Residual Capacity Research Articles

Experimental and analytical study on post-fire residual flexural behavior of corroded reinforced concrete beams after various cooling methods

To study the flexural behavior of corroded reinforced concrete (RC) beams after various cooling methods, a series of tests were carried out on twenty-four RC beams. The study delved into the effects of corrosion degree (5 %, 10 %, and 15 %), fire exposure time (60 min, 90 min, and 120 min), and cooling methods (natural cooling and water cooling) on the flexural performance of the beams. The results indicated that during the cooling phase, beams subjected to water-sprayed cooling exhibited a faster cooling rate and more pronounced surface cracks in comparison to beams undergoing natural cooling. All beam specimens showed flexural failure mode, but it should be noted that water-spraying cooling may induce brittle failure in beams post-fire. The descending segment of the load-deflection curve for failed specimens with over-reinforcement was steep, indicative of poor ductility. The peak load of the specimens decreased by 36 % from unexposed to 120 min of exposure. Notably, the impact of fire exposure time on peak load was more pronounced than that of the corrosion degree. In terms of cooling methods, the flexural capacities exhibited a more significant decline in beams subjected to water-spraying cooling compared to those under natural cooling, with a reduction of 42 %. The residual flexural capacities of corroded RC beams were predicted using a simplified analytical model incorporating heat transfer analysis and cross-section analysis methods. The predictions demonstrated excellent agreement with the experimental results. The conclusions can provide theoretical guidance for fire rescue after exposure to fire.

Slowing lung deflation by increasing the expiratory resistance enhances FRC in preterm rabbits.

As very preterm infants have surfactant-deficient and highly incompliant lungs, slowing lung deflation during expiration might help preserve functional residual capacity(FRC) during lung aeration. In this study, we investigated the effect of expiratory resistance(Re) on lung aeration during positive pressure ventilation in preterm rabbits immediately after birth. Preterm rabbit pups were delivered at 29 days gestation, mechanically ventilated from birth and simultaneously imaged to measure lung aeration using phase-contrast X-ray. Re was varied by altering the length (0, 60 or 1000 mm) of the expiratory circuit. Increasing Re led to a decrease in lung deflation rates and both peak expiratory flows and flow rates at mid-deflation. As a result, the rate of de-acceleration(slowing) in lung deflation when approaching FRC was markedly reduced with increasing resistance. During lung aeration, FRC was significantly different between resistance groups and was significantly higher over time in the high compared to the low resistance group. While FRC values tended to be higher with higher Re, they were not significantly different at end-ventilation (t = 7 min). Increasing Re of the ventilation circuit during lung aeration in preterm rabbits immediately after birth decreased lung deflation rates and increased the accumulation of FRC over time. The expiratory phase of the ventilatory cycle has been largely overlooked as an opportunity to improve ventilation in preterm infants after birth. Increasing the expiratory resistance of the ventilator circuit during lung aeration in preterm rabbits immediately after birth markedly decreased lung deflation rates and increased FRC accumulation, compared to a low expiratory resistance. This indicates that ventilation devices that reduce the "work of breathing" by reducing the expiratory resistance, may have the unintended effect of reducing FRC, particularly in extremely preterm infants that have surfactant deficient highly incompliant lungs.

Experimental behavior of axially loaded circular high-strength concrete-filled high-strength steel tubular stub columns after exposure to fire

The high-strength concrete-filled high-strength steel tubular (HCFHST) column is an innovative type of high-performance steel-concrete composite component, which has a broad prospect for engineering applications. To investigate the axial compressive behavior of post-fire HCFHST stub columns with circular cross-sections, twenty-five specimens were heated following ISO 834 standard fire and then loaded to failure under axial compression after being cooled. The effects of various heating durations, concrete and steel strength on the temperature distribution, spalling of the steel-concrete interface, post-fire ultimate bearing capacity and axial stiffness were analyzed. The residual ultimate capacity and axial stiffness of HCFHST stub columns experience a pronounced decrease as the heating duration increases. High strength steel has no significant contribution to the enhancement of the post-fire axial stiffness of HCFHST stub columns, and the effect level of high-strength concrete on the failure load of composite columns subjected to different heating durations is similar. Finally, the applicability of relevant equations for the residual compressive capacity of the ordinary strength CFST column to HCFHST stub columns was evaluated. The evaluation results revealed that available methods of conventional strength CFST stub columns cannot obtain accurate post-fire resistance predictions of circular HCFHST stub columns.

Spatial variation of methane oxidation and carbon dioxide sequestration in landfill biogeochemical cover

ABSTRACT The study investigated the spatial variation of potential methane (CH4) oxidation and residual carbon dioxide (CO2) sequestration in biogeochemical cover (BGCC) system designed to remove CH4, CO2, and hydrogen sulfide (H2S) from landfill gas (LFG) emissions. A 50 cm x 50 cm x 100 cm tank simulated BGCC system, comprising a biochar-amended soil (BAS) layer for CH4 oxidation, a basic oxygen furnace (BOF) slag layer for CO2 and H2S sequestration, and an upper topsoil layer. Synthetic LFG was flushed through the system in five phases, with each corresponding to different compositions and flow rates. Following monitoring, the system was dismantled, and samples were extracted from different depths and locations to analyze spatial variations, focusing on moisture content (MC), organic content (OC), pH, and electrical conductivity (EC). Additionally, batch tests on selected samples from BAS and BOF slag layers were performed to assess potential CH4 oxidation and residual carbonation capacity. The aim of study was to evaluate the BGCC's effectiveness in LFG mitigation, however this study focused on assessing spatial variations in physico-chemical properties, CH4 oxidation in the BAS layer, and residual carbonation in the BOF slag layer. Findings revealed CH4 oxidation in the BAS layer varied between 22.4 and 277.9 µg CH4/g-day, with higher rates in the upper part, and significant spatial variations at 50 cm below ground surface (bgs) compared to 85 cm bgs. The BOF slag layer showed a residual carbonation capacity of 40-49.3 g CO2/kg slag, indicating non-uniform carbonation. Overall, CH4 oxidation and CO2 sequestration capacities varied spatially and with depth in the BGCC system.

Effect of Intraoperative Lung Recruitment and Transversus Abdominis Plane Block in Laparoscopic Bariatric Surgery on Postoperative Lung Functions: A Randomized Controlled Study

Abstract Background Morbid obesity may cause a restrictive condition. general anesthesia (GA) and supine posture both result in a decrease in lung capacity and Functional residual capacity (FRC), encouraging the development of atelectasis, altering the ventilation/perfusion ratio and raising the pulmonary shunt. This study evaluated the impact of recruitment maneuver (RM) and Transversus Abdominis Plane (TAP) block performed during laparoscopic bariatric surgery on spirometry, oxygenation, hemodynamic variables, opioid requirements and pain score assessed after surgery. Methods This pilot prospective randomized controlled study included 80 patients scheduled for elective laparoscopic bariatric surgeries (e.g., laparoscopic sleeve gastrectomy, and laparoscopic gastric bypass) under GA. Patients were divided into four equal groups. All patients had received standardized postoperative analgesia regimen, group I (control group), group II received TAP block after intubation and before surgical incision, group III received RM after intubation and after pneumoperitoneal exsufflation, and group IV received RM after intubation and after pneumoperitoneal exsufflation and TAP block after intubation and before surgical incision. Results Forced Vital Capacity “FVC”, Forced Expiratory Volume “FEV1” were found to be significantly higher after operation in group IV compared to other groups. FEV1/FVC was insignificantly different among the four groups before and after operation. Intraoperative PaO2, PaO2/FiO2 were significantly higher in group III and IV compared to other groups. Numerical rating scale (NRS) at 1, 2, 4, 6 and 12hr had significantly decreased in group II and IV compared to other groups. Heart rate (HR) and mean arterial blood pressure (MAP) were insignificantly different among the four groups. Morphine consumption was significantly lower in group II and IV compared to other groups. Conclusions TAP block combined with RM group exhibited better postoperative pulmonary function tests (PFTs). Intraoperative oxygenation was higher in RM groups. NRS and opioid consumption were lower in TAP groups in postoperative period.

Study of the functional residual capacity of the lungs caused by nitrogen leaching during multiple respirations and the diffusion capacity of the lungs in patients with bronchial asthma and chronic obstructive pulmonary disease

Relevance. This article discusses the use of nitrogen depletion and lung diffusivity measurements to assess functional lung capacity (FLC) in patients with bronchial asthma (BA) and chronic obstructive pulmonary disease (COPD).Relevance. This article discusses the use of nitrogen depletion and lung diffusivity measurements to assess functional lung capacity (FLC) in patients with bronchial asthma (BA) and chronic obstructive pulmonary disease (COPD).The purpose. Comparative assessment of FRC values measured using diffusion tests and nitrogen-leaching methods during multiple respirations.Material and methods. An observational cross-sectional study was conducted. The examination results of the two groups were compared. Group 1: included 30 patients with BA of 3–4 severity — 13 men (43.4 %) and 17 women (56.6 %); the average age was 50.6±4.3 years at the stage of subsiding exacerbation. Group 2: included 30 patients with moderate COPD — 13 men (43.4 %) and 17 women (56.6 %), average age was 50.6±4.3 years. The functional residual capacity of the lungs was determined using the multiple-breath nitrogen washout method, whereas the diffusion capacity of the lungs. The statistical analysis and visualization of the obtained data were performed using the statistical computing environment R 4.3.0 (R Foundation for Statistical Computing, Vienna, Austria). Differences were considered statistically significant at a p<0.05. The Bland — Altman method was used to assess the consistency of the FRC measurements obtained from the two methods.Results. Two groups of patients were examined: first group — 30 patients with BA of 3–4 severity; second group — 30 patients with COPD. When statistically analyzed between the two methods, no significant differences were observed in the FRC values using the nitrogen washout method and lung diffusivity. The Bland-Altman method produced similar statistical results.Conclusion. Measurement of FRC in patients with asthma and COPD can be performed using both lung diffusivity and multibreath nitrogen washout methods.

Effect of alkaline rice straw fibers content and curing ages on static mechanical properties of cemented lithium mica tailings backfill

Alkaline rice straw fibers (ARSF), as a widely available and recyclable plant fiber source, can provide new insights for improving the mechanical properties of backfill and the treatment of agricultural waste resources research. Different amounts of ARSF were prepared to enhance the cemented lithium mica tailings backfill (CLMTB), and uniaxial compression strength (UCS) tests and Brazilian splitting tensile strength tests were conducted to study the influence of ARSF on the static mechanical properties of CLMTB samples. Firstly, the flowability of mortars with different ARSF content was tested, the results showed that the flowability decreased by a maximum of 5.4 %, which met the construction requirements of cement mortar in the construction process. The UCS showed an increasing trend and then reduced with the increased ARSF content, with 0.15 % being the optimal content, showing a maximum increase of 14.2 %. Under Brazilian splitting loading conditions, the tensile strength gradually increased with the increased ARSF content, with 0.60 % being the optimal content. The UCS of the CLMTB samples showed exponential growth with increased curing age. Additionally, there was a linear functional relationship between the curing age and the tensile strength of the CLMTB samples. The experimental results indicate that the ARSF improved the toughness and changed the failure mode of the CLMTB samples. In the meantime, it increased the residual bearing capacity and the peak tensile strain of the CLMTB samples.

Rotor speed signature analysis‐based inter‐turn short circuit fault detection for permanent magnet synchronous machines

AbstractA rotor speed signature analysis‐ (RSSA‐)based inter‐turn short circuit (ITSC) fault diagnostic method is proposed, which is robust with regard to speed‐ and current‐loop bandwidths of permanent magnet synchronous machine (PMSM) drive systems. Conventional ITSC fault detection solutions that rely on current signals or extra devices. Thus, an initial step of investigation on the validity of RSSA is taken for residual insulation capacity monitoring of the ITSC fault at the incipient stage. The Vold–Kalman filtering order tracking method is employed for the real‐time extraction of fault features. Besides, the impact of speed‐ and current‐loop controller bandwidths on ITSC fault diagnosis is also analysed and an Adaline estimator is designed to decouple their impacts. Finally, the effectiveness of the proposed method is verified on a faulty PMSM, which exhibits satisfying results in tracking the degradation of residual insulation, even if the phase currents are significantly distorted due to low switching frequency of the inverter.

Experimental study on compressive capacity of stainless steel S35657 columns with welded box section and I-section under axial compression

Compared with conventional stainless steel, a new type of stainless steel, S35657, has broad application prospects owing to its advantages of high strength and low production costs. In this study, the compressive capacity of stainless steel S35657 columns was investigated. A total of 13 specimens were designed and tested, including 4 box section specimens and 9 I-section specimens (4 buckling around the major axis and 5 buckling around the minor axis). Complementary chemical composition analyses, material tensile tests, residual stress measurements, and initial geometric imperfection measurements were also conducted. The mechanical properties of the material, as well as its residual stress distribution model, failure mode, load-displacement curve, and compressive capacity, were reported and analyzed. For box section columns, when the slenderness ratio increased from 29 to 55.2, the compressive capacity of the column decreased by 27.6 %. The accuracy and safety of design methods specified in European standard EN 1993–1–4, American specification ASCE-8–02, and Chinese specification CECS 410 were assessed based on the test results. The result shows that EN 1993–1–4 is overly conservative in its compressive capacity calculations, whereas ASCE-8–02 overestimates the compressive capacity with a higher level of scatter exhibited. The methods of CECS 410 for predicting the compressive capacity of welded stainless steel S35657 columns are more accurate compared with the methods of EN 1993–1–4 and ASCE-8–02.

Experimental study on full-scale glass roof panels with embedded laminated connections under the short-term and long-term loading

This experimental study covers a problematic of full-scale roof panels with four embedded laminated point connections under two types of loads - short-term loads on intact panels, and long-term uniform loads after the fracture of a thermally treated glass pane. Two types of panels consisting either of fully tempered, or heat strengthened glass plies in combination with float glass, were tested, and a specific type of Ethylene Vinyl Acetate foil was used as the interlayer. The first part of the study investigates short-term load bearing capacity of horizontally suspended panels. The load was applied in several loading and unloading cycles until the collapse of any connection. The second part of the study is focused on the residual load-bearing capacity of the roof panels after a partial failure, whereas a first step, the thermally treated glass plies were intentionally fractured. The long-term part of the experiment was performed within 65 days. During this period, the load was increasing until a collapse of any connection. In both types of experiment, a difference between specimens with fully tempered and heat strengthened glass was observed. In the short-term part of the experiment, the specimens with fully tempered glass failed in two steps and therefore, showed considerable post-failure load bearing capacity. On the other hand, the specimens with heat strengthened glass collapsed suddenly in one moment giving no post-failure capacity. In the long-term part of the experiment, the resistance of specimens with heat strengthened glass was higher than the resistance of specimens with fully tempered glass. Therefore, both types of panels might find its purpose in real applications if the needs of the structure are properly considered.

Evaluation of Residual Structural Capacity in Corroded Reinforced Concrete Structures

Reinforcement corrosion is a critical issue that affects the durability and service life of reinforced concrete structures. This study focuses on evaluating the effectiveness of natural corrosion inhibitors in mitigating the corrosion attack on reinforced concrete beams in saline environments. The study utilizes extruded exudates/resins obtained from plants and characterizes their potential eco-friendly and non-hazardous properties. The corrosion resistance of uncoated and coated steel reinforcements is examined through exposure to a 5% sodium chloride solution for 360 days. The samples are subjected to flexural beam tests at regular intervals to assess changes in mechanical properties. The results indicate that natural corrosion inhibitors can effectively improve durability and maintain higher residual strength capacities, even under severe exposure conditions. Coated bars show higher residual capacities and yield strengths compared to uncoated bars, attributed to the protective effect of the coatings. The inhibitors also reduce corrosion rates and preserve mechanical properties like yield strength and ductility, enhancing the service life of reinforced concrete structures. The study emphasizes the use of locally available materials to counteract the negative effects of corrosion attack in marine environments.

Innovative bridge deck solutions: Examining the impact response and capacity of UHPC with FRP stay-in-place formworks

This study investigates the impact behaviour of bridge decks constructed with ultra-high-performance concrete (UHPC) and fibre-reinforced polymer (FRP) stay-in-place (SIP) formwork. Eight scaled bridge decks were fabricated and tested under pendulum impacts. Two different FRP SIP formwork configurations, i.e., square hollow section (SHS) and Y-shaped stiffened, were considered. Two types of reinforcing bars, i.e., steel and glass FRP (GFRP), were adopted for these samples. The influence of impact velocity on the transient response and progressive damage of the concrete decks under impact loading was investigated. The test results showed that UHPC and Y-shaped stiffeners were effective in decreasing the peak and residual displacements of decks by up to 70 % when compared to decks made with normal strength concrete. UHPC and Y-shaped stiffeners greatly improved the impact and residual impact capacities. The use of GFRP rebars instead of steel reinforcement changed the failure mode and FRP SIP formwork reduced deck damage and mitigated scabbing failure under impact loads. The configuration of FRP SIP formwork had a substantial influence on the impact force and thus the deck’s performance. Especially, this study has observed an interesting phenomenon under impact, i.e., reaction force could be greater than impact force, which has not been reported in the literature yet.

Axial compression performance of rubberized concrete-filled steel tubular stub columns after fire exposure: Experimental investigation and calculation models

Rubberized concrete (RuC) has emerged as a promising eco-friendly solution for structural elements, offering improved energy dissipation, damping characteristics, and ductility. Incorporating rubber particles into concrete-filled steel tubular (CFST) columns presents an environmentally conscious alternative for various structural applications. However, understanding its performance post-fire is crucial for safe design application, an area currently lacking comprehensive research. This study investigates the structural behavior of sixteen axially loaded circular RuCFST columns after exposure to fire. The columns, with diameters of 219 mm and 377 mm, are filled with normal concrete and RuC, containing 5 %, 15 %, and 30 % replacement of natural fine and coarse aggregate with rubber particles. Following ISO-834 fire standards, the specimens undergo elevated temperatures and subsequent application of compressive axial loads to determine their post-fire behavior. Analysis includes examination of failure modes, temperature-time relationships, axial load-deformation curves, and strain and stress development in the columns. Microstructural analysis using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) is conducted to study internal morphology before and after exposure to high temperatures. Results indicate non-uniform and nonlinear distributions of maximum temperatures across cross-sections, with historical temperature affecting residual capacity more significantly with increased rubber content and decreased column size. Load-bearing capacities decrease by up to 30 % and 22 % for small and large RuCFST columns, respectively, after exposure to fire. Residual axial stiffness also declines, with reductions of nearly 55 % and 42 % for small and large columns, respectively. In contrast, ductility improves in fire-exposed specimens, with columns having a 30 % rubber replacement ratio showing the highest enhancement. A novel method for calculating post-fire residual load capacity based on the average historical maximum temperature is introduced, demonstrating high accuracy and offering a valuable tool for assessing and reinforcing RuCFST columns after fire exposure.

Improvements of the shape and strength of the diaphragm after endoscopic lung volume reduction

RationaleEndoscopic lung volume reduction improves lung function, quality of life and exercise capacity in severe emphysema patients. However, its effect on the diaphragm function is not well understood. We hypothesised...

Resilient and Sustainable Structures through EMI-Based SHM Evaluation of an Innovative C-FRP Rope Strengthening Technique

Reinforced Concrete (RC) members in existing RC structures are susceptible to shear-critical due to their under-reinforced design. Thus, implementing a retrofitting technique is essential to eliminate the casualties that could arise from sudden and catastrophic collapses due to these members’ brittleness. Among other proposed techniques, using Carbon-Fiber Reinforced Polymers (C-FRP) ropes to increase the shear strength of RC structural elements has proved to be a promising reinforcement application. Moreover, an Electro-Mechanical Impedance (EMI-based) method using Lead Zirconate Titanate (PZT-enabled) was employed to assess the efficiency of the strengthening scheme. Initially, the proposed technique was applied to C-FRP rope under the subjection of pullout testing. Thus, a correlation of the rope’s tensile strength with the EMI responses of the PZT patch was achieved using the Root Mean Square Deviation (RMSD) metric index. Thereafter, the method was implemented to the experimentally acquired data of C-FRP ropes, used as shear reinforcement in a rectangular deep beam. The ropes were installed using the Embedded Through Section (ETS) scheme. Furthermore, an approach to evaluate the residual shear-bearing capacity based on the EMI responses acquired by being embedded in and bonded to the ropes’ PZTs was attempted, demonstrating promising results and good precision compared to the analytical prediction of the C-FRP ropes’ shear resistance contribution.

Li2ZrO3 coated LiFe0.4Mn0.6PO4/C with enhanced cycling performance at elevated temperature for lithium-ion batteries

Lithium iron manganese phosphate (LFMP) is regarded as one of the most promising cathode materials for lithium-ion batteries due to its high energy density and low cost. However, the Jahn-Teller effect of Mn3+ inevitably causes the dissolution of Mn during the cycling process, is accompanied by a severe decrease in the discharge capacity and a decline in capacity retention rate, which is more serious at elevated temperature. Here, the LiFe0.4Mn0.6PO4/C (LFMP-0LZO) cathode material is prepared via carbothermal reduction method, and its surface is modified by Li2ZrO3 (LFMP-1LZO) to enhance the surface stability and improve the cycling performance at room temperature and elevated temperature. The residual capacities of LFMP-0LZO sample is 113.7 mAh g−1, with a capacity retention rate of only 75.55 % after 150 cycles at 55 °C and a current density of 1C (1C = 170 mA g−1), while the discharge capacity of 1 wt% Li2ZrO3-coated material (LFMP-1LZO) under the same conditions is 134.85 mAh g−1, with a higher capacity retention rate of 87.49 %. Furthermore, a series of characterization experiments show that the surface modification of LiFe0.4Mn0.6PO4/C with Li2ZrO3 can effectively inhibit the side reaction between the electrode/electrolyte interface and reduce the dissolution of Mn in the active substance.

INCREASING THE EFFECTIVENESS OF CIVIL PROTECTION BY THE DESIGN OPTIMIZING: THE REVIEW

Due to today's conditions, it is necessary to reconsider the purpose of buildings and structures that use a significant number of reinforced concrete elements subjected to complex stress-strain states. The researchers are faced with the task of determining the residual bearing capacity of an element with uneven damage, which will allow choosing the most optimal option for calculating and selecting materials. A detailed analysis of the most common damages to reinforced concrete structures, including protective structures and shelters, from the effects of explosives and weapons of various types was carried out to optimize and maintain strength and durability. It is also important to study the impact of damage that causes a stress-strain state that cannot be predicted by calculation.

Flexural failure mechanism of bamboo composite plates with different construction technologies and tectonic patterns

To investigate the failure mechanism of bamboo fiber reinforced composite (BFRC) plates with different construction technologies and tectonic patterns, flexural experiments were performed. The flexural property of the parallel bamboo strand lumbers (PBSL) is better than that of the glued laminated bamboo (GLB), where the cracking load is increased by 141 % at most and the peak load is increased by 57 % at most. The orthogonal structure for the cross-laminated bamboo (CLB) improves the flexural property to a certain extent by inhibiting the initial cracking whether it is PBSL or GLB, and the peak load is increased by 9.83 % and 11.40 %, respectively. The residual bearing capacity of the PBSL is better than that of the CLB, the PBSL can basically maintain half of the ultimate bearing capacity while the damage factor of CLB is as high as 0.84 when the structure is damaged, revealing that the orthogonal layup structure results in weak interlayer interface after explosion. Orthotropic plate theory and composite failure criteria were proposed and consistently predicted the cracking load and the ultimate load. It is found that matrix fracture controls the cracking load, while fiber fracture determines the ultimate load.

Experimental investigation on axial quasi-static compression and low-velocity impact behaviors of perforated thermoplastic composite cylindrical shells

Perforation in cylindrical shells is commonly a typical technique to fulfill relevant functional requirements. However, how the perforation influence the mechanical performance of thermoplastic composite cylindrical shells (TPCCS) is incompletely understood. Hence, a systematic investigation through quasi-static compression and low-velocity impact (LVI) experiments was carried out in this paper. The full-field strain distributions of TPCCS intact tubes (IT) and perforated tubes (PT) were monitored by using 3D-DIC, and the residual properties were also characterized by compression-after-impact (CAI) tests. The results show that under quasi-static compression, the structural stiffness decreases significantly with increasing perforation diameter. The perforation reduces the interference of internal random defects on the structural deformation mode, which leads to a significant strain concentration in PT. The peak force and initial stiffness under LVI are smaller than those under quasi-static compression, with IT displaying higher sensitivity to dynamic loading compared to PT. At the impact energy of 100 J, IT and PT exhibit “S”- and “X”-shaped deformation modes, respectively. CAI tests indicate that although PT has a poorer residual load-carrying capacity than IT, it retains good structural integrity and secondary energy absorption capacity. This study provides a valuable reference for the assessment and application of perforated TPCCS.

Cation doping for enhanced layer spacing and electrochemical performance in Li-rich Mn-based lithium-ion cathode materials

Lithium-rich manganese-based cathode materials offer promising research avenues owing to their high capacity. This study delved into the impact of cation doping on Li1.2Ni0.13Co0.13Mn0.54O2(LNCMO). A range of layered Li1.2BXNi0.13Co0.13Mn0.54O2 (LNCMOxB, B = Ca, Na, Al) cathode materials were produced utilizing calcium, sodium, and aluminum chloride as dopants. Combining these elements with the lithium-rich materials improves the capacity retention of the positive electrode and mitigates voltage decay. X-ray diffraction analysis, Rietveld structural refinement, SEM, and XPS verified the inclusion of Ca, Na, and Al in the synthesized samples. Electrochemical analysis revealed that the LNCMO-0.01Na sample, possessing the largest dopant radius, exhibited favorable cyclic stability at 0.2C. Conversely, the LNCMO-0.01Al sample, featuring the smallest doped cation radius, demonstrated superior rate performance. Specifically, after 30 cycles at varying rates, the capacity reached 170 mAh·g−1 at 0.2C. The LNCMO-0.007Ca sample exhibited the highest residual capacity, maintaining 151.4 mAh·g−1 after 100 cycles at 0.2C. Doping Li sites in Li1.2Ni0.13Co0.13Mn0.54O2 materials with appropriately sized divalent cations significantly enhances their overall electrochemical performance. This enhancement is attributed to ion doping within the Li and TM layers, expediting the diffusion kinetics of Li ions, and augmenting ion and electronic conductivity. Investigating the doping modification of lithium-rich manganese-based oxide microspheres is instrumental in advancing positive electrode materials for lithium-ion batteries, aiming for increased specific capacity and more stable material structures.