Clarifying the Relationship between the Lithium Deposition Coverage and Microstructure in Lithium Metal Batteries

Improving the reversibility of lithium metal batteries is one of the challenges in current battery research. This requires better fundamental understanding of the evolution of the lithium deposition morphology, which is very complex due to the various parameters involved in different systems. Here, we clarify the fundamental origins of lithium deposition coverage in achieving highly reversible and compact lithium deposits, providing a comprehensive picture in the relationship between the lithium microstructure and solid electrolyte interphase (SEI) for lithium metal batteries. Systematic variation of the salt concentration offers a framework that brings forward the different aspects that play a role in cycling reversibility. Higher nucleation densities are formed in lower concentration electrolytes, which have the advantage of higher lithium deposition coverage; however, it goes along with the formation of an organic-rich instable SEI which is unfavorable for the reversibility during (dis)charging. On the other hand, the growth of large deposits benefiting from the formation of an inorganic-rich stable SEI is observed in higher concentration electrolytes, but the initial small nucleation density prevents full coverage of the current collector, thus compromising the plated lithium metal density. Taking advantages of the paradox, a nanostructured substrate is rationally applied, which increases the nucleation density realizing a higher deposition coverage and thus more compact plating at intermediate concentration (∼1.0 M) electrolytes, leading to extended reversible cycling of batteries. RST/Storage of Electrochemical EnergyRID/TS/Instrumenten groe

High-Density Microporous Li₄Ti₅O₁₂ Microbars with Superior Rate Performance for Lithium-Ion Batteries

Nanosized Li4Ti5O12 (LTO) materials enabling high rate performance suffer from a large specific surface area and low tap density lowering the cycle life and practical energy density. Microsized LTO materials have high density which generally compromises their rate capability. Aiming at combining the favorable nano and micro size properties, a facile method to synthesize LTO microbars with micropores created by ammonium bicarbonate (NH4HCO3) as a template is presented. The compact LTO microbars are in situ grown by spinel LTO nanocrystals. The as-prepared LTO microbars have a very small specific surface area (6.11 m2 g−1) combined with a high ionic conductivity (5.53 × 10−12 cm−2 s−1) and large tap densities (1.20 g cm−3), responsible for their exceptionally stable long-term cyclic performance and superior rate properties. The specific capacity reaches 141.0 and 129.3 mAh g−1 at the current rate of 10 and 30 C, respectively. The capacity retention is as high as 94.0% and 83.3% after 500 and 1000 cycles at 10 C. This work demonstrates that, in situ creating micropores in microsized LTO using NH4HCO3 not only facilitates a high LTO tap density, to enhance the volumetric energy density, but also provides abundant Li-ion transportation channels enabling high rate performance.RST/Fundamental Aspects of Materials and Energ

Quantification of the Li-ion diffusion over an interface coating in all-solid-state batteries via NMR measurements

A key challenge for solid-state-batteries development is to design electrode-electrolyte interfaces that combine (electro)chemical and mechanical stability with facile Li-ion transport. However, while the solid-electrolyte/electrode interfacial area should be maximized to facilitate the transport of high electrical currents on the one hand, on the other hand, this area should be minimized to reduce the parasitic interfacial reactions and promote the overall cell stability. To improve these aspects simultaneously, we report the use of an interfacial inorganic coating and the study of its impact on the local Li-ion transport over the grain boundaries. Via exchange-NMR measurements, we quantify the equilibrium between the various phases present at the interface between an S-based positive electrode and an inorganic solid-electrolyte. We also demonstrate the beneficial effect of the LiI coating on the all-solid-state cell performances, which leads to efficient sulfur activation and prevention of solid-electrolyte decomposition. Finally, we report 200 cycles with a stable capacity of around 600 mAh g−1 at 0.264 mA cm−2 for a full lab-scale cell comprising of LiI-coated Li2S-based cathode, Li-In alloy anode and Li6PS5Cl solid electrolyte.RST/Storage of Electrochemical EnergyInstrumenten groe

Abundant grain boundaries activate highly efficient lithium ion transportation in high rate Li₄Ti₅O₁₂ compact microspheres

It is a huge challenge for high-tap-density electrodes to achieve high volumetric energy density but without compromising the ionic transportation. Herein, we prepared compact Li4Ti5O12 (LTO) microspheres consisting of densely packed primary nanoparticles. The real space distribution of lithium ions inside the compact LTO was revealed by using scanning transmission electron microscopy with electron energy loss spectroscopy (STEM-EELS) to identify the function of grain boundaries for lithium ion transportation during lithiation. The as-prepared LTO microspheres possess a high tap density (1.23 g cm-3) and an ultra-small specific surface area (2.40 m2 g-1). Impressively, the compact LTO microspheres present excellent electrochemical performance. At high rates of 5C, 10C and 20C, the LTO microspheres show a specific capacity of 146.6, 138.2 and 111 mA h g-1, respectively. The capacity retention remains at 97.8% at 5C after 500 cycles. The STEM-EELS results indicate that the lithiation reaction of LTO is firstly initiated at grain boundaries during the high rate lithiation process and then diffuses to the bulk area. The abundant grain boundaries in compact LTO microspheres can form a highly efficient conductive network to preferentially transport the ions, which contributes to high volumetric and gravimetric energy density simultaneously.Accepted Author ManuscriptRST/Fundamental Aspects of Materials and EnergyRST/Storage of Electrochemical Energ

Author Correction: Quantification of the Li-ion diffusion over an interface coating in all-solid-state batteries via NMR measurements (Nature Communications, (2021), 12, 1, (5943), 10.1038/s41467-021-26190-2)

The original version of this article contained errors in Figure 3a and Figure 3f. In Figure 3a, the activation energies (Ea) were calculated using a log scale instead of a logarithm ln scale. In Figure 3f, the y-axis interval was not properly selected. The correct y-axis interval in Figure 3f and the numerical values of the activation energy are now provided in Figure 3a and the main text. These errors have been corrected in the HTML and PDF versions of the article.Corrections & amendments DOI 10.1038/s41467-021-26190-2RST/Storage of Electrochemical EnergyRID/TS/Instrumenten groe

Importance of vegetation classes in modeling CH4 emissions from boreal and subarctic wetlands in Finland

Boreal/arctic wetlands are dominated by diverse plant species, which vary in their contribution to CH4 production, oxidation and transport processes. Earlier studies have often lumped the processes all together, which may induce large uncertainties into the results. We present a novel model, which includes three vegetation classes and can be used to simulate CH4 emissions from boreal and arctic treeless wetlands. The model is based on an earlier biogeophysical model, CH4MOD(wetland). We grouped the vegetation as graminoids, shrubs and Sphagnum and recalibrated the vegetation parameters according to their different CH4 production, oxidation and transport capacities. Then, we used eddy-covariance-based CH4 flux observations from a boreal (Siikaneva) and a subarctic fen (Lompolojaka) in Finland to validate the model. The results showed that the recalibrated model could generally simulate the seasonal patterns of the Finnish wetlands with different plant communities. The comparison between the simulated andmeasured daily CH4 fluxes resulted in a correlation coefficient (R-2) of 0.82 with a slope of 1.0 and an intercept of -0.1 mg m(-2) h(-1) for the Siikaneva site (n = 2249, p < 0.001) and an R-2 of 0.82 with a slope of 1.0 and an intercept of 0.0 mg m(-2) h(-1) for the Lompolojankka site (n = 1826, p < 0.001). Compared with the original model, the recalibrated model in this study significantly improved the model efficiency (EF), from - 5.5 to 0.8 at the Siikaneva site and from -0.4 to 0.8 at the Lompolojankka site. The simulated annual CH4 emissions ranged from 7 to 24 gm(-2) yr(-1), which was consistent with the observations (7-22 gm(-2) yr(-1)). However, there are some discrepancies between the simulated and observed daily CH4 fluxes for the Siikaneva site (RMSE = 50.0%) and the Lompolojankka site (RMSE = 47.9%). Model sensitivity analysis showed that increasing the proportion of the graminoids would significantly increase the CH4 emission levels. Our study demonstrated that the parameterization of the different vegetation processes was important in estimating long-term wetland CH4 emissions. (C) 2016 Elsevier B.V. All rights reserved

Agricultural reclamation effects on ecosystem CO2 exchange of a coastal wetland in the Yellow River Delta

Little is known about the impacts of agricultural exploitation of coastal wetlands on ecosystem CO2 exchange, although coastal wetlands have been widely reclaimed for agricultural use across the world. We measured net ecosystem CO2 exchange (NEE) and its major components, gross primary production (GPP) and ecosystem respiration (R-eco) using an eddy covariance flux technique in a natural coastal wetland (reed) and an adjacent, newly reclaimed farmland (cotton) in the Yellow River Delta, China. The results showed that agricultural reclamation changed the ecosystem CO2 exchange of the coastal wetland at three distinct levels. Initially, the conversion from the wetland to farmland changed the light response parameters (alpha, A(max), and R-eco, day) of NEE and temperature sensitivity (Q(10)) of R-eco mainly by changing the dominant vegetation type. Over the growing season, NEE, R-eco and GPP were significantly correlated with LAI at both sites and aboveground biomass at the farmland site. Next, the reclamation of wetland modified the diurnal and seasonal dynamics of ecosystem CO2 exchange. Significant differences in diurnal variations of NEE between the wetland and farmland sites were found during the growing season (with the exception of June and July). Seasonal means of daily GPP and R-eco values at the wetland site were higher than those at the farmland. Ultimately, the agricultural reclamation altered the CO2 sequestration capacity of the coastal wetland. The cumulative NEE in the wetland (-237.4 g Cm-2) was higher than that in the farmland (-202.0 g Cm-2). When biomass removal was taken into account, the farmland was a strong source for CO2 of around 131.9 g Cm-2 during the growing season. Overall, land use changes by reclamation altered ecosystem CO2 exchange at several ecological scales by changing the dominant vegetation type and altering the ecosystem's natural development. (C) 2013 Elsevier B.V. All rights reserved.Little is known about the impacts of agricultural exploitation of coastal wetlands on ecosystem CO2 exchange, although coastal wetlands have been widely reclaimed for agricultural use across the world. We measured net ecosystem CO2 exchange (NEE) and its major components, gross primary production (GPP) and ecosystem respiration (R-eco) using an eddy covariance flux technique in a natural coastal wetland (reed) and an adjacent, newly reclaimed farmland (cotton) in the Yellow River Delta, China. The results showed that agricultural reclamation changed the ecosystem CO2 exchange of the coastal wetland at three distinct levels. Initially, the conversion from the wetland to farmland changed the light response parameters (alpha, A(max), and R-eco, day) of NEE and temperature sensitivity (Q(10)) of R-eco mainly by changing the dominant vegetation type. Over the growing season, NEE, R-eco and GPP were significantly correlated with LAI at both sites and aboveground biomass at the farmland site. Next, the reclamation of wetland modified the diurnal and seasonal dynamics of ecosystem CO2 exchange. Significant differences in diurnal variations of NEE between the wetland and farmland sites were found during the growing season (with the exception of June and July). Seasonal means of daily GPP and R-eco values at the wetland site were higher than those at the farmland. Ultimately, the agricultural reclamation altered the CO2 sequestration capacity of the coastal wetland. The cumulative NEE in the wetland (-237.4 g Cm-2) was higher than that in the farmland (-202.0 g Cm-2). When biomass removal was taken into account, the farmland was a strong source for CO2 of around 131.9 g Cm-2 during the growing season. Overall, land use changes by reclamation altered ecosystem CO2 exchange at several ecological scales by changing the dominant vegetation type and altering the ecosystem's natural development. (C) 2013 Elsevier B.V. All rights reserved