High Loading Density Research Articles

Outside-In Nanostructure Fabricated on LiCoO2 Surface for High-Voltage Lithium-Ion Batteries.

The energy density of batteries with lithium cobalt oxide (LCO) can be maximized by increasing the cut‐off voltage to approach the theoretical capacity limit. However, it is not realized in the practical applications due to the restricted cycle life caused by vulnerable cathode surface in deep delithiation state, where severe side reactions, oxygen/cobalt loss and structure degradation often happen. Here, an outside‐in oriented nanostructure on LiCoO2 crystals is fabricated. The outer electrochemically stable LiF and Li2CoTi3O8 particles perform as physical barrier to prevent damage of both cathodes and electrolytes, while the inner F doping promote Li ions diffusivity and stabilize the lattice oxygen. With the spinel‐like transition layer between them, a solid and complete lithium‐ion transport channel generation along the lithium concentration gradient. Under the protection from this structure, the LiCoO2 withstand the high voltage of 4.6 V and the LCO/graphite pouch full cell with high loading density exhibits 81.52% energy density retention after 135 cycles at 4.5 V.

Spatially hierarchical carbon enables superior long-term cycling of ultrahigh areal capacity lithium metal anodes

•A distinct leaf-vein-inspired spatially modulated hosting strategy •Spatial synergy of low-tortuosity channeling and carbon nanofiber mat blanketing •Extraordinary cyclic stability at high areal loading and high current density A leaf-vein-inspired spatially modulated host strategy is proposed for lithium anodes, and a self-supporting carbon membrane with vertical micro-channels blanketed by carbon nanofiber mats is developed. In such a spatially modulating design, the low-tortuosity channeling membrane allows rapid transport of lithium ions in the long range and better accommodation of the volume change upon cycling. More importantly, in the short range, the nanofiber mats confer strong capillarity and function as localized micro-reservoirs to hold up the electrolyte, thereby promoting uniform lithium ion distribution and scalable lithium deposition. Impressively, the fabricated electrodes exhibited outstanding cycling stability under various conditions of high areal capacity (up to 40 mAh cm−2) and high current density (up to 40 mA cm−2), including exceptionally stable dendrite-free cycling up to 1,080 cycles at 30 mAh cm−2 and 10 mA cm−2. This study offers a spatially hierarchical paradigm for rational design and construction of viable metal battery anodes. A leaf-vein-inspired spatially modulated host strategy is proposed for lithium anodes, and a self-supporting carbon membrane with vertical micro-channels blanketed by carbon nanofiber mats is developed. In such a spatially modulating design, the low-tortuosity channeling membrane allows rapid transport of lithium ions in the long range and better accommodation of the volume change upon cycling. More importantly, in the short range, the nanofiber mats confer strong capillarity and function as localized micro-reservoirs to hold up the electrolyte, thereby promoting uniform lithium ion distribution and scalable lithium deposition. Impressively, the fabricated electrodes exhibited outstanding cycling stability under various conditions of high areal capacity (up to 40 mAh cm−2) and high current density (up to 40 mA cm−2), including exceptionally stable dendrite-free cycling up to 1,080 cycles at 30 mAh cm−2 and 10 mA cm−2. This study offers a spatially hierarchical paradigm for rational design and construction of viable metal battery anodes.

Power loss minimization and voltage profile improvement on electrical power distribution systems using optimal capacitor placement and sizing

Distribution system operators are having difficulties maintaining a correct voltage profile across its network. As the standard of living of its customers increases, suppressed loads tend to come up and this in turn would require and increased demand in power supply. The increase in power demand and high load density at distribution ends have been seen to have key consequences of increasing the power loss and reducing the voltage profile in power systems, which seriously jeopardizes the ability of radial distribution networks to faithfully account for the power received from transmission stations. This work is aimed at improving the power quality that gets to the end users. Shunt capacitors have been suggested to be a suitable solution to this problem as they supply the reactive power needed for compensation. As a result, the optimum placement and size of these shunt capacitors have received a great deal of attention. Despite its efficacy, meta-heuristic algorithms are seldom utilized in the Nigerian RDS (radial distribution system), since most published research instead uses analytical and numerical programming methods. As a result, this research explains how to use a Hybrid Solution (HS) of Particle Swarm Optimization (PSO and GA) to identify and size shunt capacitors for real-time power loss reduction on an 11-kV distribution feeder. The backward-forward sweep load flow method with Loss Sensitivity Factor (LSF) is used to identify suitable buses for shunt capacitor installation, and the HS algorithm is then used to estimate the optimum size. This method was discovered to decrease the system's real power loss by 54.88% while raising the minimum bus voltage magnitude to the acceptable limit and thus improving the minimum system Voltage Stability Index (VSI). Based on these findings, the suggested technique is regarded as a viable way for placement and determining the size of shunt capacitors in a real-world Radial Distribution System. The numerical results shows that the approach has a high capability of improving the voltage profile of the distribution network, leading to an improved system power quality, minimize the system losses, correct the power factor, and maximize the net savings. The numerical results were gotten by using MATLAB package.

Endoplasmic-reticulum-like catalyst coating on separator to enhance polysulfides conversion for lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries with high theoretical specific energy of 2600 Wh kg−1 are one of promising candidates for next-generation energy storage devices. However, the severe shuttle effect of intermediate polysulfides leads to rapid capacity decay during battery cycling, especially at high sulfur loading and high current density. Herein, the MnO nanoparticles covered carbon with endoplasmic-reticulum-like structure (MnO@ERC) as separator coating for Li-S batteries is proposed. The MnO@ERC coating can act as upper current collector to enhance electrical conductivity of cathode and decrease the interface impedance of the whole battery. More importantly, both the polar MnO nanoparticles and Mn3O4 formed at the end of the charging process can catalyze the conversion of lithium polysulfides, which is convinced by the high adsorption energy and the elongate S–S bond. As a result, Li-S batteries based on MnO@ERC coating separator showed stable cycle for 350 cycles under 0.5C, high discharge specific capacity of 783.6 mAh g−1 after 100 cycles at 0.2 C, 534.7 mAh g−1 after 100 cycles under the sulfur loading of 5.26 mg cm−2 and low self-discharge rate of 9.1% after resting 48 h..

Preparation of CuWO4 foam and its use as a heterogeneous catalyst for dimethyl sulfoxide oxidation in a scale-up microreactor

BackgroundMetal foam has been demonstrated numerous advantages in fine chemistry when used as catalyst support. In this research, a novel strategy for the fabrication of copper tungstate (CuWO4) foam as heterogeneous catalysis to conduct dimethyl sulfoxide (DMSO) oxidation reaction in a scale-up microreactor was proposed. MethodsA series of three-dimensional skeleton CuWO4 foams were prepared by a continuous sintering approach. The obtained CuWO4 catalysis inherited the porous structure from the copper foam and had a high loading density of CuWO4 crystal particles. Afterwards, DMSO oxidation was employed as a probe reaction to explore the catalytic performance of CuWO4 foam. Significant findingsCuWO4 foam showed prefect catalytic activity in a scale-up microreactor. The average crystallite size of CuWO4 were increased from 52.8 to 57.7 nm with extension of sintering time. Under the optimum condition (residence time was 40 min, CuWO4 catalyst was CuWO4F-5 and reaction temperature was 80 oC), a high dimethyl sulfone yield of 65.4% was obtained. The yield of MSM reached nearly 65.3% in the run time of 1 h and showed a value of 50.4% even in the run time of 4 h. Higher reaction contact surface and larger crystal particles of CuWO4 foam are conducive to enhancing the catalytic performance of CuWO4 foam. This research indicates the potential opportunity to apply CuWO4 foam in a scale-up microreactor.

Combined effects of weather conditions, transportation time and loading density on carcass damages and meat quality of market-weight pigs.

This study investigated the interactive effects of weather conditions, transportation time and loading density on carcass damages and meat quality traits of market-weight pigs under commercial conditions. The following pork quality parameters were measured: pH and temperature; colour; drip, thawing and cooking loss; and textural traits. Pigs were assigned to one of eight groups arranged in a 2 2 2 factorial design according to the weather conditions (hot and cold), transportation time (short and long) and loading density (high and low). A three-way ANOVA and Tukey's post-test (multiple comparisons) were performed to assess the differences between groups in examined pork quality traits. Pigs exposed to short transportation ( 20 ) at high loading density (0.29 ) during hot weather conditions produced meat with the lowest initial and ultimate meat pH value and sensory colour scores, and the highest initial temperature and the occurrence of pale, soft and exudative pork. The occurrence of pale, soft and exudative pork was reduced 5-fold during hot weather conditions when pigs were exposed to longer transportation ( 210 ) and low loading density (0.53 ). Pigs exposed to short transportation ( 20 ) at high loading density (0.41 ) during cold weather conditions produced the highest quality pork (the highest percentage of red, firm and non-exudative pork) characterised by lowest drip loss and value and the highest sensory colour scores. The highest percentages of carcass damages were recorded in pigs exposed to both low (0.50 ) and high (0.33 ) loading density during long transportation ( 210 ) in cold weather conditions. In conclusion, weather conditions and loading density are of greater importance for the occurrence of carcass damages and pork quality variation than transportation time.

Diphenyl Azidophosphate as a Functional Electrolyte Additive for High-Conductivity Film Construction over Lithium Metal Battery

Lithium metal batteries (LMBs) with high loading and high current density can be achieved by tailoring electrolyte components. As an effective film-forming electrolyte additive, diphenyl azidophosphate (DPPA) has been proposed here to construct high conductive solid electrolyte interphase (SEI) layers on the Li metal anode surface enriched with Li3N and P–O compounds. Compared with cells without DPPA additive, the Li∣∣Cu cells with 1% DPPA demonstrate evaluated accurate Coulombic efficiency (CE) from 77.9% to 93.8%, and Li∣∣Li symmetric cells are able to cycle for more than 250 h at the current density of 2 mA cm−2. The high conductive SEI layer increases the exchange current density of Li metal anode from 0.247 mA cm−2 to 0.760 mA cm−2. The Li∣∣LiNi0.8Co0.1Mn0.1O2 (NCM811) cell maintain 80.8% capacity retention after 250 cycles in the DPPA-containing electrolyte. Discharge capacity of the Li∣∣NCM811 cell can reach 142 mA h g−1 at a high discharge current of 13.2 mA cm−2. Further theoretical calculations indicate that the DPPA additive can be preferentially reduced to form a stable SEI layer with high conductivity.

Stable Cycling of a 4 V Class Lithium Polymer Battery Enabled by In Situ Cross-Linked Ethylene Oxide/Propylene Oxide Copolymer Electrolytes with Controlled Molecular Structures.

Commercial lithium-ion batteries are vulnerable to fire accidents, mainly due to volatile and flammable liquid electrolytes. Although solid polymer electrolytes (SPEs) are considered promising alternatives with antiflammability and processability for roll-to-roll mass production, several requirements have not yet been fulfilled for a viable lithium polymer battery. Such requirements include ionic conductivity, electrochemical stability, and interfacial resistance. In this work, the ionic conductivity of the SPEs is optimized by controlling the molecular weight and structural morphology of the plasticizers as well as introducing propylene oxide (PO) groups. Electrochemical stability is also enhanced using ethylene oxide (EO)/PO copolymer electrolytes, making the SPEs compatible with high-Ni LiNixCoyMn1-x-yO2 cathodes. The in situ cross-linking method, in which a liquid precursor first wets the electrode and is then solidified by a subsequent thermal treatment, enables the SPEs to soak into the 60 μm thick electrode with a high loading density of more than 8 mg cm-2. Thus, interfacial resistance between the SPE and the electrode is minimized. By using the in situ cross-linked EO/PO copolymer electrolytes, we successfully demonstrate a 4 V class lithium polymer battery, which performs stable cycling with a marginal capacity fading even over 100 cycles.

Microbial load of healthcare wastes in Aba Metropolis, Abia State

Introduction: Healthcare waste is the total waste both solid and liquid from healthcare establishment and laboratories. A hospital produces waste by giving their services to the patients. Purpose: This study examined the microbial load of waste from selected healthcare facilities in Aba metropolis, Abia State.
 Methodology: Tenfold serial dilution was used for processing of all the samples. After the dilutions, exactly 0.5ml of each the sample was planted on the media using the spread plate method and evaluated using the standard microbiological techniques.
 Results: The viable count (TVC) ranged from 1.0×103cfu/g to 0.3×108cfu/g, coliform count (TCC) ranged from 0.4×102 cfu/g to 4.2×104 cfu/g, staphylococcal count (TSC) ranged from 1.0×101 cfu/g to 1.4×102 and fungal counts ranged from 2.0×102 cfu/g to 0.8×103cfu/g in the microbial count of various waste samples within the Aba metropolis, Abia State. The laboratory waste had the highest microbial counts, followed by the Out-patient department waste and the least was the pharmaceutical waste. The microorganisms isolated from the hospital wastes were Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Aspergillus niger, A. Fumigatus, Candida albicans and among others.
 Unique contribution to theory, practice and policy: This research has revealed that healthcare waste contained pathogens with high microbial load densities, suggesting that the hospital wastes may pose a major health and environmental threat, if not properly managed. The study recommends that, the government should ensure that there is a policy on hospital waste management in line with recommended international best practices, which should be monitored and enforced.

Direct conjugation of fluorescent quantum dots with E. coli via surface-displayed histidine-containing peptides

Biocompatible approaches to labeling bacteria with fluorescent nanoparticles are essential in order to create living bacterial bioconjugates for imaging, biosensors, medicine, and other applications. Herein we report the direct conjugation of carboxyl quantum dots (QDs) with E. coli outer membrane via surface-displayed binding peptides. The histidine-containing peptide H6G9 was displayed at the N-terminus of membrane-embedded enhanced circularly permuted outer membrane protein X (eCPX) scaffold, which was expressed upon chemical induction. The presence of the binding peptide creates an environment distinct from the negatively charged E. coli surface and provides strong binding affinity to carboxyl quantum dots (QDs). Transmission electron microscopy (TEM) analysis of E. coli-QD bioconjugates revealed high loading densities of these QDs immobilized on the cell surface, even when adding a very low concentration (10 μg/mL) of QDs in order to reduce the cell exposure. These hybrid cells strongly fluoresce with each of the distinct colors of loaded QDs with different emission wavelengths, which can be easily visualized by fluorescence microscopy or differentiated using flow cytometry. Importantly, the E. coli–QD bioconjugates were highly viable and maintained the ability to grow and divide. This study demonstrates a simple, direct, and highly efficient method for labelling bacteria with QDs, without significantly compromising the vitality of the cells.

Recent progress on the preparation of three-dimensional vertically aligned graphene and its applications insupercapacitors

<p indent=0mm>As the key parts of the electrode, materials and structure design are the most important factors to determine the properties of supercapacitors. The structure design of the electrode plays a critical role in deciding its reaction kinetics, ion transportation, and consequently the electrochemical performance of energy storage system. Graphene, as a building block of sp² carbon materials, is characterized by large surface area, excellent electron transfer and great chemical stability, allowing it as the most promising material for energy storage and the results from many laboratories confirm its potential to change today’s energy-storage landscape. Typically, graphene-based materials are randomly oriented with respect to the current collectors in a conventional stacked geometry in supercapacitors. However, increasing the mass loading or film thickness seriously declines the charge storage capability, including specific capacitance and rate capability. This is mainly due to the moderate electrical conductivity, slow ion diffusion, and poor mechanical stability. Control of structure and morphology is key for carbon-based electrodes to allow the effective permeation of the electrolyte to establish electrical double layers in supercapacitors. Three-dimensional vertically aligned graphene (3DVAG) on the current collector is believed to provide an ideal structure for supercapacitors electrode capable of high energy density. 3DVAG electrodes have attracted much research interest owing to their excellent reaction kinetics and mass-transfer capability. The unique properties such as large surface area, vertical open channels and low pore tortuosity, can enhance the ion/electron transfer and increase mass loading of active materials, and thereby ultimately improves the rate capability and energy density of the electrode material. Compared with the traditional graphene-based electrode, 3DVAG electrode has short ion diffusion pathways, better electrochemical performance and also inherits the excellent cycle stability of graphene-based electrodes. At present, the main preparation methods of 3DVAG include directional freezing, plasma-enhanced chemical vapor deposition, KOH assisted hydrothermal and others (e.g.,<italic> </italic>rolling and cutting rGO, electric field deposition, magnetic field alignment). Through manipulating the preparation processes, 3DVAG materials with highly ordered microstructure, tight pore density and high conductivity will be obtained. In this contribution, we review the ongoing research progress in preparation of 3DVAG and its applications in supercapacitors. Firstly, the main preparation methods, the mechanism and the influence of process parameters on the texture of 3DVAG are emphasized. Secondly, the application of 3DVAG materials in the field of supercapacitors including double electric layer capacitors (EDLCs), the related composites for pseudocapacitors (SCs) and hybrid supercapacitors (HSCs) are highlighted. Finally, the challenges and opportunities of further development and application of 3DVAG materials are discussed. The purpose of this review is to introduce a new type of graphene structure with vertically aligned microtexture, providing ideas for the effective utilization of graphene, and with its good vertical channels, it provides a feasible solution for development of high mass loading and high energy density electrode materials.

Pulsed Laser Confinement of Single Atomic Catalysts on Carbon Nanotube Matrix for Enhanced Oxygen Evolution Reaction.

The design of atomically dispersed single atom catalysts (SACs) must consider high metal-atom loading amount, effective confinement, and strong interactions with matrix, which can maximize their catalytic performance. Here reported is a promising method to synthesize SACs on highly conductive multiwall carbon nanotube (MWCNT) supports using pulsed laser confinement (PLC) process in liquid. Atomic cobalt (Co) and phosphorus (P) with a high loading density are homogeneously incorporated on the outer wall of the MWCNT (Co-P SAC MWCNT). Density functional theory (DFT) calculations in combination with systematic control experiments found that the incorporated Co and P adatoms act as an adsorption energy optimizer and a charge transfer promoter, respectively. Hence, favorable kinetics and thermodynamics in Co-P SAC MWCNT can be simultaneously achieved for water oxidation resulting in a superior catalytic performance than the benchmark RuO2 catalyst. Crucially, total processing time for assembling Co-P SAC MWCNT via PLC process is less than 60 min, shedding light on the promising practical applications of our SAC design strategy.

Investigation on initial atmospheric corrosion of copper and inhibition performance of 2-phenyl imidazoline based on electrical resistance sensors

The initial atmospheric corrosion of copper was investigated by electrical resistance sensor under different environmental factors (relative humidity, temperature, and NaCl loading density). The corrosion rate of Cu increases evidently with NaCl loading density, temperature and RH, but decreases with prolonged test. 2-phenyl imidazoline (2-PI) presents increasing inhibition efficiency on Cu with elevated temperatures at low NaCl loading density (≤40 μg/cm2), mainly due to that elevated temperature enhances the vapour pressure of 2-PI, however, 2-PI shows inferior performance on pre-corroded Cu at high NaCl loading density, possibly due to that the defective corrosion product layer formed at high RH retards the adsorption of 2-PI. Finally, molecular dynamic simulations were conducted to evidence the competitive adsorption advantage of 2-PI against H2O on Cu2O surface through chelation of 1-N of imidazoline with Cu(I).

Hierarchical Plasmonic-Fluorescent Labels for Highly Sensitive Lateral Flow Immunoassay with Flexible Dual-Modal Switching

Lateral flow immunoassay (LFIA), as a prominent point-of-care (POC) test platform, has been extensively adopted for rapid, on-site, and facile diagnosis of pathogen infections and disease biomarkers. Exploring novel structured optical labels of LFIA with amplified signal and complementary detection modes favors the sensitive and flexible POC diagnosis. Here, bimodal labels with both colorimetric and fluorescent readout were fabricated via a layered sequential assembly strategy based on affinity templates and hydrophobic metal-containing nanounits. High-quality colorimetric and fluorescent nanoparticles were densely incorporated into the colloidal supports and confined in separated regions, without interfering with each other. The hierarchical integration of gold nanoparticles and quantum dots with high loading density and good optical preservation realized dual readout and amplified signals from the assemblies of individual single nanoparticles. The "all-in-one" optical labels allowed both colorimetric and fluorescent detection of cystatin C (Cys C) after surface conjugation with antibodies. The LFIA strips revealed noninterfering dual signals for both visual inspection and quantitative detection of Cys C via the naked eye and portable devices, respectively. The limits of detection by colorimetric and fluorescent modes were 0.61 and 0.24 ng mL-1, respectively. The novel LFIA platform demonstrated sensitive, specific, and reproducible POC testing of biomarkers with flexible detection modes and was reliable for clinical diagnosis.

A Facile Method for the Fabrication of Silver Nanoparticles Surface Decorated Polyvinyl Alcohol Electrospun Nanofibers and Controllable Antibacterial Activities.

Polyvinyl alcohol (PVA) electrospun nanofibers (NFs) are ideal carriers for loading silver nanoparticles (Ag NPs) serving as antibacterial materials. However, it is still a challenge to adjust the particles size, distribution, and loading density via a convenient and facile method in order to obtain tunable structure and antimicrobial activities. In this study, Ag NPs surface decorated PVA composite nanofibers (Ag/PVA CNFs) were fabricated by the solvothermal method in ethylene glycol, which plays the roles of both reductant and solvent. The morphology and structure of the as-fabricated Ag/PVA CNFs were characterized by scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, X-ray diffraction, UV-visible spectroscopy, and Fourier transform infrared spectroscopy. Ag NPs had an average diameter of 30 nm, the narrowest size distribution and the highest loading density were successfully decorated on the surfaces of PVA NFs, at the AgNO3 concentration of 0.066 mol/L. The antibacterial properties were evaluated by the methods of absorption, turbidity, and growth curves. The as-fabricated Ag/PVA hybrid CNFs exhibit excellent antimicrobial activities with antibacterial rates over 98%, especially for the sample prepared with AgNO3 concentration of 0.066 mol/L. Meanwhile, the antibacterial effects are more significant in the Gram-positive bacteria of Staphylococcus aureus (S. aureus) than the Gram-negative bacteria of Escherichia coli (E. coli), since PVA is more susceptive to S. aureus. In summary, the most important contribution of this paper is the discovery that the particles size, distribution, and loading density of Ag NPs on PVA NFs can be easily controlled by adjusting AgNO3 concentrations, which has a significant impact on the antibacterial activities of Ag/PVA CNFs.

Stress Relief Principle of Micron‐Sized Anodes with Large Volume Variation for Practical High‐Energy Lithium‐Ion Batteries

AbstractPractical applications of high gravimetric and volumetric capacity anodes for next‐generation lithium‐ion batteries have attracted unprecedented attentions, but still faced challenges by their severe volume changes, rendering low Coulombic efficiency and fast capacity fading. Nano and void‐engineering strategies had been extensively applied to overcome the large volume fluctuations causing the continuous irreversible reactions upon cycling, but they showed intrinsic limit in fabrication of practical electrode condition. Achieving high electrode density is particularly paramount factor in terms of the commercial feasibility, which is mainly dominated by the true density and tapping density of active material. Herein, based on finite element method calculation, micron‐sized double passivation layered Si/C design is introduced with restrictive lithiation state, which can withstand the induced stress from Li insertion upon repeated cycling. Such design takes advantage in structural integrity during long‐term cycling even at high gravimetric capacity (1400 mAh g−1). In 1 Ah pouch‐type full‐cell evaluation with high mass loading and electrode density (≈3.75 mAh cm−2 and ≈1.65 g cm−3), it demonstrates superior cycle stability without rapid capacity drop during 800 cycles.

Research on Development Technology of AC / DC Hybrid Distribution Network Construction in Smart Grid

At present, the flexible interconnection of flexible power grids based on flexible DC and the combination of AC and DC distribution networks in smart grids will bring great changes and challenges to the operation of traditional power distribution systems. The AC / DC hybrid distribution network can better accept distributed power and DC loads, alleviate the contradiction between limited corridors and high load density in urban power grid stations, and provide dynamic reactive power support at the load centre, which can effectively improve the urban distribution system. Power quality, reliability and operating efficiency. This article summarizes and analyses key technical issues such as the topology, optimization planning, dispatch control, and economic evaluation of AC-DC hybrid distribution networks. Finally, the application prospects of AC-DC hybrid distribution networks are prospected.

Electrical modification of a composite electrode for room temperature operable polyethylene oxide-based lithium polymer batteries

Lithium polymer batteries (LPBs) are considered to be the most promising alternatives to current lithium-ion batteries (LIBs), which have been known to exhibit certain safety issues. However, the relatively poor electrochemical performances of LPBs hinder their practical usage, particularly at high C-rates, moderate temperatures, and/or with high loading densities. Therefore, this study analyzes the use of a novel composite electrode for manufacturing room-temperature operable LPBs with high loading densities. Rapid decay in the rate capabilities of LPBs at high C-rates is found to be attributable to the increased electrical resistance in an electrode. To account for this, this study modified the composite electrode with various conducting fillers. Subsequently, the effect of the type and content of the conducting fillers on the performance of LPBs was systematically investigated using the composite electrode. The incorporation of the conducting fillers in the lithium iron phosphate (LFP) composite electrode was found to effectively reduce the electrical resistance and consequently improve the electrochemical performance of LPBs. Furthermore, LFP composite electrodes with a mixture of structurally different graphene (G) and carbon nanotube (CNT) (1 wt%) were observed to demonstrate synergistic effects on improving the electrochemical performance of LPBs. The results obtained in this study elucidate that the facilitated electrical conduction within a composite electrode is critically important for the performance of LPBs and the expedited diffusion of Li+.

Understanding capacity fading mechanism of thick electrodes for lithium-ion rechargeable batteries

The use of thick electrodes with high-loading density of active material is one of the most practical strategies to increase the volumetric/specific energy density of lithium-ion battery, while taking advantage of the current electrode chemistry. However, their use is accompanied by serious deterioration of electrochemical performance, especially exhibiting poor capacity retention with low power capability. Here, the degradation behavior of the LiNi0·6Co0·2Mn0·2O2, one of widely adopted cathodes, is comparatively investigated under high loading levels as high as 28 mg cm−2 over the extended cycling. It is revealed that the charge transport limitation is cumulatively dominated by the lithium ionic diffusion rather than the electronic conduction in the thick electrode. More importantly, as the cycle proceeds, the thick electrode gets exposed to a serious reaction inhomogeneity because of the negative feedback between the accumulated ion transport limitation and locally increasing resistance. It leads to the generation of current hot spot in the electrode and the corresponding local material degradation, which further inhibit the charge transport, resulting in unavoidable capacity fading. This finding proposes that rational electrode architecture detouring the hot spot generation needs to be considered with respect to the ion transport and the electrode material degradation toward the high-loading electrodes.

A strategy to achieve high loading and high energy density Li-S batteries

A 3D sulfur cathode scaffold was fabricated by coaxially coating polar Ti 3 C 2 T x flakes on sulfur-impregnated carbon cloth (Ti 3 C 2 T x @S/CC) that exhibits an excellent electrochemical performance at higher loading. Lithium-sulfur (Li-S) batteries are one of the most promising rechargeable storage devices due to the high theoretical energy density. However, the low areal sulfur loading impedes their commercial development. Herein, a 3D free-standing sulfur cathode scaffold is rationally designed and fabricated by coaxially coating polar Ti 3 C 2 T x flakes on sulfur-impregnated carbon cloth (Ti 3 C 2 T x @S/CC) to achieve high loading and high energy density Li-S batteries, in which, the flexible CC substrate with highly porous structure can accommodate large amounts of sulfur and ensure fast electron transfer, while the outer-coated Ti 3 C 2 T x can serve as a polar and conductive protective layer to further promote the conductivity of the whole electrode, achieve physical blocking and chemical anchoring of lithium-polysulfides as well as catalyze their conversion. Due to these advantages, at a sulfur loading of 4 mg cm −2 , Li-S cells with Ti 3 C 2 T x @S/CC cathodes can deliver outstanding cycling stability (746.1 mAh g −1 after 200 cycles at 1 C), superb rate performance (866.8 mAh g −1 up to 2 C) and a high specific energy density (564.2 Wh kg −1 after 100 cycles at 0.5 C). More significantly, they also show the commercial potential that can compete with current lithium-ion batteries due to the high areal capacity of 6.7 mAh cm −2 at the increased loading of 8 mg cm −2 .