Understanding the electrochemical performance of LiNi0. 5Mn1.5O4 coated with Yttria and distributed over graphene nanosheets as cathode in li-ion batteries

LiNi0.5Mn1.5O4 is a promising cathode material for lithium-ion batteries with a high-voltage spinel structure. A microwave-assisted chemical co-precipitation method was used to synthesize Y2O3 coated quasi-spheres of LiNi0.5Mn1.5O4. The coating of Y2O3 and subsequent wrapping of quasi-spheres in graphene nanosheets does not alter the volume or promote the formation of unwanted phases. TGA analysis shows high thermal stability in the material. The material has an initial capacity of 133 mAh g−1 at C/10 with a retention of 98% after 100 cycles. In addition, cathode samples show a good capacity of 132 g−1 after 20 cycles at higher temperatures (55 °C). Oxide coatings protect the particles from ionic leaching but limit the electrical conductivity of the materials. However, graphene enhances the conductivity of the synthesized material and wraps active particles in a conductive channel. Due to the synergistic design of the material and the robust manufacturing technique, parasitic reactions are suppressed without affecting the electrical conductivity. To increase their cyclic performance, the suggested material synthesis approach may successfully be applied to various electrode materials

Graphene wrapped Y2O3 coated LiNi0.5Mn1.5O4 quasi-spheres as novel cathode materials for lithium-ion batteries

LiNi0.5Mn1.5O4 with a high-voltage spinel structure is a potential cathode material for high-energy lithium-ion batteries (LIBs). Y2O3 coated quasi-spheres of LiNi0.5Mn1.5O4 covered in graphene (LNMO-YO-G) have been synthesized by a microwave-assisted chemical co-precipitation technique. The coating of quasi-spheres with Y2O3 and subsequent wrapping in graphene nanosheets does not modify the bulk structure and inhibits the production of undesirable phases. Thermal analysis indicates that the developed materials demonstrate good thermal stability. The material exhibits an initial capacity of 133 mAh g−1 at the C/10 rate with a capacity retention of 98% after 100 cycles. Remarkably, a discharge capacity of 115 mAh g−1 is achieved in LNMO-YO-G at a 10C rate, reflecting its extraordinary improvement in the rate capability. Furthermore, after 20 cycles at higher temperature (55 °C), the cathode samples exhibit an excellent capacity of 132 mAh g−1. Y2O3 coating reduces the leaching of ions from the electrode, but such coatings reduce the electrical conductivity. Conversely, graphene increases the electrical conductivity, wraps the active particles along an electrically conductive path, and prevents agglomeration. Parasitic reactions are inhibited without compromising electrical conductivity due to the synergistic material design and fast microwave synthesis method. The proposed material synthesis strategy can be effectively extended to other classes of electrode materials to improve their cyclic performance.This publication was made possible by NPRP Grant # NPRP11S-1225-170128 from Qatar National Research Fund (a member of the Qatar Foundation). This publication was also made possible by the Qatar University Internal Grant ( QUCG-CENG-20/21-2 ). Open Access funding provided by the Qatar National Library. Statements made herein are solely the responsibility of the authors. Microstructural analyses (FE-SEM/EDX and HR-TEM) were accomplished at the Central Laboratory Unit (CLU), Qatar University, Doha, Qatar. XPS analysis was accomplished at the Gas Processing Center (GPC), Qatar University, Doha, Qatar.Scopu

Influence of graphene wrapped-cerium oxide coating on spherical LiNi0.5Mn1.5O4 particles as cathode in high-voltage lithium-ion batteries

Cobalt-free LiNi0.5Mn1.5O4 (Lithium Nickel Manganese Oxide; LNMO) has garnered considerable interest as a cathode material due to its high working voltage, lower cost, and environmental friendliness. However, LNMO cathodes currently exhibit low cyclability and capacity deterioration, severely restricting their use on a broader scale. To this end, microwave-assisted chemical co-precipitation was used to produce spherical aggregated nanoparticles of LiNi0.5Mn1.5O4 (LNMO) coated with CeO2 (LNMO-Ce) and wrapped in graphene (LNMO-Ce-GO). Structural analysis demonstrates that the ceria coating along with the graphene wrapping prevents unwanted phases from forming and altering the morphology of the LNMO microspheres. LNMO-Ce-GO exhibits a discharge capacity of 132.4 mAhg−1 at the C/10 rate with a capacity retention of 95.3 % after 100 cycles, compared to LNMO-Ce and bare LNMO samples that provide a capacity retention of 91.6 % and 84.7 % respectively. DSC analysis elucidate that the ceria coating helps to suppress the adverse reactions at the electrode/electrolyte interface and reduce the Mn3+ dissolution due to the Jahn Teller effect, increasing cell cyclability. The graphene wrapping reduces material aggregation and provides conductive pathways that significantly improve the electrochemical performance of the LNMO cathode. This innovative material design strategy can be efficiently expanded to other classes of lithium-ion battery cathode materials to enhance their electrochemical performance.This publication was supported by the Qatar National Research Fund's NPRP Grant # NPRP11S-1225-170128 (a member of the Qatar Foundation). This publication also sponsored via an internal grant from Qatar University (QUCG-CENG-20/21-2). Open Access funding provided by the Qatar National Library. The writers are entirely responsible for the statements stated herein. Moreover, the authors would like to express gratitude to the Central Laboratory Unit (CLU) at Qatar University, for conducting microstructural investigations (FE-SEM/EDX and HR-TEM). The authors would also like to thank Jeffin James Abraham for his technical assistance with various electrochemical characterizations.Scopu

Sodium and lithium incorporated cathode materials for energy storage applications - A focused review

The idea of lithium (Li)/sodium (Na) incorporated cathodes for both Li/Na-ion batteries has gained significant consideration throughout the past decade. The encouraging performance of various reported Li/Na incorporated cathode systems has the potential to review their exciting developments made so far to clearly understand the effect of numerous variables in improving the electrochemical performance. The current manuscript provides a focused review on the synthesis and electrochemical performance of these Li/Na incorporated cathode materials for Na/Li-ion batteries. Furthermore, the ruling mechanisms affecting the electrochemical performance of Li/Na incorporated cathode materials have been summarized. The majority of the synthesized Li/Na incorporated cathodes demonstrate good electrochemical cyclic stability, capacity retention, rate capability, charge/discharge capacity, etc. Li incorporated Na-based cathodes, show improved performance that can be attributed to the prevention of phase transformation at high voltages and loss of transition metal from the cathode. In the case of Na addition to Li-based cathodes, the Na pillaring effect significantly improves the Li interface layer stability, increases Li-ion diffusion, and retardation of Li and/or transition metal disordering. Various factors affecting the performance of Li/Na incorporated cathode families have been discussed that can be taken into account for development of future novel cathode materials demonstrating decent performance.The authors would like to acknowledge the financial support of Qatar University (QU) internal grant-QUCG-CENG-20/21-2. This publication was also made possible by NPRP Grant # NPRP11S-1225-170128 from Qatar National Research Fund (QNRF) (a member of the Qatar Foundation). Open Access funding provided by the Qatar National Library. Statements made here are the responsibility of the authors.Scopu

Combustion-Free Synthesis of Lithium Manganese Oxide Composites with CNTs/GNPs by Chemical Coprecipitation for Energy Storage Devices

Nano Spinel Lithium Manganese Oxide (LiMn2O4) was distributed properly on carbon nanotubes ( CNTs) and graphene nanoplatelets (GNPs) using chemical coprecipitation method. The original particle size was less than 40 nm, and the average size of the crystallite was 20 nm without the application of any capping agents. Characteristic spectra of spinel structure and a peak of CNTs & GNPs obtained using X-ray powder diffraction (XRD). CNTs and GNPs in energy storage systems improve the rate capabilities and cyclic efficiency of cathode materials. The suggested technique, chemical coprecipitation, provides new avenues for the production of nano-sized lithium transition metal oxide composites with CNTs and GNPs in an inexpensive and simple way. Higher density energy storage systems raise significant safety issues, and for safety, they are restricted to 30 percent to 50 percent of their ability. The proposed composite would enable the energy storage systems to be used even at high temperatures and higher discharge rates above 60 percent of their ability. Besides, the parasitic reaction between the electrode surface and the electrolyte will decrease, which will increase the battery's projected life span. As an all-solid-state device, the new composite batteries would make the system non-flammable, immune from side reactions, and resistant to capacity erosion

Impact of coatings on the electrochemical performance of LiNi0.5Mn1.5O4 cathode materials: A focused review

The application of Lithium-ion batteries (LIBs) in portable electronics and electric vehicles (EVs) has increased in the past decade. Extended commercialization of LIBs for advanced applications requires the development of high-performance electrode materials. LiNi0.5Mn1.5O4 (Lithium Nickel Manganese Oxide referred to as LNMO) has attracted much attention as a cathode material due to its high voltage and energy density, lower cost, and environmental friendliness. However, LNMO cathodes are currently suffering from poor cyclability and capacity degradation at elevated temperatures. Many strategies have been suggested in the literature to address the challenges associated with numerous families of cathode materials. Among those, surface modification techniques like surface coatings have proven to be promising. Surface coatings have a good effect on the electrochemical performance of LNMO, as these result in increasing electronic and ionic conductivity, fast ions mobility and high diffusivity. Towards this direction, a systematic review of research progress carried out in the area of coated LNMO has been summarized. More precisely, the impact of numerous coating materials in improving cyclability and capacity retention at elevated temperatures of LNMO has been discussed along with a variety of coating synthesis technologies.This work was supported by NPRP Grant # NPRP11S-1225-170128 from Qatar National Research Fund (a member of the Qatar Foundation ). This work was also made possible by the Qatar University Internal Grant ( QUCG-CENG-20/21-2 ). Statements made herein are solely the responsibility of the authors.Scopu

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population