16 research outputs found
Interface Investigations of a Commercial Lithium Ion Battery Graphite Anode Material by Sputter Depth Profile X‑ray Photoelectron Spectroscopy
Here we provide a detailed X-ray
photoelectron spectroscopy (XPS)
study of the electrode/electrolyte interface of a graphite anode from
commercial NMC/graphite cells by intense sputter depth profiling using
a polyatomic ion gun. The uniqueness of this method lies in the approach
using 13-step sputter depth profiling (SDP) to obtain a detailed model
of the film structure, which forms at the electrode/electrolyte interface
often noted as the solid electrolyte interphase (SEI). In addition
to the 13-step SDP, several reference experiments of the untreated
anode before formation with and without electrolyte were carried out
to support the interpretation. Within this work, it is shown that
through charging effects during X-ray beam exposure chemical components
cannot be determined by the binding energy (BE) values only, and in
addition, that quantification by sputter rates is complicated for
composite electrodes. A rough estimation of the SEI thickness was
carried out by using the LiF and graphite signals as internal references
Different Efforts but Similar Insights in Battery R&D: Electrochemical Impedance Spectroscopy <i>vs</i> Galvanostatic (Constant Current) Technique
Electrochemical impedance spectroscopy (EIS) using alternating
currents is a widely established technique to investigate
kinetic aspects of batteries and their components, though it requires
an interruption of battery operation with extra measurement time and
effort. In this work, EIS is compared with the conventional galvanostatic
(constant current) technique, which is based on direct currents, being the standard operation mode of batteries. Data from constant
current measurements not only are representing application conditions
but also are automatically and continuously generated during routine
charge/discharge processes, i.e., without extra measurement efforts, and do give kinetic insights
via the characteristic overvoltage (= resistance-reasoned voltage
rise/decrease), as well. In fact, distinguishing between even very
similar values for ohmic (RΩ), charge
transfer (Rct), and mass
transport (Rmt) resistances
can be done via analysis of overvoltage data from constant current
measurements, as exemplarily demonstrated in symmetric Li||Li and
LiNi0.6Mn0.2Co0.2O2 (NMC622)||Li
cells with poly(ethylene oxide)-based solid polymer electrolyte, finally
proving their validity. From a practical point of view, direct-current
methods can be beneficial for R&D of kinetic aspects in batteries,
as data is directly obtained and, thus, application-oriented
Invasive species influence macroinvertebrate biomonitoring tools and functional diversity in British rivers
Biological invasions could have major implications for the management and conservation of freshwater systems if they lead to a misclassification of waterbodies. However, there is limited understanding of the sensitivity of existing biomonitoring tools to invasive species in rivers; and even less known regarding how they influence community taxonomic and functional measures. This research explores the response of freshwater macroinvertebrate communities to biological invasion using taxonomic and functional indices. Utilising a long-term dataset (spanning 2000–2019, 5,988 samples) from rivers in England, the performance of four biomonitoring tools (WHPT, WHPT-ASPT, LIFE and PSI) and two community functional indices (functional richness and redundancy) was examined before and after the colonisation of the invasive species, Dikerogammarus haemobaphes (Eichwald, 1841; Crustacea: Gammaridae). This species represents a recent (first record 2012) and highly successful invader, allowing its range expansion within waterbodies to be examined in detail. Spatial (national and basin level) and seasonal (spring and autumn) effects were investigated using a before–after control–impact (BACI) experimental framework and linear mixed effects models. Results indicated that invasion by D. haemobaphes resulted in significant reductions to the WHPT index and functional diversity metrics (richness and redundancy) while more subtle patterns were observed for other metrics. Analysis of seasonal and individual river basins (River Trent and R. Thames) identified largely consistent responses. The establishment of D. haemobaphes also resulted in some modifications to the functional composition of aquatic communities primarily associated with voltinism and resistance features. Synthesis and applications. Our findings indicate that Dikerogammarus haemobaphes should be considered a significant pressure to riverine communities. These results have implications for biomonitoring, which informs managerial actions as effects may not be detected using a single taxonomic index. Community functional measures are useful in characterising the effects of invasive species and may form a valuable part of the ‘toolbox’ used for studying biological invasions in rivers. The research illustrates the need to consider the wider threats posed by invasive species on the long-term integrity of freshwaters and the efficacy of freshwater biomonitoring tools
Supramolecular Self-Assembly of Methylated Rotaxanes for Solid Polymer Electrolyte Application
Li<sup>+</sup>-conducting
solid polymer electrolytes (SPEs) obtained
from supramolecular self-assembly of trimethylated cyclodextrin (TMCD),
polyÂ(ethylene oxide) (PEO), and lithium salt are investigated for
application in lithium-metal batteries (LMBs) and lithium-ion batteries
(LIBs). The considered electrolytes comprise nanochannels for fast
lithium-ion transport formed by CD threaded on PEO chains. It is demonstrated
that tailored modification of CD beneficially influences the structure
and transport properties of solid polymer electrolytes, thereby enabling
their application in LMBs. Molecular dynamics (MD) simulation and
experimental data reveal that modification of CDs shifts the steady
state between lithium ions inside and outside the channels, in this
way improving the achievable ionic conductivity. Notably, the designed
SPEs facilitated galvanostatic cycling in LMBs at fast charging and
discharging rates for more than 200 cycles and high Coulombic efficiency
Failure Mechanisms at the Interfaces between Lithium Metal Electrodes and a Single-Ion Conducting Polymer Gel Electrolyte
Polymer electrolytes have the potential to enable rechargeable
lithium (Li) metal batteries. However, growth of nonuniform high surface
area Li still occurs frequently and eventually leads to a short-circuit.
In this study, a single-ion conducting polymer gel electrolyte is
operated at room temperature in symmetric Li||Li cells. We use X-ray
microtomography and electrochemical impedance spectroscopy (EIS) to
study the cells. In separate experiments, cells were cycled at current
densities of 0.1 and 0.3 mA cm–2 and short-circuits
were obtained eventually after an average of approximately 240 cycles
and 30 cycles, respectively. EIS reveals an initially decreasing interfacial
resistance associated with electrodeposition of nonuniform Li protrusions
and the concomitant increase in electrode surface area. X-ray microtomography
images show that many of the nonuniform Li deposits at 0.1 mA cm–2 are related to the presence of impurities in both
electrolyte and electrode phases. Protrusions are globular when they
are close to electrolyte impurities but are moss-like when they appear
near the impurities in the lithium metal. At long times, the interfacial
resistance increases, perhaps due to additional impedance due to the
formation of additional solid electrolyte interface (SEI) at the growing
protrusions until the cells short. At 0.3 mA cm–2, large regions of the electrode–electrolyte interface are
covered with mossy deposits. EIS reveals a decreasing interfacial
resistance due to the increase in interfacial area up to short-circuit;
the increase in interfacial impedance observed at the low current
density is not observed. The results emphasize the importance of pure
surfaces and materials on the microscopic scale and suggest that modification
of interfaces and electrolyte may be necessary to enable uniform Li
electrodeposition at high current densities
Toward Na-ion Batteriesî—¸Synthesis and Characterization of a Novel High Capacity Na Ion Intercalation Material
The rapid growth of the worldwide demand of lithium for
batteries
(LIBs) can possibly lead to a shortage of its reserves. Sodium batteries
represent a promising alternative because they enable much higher
energy densities than other battery systems, with the exception of
LIBs, and are not limited by sodium availability. Herein, we present
a novel, Na<sup>+</sup> ion intercalation material, Na<sub>0.45</sub>Ni<sub>0.22</sub>Co<sub>0.11</sub>Mn<sub>0.66</sub>O<sub>2</sub> (space
group <i>P</i>6<sub>3</sub>/<i>mmc</i>) synthesized
in air by a coprecipitation method followed by a thermal treatment
and a water-rinsing step. This material performs a specific capacity
of 135 mA h g<sup>–1</sup> with a Coulombic efficiency exceeding
99.7%. Upon long-term cycling tests the material shows excellent capacity
retention after more than 250 cycles. Such an overall performance,
superior to that of presently known sodium-ion cathodes, represents
a step further toward the realization of sustainable batteries for
efficient stationary energy storage
Highly Effective Solid Electrolyte Interphase-Forming Electrolyte Additive Enabling High Voltage Lithium-Ion Batteries
The electrochemical
and thermal stabilities of commonly used LiPF<sub>6</sub>/organic
carbonate-based electrolytes are still a bottleneck
for the development of high energy density lithium-ion batteries (LIBs)
operating at elevated cell voltage and elevated temperature. The use
of intrinsic electrochemically stable electrolyte solvents, e.g. sulfones
or dinitriles, has been reported as one approach to enable high voltage
LIBs. However, the major challenge of these solvents is related to
their poor reductive stability and lack of solid electrolyte interphase
(SEI)-forming ability on the graphite electrode. Here, 3-methyl-1,4,2-dioxazol-5-one
(MDO) is synthesized and investigated as new highly effective SEI-forming
electrolyte additive which can sufficiently suppress electrolyte reduction
and graphite exfoliation in propylene carbonate (PC)-based electrolytes.
With the addition of only 2 wt % MDO, LiNi<sub>0.5</sub>Mn<sub>0.3</sub>Co<sub>0.2</sub>O<sub>2</sub> (NMC532)/graphite full cells containing
a 1 M LiPF<sub>6</sub> in PC electrolyte reach a cycle life of more
than 450 cycles while still having a capacity retention of 80%. In
addition, MDO has proven to be oxidatively stable until potentials
as high as 5.3 V vs Li/Li<sup>+</sup>. Further development of MDO
and its derivatives as electrolyte additives is a step forward to
high voltage stable electrolyte formulations based on alternative
electrolyte solvents and high energy density LIBs
Supplemental_Material – Supplemental material for Automated MALDI Target Preparation Concept
<p>Supplemental material, Supplemental_Material for Automated MALDI Target Preparation Concept by Martin Winter, Robert Ries, Carola Kleiner, Daniel Bischoff, Andreas H. Luippold, Tom Bretschneider and Frank H. Büttner in SLAS Technology</p
Supplemental_Table_S1 – Supplemental material for Automated MALDI Target Preparation Concept
<p>Supplemental material, Supplemental_Table_S1 for Automated MALDI Target Preparation Concept by Martin Winter, Robert Ries, Carola Kleiner, Daniel Bischoff, Andreas H. Luippold, Tom Bretschneider and Frank H. Büttner in SLAS Technology</p
In Situ Diffuse Reflectance Infrared Fourier-Transform Spectroscopy Investigation of Fluoroethylene Carbonate and Lithium Difluorophosphate Dual Additives in SEI Formation over Cu Anode
The synergetic effect of fluoroethylene carbonate (FEC)
and lithium
difluorophosphate (LiPO2F2) dual additives on
the cycling stability of lithium metal batteries has been previously
reported. This study applies in situ diffuse reflectance infrared
Fourier-transform spectroscopy (DRIFTS) to examine the impact of these
two additives on SEI species formation over Cu anode using a base
electrolyte of LiPF6 in ethylene carbonate (EC) and diethyl
carbonate (DEC). The results indicate that all electrolyte components
and additives can be electrochemically reduced over the Cu anode following
a potential sequence of LiPO2F2 > FEC >
EC >
DEC. The results illustrate that LiPF6 likely interacts
with the Cu anode upon contact, resulting in LixPFy, which can lead to a reduction
peak at ∼1.44 V in CV. With the base electrolyte, reduced species
from LixPFy lead to the formation of alkyl phosphorus fluorides (RPF), which
can be suppressed by the presence of FEC and/or LiPO2F2. Similar to previous reports, FEC reduction in the 1st lithiation
cycle leads to the continuous formation of poly(FEC), while EC is
electrochemically reduced to (CH2OCO2Li)2 and Li2CO3 and DEC is reduced to CH3CH2OCO2Li and Li2CO3. With only the LiPO2F2 additive, the redox
of LiPO2F2 can be found in CV with LixPOy as the possible reduced
product. In addition, Li2CO3 formation from
EC and DEC reduction was relatively suppressed by the presence of
LiPO2F2. The simultaneous presence of the FEC
additive can suppress the redox of LiPO2F2 and
partly the decomposition of LiPF6 likely via the preferential
adsorption of FEC on Cu. Similar DRIFTS observations are found over
the Li anode. The electrolyte with dual additives demonstrates a possible
advantage from poly(FEC) and LixPOy species formation, suppressing the reduction
of LixPFy,
EC, and DEC though not completely