Synergetic effects of LiFe0.3Mn0.7PO4–LiMn1.9Al0.1O4 blend electrodes

AbstractComposite cathodes are prepared by blending the olivine LiFe0.3Mn0.7PO4 (LFMP) and spinel LiMn1.9Al0.1O4 (LMO) in order to combine the high capacity of LFMP with the rate capability of the spinel. While tap density, capacity and energy density show a linear dependency on the blend ratio, a remarkable synergetic effect between LFMP and LMO improving the electrochemical performance at higher C-rates is demonstrated. Potential curves of blend electrodes at rates of 3C reveal a less pronounced polarization for the Mn2+/3+ plateau than expected from theoretical calculations. This buffer effect is also observed for high current pulses (5C) where blend electrodes resemble the behavior of pure spinel electrodes. In terms of power density at high states of charge (SoC), the performance of the Blend(50LFMP/50LMO cap%) exceeds even that of pure spinel. In addition, the spinel-related manganese dissolution can be drastically reduced by blending spinel with LFMP. This study shows the expected and synergetic effects of LFMP/spinel blends and compares the results with theoretical calculations

Study of the Binder Influence on Expansion/Contraction Behavior of Silicon Alloy Negative Electrodes for Lithium-Ion Batteries

In lithium-ion batteries, Si-based materials such as silicon alloys are regarded as a promising alternative to graphite negative electrode to achieve higher energy. Unfortunately, they often suffer from a large volume change that can result in poor cycle life. We monitored the electrode expansion/contraction that occurs during lithiation/delithiation in real time by electrochemical dilatometry. Volume changes of Si alloy-based electrode with three different polymer binders have been compared. Electrode manufactured with lithiated polyacrylic acid (LiPAA) exhibited the greatest expansion but also demonstrated the highest reversibility as well as the best cycling performance. Ex situ SEM imaging along with dilatometer measurements revealed that electrode porosity after contraction (delithiation) increases compared to that after precedent expansion (lithiation), which can buffer volume expansion at the subsequent cycle. Proof-of-concept in situ optical microscopy (IOM) experiments were carried out with the best performing LiPAA electrode. The results demonstrated that LiPAA electrode in the IOM cell expanded much less than the same electrode in the dilatometer cell. This implies that internal pressure existing in a lithium-ion cell has a great impact on total electrode expansion

Biphenyl-Bridged Organosilica as a Precursor for Mesoporous Silicon Oxycarbide and Its Application in Lithium and Sodium Ion Batteries

Silicon oxycarbides (SiOC) are an interesting alternative to state-of-the-art lithium battery anode materials, such as graphite, due to potentially higher capacities and rate capabilities. Recently, it was also shown that this class of materials shows great prospects towards sodium ion batteries. Yet, bulk SiOCs are still severely restricted with regard to their electrochemical performance. In the course of this work, a novel and facile strategy towards the synthesis of mesoporous and carbon-rich SiOC will be presented. To achieve this goal, 4,4′-bis(triethoxysilyl)-1,1′-biphenyl was sol–gel processed in the presence of the triblock copolymer Pluronic P123. After the removal of the surfactant using Soxhlet extraction the organosilica material was subsequently carbonized under an inert gas atmosphere at 1000 °C. The resulting black powder was able to maintain all structural features and the porosity of the initial organosilica precursor making it an interesting candidate as an anode material for both sodium and lithium ion batteries. To get a detailed insight into the electrochemical properties of the novel material in the respective battery systems, electrodes from the nanostructured SiOC were studied in half-cells with galvanostatic charge/discharge measurements. It will be shown that nanostructuring of SiOC is a viable strategy in order to outperform commercially applied competitors

Arrhenius plots for Li-ion battery ageing as a function of temperature, C-rate, and ageing state – An experimental study

Gints Kucinskis acknowledges Latvian Council of Science project “Cycle life prediction of lithium-ion battery electrodes and cells, utilizing current-voltage response measurements”, project No. LZP-2020/1–0425. Institute of Solid-State Physics, University of Latvia as the Centre of Excellence has received funding from the European Union's Horizon 2020 Framework Program H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2. ZSW acknowledges funding of the project GradiBatt by the industrial collective research programme (IGF no. 20884 N/2) which was supported by the German Federal Ministry for Economic Affairs and Climate Action (BMWK) through the AiF (German Federation of Industrial Research Associations eV) and of the projects RollBatt (03XP0245A) and CharLiSiKo (03XP0333A) funded by the German Federal Ministry of Education and Research (BMBF).We present an extensive analysis of Li-ion battery ageing via Arrhenius plots. The V-shaped Arrhenius plots show minima at an optimum temperature corresponding to the longest cycle-life. The V-shape of the Arrhenius plots signifies the crossover between the two dominating ageing mechanisms – solid electrolyte interphase (SEI) growth in the high temperature range and lithium deposition in the low temperature range. Subjects of our investigations are commercial 5 Ah high energy 21,700-type cells with LiNi0.90Co0.05Al0.05O2 + LiNiO2 (NCA + LNO) cathode and Si/graphite anode (∼3% Si) and 0.1 Ah lab-made pouch cells with LiNi1/3Mn1/3Co1/3O2 (NMC111) cathode and a graphite anode. The results of the Arrhenius plots are analysed in the context of C-rate, cell ageing, and electrode properties. We find that the crossover between the dominating ageing mechanism and hence the optimum operating temperature of the Li-ion cells depend on C-rate, anode coating thickness/particles sizes, the state of health, and the shape of the capacity fade curve. Considering the change of the dominant ageing mechanism can help designing battery systems with longer service life. Additionally, we show a lifetime estimation for temperature dependent cycling of batteries emphasizing the merit of Arrhenius plots in the context of battery cell ageing. --//-- Gints Kucinskis, Maral Bozorgchenani, Max Feinauer, Michael Kasper, Margret Wohlfahrt-Mehrens, Thomas Waldmann, Arrhenius plots for Li-ion battery ageing as a function of temperature, C-rate, and ageing state – An experimental study, Journal of Power Sources, Volume 549, 2022, 232129, ISSN 0378-7753, https://doi.org/10.1016/j.jpowsour.2022.232129. Published under the CC BY licence.Latvian Council of Science project No. LZP-2020/1–0425; Institute of Solid-State Physics, University of Latvia as the Centre of Excellence has received funding from the European Union's Horizon 2020 Framework Program H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2; project GradiBatt (IGF no. 20884 N/2), RollBatt (03XP0245A) and CharLiSiKo (03XP0333A)

Chemical induced delithiation on LixMnPO4: an investigation about the phase structure

Understanding the LiMnPO4/MnPO4 phase transition is of great interest in order to further improve the electrochemical performance of this cathode material. Since most of the previously published literature deals with characterization of chemically delithiated Lix MnPO4, the aim of this study is to compare and study the composition and structure of the different phases that are generated upon chemical delithiation of LixMnPO4. Bare and carboncoated lithium manganese phos-phates are prepared via a combined coprecipitation-calcination method. Partial delithiation to two different degrees of delithiation Lix MnPO4 (x = 0.24/0.23 and 0.45) for carbon-coated and/or bare materials is achieved using an excess of nitro-nium tetrafluoroborate in acetonitrile. The effect of carboncoating has been also considered. Standard materials characterization with XRD (X-Ray Diffraction) and ICPOES (Inductive Coupled Plasma spectrometry and Optical Emission Spectroscopy) analysis are in accordance with literature data, but further cerimetric analysis revealed serious deviations, showing differences in the degree of delithiation to the average degree of oxidation. A structural characterization of the atomic and electronic local structure of the materials is also ob-tained using XAS (X-ray Absorption Spectroscopy) technique

Study of water-based lithium titanate electrode processing: the role of pH and binder molecular structure

This work elucidates the manufacturing of lithium titanate (Li$_{4}$Ti$_{5}$O$_{12}$, LTO) electrodes via the aqueous process using sodium carboxymethylcellulose (CMC), guar gum (GG) or pectin as binders. To avoid aluminum current collector dissolution due to the rising slurries’ pH, phosphoric acid (PA) is used as a pH-modifier. The electrodes are characterized in terms of morphology, adhesion strength and electrochemical performance. In the absence of phosphoric acid, hydrogen evolution occurs upon coating the slurry onto the aluminum substrate, resulting in the formation of cavities in the coated electrode, as well as poor cohesion on the current collector itself. Consequently, the electrochemical performance of the coated electrodes is also improved by the addition of PA in the slurries. At a 5C rate, CMC/PA-based electrodes delivered 144 mAh·g$^{-1}$, while PA-free electrodes reached only 124 mAh·g$^{-1}$. When GG and pectin are used as binders, the adhesion of the coated layers to the current collector is reduced; however, the electrodes show comparable, if not slightly better, electrochemical performance than those based on CMC. Full lithium-ion cells, utilizing CMC/PA-made Li[Ni$_{0.33}$Mn$_{0.33}$Co$_{0.33}$]O$_{2}$ (NMC) cathodes and LTO anodes offer a stable discharge capacity of ~120 mAh·g$^{ 1}$$_{(NMC)}$ with high coulombic efficiencies

Deriving structure-performance relations of chemically modified chitosan binders for sustainable high-voltage LiNi0.5Mn1.5O4 cathode

Invited for this month's cover picture is the group of Prof. Dr. Stefano Passerini. The front cover illustrates the use of citric acid (co-)crosslinked bio-derived polymers, with chitosan and guar gum, as water-soluble binders for sustainable lithium-ion battery cathodes. Read the full text of the Article at 10.1002/batt.201900140. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinhei

Deriving Structure-Performance Relations of Chemically Modified Chitosan Binders for Sustainable High-Voltage LiNi0.5_{0.5}Mn1.5_{1.5}O4_{4} Cathodes

The implementation of aqueous electrode processing for lithium‐ion positive electrodes is key towards the realization of environmentally benign and cheap battery production. One of the water‐soluble binders that has attracted most attention is chitosan, the second‐most abundant natural biopolymer. Herein, the use of chitosan for high‐voltage, cobalt‐free LiNi$_{0.5}$Mn$_{1.5}$O$_{4}$ cathodes is reported for the first time. A detailed comparison of three different grades of chitosan with varying chain length and degrees of deacetylation (DD) is provided to explore the impact of these properties on the electrochemical performance. In fact, bio‐derived chitosan with a relatively lower DD outperforms synthetic chitosan‐especially after crosslinking with citric acid‐yielding about 10 % higher capacities. Higher molecular weight appears additionally advantageous for the cycling stability. Finally, guar gum is employed as slurry thickener, co‐crosslinking with chitosan. This allows for achieving 50 % higher mass loadings than for chitosan only and stable capacities above 130 and 120 mAh g$^{-1}$ at C/3 and 1 C, respectively