 12 physicians and nurses will be randomized into control and test groups. The groups shall be provided with 20 scenarios of purposefully sampled patients. The clinicians will be asked to take decisions on the next action regarding a patient. The test group will be provided with the 10 scenarios containing patient data from electronic health records and an outcome from an ML-based CDS model on the risk level for readmission of the same patients. The control group will have 10 other scenarios without the CDS model output and containing only the patients' data from electronic medical records. The groups will switch roles for the next 10 scenarios. This study will collect data through interviews and observations. The key outcome measures are decision consistency, decision quality, work efficiency, perceived benefits of using the CDS model, reliability, validity, and confidence in the CDS model outcome, integrability in the routine workflow, ease of use, and intention to use. This study will be carried out in collaboration with Cambio Healthcare Systems. The project is part of the Center for Applied Intelligent Systems Research Health research profile, funded by the Knowledge Foundation (2021-2028). Ethical approval for this study was granted by the Swedish ethical review authority (2022-07287-02). The recruitment process of the clinicians and the patient scenario selection will start in September 2023 and last till March 2024. This study protocol will contribute to the development of future formative evaluation studies to test ML models with clinical professionals. PRR1-10.2196/52744.

Pre-oxidized and composite strategy greatly boosts performance of polyacrylonitrile/LLZO nanofibers for lithium-metal batteries

The active cyano-group in polyacrylonitrile has severe passivation of lithium anode under larger current density, which restricts the wide application of polyacrylonitrile(PAN) in lithium metal batteries. Herein, in order to address the excessive passivation of lithium metal by PAN, inspired by the pre-oxidation of carbon fibers, PAN was pre-oxidized at 230 °C, which transformed part of the cyano group into a more chemically stable cyclized structure. The electrochemical and mechanical properties of the composite solid electrolyte were effectively improved by introducing the fast ionic conductor Li6.25La3Zr2Al0.25O12 into PAN by electrospinning. The oxidized PAN-based composite solid electrolyte presents high ionic conductivity (3.05 × 10−3 S·cm−1) and high lithium transference number of 0.79 at 25 °C, further contributing to a high electrochemical window (5.3 V). The solid-state batteries assembled by Li||10 wt%-LLZAO@230-oxy-PAN||NCM523 behave superb electrochemical performance, delivering a high initial discharge capacity of 157 mAh g−1 at 0.2 C. After 100 cycles, the capacity retention was 93.3 %, indicating the electrolyte displays great electrochemical stability. This work provides new insights into the structural design of polymer-based high-voltage batteries.

In Situ Construction of LiF-Li3N-Rich Interface Contributed to Fast Ion Diffusion in All-Solid-State Lithium-Sulfur Batteries.

All-solid-state lithium-sulfur batteries (ASSLSBs) have attracted wide attention due to their ultrahigh theoretical energy density and the ability of completely avoiding the shuttle effect. However, the further development of ASSLSBs is limited by the poor kinetic properties of the solid electrode interface. It remains a great challenge to achieve good kinetic properties, by common strategies to substitute sulfur-transition metal and organosulfur composites for sulfur without reducing the specific capacity of ASSLSBs. In this study, a sulfur-(Ketjen Black)-(bistrifluoromethanesulfonimide lithium salt) (S-KB-LiTFSI) composite is constructed by introducing LiTFSI into the S-KB composite. The initial discharge capacity reaches up to 1483 mA h g-1, benefited from the improved ionic conductivity and diffusion kinetics of the S-KB-LiTFSI composite, where numerous LiF interphases with a Li3N component are in situ formed during cycling. Combined with DFT calculations, it is found that the migration barriers of LiF and Li3N are much smaller than that of the Li6PS5Cl solid electrolyte. The fast ionic conductors of LiF and Li3N not only enhance the Li+ transfer efficiency but also improve the interfacial stability. Therefore, the assembled ASSLSBs operate stably for 600 cycles at 200 mA g-1, and this study provides an effective strategy for the further development of ASSLSBs.

Highly Conductive Imidazolate Covalent Organic Frameworks with Ether Chains as Solid Electrolytes for Lithium Metal Batteries.

Poly(ethylene oxide) (PEO)-based electrolytes are often used for Li+ conduction as they can dissociate the Li salts efficiently. However, high entanglement of the chains and lack of pathways for rapid ion diffusion limit their applications in advanced batteries. Recent developments in ionic covalent organic frameworks (iCOFs) showed that their highly ordered structures provide efficient pathways for Li+ transport, solving the limitations of traditional PEO-based electrolytes. Here, we present imidazolate COFs, PI-TMEFB-COFs, having methoxyethoxy chains, synthesized by Debus-Radziszewski multicomponent reactions and their ionized form, Li+@PI-TMEFB-COFs, showing a high Li+ conductivity of 8.81 mS cm-1 and a transference number of 0.974. The mechanism for such excellent electrochemical properties is that methoxyethoxy chains dissociate LiClO4, making free Li+, then those Li+ are transported through the imidazolate COFs' pores. The synthesized Li+@PI-TMEFB-COFs formed a stable interface with Li metal. Thus, employing Li+@PI-TMEFB-COFs as the solid electrolyte to assemble LiFePO4 batteries showed an initial discharge capacity of 119.2 mAh g-1 at 0.5 C, and 82.0 % capacity and 99.9 % Coulombic efficiency were maintained after 400 cycles. These results show that iCOFs with ether chains synthesized via multicomponent reactions can create a new chapter for making solid electrolytes for advanced rechargeable batteries.

Highly Conductive Imidazolate Covalent Organic Frameworks with Ether Chains as Solid Electrolytes for Lithium Metal Batteries

AbstractPoly(ethylene oxide) (PEO)‐based electrolytes are often used for Li+ conduction as they can dissociate the Li salts efficiently. However, high entanglement of the chains and lack of pathways for rapid ion diffusion limit their applications in advanced batteries. Recent developments in ionic covalent organic frameworks (iCOFs) showed that their highly ordered structures provide efficient pathways for Li+ transport, solving the limitations of traditional PEO‐based electrolytes. Here, we present imidazolate COFs, PI‐TMEFB‐COFs, having methoxyethoxy chains, synthesized by Debus–Radziszewski multicomponent reactions and their ionized form, Li+@PI‐TMEFB‐COFs, showing a high Li+ conductivity of 8.81 mS cm−1 and a transference number of 0.974. The mechanism for such excellent electrochemical properties is that methoxyethoxy chains dissociate LiClO4, making free Li+, then those Li+ are transported through the imidazolate COFs’ pores. The synthesized Li+@PI‐TMEFB‐COFs formed a stable interface with Li metal. Thus, employing Li+@PI‐TMEFB‐COFs as the solid electrolyte to assemble LiFePO4 batteries showed an initial discharge capacity of 119.2 mAh g−1 at 0.5 C, and 82.0 % capacity and 99.9 % Coulombic efficiency were maintained after 400 cycles. These results show that iCOFs with ether chains synthesized via multicomponent reactions can create a new chapter for making solid electrolytes for advanced rechargeable batteries.

Locally Concentrated Deep Eutectic Liquids Electrolytes for Low-Polarization Aluminum Metal Batteries.

Low-cost and nontoxic deep eutectic liquid electrolytes (DELEs), such as [AlCl3]1.3[Urea] (AU), are promising for rechargeable non-aqueous aluminum metal batteries (AMBs). However, their high viscosity and sluggish ion transport at room temperature lead to high cell polarization and low specific capacity, limiting their practical application. Herein, non-solvating 1,2-difluorobenzene (dFBn) is proposed as a co-solvent of DELEs using AU as model to construct a locally concentrated deep eutectic liquid electrolyte (LC-DELE). dFBn effectively improves the fluidity and ion transport without affecting the ionic dynamics in the electrolyte. Moreover, dFBn also modifies the solid electrolyte interphase growing on the aluminum metal anodes and reduces the interfacial resistance. As a result, the lifespan of Al/Al cells is improved from 210 to 2000h, and the cell polarization is reduced from 0.36 to 0.14V at 1.0mAcm-2. The rate performance of Al-graphite cells is greatly improved with a polarization reduction of 0.15 and 0.74V at 0.1 and 1Ag-1, respectively. The initial discharge capacity of Al-sulfur cells is improved from 94 to 1640mAhg-1. This work provides a feasible solution to the high polarization of AMBs employing DELEs and a new path to high-performance low-cost AMBs.

Research on Sodium Storage Performance of Cu and Mg Doped P2 Type Layered Oxide Cathode Materials

The P2-type Ni–Mn-based oxide cathode materials have drawbacks such as the Jahn-Teller effect and crystal phase transition under high pressure. In this study, Cu and Mg modifications were introduced to inhibit the P2–O2 phase transition and increase the lattice spacing, thereby reducing the resistance of sodium ion de-embedding and intercalation to improve the overall electrochemical performance of the battery. A series of P2-type Na0.67Ni0.33−xMn0.67CuxO2 and Na0.67Ni0.33−xMn0.67MgxO2 cathode materials were synthesized through solid-state reaction. Cu substitution significantly alters the structural stability and electrochemical properties. In the voltage range from 1.5 V to 4.2 V and at 0.1 C, the initial discharge specific capacity of Na0.67Ni0.18Mn0.67Cu0.15O2 was 167 mAh·g−1, with 86 mAh·g−1 remaining after 100 cycles at 1 C. Additionally, a high discharge specific capacity of 207 mAh·g−1 was achieved with 0.075 Mg doping, suggesting that part of O2− participated in the internal electrochemical reaction. Furthermore, the rate performance of Na0.67Ni0.28Mn0.67Mg0.05O2 was found to be the best. This phenomenon was attributed to the inactive Mg2+ retaining more Na+ in the interlayer, inhibiting crystal structure transformation and Jahn-Teller distortion. The larger radius of Mg2+ increased the layer spacing, widened the Na+ de-embedding channels, and increased the diffusion coefficient.

Controlling the structural features of tin dioxide nanoparticles embedded reduced graphene oxide on carbon cloth to serve as high stability fast charging anode for Li-ion cells

Tin dioxide or stannic oxide (SnO2) is an n-type semiconductor that has profound applications in gas sensors, solar cells, and energy storage devices like Li-ion batteries. Due to their high theoretical capacity (1494 mAh g−1) affordability, eco-friendliness, and safe operating conditions, SnO2 based anode materials are being extensively studied. Electrochemical capacity and stability for energy storage can be enhanced by embedding facet exposed SnO2 nanoparticles in reduced graphene oxide (rGO). In this study, SnO2 nanoparticles are synthesized and incorporated into rGO network via a simple solvo-thermal method is applied onto a carbon cloth substrate and used as anode for SnO2/rGO based Li-ion cell. The initial discharge capacity is found to be 1415 mAh g−1 and the charge capacity to be 1236 mAh g−1 with an initial Coulombic efficiency of 87 % at a current rate of 0.1 A g−1. The cell also exhibits excellent cycling stability and rate capability, with a discharge capacity of 1034 mAh g−1 and a charge capacity of 998 mAh g−1 at a current rate of 0.3 A g−1. This electrode is stable at a higher current rate of 2C (3 A g−1) and hence offers high prospects as anode material for application in fast-charging rechargeable cells.

Fast breakdown process and characteristics diagnosis of nanosecond pin–pin discharge

In this paper, the characteristics of a nanosecond spark discharge with a pin–pin electrode configuration have been systematically studied. Both a streak camera with high temporal resolution and an intensified charge-coupled device (ICCD) camera are employed together to investigate the breakdown and evolution process of the discharge. The formation of initial breakdown and mode transition from streamer to spark in the electrode gap are clearly observed on the time scale of several nanoseconds with a temporal resolution of 100 ps. In addition, the time-resolved spectra technology is also used to analyze the generation and quenching mechanisms of reactive species, the electron density, and the electron temperature. The results show that there is a 1.25 ns initial discharge breakdown and that a bright cathode spot exists before the transformation from streamer to spark channel. After a faster cathode filament and a slower anode filament propagate and merge at the electrode gap, the spark discharge phase begins. The generation processes of different reactive species depend on the discharge phase to a great extent. The N2* is first generated during the streamer phase while the O*, N*, and N+ are mainly generated under the spark phase, in which the electron temperature calculated by Boltzmann plots is 2.74 eV, and the electron density determined from the Stark broadening of O lines is on the order of 1016 cm−3.

Magnesium-calcium thin films at low calcium concentrations for anode materials in biodegradable implantable primary batteries

A Mg–Ca thin film combinatorial library was produced by thermal co-evaporation targeting a compositional spread of Ca from 0.2 to 3 at.%. Microstructure characterizations proved all alloys to have single-phase microstructures, displaying a gradual refinement with increasing Ca concentration. Electrochemical characterizations conducted using scanning droplet cell microscopy (SDCM), showed that the incorporation of Ca resulted in an improvement of the corrosion resistance of Mg thin films. The Mg-1.2 at.% Ca thin film alloy screened from the library showed an optimal initial cell potential and total discharge time.

Scalable spray-dried high-capacity MoC1-x/NC-Li2C2O4 prelithiation composite for lithium-ion batteries

Li2C2O4 is recognized as a promising prelithiation reagent for compensating active lithium owing to its residue-free, high-capacity, air-stable and cost-effective advantages. However, the inherent challenges of low conductivity and high reaction energy barriers necessitate the incorporation of a catalyst to expedite charge conduction and enhance electrochemical activity. It is essential to achieve an efficient composite Li2C2O4 with the catalyst while maintaining substantial prelithiation capacity. Herein, a scalable spray-dried strategy is developed to fabricate MoC1-x/NC-Li2C2O4 composites. The defect-rich nano-MoC1-x/NC catalysis facilitates intimate contact with Li2C2O4, leading to the formation of homogeneous microspheres that promote efficient solid-solid catalysis. Remarkably, the specific capacity of MoC1-x/NC-Li2C2O4 can reach up to 1117 mAh g−1 (calculation based on the complete release of CO2) with a low ratio of catalysts, demonstrating significant application potential. Furthermore, the activation potential of homogeneous MoC1-x/NC-Li2C2O4 composite can be reduced to 4.12 V at 50 °C, while maintaining favorable electrode integrity and wettability. Upon implementation in Gr||NCM622 and SiC||NCM622 full cell, the initial discharge specific capacity is improved by 10.5 % and 11.6 %, respectively. Notably, sufficient active lithium post-prelithiation preserves the cathode and SEI structural stability, ensuring a stable cycling performance. This work presents a scalable prelithiation material with great promise for advanced lithium-ion battery applications.