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Dimethyl terephthalate (DMT) is a redox shuttle molecule that leads to unwanted self-discharge of lithium-ion cells. It can be created in-situ as a breakdown product of polyethylene terephthalate (PET), which is a surprisingly common polymer for the adhesive tapes found in commercial cells. This study investigates the shuttling mechanism and electrochemical stability of DMT, as well as its impact on the performance of LFP/graphite pouch cells with LiFSI and LiPF6 conducting salts. Cyclic voltammetry shows that DMT has a redox potential of 1.5 V vs. Li+/Li and is redox active in the full voltage range of LFP/graphite cells. Ultra-high precision coulometry and open-circuit storage experiments show that DMT lowers the coulombic efficiency, increases the charge endpoint capacity slippage, and dramatically accelerates the reversible self-discharge of LFP/graphite pouch cells. Gas chromatography-mass spectrometry shows that DMT is stable over weeks in cells with LiPF6, but only for several days in cells with LiFSI. A well-insulating solid-electrolyte interphase layer derived from vinylene carbonate can prevent DMT from shuttling. However, VC can be consumed, and passivation layers can deteriorate in aged cells, so the best way to prevent DMT-induced self-discharge of lithium-ion batteries is to eliminate PET components.

Polyethylene terephthalate (PET) tape is widely used by well-known lithium-ion battery manufacturers to prevent electrode stacks from unwinding during assembly. PET tape is selected since it has suitable mechanical and electrical properties, but its chemical stability has been largely overlooked. In the absence of effective electrolyte additives, PET can depolymerize into its monomer dimethyl terephthalate (DMT), which is an unwanted redox shuttle that induces significant self-discharge in a lithium-ion cell. This study presents a chemical screening experiment to probe the PET decomposition mechanism involving in situ generated methanol and lithium methoxide from dimethyl carbonate, one of the most common electrolyte solvents in lithium-ion cells. By screening other polymers, it is found that polypropylene (PP) and polyimide (Kapton) are stable in the electrolyte. Finally, it is demonstrated that reversible self-discharge of LiFePO4/graphite cells can be virtually eliminated by replacing PET jellyroll tape with chemically stable PP tape.

This reply provides updated energy consumption estimates at clearly defined separation conditions for electrochemical desalination concepts.

Prussian White is a promising active material for the positive electrode of sodium-ion batteries as it is comprised of Na, Mn, Fe, C, and N and thus offers high sustainability and low cost. However, exposure of Prussian White to moisture results in chemical changes due to the formation of surface contaminants, as well as structural changes due to the absorption of water into the bulk crystal structure. Here we report an analysis of the formation rate of surface contaminants and bulk water absorption by weight tracking, infrared spectroscopy, and X-ray diffraction over extended periods of storage in high relative humidity air for fully sodiated Na1.8Mn0.8Fe0.2[Fe(CN)6]0.9 and partially sodiated Na1.3Mn0.8Fe0.2[Fe(CN)6]0.9. Fully sodiated Prussian White gains almost 20% in mass due to the formation of interstitial water during 20 h of storage in 100% relative humidity at 25 °C. Surface hydroxides and carbonates are found after storage and a structural change from the rhombohedral to a monoclinic crystal structure is observed. It is found that vacuum drying of Prussian White powder or electrodes at 150 °C can remove the majority of interstitial water and restore the rhombohedral crystal structure, but not remove surface contaminants. Prussian White immersed in water during aqueous electrode processing also shows interstitial water and a monoclinic crystal structure, but no surface contaminants. This suggests that aqueous electrode processing of Prussian White is feasible when effective drying strategies are employed. Indeed, Prussian White electrodes made from H2O-based slurries with CMC/NaPAA binder vacuum-dried at 150 °C show higher specific capacity and similar capacity retention in full cells as Prussian White electrode made from NMP-based slurries with PVDF binder.

Unwanted self-discharge of LFP/AG and NMC811/AG cells can be caused by in situ generation of a redox shuttle molecule after formation at elevated temperature with common alkyl carbonate electrolyte. This study investigates the redox shuttle generation for several electrolyte additives, e.g., vinylene carbonate and lithium difluorophosphate, by measuring the additive reduction onset potential, first cycle inefficiency and gas evolution during formation at temperatures between 25 and 70 °C. After formation, electrolyte is extracted from pouch cells for visual inspection and quantification of redox shuttle activity in coin cells by cyclic voltammetry. The redox shuttle molecule is identified by GC-MS and NMR as dimethyl terephthalate. It is generated in the absence of an effective SEI-forming additive, according to a proposed formation mechanism that requires residual water in the electrolyte, catalytic quantities of lithium methoxide generated at the negative electrode and, surprisingly, polyethylene terephthalate tape within the cell.

Unwanted parasitic reactions in lithium-ion cells lead to self-discharge and inefficiency, especially at high temperatures. To understand the nature of those reactions this study investigates the open circuit storage losses of LFP/graphite and NMC811/graphite pouch cells with common alkyl carbonate electrolytes. The cells perform a storage test at 40 °C with a 500 h open circuit period after formation at temperatures between 40 °C and 70 °C. Cells formed at elevated temperature showed a high reversible storage loss that could be assigned to a redox shuttle generated in the electrolyte during formation. A voltage hold after formation can reduce the shuttle-induced self-discharge as indicated by significantly lower reversible storage losses, the absence of shuttling currents in cyclic voltammetry and improved metrics in ultra-high precision cycling. The addition of two weight percent vinylene carbonate can prevent redox shuttle generation and leads to almost zero reversible self-discharge.

Since e-Mobility is on the rise worldwide, large charging infrastructure networks are required to satisfy the upcoming charging demand. Planning these networks not only involves different objectives from grid operators, drivers and Charging Station (CS) operators alike but it also underlies spatial and temporal uncertainties of the upcoming charging demand. Here, we aim at showing these uncertainties and assess different levers to enable the integration of e-Mobility. Therefore, we introduce an Agent-based model assessing regional charging demand and infrastructure networks with the interactions between charging infrastructure and electric vehicles. A global sensitivity analysis is applied to derive general guidelines for integrating e-Mobility effectively within a region by considering the grid impact, the economic viability and the Service Quality of the deployed Charging Infrastructure (SQCI). We show that an improved macro-economic framework should enable infrastructure investments across different types of locations such as public, highway and work to utilize cross-locational charging peak reduction effects. Since the height of the residential charging peak depends up to 18% on public charger availability, supporting public charging infrastructure investments especially in highly utilized power grid regions is recommended.

The impact of liquid electrolyte soaking on the interfacial resistance between the garnet-structured Li7La3Zr2O12 (LLZO) solid electrolyte and metallic lithium has been studied. Lithium carbonate (Li2CO3) formed by inadvertent exposure of LLZO to ambient conditions is generally known to increase interfacial impedance and decrease lithium wettability. Soaking LLZO powders and pellets in the electrolyte containing lithium tetrafluoroborate (LiBF4) shows a significantly reduced interfacial resistance and improved contact between lithium and LLZO. Raman spectroscopy, X-ray diffraction, and soft X-ray absorption spectroscopy reveal how Li2CO3 is continuously removed with increasing soaking time. On-line mass spectrometry and free energy calculations show how LiBF4 reacts with surface carbonate to form carbon dioxide. Using a very simple and scalable process that does not involve heat-treatment and expensive coating techniques, we show that the Li-LLZO interfacial resistance can be reduced by an order of magnitude.

We conduct a techno-economic analysis of electrochemical water deionization technologies. The objective of the analysis is to compare cost, volume, and energy consumption of membrane capacitive deionization (mCDI) to intercalative deionization techniques. Here, we first explore the concept of hybrid capacitive deionization (HCDI), i.e., a cation intercalation electrode paired with an activated carbon capacitive electrode. Then we explore in detail a novel device concept, fully intercalative water deionization (IDI), which relies entirely on the cation intercalation principle. The intercalation host materials in our study are Prussian blue analogs (PBAs), e.g., NiFe(CN)6 or CuFe(CN)6, that offer ∼3–5× higher gravimetric salt removal capacities than typical activated carbon. Our analysis shows that IDI should be superior to mCDI in module cost, volume, and energy efficiency, despite a more complex module architecture. Making careful assumptions on material costs, we provide a cost breakdown for mCDI, HCDI, and IDI modules and show that IDI is the only concept that is not dominated by ion exchange membrane costs. The environmental impact of electrochemical water deionization is illustrated by estimating the carbon footprint of currently installed reverse osmosis capacity in different world regions and comparing it to the respective carbon footprint of mCDI, HCDI, and IDI at similar capacity.

This work quantifies in-plane spatial heterogeneity (polymer electrolyte fuel cell cathode inlet vs outlet) in Pt particle size growth and distribution as a function of nitrogen (N2) flow rate during a square-wave accelerated stress test (AST). The average Pt particle sizes for membrane electrode assemblies (MEAs) subjected to N2 flow rates ranging from 4–16 sccm cm−2 are in the range 9–10.5 nm at the end-of-life (EOL) with similar electrochemically active surface area (ECSA) loss (∼65%). However, Pt particle size at EOL exhibits spatial heterogeneity: greater Pt particle size growth occurs near the flow field outlet than the inlet. The spatial heterogeneity for a fully-humidified N2 flow is believed to originate from non-uniform humidification (outlet is more humidified than the inlet) across the cell for a co-flow arrangement. A first-order rate model for ECSA loss predicts linear increase of the rate constant with N2 flow rate. The polarization losses of the aged MEAs over a wide range of operating conditions increase with N2 flow rate. From the results of this work, for holistically assessing durability of Pt catalysts in fuel cells at high humidity conditions, it is recommended to include purge gas flow rate as a stressor during an AST.

The increasing share of renewables in our electricity grid requires affordable and scalable battery technology that uses sustainable materials and has long lifetime. At the same time, growing water scarcity necessitates new desalination technologies with a similar requirement for sustainability and lifetime. Prussian blue analogs (PBAs), e.g., manganese hexacyanoferrate, MnFe(CN)6, or nickel hexacyanoferrate, NiFe(CN)6, are promising intercalation materials for secondary batteries.1–4 Recently, this material class has been shown to be suitable for a novel energy-efficient water desalination approach, based on sodium intercalation into PBAs, sometimes referred to as battery desalination.5–8 Hence, PBAs are potentially suitable electrode materials for, both, energy storage and water desalination, but it is important to investigate the materials’ stability to processing conditions and repeated ion intercalation. Prussian blue analogs like NaxMnFe(CN)6, 09,10 Different approaches can be utilized to mitigate this issue, such as surface coating or handling of the material under strictly inert conditions, starting from the storage of powder to slurry preparation and electrode processing.9,11 In this study, we investigated the changes in surface chemistry during ambient storage, water exposure and subsequent heating of stored PBAs. Infrared spectroscopy (ATR-FTIR) and thermal analysis (TGA-MS) of materials stored for different times ranging from one hour to one week show a sharp increase in the moisture content of the active material. X-ray diffraction of exposed materials shows a clear trend between hydration state and crystal structure. Furthermore, surface hydroxides and carbonates are found by ATR-FTIR. A reheating step at relatively low temperature shows the release of adsorbed and interstitial water, but hydroxides and carbonates remain on the surface of the active material. The moisture stability of PBAs has important implications for aqueous electrode processing in energy storage applications and water-based device operation in desalination applications. We demonstrate effective drying strategies of electrodes made with aqueous slurries and appropriate binders. The as-prepared water-based electrodes show similar cycling stability as their non-aqueous counterparts. In the desalination context, exposure of the active material to water is unavoidable and may reduce performance and lifetime since the material remains hydrated during operation. We quantify performance and lifetime metrics of the novel battery desalination cells that employ NiFe(CN)6 electrodes at opposite state-of-charge separated by an anion exchange membrane.12 Using objective metrics like retention of specific capacity (mAh/g), energy consumption (Wh/l) and productivity (l/h/m2) we show that these cells achieve vastly different performance for removal of monovalent and divalent ions. Stable charge/discharge cycling can be achieved for over 500 cycles with NaCl feed water, but rapid aging is observed with CaCl2 feeds. Synchrotron-based characterization of NiFe(CN)6 electrodes from the battery desalination cells is used to elucidate the reason for capacity fade (see Figure 1). X-ray absorption spectroscopy and X-ray fluorescence spectroscopy reveal Fe dissolution from the NiFe(CN)6 active material as a primary aging mode with CaCl2 water feeds. Based on the performance of Prussian blue analogs in, both, energy storage and water desalination, we will discuss potential synergies between these fields and strategies for efficient device design.13 References C. D. Wessells, S. V. Peddada, R. A. Huggins, and Y. Cui, Nano Lett., 11, 5421–5425 (2011). C. D. Wessells et al., ACS Nano, 6, 1688–1694 (2012). M. Pasta et al., Nat. Commun., 5, 1–9 (2014). A. Firouzi et al., Nat. Commun., 9 (2018). M. Pasta, C. D. Wessells, Y. Cui, and F. La Mantia, Nano Lett., 12, 839–843 (2012). J. Lee, S. Kim, and J. Yoon, ACS Omega, 2, 1653–1659 (2017). T. Kim, C. A. Gorski, and B. E. Logan, Environ. Sci. Technol. Lett., 4, 444–449 (2017). S. Porada, A. Shrivastava, P. Bukowska, P. M. Biesheuvel, and K. C. Smith, Electrochim. Acta, 255, 369–378 (2017). D. O. Ojwang et al., ACS Appl. Mater. Interfaces, 13, 10054–10063 (2021). J. Song et al., J. Am. Chem. Soc., 137, 2658–2664 (2015). L. Yang et al., J. Power Sources, 448, 227421 (2020). M. M. Besli et al., Desalination, 517, 115218 (2021). M. Metzger et al., Energy Environ. Sci., 13, 1544–1560 (2020). Figure 1. (a) Three-electrode cells for evaluation of electrochemical stability of NiFe(CN)6 towards mono- and divalent ion intercalation. (b) Specific capacity versus cycle number for 1C cycling with high and low concentrations of NaCl or CaCl2. (c) Visual inspection of electrolyte, revealing strong discoloration and brown precipitate after 300 cycles with 1 M CaCl2, and no discoloration after 400 cycles with 1 M NaCl. Figure 1

Recent observations by our group show the creation of a reversible shuttle species in LFP/graphite and NMC811/graphite cells with 3:7 ethylene carbonate:dimethyl carbonate (EC:DMC) based electrolytes. This is indicated by a high reversible self-discharge of these cells in the absence of electrolyte additives. Electrolyte extraction from pouch cells after formation allowed to directly investigate the electrolytes for redox shuttle currents. For this purpose, the extracted electrolytes were inserted into coin cells with an Al foil as the working electrode (WE) and a Li foil as the counter electrode (CE). The measured cyclic voltammetry (CV) of the coin cells show a clear relationship between high formation temperature and high shuttle currents. Interestingly, the addition of vinylene carbonate (VC) to the electrolyte completely prevents the shuttle current, even at elevated formation temperatures. [1] In this study, we systematically investigate the effect of various electrolyte additives on the generation of shuttle molecules. LFP/graphite and NMC811/graphite pouch cells were filled with electrolyte consisting of 3:7 EC:DMC with 1.5 M lithium hexafluorophosphate (LiPF6) and different additives. The pouch cells were formed at different temperatures, TF. The electrolytes were then extracted and inserted into the aforementioned coin cell setup for CV measurements. We have found that additives such as VC, fluoroethylene carbonate (FEC), ethylene sulfate (DTD), prop-1-ene-1,3-sultone (PES), and triallyl phosphate (TAP), which are known to create a stable solid electrolyte interphase (SEI), [2-4] prevent shuttle current in the CV. On the other hand, additives such as succinonitrile (SN) and trimethylsilyl isothiocyanate (TMSNCS), which do not contribute to the formation of a better SEI, [5,6] cannot prevent the shuttle current. This suggests that the formation of the shuttles is due to a poor SEI and therefore occurs at the interface between electrolyte and graphite anode. Analogue experiments with DMC as only solvent instead of 3:7 EC:DMC show similar shuttle currents in CVs, which suggests that linear carbonates such as DMC are required to form the shuttle. Figure 1 shows CVs for 1.5 M LiPF6 DMC electrolyte. The shuttle current appears to be the same for electrolyte extracted from LFP/graphite and NMC811/graphite cells ranging up to 6 μA in both cases. This indicates that the shuttle is formed independently of the cathode material, and therefore gives rise to the hypothesis that it is formed at the anode-electrolyte interface. Figure 1 also shows that the shuttle current increases with higher formation temperatures TF. References: Boulanger, A. Eldesoky. S. Buechele, T. Taskovic, S. Azam, C. Aiken, E. Logan, M. Metzger, Investigation of redox shuttle generation in LFP/graphite and NMC811/graphite cells, Submitted (2022). Song, J. Harlow, E. Logan, H. Hebecker, M. Coon, L. Molino, M. Johnson, J. Dahn, M. Metzger, A Systematic Study of Electrolyte Additives in Single Crystal and Bimodal LiNi 0.8 Mn 0.1 Co 0.1 O 2 /Graphite Pouch Cells , J. Electrochem. Soc. 168 (2021) 090503. doi:10.1149/1945-7111/ac1e55. J. Nelson, J. Xia, J.R. Dahn, Studies of the Effect of Varying Prop-1-ene-1,3-sultone Content in Lithium Ion Pouch Cells, J. Electrochem. Soc. 161 (2014) A1884–A1889. doi:10.1149/2.0791412jes. Xia, L. Madec, L. Ma, L.D. Ellis, W. Qiu, K.J. Nelson, Z. Lu, J.R. Dahn, Study of triallyl phosphate as an electrolyte additive for high voltage lithium-ion cells, J. Power Sources. 295 (2015) 203–211. doi:10.1016/j.jpowsour.2015.06.151. Chen, F. Liu, Y. Chen, Y. Ye, Y. Huang, F. Wu, L. Li, An investigation of functionalized electrolyte using succinonitrile additive for high voltage lithium-ion batteries, J. Power Sources. 306 (2016) 70–77. doi:10.1016/j.jpowsour.2015.10.105. G. Han, M.Y. Jeong, K. Kim, C. Park, C.H. Sung, D.W. Bak, K.H. Kim, K.M. Jeong, N.S. Choi, An electrolyte additive capable of scavenging HF and PF5 enables fast charging of lithium-ion batteries in LiPF6-based electrolytes, J. Power Sources. 446 (2020) 227366. doi:10.1016/j.jpowsour.2019.227366. Acknowledgements This work was funded under the auspices of the NSERC/Tesla Canada Alliance Grant program. Figure 1

Prussian whites, such as the here tested NaxMn0.8Fe1.2(CN)6 (PW), are promising candidates as Na-Ion cathode active materials for cost-effective and safe battery technologies. The use of abundant elements such as sodium, iron or manganese obtained in a sustainable way makes this technology extremely attractive, especially in grid storage applications where high energy densities are not of major concern.1,2 However, PWs still suffer from low electronic conductivity, limited capacity retention, and a high sensitivity towards moisture which results in structural changes and loss of cyclable Na.3,4 Different approaches can be utilized to mitigate these issues, such as surface coatings or strict handling of the materials under inert conditions, starting from the storage of PWs powders to slurry preparations and to the handling of electrodes.3,5 In this study, we investigated the changes in surface chemistry during ambient storage (here called wet storage) and during subsequent heating of stored material. ATR-IR and TGA-MS data of materials stored for different times ranging from 1 h to up to a week showed a sharp increase in moisture-content in the material. The increase plateaued after 24 h of storage. XRD analysis of stored material showed a clear trend of structural changes upon even small storage times ( By conducting electrochemical testing in coin-cells we analyzed the difference in cycling performance of as-received and ambient stored materials, and materials washed in water. As seen in earlier studies we also saw a drastic change in the charge profile after storage, due to changes in crystal structure.4 Interestingly, we found that this detrimental effect is reversible if the electrodes are dried at elevated temperatures. The pH of water after washing PW materials was neutral indicating the absence of major ion exchange.6 This finding, combined with the effective drying of hydrated electrodes resulted in the formulation of a water-based slurry process. As seen in Figure 1, a cell built with electrodes made from a 1 week wet-stored CAM which were dried at 120 °C (blue lines) showed a drastic different charge profile, compared to a cell built with an as-received electrode (black lines, panel a). Interestingly a cell built with CAM stored for 1 week and heated to 150 °C (orange lines, panel b) and a cell built with a cathode from a H2O-based coating which was dried at 150 °C (green lines, panel b), looks almost identical to the NMP-cells. Therefore, we assume that most water can be removed easily, and a water-based slurry process is possible. Cycling tests of water-based and environmentally more sustainable hard-carbon/PW full-cells reveal a similar cycling stability in comparison to cells with electrodes made from a traditional NMP process. References: N. Tapia-Ruiz et al., JPhys Energy, 3, 031503 (2021). Q. Liu et al., Adv. Funct. Mater., 30, 1–15 (2020). D. O. Ojwang et al., ACS Appl. Mater. Interfaces, 13, 10054–10063 (2021). J. Song et al., J. Am. Chem. Soc., 137, 2658–2664 (2015). L. Yang et al., J. Power Sources, 448, 227421 (2020). D. Pritzl et al., J. Electrochem. Soc., 166, A4056–A4066 (2019). Acknowledgements The authors acknowledge the financial support of NSERC and Tesla Canada under the auspices of the Industrial Research Chair program. Figure 1: panel a: First cycle capacity of Na/PW half-cells with cathodes either made from an as-received CAM in a NMP-based slurry (black lines), or 1 week wet-stored material made with the same slurry process (blue lines) dried at low temperatures (120 °C). First cycle capacity of Na/PW half-cells with cathodes made from either 1 week stored material heated to 150 °C (orange lines) or of an as-received material, but the slurry was done in a water-based slurry and the electrodes were dried at 150 °C (green lines)). The half-cells were cycled at 30 °C (CC mode, C/20), using an FEC/DMC (2:8) electrolyte with 1.5 m NaPF6. Figure 1

LFP/Graphite cells are attractive because they are cheaper[1], safer[2,3] and can achieve acceptable energy density for most applications. A limitation of the LFP/Graphite cells is their inferior capacity retention at elevated temperature when compared to NMC/Graphite cells especially in the absence of electrolyte additives, e.g., VC (Vinylene carbonate), as observed by our group in a recent study[4].The time it takes for a LFP graphite cell to completely self-discharge at 60oC is around 500 hours with a base electrolyte of 1.5 M LiPF6 (Lithium hexafluorophosphate) dissolved in 7:3 DMC:EC (Dimethyl carbonate/ethylene carbonate)[4]. It also has been observed that during cycling some Fe will accumulate on the anode which can be explained by dissolution of Fe from the cathode and subsequent deposition on the anode. With the same electrolyte as mentioned before we can observe up to 0.2 μg/cm2 on the anode after 60 cycles at 40⁰C[4]. The goal of this research is to understand what is happening inside the LFP/Graphite cells by analyzing the electrolyte from cells that only did a formation procedure. We were able to extract different electrolytes from LFP/Graphite and NMC811/Graphite pouch cells. We expected the electrolyte to stay clear as it was just after preparation, but we observed yellow and red colors depending on the temperature of formation. If the electrolyte contained 2%wt VC, no color change was observed. The different electrolytes used for the experiments were LiPF6, LiFSI (Lithium bis(fluorosulfonyl)imide) and LiPF6+2%wt VC all dissolved in 7:3 DMC:EC. The extracted electrolytes were put inside coin cells with an Al foil working-electrode (WE) and a Li foil counter-electrode (CE) and cyclic voltammetry (CV) was done on them from 2.6 V - 3.75 V vs. Li+/Li. The CV traces show the presence of current in the μA range for electrolyte without VC extracted from LFP cells, indicating the presence of a reversible shuttle species. The electrolyte with no VC expected from LFP cells showed more current than the corresponding electrolyte extracted from NMC811 cells. There was almost no current in the coin cells using electrolytes with 2% VC extracted from the LFP and NMC811 cells. We also made systematic experiments at different formation temperature and different wait times before extraction. Figure 1: Observation of the different electrolytes extracted from LFP/Graphite cells with a) 1.5 M LiPF6 EC:DMC 3:7 and b) 1.5 M LiPF6 +2%wt VC EC:DMC 3:7 that did formation at 25, 40 ,55 and 70⁰C (left to right). References W. Li, Y. Cho, W. Yao, Y. Li, A. Cronk, R. Shimizu, M. A. Schroeder, Y. Fu, F. Zou, V. Battaglia, A. Manthiram, M. Zhang, and Y. S. Meng. “Enabling high areal capacity for Co-free high voltage spinel materials in next-generation Li-ion batteries”, Journal of Power Sources, 473 (2020). D. Jian, T. Xuan, D. Haifeng, Y. Ying, W. Wangyan, W. Xuezhe, and H. Yunhui. “Building Safe Lithium-Ion Batteries for Electric Vehicles: A Review”, Electrochem. Energ. Rev. 3, 1–42 (2020). W. Li, H. Wang, Y. Zhang, and M. Ouyang. “Flammability characteristics of the battery vent gas: A case of NCA and LFP lithium-ion batteries during external heating abuse”, Journal of Energy Storage, 24 (2019) E. R. Logan, H. Hebecker, A. Eldesoky, A. Luscombe, M. B. Johnson, and J. R. Dahn. “Performance and Degradation of LiFePO4/Graphite Cells: The Impact of Water Contamination and an Evaluation of Common Electrolyte Additives”, Journal of The Electrochemical Society, 167, 13 (2020) Figure 1

Prussian blue analogs, e.g., nickel hexacyanoferrate, NiFe(CN)6 or NiHCF, are promising candidates as low-cost and high-rate intercalation materials for secondary batteries.1–4 Recently, this material class has been shown to possess tremendous potential for a novel energy-efficient water desalination approach.5–8 Rising water demands are exacerbating water scarcity in many world regions. It is estimated that 60% of the global population will face severe water scarcity by 2025.9 The growing water demand necessitates new desalination technologies with high energy efficiency, low capital and operating cost and high freshwater output. In this work, we assess the performance and lifetime of electrochemical water desalination cells based on sodium intercalation into nickel hexacyanoferrate.10–12 The battery desalination cells feature a symmetric design, with two NiHCF electrodes at opposite state-of-charge (SOC), capable of intercalating Na+-ions into their crystal structure. The electrodes are separated by an anion exchange membrane, a porous functionalized polyether ether ketone (PEEK) membrane, that only permits negatively charged ions, e.g., Cl--ions, to pass. Two feed water streams with 20 mM NaCl enter the symmetric cell on either side (see Figure 1a). During charge of the symmetric cell, incoming Na+-ions are removed from one water stream and intercalated into the NiHCF electrode at low SOC. Simultaneously, Na+-ions are deintercalated from the opposite NiHCF electrode at high SOC. In order to maintain charge neutrality, Cl--ions cross the anion exchange membrane. Thus, during every charge/discharge cycle, one water stream is desalinated forming a freshwater stream, while the other is enriched in NaCl forming a brine waste stream (see Figure 1b). In order to quantify performance and lifetime of the novel battery-type water desalination cells, we define and measure objective metrics. We see that energy consumption (Wh/l) and productivity (l/h/m2) of NiHCF/NiHCF cells are superior to cells based on membrane capacity deionization (mCDI). Stable charge/discharge cycling of NiHCF/NiHCF cells can be achieved for over 500 cycles with NaCl feed water, but rapid aging is observed with CaCl2 feeds. Synchrotron-based characterization of NiHCF/NiHCF cells is used to elucidate the reason for capacity fade. X-ray absorption spectroscopy and X-ray fluorescence spectroscopy reveal Fe dissolution from the NiHCF active material as a primary aging mode with CaCl2 water feeds. References Wessells, C. D., Peddada, S. V., Huggins, R. A. & Cui, Y. Nickel hexacyanoferrate nanoparticle electrodes for aqueous sodium and potassium ion batteries. Nano Lett. 11, 5421–5425 (2011). Wessells, C. D. et al. Tunable reaction potentials in open framework nanoparticle battery electrodes for grid-scale energy storage. ACS Nano 6, 1688–1694 (2012). Pasta, M. et al. Full open-framework batteries for stationary energy storage. Nat. Commun. 5, 1–9 (2014). Firouzi, A. et al. Monovalent manganese based anodes and co-solvent electrolyte for stable low-cost high-rate sodium-ion batteries. Nat. Commun. 9, (2018). Pasta, M., Wessells, C. D., Cui, Y. & La Mantia, F. A desalination battery. Nano Lett. 12, 839–843 (2012). Lee, J., Kim, S. & Yoon, J. Rocking Chair Desalination Battery Based on Prussian Blue Electrodes. ACS Omega 2, 1653–1659 (2017). Kim, T., Gorski, C. A. & Logan, B. E. Low Energy Desalination Using Battery Electrode Deionization. Environ. Sci. Technol. Lett. 4, 444–449 (2017). Porada, S., Shrivastava, A., Bukowska, P., Biesheuvel, P. M. & Smith, K. C. Nickel Hexacyanoferrate Electrodes for Continuous Cation Intercalation Desalination of Brackish Water. Electrochim. Acta 255, 369–378 (2017). Jones, E., Qadir, M., van Vliet, M. T. H., Smakhtin, V. & Kang, S. mu. The state of desalination and brine production: A global outlook. Sci. Total Environ. 657, 1343–1356 (2019). Metzger, M. et al. Techno-economic analysis of capacitive and intercalative water deionization. Energy Environ. Sci. 13, 1544–1560 (2020). Sebti, E. et al. Removal of Na+ and Ca2+ with Prussian blue analogue electrodes for brackish water desalination. Desalination 487, (2020). Besli, M. M. et al. Performance and lifetime of intercalative water deionization cells for mono- and divalent ion removal. Desalination 517, 115218 (2021). Figure 1. (a) Battery-type water desalination approach in symmetric NiHCF/NiHCF cells with two salt water streams entering the cell and a brine stream and freshwater stream exiting the cell. (b) During galvanostatic charge/discharge cycling the salt concentrations of brine and freshwater stream can be monitored with microfluidic operando conductivity probes to determine important performance metrics. Figure 1

In order to reach the goals of the United Nations Framework Convention on Climate Change, a stepwise reduction of energy related greenhouse gas emissions as well as an increase in the share of renewable energies is necessary. For a successful realization of these changes in energy supply, an integrated view of multiple energy sectors is necessary. The coupling of different energy sectors is seen as an option to achieve the climate goals in a cost-effective way. In this paper, a methodical approach for multi-modal energy system planning and technology impact evaluation is presented. A key feature of the model is a coupled consideration of the sectors electricity, heat, fuel and mobility. The modeling framework enables system planners to optimally plan future investments in a detailed transition pathway of the energy system of a country, considering politically defined climate goals. Based on these calculations, in-depth analyses of energy markets as well as electrical transmission and distribution grids can be performed using the presented optimization models. Energy demands, conversion and storage technologies in households, the Commerce, Trade and Services (CTS) area and the industry are modeled employing a bottom-up modeling approach. The results for the optimal planning of the German energy system until 2050 show that the combination of an increased share of renewable energies and the direct electrification of heat and mobility sectors together with the use of synthetic fuels are the main drivers to achieve the climate goals in a cost-efficient way.

Innovative Solutions for Energy Transitions / Edited by Jinyue Yan, Hong-xing Yang, Hailong Li, Xi Chen 10th International Conference on Applied Energy, ICAE2018, Hong Kong, Hong Kong, 22 Aug 2018 - 25 Aug 2018; Amsterdam [u.a.] : Elsevier, Energy Procedia 158, 3482-3487 (2018). doi:10.1016/j.egypro.2019.01.923, Published by Elsevier, Amsterdam [u.a.]

The structural integrity of layered Ni-rich oxide cathode materials is one of the most essential factors that critically affect the performance and reliability of lithium-ion batteries. Prolonged battery operation often involves repeated phase transitions, buildup of mechanical stresses, and could provoke thermal spikes. Such sophisticated chemo-thermo-mechanical interplay can cause performance degradation through structural disintegration of the cathode active materials (CAMs). Herein, we systematically investigate the thermal decomposition, fracture, and oxygen evolution of chemically delithiated Li0.3Ni0.8Co0.15Al0.05O2 (NCA) particles upon heating from 25 °C to 450 °C using a number of advanced X-ray and electron probes. We observed a continuous reduction of the Ni oxidation state upon heating, as well as the release of oxygen from the NCA lattice that undergoes the thermally induced phase transformations. The release of oxygen also created numerous mesopores throughout the analyzed particles, which could significantly affect the chemical and mechanical properties of the electrode. In addition, intergranular and intragranular fracturing at elevated temperatures also contribute to the degradation of the NCA cathode under these conditions. Our investigation of the mechanical integrity at elevated temperatures provides a fundamental understanding of the thermally driven chemomechanical breakdown of the NCA cathode active materials.

Melt synthesis is a fast and simple process to make dense LiMnyFe1-yPO4 (LMFP with 0 ≤ y ≤ 1) from all-dry, low-cost precursors with zero waste. This study characterizes melt LMFP materials with 0%–100% Mn after particle size reduction by planetary milling and carbon coating with glucose. The melt LMFP samples show higher electrical conductivity at similar pellet density than LFP (0% Mn) and LMFP (79% Mn) reference samples made by traditional methods. The melt LMFP samples exhibit higher crystallinity than the reference samples and show no crystalline impurities. Their unit cell volume and crystallographic density scale with Mn content; the percentage of Fe and/or Mn in Li positions is below 1.5%, which is comparable to reference samples. Crystallite sizes of at least 100 to 175 nm are observed for melt LMFP, which is larger than the fine ∼50 nm crystallites of reference LMFP. Melt LFP shows specific discharge capacity and cycling stability comparable to reference LFP, but the melt LMFP samples with 25%–100% Mn shows worse performance than reference LMFP (79% Mn). Part two of this study will quantify the solid-state lithium diffusion coefficient in melt LMFP materials and correlate it to their electrochemical performance.

Melt synthesis is a fast and simple process to make dense LiMnyFe1−yPO4 (LMFP with 0 ≤ y ≤ 1) from all-dry, low-cost precursors with zero waste. Part one of this study confirmed that highly crystalline and phase pure LMFP materials can be made by melt synthesis. This part shows that planetary milling can reduce the primary particle size of melt LMFP (0%–75% Mn) to ∼200 nm, which is smaller than the primary particles in commercial LFP reference material (0% Mn). However, further particle size reduction is needed to reach particle sizes below 70 nm observed in reference LMFP (79% Mn). Melt LFP shows almost identical specific capacity and charge/discharge voltage as reference LFP. Melt LMFP materials show a high voltage Mn plateau at ∼4 V associated with the Mn2+/3+ redox, the length of which scales with Mn content. The Mn plateau raises the average discharge voltage of LMFP; hence a minimum specific discharge capacity between 160 mAh g−1 (0% Mn) and 145 mAh g−1 (80% Mn) is sufficient to match the volumetric energy density of LFP. The Atlung Method for Intercalant Diffusion shows that the lithium diffusion coefficient in LMFP is ∼1 order of magnitude higher in the voltage region of the Fe2+/3+ redox couple (3.75–3.1 V vs Li+/Li) than in the voltage region of the Mn2+/3+ redox couple (4.3–3.75 V vs Li+/Li). This emphasizes the need for very small primary particles when making LMFP with relatively high Mn content.

Single crystal Li[Ni0.5Mn0.3Co0.2]O2//graphite (NMC532) pouch cells with only sufficient graphite for operation to 3.80 V (rather than ≥4.2 V) were cycled with charging to either 3.65 V or 3.80 V to facilitate comparison with LiFePO4//graphite (LFP) pouch cells on the grounds of similar maximum charging potential and similar negative electrode utilization. The NMC532 cells, when constructed with only sufficient graphite to be charged to 3.80 V, have an energy density that exceeds that of the LFP cells and a cycle-life that greatly exceeds that of the LFP cells at 40 °C, 55 °C and 70 °C. Excellent lifetime at high temperature is demonstrated with electrolytes that contain lithium bis(fluorosulfonyl)imide (LiFSI) salt, well beyond those provided by conventional LiPF6 electrolytes. Ultra-high precision coulometry and electrochemical impedance spectroscopy are used to complement cycling results and investigate the reasons for the improved performance of the NMC cells. NMC cells, particularly those balanced and charged to 3.8 V, show better coulombic efficiency, less capacity fade and higher energy density compared to LFP cells and are projected to yield lifetimes approaching a century at 25 °C.

Unwanted redox shuttles can lead to self-discharge and inefficiency in lithium-ion cells. This study investigates the generation of a redox shuttle in LFP/graphite and NMC811/graphite pouch cells with common alkyl carbonate electrolyte. Visual inspection of the electrolyte extracted after formation at temperatures between 25 and 70 °C reveals strong discoloration. Such extracted electrolytes with intense red and brown color show relatively large shuttling currents in Al/Li coin cells. Two weight percent of vinylene carbonate is effective at preventing the redox shuttle generation as indicated by the absence of electrolyte discoloration and shuttling current. Ultra-high precision coulometry demonstrates that the presence of the shuttle molecule during cycling of LFP/graphite and NMC811/graphite pouch cells leads to significant charge endpoint capacity slippage and coulombic inefficiency. A brief constant voltage hold at 4.2 V can eliminate the shuttle molecule.

Complex chemomechanical interplay exists over a wide range of length scales within the hierarchically structured lithium-ion battery. At the mesoscale, the interdependent structural complexity and ...

Since E-Mobility is on the rise worldwide, large Charging Infrastructure (CI) networks are required to satisfy the upcoming Charging Demand (CD). Understanding this CD with its spatial and temporal uncertainties is important for grid operators to quantify the grid impact of Electric Vehicle integration and for Charging Station (CS) operators to assess long-term CI investments. Hence, we introduce an Agent-based E-Mobility Model assessing regional CI systems with their multi-directional interactions between CSs and vehicles. A Global Sensitivity Analysis (GSA) is applied to quantify the impact of 11 technical levers on 17 relevant charging system outputs. The GSA evaluates the E-Mobility integration in terms of grid impact, economic viability of CSs and Service Quality of the deployed Charging Infrastructure (SQCI). Based on this impact assessment we derive general guidelines for E-Mobility integration into regional systems. We found, inter alia, that CI policies should aim at allocating CSs across different types of locations to utilize cross-locational effects such as CSs at public locations affecting the charging peak in residential areas by up to 18%. Additionally, while improving the highway charging network is an effective lever to increase the SQCI in urban areas, public charging is an even stronger lever in rural areas.