Controlling Li dendritic growth in graphite anodes by potassium electrolyte additives for Li-ion batteries

Fast charging promotes Li dendrite formation and its growth on graphite anodes, which affects cell performance in Li-ion batteries (LIBs). This work reports the formation of a robust SEI layer by introducing a KPF6 inorganic additive into the electrolyte. An optimal concentration of 0.001 M KPF6 effectively inhibits the growth of Li dendrites at 2C charging rates, compared with a commercial electrolyte. Electrolytes containing a KPF6 additive are shown here to deliver dual effects to mitigate the growth of dendrites. A thin LiF-rich SEI layer is formed on graphite, which blocks the electron leakage pathways. Additionally, K+ resides at defect sites (such as particle boundaries) due to its faster diffusion rate and blocks the incoming Li+ and restricts the growth of Li dendrites. The electrolyte with optimum concentration of KPF6, i.e., 0.001 M, effectively directs Li+ transport through the thin, durable, and low resistance LiF-rich SEI layer. This has implications for fast charging through optimization of the electrode/electrolyte interphase by controlling additive concentrations

Assessing the impact of first-life lithium-ion battery degradation on second-life performance

The driving and charging behaviours of Electric Vehicle (EV) users exhibit considerable variation, which substantially impacts the battery degradation rate and its root causes. EV battery packs undergo second-life application after first-life retirement, with SoH measurements taken before redeployment. However, the impact of the root cause of degradation on second-life performance remains unknown. Hence, the question remains whether it is necessary to have more than a simple measure of state of health (SoH) before redeployment. This article presents experimental data to investigate this. As part of the experiment, a group of cells at around 80% SoH, representing retired EV batteries, were cycled using a representative second-life duty cycle. Cells with a similar root cause of degradation in the first life (100–80% SoH) exhibited the same degradation rate in second life after being cycled with the same duty cycle during the second life. When the root cause of degradation in the first life is different, the degradation rate in the second life may not be the same. These findings suggest that the root cause of a cell’s first-life degradation impacts how it degrades in its second life. Postmortem analysis (photographic and SEM images) reveals the similar physical condition of negative electrodes which have similar degradation rates in their second life cycle. This demonstrates that cells with a similar first life SoH and root cause of degradation indeed experience a similar life during their second life. The experimental results, along with the subsequent postmortem analysis, suggest that relying solely on SoH assessment is insufficient. It is crucial to take into account the root causes of cell degradation before redeployment

A study on the influence of lithium plating on battery degradation

Within Li-ion batteries, lithium plating is considered as one of the main reasons behind the capacity fade that occurs during low temperature and fast charging conditions. Previous studies indicate that plating is influenced by the levels of loss of lithium inventory (LLI) and the loss of active material (LAM) present in a battery. However, it is not clear from the literature on how lithium plating influences battery degradation in terms of LAM and LLI. Quantifying the undesirable impacts of lithium plating can help in understanding its impact on battery degradation and feedback effects of previous lithium plating on the formation of present plating. This study aims to quantify the degradation modes of lithium plating: LLI, LAM at the electrode level. A commercial Li-ion cell was first, aged using two different cases: with and without lithium plating. Second, a degradation diagnostic method is developed to quantify the degradation modes based on their measurable effects on open-circuit voltage (OCV) and cell capacity. The results highlight that LAMNE and LLI levels under the fast charge profile are increased by 10% and 12%, respectively, compared to those under the less aggressive charge profile. Further, limitations of the degradation analysis methods are discussed

Development and application of a poly(acrylic acid)-grafted styrene–butadiene rubber as a binder system for silicon-graphite anodes in Li-Ion batteries

Silicon anodes require polymer binder systems that are both mechanically robust and electrochemically stable, to accommodate the dramatic volume expansion experienced during cycling operation. Herein, we report the use of a poly(acrylic acid)-grafted styrene–butadiene rubber (PAA-g-SBR) with 80% partially neutralized Na-PAA as the binder system for silicon-graphite anodes. The PAA-g-SBR graft copolymer was synthesized by grafting tert-butyl acrylate onto SBR and treating the intermediate with H3PO4. The PAA-g-SBR/Na-PAA binder system was found to provide superior electrochemical performances to that of a Na-PAA/SBR system. The Na-PAA/PAA-g-SBR system had a stable capacity retention of 673 mAh g–1 for 130 cycles, while the capacity retention of the Na-PAA/SBR system was found to decline immediately. The Na-PAA/PAA-g-SBR system also displayed more preferable mechanical properties, with a lower Young’s modulus value and a larger strain at failure compared to that of the Na-PAA/SBR system. Overall, these findings indicate a promising and robust polymer binder system for the application of silicon anodes in the next generation of lithium-ion batteries

Development of Broad Spectrum and Durable Bacterial Blight Resistant Variety through Pyramiding of Four Resistance Genes in Rice

Not AvailableBacterial blight (BB) disease caused by Xanthomonas oryzae pv. oryzae is a major biotic constraint on obtaining higher grain yields in rice. Marker-assisted backcross breeding (MABB) was performed by the pyramiding of Xa4, xa5, xa13 and Xa21 resistance genes in the popular variety, Ranidhan. A foreground selection in BC1F1, BC2F1, and BC3F1 progenies detected all the target genes in 12, 7 and 16 progenies by using the closely linked markers from a population size of 426, 410, and 530, respectively. The BB-positive progenies carrying the target genes with a maximal similarity to the recipient parent was backcrossed in each backcross generation. A total of 1784 BC3F2 seeds were obtained from the best BC3F1 progeny. The screening of the BC3F2 progenies for the four target genes resulted in eight plants carrying all the four target genes. A bioassay of the pyramided lines conferred very high levels of resistance to the predominant isolates of bacterial blight disease. In addition, these pyramided lines were similar to Ranidhan in 16 morpho-quality traits, namely, plant height, filled grains/panicle, panicles/plant, grain length, grain breadth, grain weight, milling, head rice recovery, kernel length after cooking, water uptake, the volume expansion ratio, gel consistency,alkali-spreading value, and the amylose content.Not Availabl

Controlling dendrite growth in graphite anodes using potassium electrolyte additives in Li-ion batteries

Fast charging of lithium-ion batteries is a critical requirement in the endeavour towards efficient operation of highly demanding electric vehicles. However, fast charging is one of the conditions that can provoke metallic lithium deposition and its subsequent growth to dendrites on graphite anodes, giving rise to potential safety risks. The likelihood for lithium dendrite growth becomes greater when the operating temperature falls below ambient temperature ranges. Additionally, the exfoliation of the graphite is another degradation mechanism in the presence of low temperature electrolyte solvents -such as propylene carbonate - leading to capacity fade. In this regard, an electrolyte additive needs to be employed to mitigate the dendritic growth and graphite exfoliation, hence enhancing the performance and lifetime of the battery. This research work implements an inorganic electrolyte additive, KPF6 as a mitigation strategy to enable the graphite anode to endure fast charging and low temperature operation. The key aspect of this work is to determine the optimised electrolyte and the underlying mechanism behind the mitigation process of Li dendrite growth - as well as graphite exfoliation. The electrochemical characterisation in collaboration with the post-mortem analysis provides an insight into the microstructural and compositional evolution of the anode, with respect to electrolyte composition. In order to obtain qualitative and/or quantitative information regarding the cycled graphite anode and the developed electrode/electrolyte interface, post-mortem characterisation techniques such as SEM, EDX, XRF, XRD, XPS, and SIMS are employed. This work also investigates the internal resistance developed by the additive incorporation throughout using an EIS study. This research work reports the formation of a robust SEI layer by introducing a KPF6 electrolyte additive. The optimal 0.001M KPF6 concentration effectively inhibits the growth of Li dendrite at 2C charging rate in comparison with commercial RD281 electrolyte. Firstly, KPF6 addition produces a thin LiF-rich SEI layer on graphite, which blocks the electron transfer at defect sites. Secondly, K+ resides at the defect sites such as particle boundaries due to its fast diffusion rate and blocks the incoming Li+, thereby restricting the growth of Li dendrites. The combined processes obstruct the incoming Li+ and electrons, hence inhibiting the reduction of Li+ to Li0 for further Li deposition. This improves the performance of the cell, which better directs the transport of Li+ through the thin, durable, and low resistance LiF-rich SEI layer. This study reveals the presence of metallic potassium dendrites along with decreased LiF concentration in the SEI layer, which fails to inhibit the dendritic growth as the concentration of KPF6 additive is increased in the electrolyte. The development of low temperature ternary electrolyte containing PC as co-solvent is also investigated together with a KPF6 additive. An optimised concentration of 10 vol % PC with 0.1M KPF6 enhances the electrochemical performance by suppressing the exfoliation of graphite and the growth of the dendrite. 0.1M KPF6 generates a strong LiF-rich SEI layer on graphite, which reduces the developed over-potential, thereby decreasing the likelihood for dendrite growth. The fast diffusion of K+ assists in suppressing PC decomposition, hence ensuring unexfoliated, dendritic-free graphite. This comprehensive in-depth study of the impact of KPF6 additive shows the beneficial effects of electrolyte additives for improving electrochemical performance and advancing the safety of LIBs

Correction: Tasnim Mowri et al. Assessing the Impact of First-Life Lithium-Ion Battery Degradation on Second-Life Performance. <i>Energies</i> 2024, <i>17</i>, 501

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Not AvailableIn this study, positional variation in duration of seed dormancy was studied within and between panicle in a salt tolerant dormant variety Luna Sankhi.Within a panicle, seed sampled from upper portion exhibited higher dormancy duration both in first and second panicle (28 days and 25 days respectively) compared to lower portion. This variation in dormancy duration within a variety necessitates bulking of seed from the selected panicles to be preferred while sampling for evaluating seed dormancy.Not Availabl

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Not AvailableIn the present study ten NRRI rice varieties were evaluated for their susceptibility to seed discolouration that occurred in field during maturity in Kharif 2017and also its effect on seedling vigour was observed. Reduction in seedling vigour index II (germination% x seedling dry wt of 10 day old seedling in mg.) was observed in all the discoloured seed compared to healthy seed in all the variety which was due to reduced germination value in discoloured seed indicating its effect on storability.Not Availabl

Operando electrochemical impedance spectroscopy and its application to commercial Li-ion batteries

Electrochemical impedance spectroscopy (EIS) is a non-invasive technique for examining kinetics of electrochemical systems. Applied to energy storage devices, the impedance contains information about the state-of-charge and state-of-health of a battery. Classical EIS measurements, as implemented in many cyclers, are restricted by two important assumptions: linearity and stationarity. However, Li-ion batteries are inherently nonlinear, and are nonstationary while under operation. Classical EIS can thus only be performed on batteries in steady-state, and hence, no information about batteries under operation can be extracted. In this article, operando EIS is introduced as a promising tool for measuring time-varying impedance data of Li-ion batteries. The mathematics behind the impedance extraction are detailed, starting from nonstationary and mildly nonlinear current and voltage data. The technique is then applied to reproducible experiments, while charging and discharging commercial Li-ion batteries, using a commercial potentiostat. The operando impedance is shown to be different from the classical impedance, and the nonlinear behaviour of the battery is studied. Applications of operando EIS are discussed, with the focus on the modelling of the operando impedance data through equivalent circuit models, revealing the evolution of the ECM parameters over time