White Paper

Advancing Research of Rechargeable
Batteries Using Agilent UV-Vis
Spectrophotometers
Rechargeable battery studies published by global
research groups

Introduction
Rechargeable batteries are at the forefront of global discussions as analternative to typical combustion engines, as they offer a cost-effective solution
to reducing carbon emissions and dependance on fossil fuels. The focus ofmany research groups centers around alkali metals such as lithium, sodium, andpotassium due to their high theoretical specific capacities and exceptionally low
electrochemical potentials.1 This white paper provides examples of how Agilent
UV-Vis/NIR spectrophotometers have been used by leading research groups for thecharacterization of rechargeable battery materials and components.

Agilent UV-Vis/NIR spectrophotometers
Agilent's range of UV-Vis/NIR spectrophotometers caterto a variety of analysis needs, from routine applications tohigh-end experiments (Table 1). UV-Vis/NIR instruments canperform a range of analyses in the rechargeable batteries
space such as:2,3– Quantitative analysis of electrolytes– Qualitative analysis (materials characterization)– Degradation studies– Color measurements of electrolytes andother components– Spectroelectrochemistry– Band gap calculations– Operando optical spectroscopy– Leaching studies
A number of accessories are available to be paired withAgilent UV-Vis/NIR spectrophotometers for enhanced
scalability, flexibility, cost efficiency, and measurement
capability. Accessories such as the fiber optic dip
probe provide a unique solution to analyzing volatile ormoisture‑sensitive rechargeable battery materials, suchas lithium hexafluorophosphate (LiPF6 ), in the controlledenvironment of a glovebox.

Rechargeable battery research
applications using UV-Vis/NIRResearch groups located around the world have used Agilent
UV-Vis/NIR instrumentation as an integral solution for theanalysis and characterization of various battery components,
as summarized in the following examples.

A Facile Method to Improve the Photocatalytic andLithium-Ion Rechargeable Battery Performance of TiO2
Nanocrystals4
Ting Xia and the research team have displayed that
subjecting crystalline TiO2 nanocrystals to a vacuum
treatment at moderate temperatures and low vacuum
levels can lead to significant alterations in their structural,
optical, electronic, and chemical characteristics. Compared
to untreated TiO2 nanocrystals, these vacuum-treatedcounterparts exhibit notably enhanced photocatalytic
activity and superior performance in storing lithium ions.
Consequently, this innovative approach presents a promisingavenue for enhancing the functionality of TiO2 and otheroxide nanocrystals for various practical applications. The
reflectance spectra of the TiO2 particles were measured
using an Agilent Cary 60 UV-Vis spectrometer with an opticalreflectance fiber unit, which revealed that vacuum-treated
TiO2 nanocrystals extended their absorption from UV intonear-infrared.

Lithium Bis(Trifluoromethanesulfonyl)imide Blended
in Polyurethane Acrylate Photocurable Solid Polymer
Electrolytes for Lithium-Ion Batteries5
Cristian Mendes-Felipe and collaborators formulateda UV-photocurable polyurethane acrylate (PUA) resin
incorporating lithium bis(trifluoromethanesulfonyl)imide(LiTFSI). The conductivity levels enabled the applicationof the developed materials as photocurable solid polymer
electrolytes (SPE) in Li/C-LiFePO4 half-cells, resulting ina substantial battery discharge capacity. These findings,
coupled with theoretical assessments of discharge capacityacross various C-rates and temperatures for batteries
using LiTFSI/PUA SPE underscore the potential of thedeveloped photocurable SPE for lithium-ion battery (LIB)
applications. Optical characterization of the pristine photoresin and the LiTFSI/PUA samples was characterized using
ultraviolet‑visible (UV-Vis) spectroscopy measurements.
The UV‑Vis spectroscopy was conducted using an Agilent
Cary 60 spectrophotometer, covering the range from 200 to
800 nm with a sampling interval of 1 nm and 25 accumulationscans, and showed that the pristine photo resin presents themaximum light transmittance.

2Iodine-Containing Additive Engineering for Rejuvenating
Inactive Lithium and Constructing Highly Stable Lithium
Metal Anodes6

Electrospun Core-Shell Microfiber Separator with
Thermal-Triggered Flame-Retardant Properties for
Lithium-Ion Batteries8

In their investigation, Wenchang Ma and colleagues
conducted a series of redox reactions using the redox couple
to effectively remove inactive lithium, thereby enhancing thecapacity and Coulombic efficiency of the cell in a reversible
manner. The capability of the redox couple to rejuvenate
inactive lithium was confirmed through UV spectroscopy
conducted on an Agilent Cary 3500 instrument, where signals
were observed between 200 and 400 nm.

Kai Liu and colleagues investigated to determine whether
encapsulating a flame retardant within a protective polymer
shell could prevent its direct dissolution into the electrolyte,
thereby mitigating potential adverse effects on battery
performance. In the event of a thermal runaway in thelithium-ion battery, the protective polymer shell would melt in
response to elevated temperatures, facilitating the release of
the flame retardant. This mechanism effectively suppresses
the combustion of highly flammable electrolytes. A UV-Vis
absorbance spectrum was used to quantitatively monitor thetriphenyl phosphate release behavior upon thermal triggering.
TPP exhibits three explicit absorption bands whose peaks
are located at 266, 260, and 255 nm. The spectra facilitate
a quantitative estimate of the amount of TPP that has beenreleased into the electrolyte. Measurements were performed
using an Agilent Cary 6000i UV-Vis-NIR spectrophotometerfrom 210 nm to 330 nm.

Tuning the Azo Location in Conjugated Polymers Toward
High-Performance Lithium-Ion Batteries7
Sen Zhang, et al. investigated how the positioning of azo units(para versus meta linkage, main chain versus side chain)
within conjugated polymers influences electrochemical
properties and battery performance. Both experimental andtheoretical analyses highlight "redox-pendant" and "metajunction" as effective features for designing redox‑conjugatedpolymers for superior energy storage capabilities. The
practical viability of the resulting full battery to power an
LED bulb was successfully demonstrated, highlighting its
real-world application potential. This study offers valuable
insights into structurally optimizing polymers for enhanced
battery performance. UV-Vis absorption spectra from 250 to700 nm were acquired using a Cary 3500 spectrophotometer.
The spectra allowed the characterization of the polymers; two
had identical peaks at 322 nm, while the third had a peak at
337 nm.

Solvometallurgical Recovery of Cobalt from Lithium-Ion
Battery Cathode Materials Using Deep-Eutectic Solvents9
In this work, a green, cost-effective, and safe approach is
proposed by using a choline chloride-citric acid deep‑eutecticsolvent (DES) as a lixiviant. Aluminum and copper
were evaluated as reducing agents for cobalt (III). After
optimization, lithium and cobalt were quantitatively leachedfrom LiCoO2 in the presence of aluminum and copper. Copper
was the most effective reducing agent for cobalt (III), so thatno additional reducing agents or a pre-separation step wererequired. Copper (I), copper (II), and cobalt (II) chloride salts
were dissolved in the DES with similar metal concentration as
in the pregnant leach solution (PLS), followed by recording of
the absorption spectra. These were hereafter compared withthe recorded PLS spectra for qualitative analysis. A calibration
curve was constructed by dissolving different amounts ofcobalt (II) chloride in a 35 wt% water-diluted choline chloride
solution for cobalt (II) chloride quantification in the DES.
Qualitative and quantitative analysis of the pregnant leachsolution was done by UV-Vis-NIR absorption spectroscopy
with a Cary 6000i spectrophotometer.

3Agilent Cary 60 UV-Vis
Spectrophotometer

Agilent Cary 3500 UV-Vis
Spectrophotometer Series

The Cary 60 UV-Vis spectrophotometeris a powerful tool for repetitiveand routine analysis. It operates
within the wavelength range of 190
to 1,100 nm and can be equippedwith a comprehensive range ofsampling accessories. It can performmeasurements without any warm-up
time or room light interference andeliminates sample photodegradation
to ensure a correct answer every time.
This tolerance of room light and thehighly focused beam make the Cary 60
UV-Vis ideal for measurements outside
the sample compartment using fiber
optic probes.

The Cary 3500 Multicell and Compact
UV-Vis spectrophotometers areversatile measurement tools known for
their temperature control capabilities
and ultra-fast data collection rate of
250 points per second.

The Cary 60 UV-Vis comes with a
10-year warranty on the Xenon flash
lamp, and the Cary 60 UV-Vis has been
independently audited and verified
for its environmental impact and hasreceived the ACT (Accountability,Consistency, and Transparency) label,published by My Green Lab.

4The Cary 3500 Flexible UV-Vis
spectrophotometer features a uniquelarge sample compartment with small
footprint for analyzing liquid samples
that require long pathlength cuvettes,
as well as characterizing solidsamples. It operates effectively within
the range of 190 to 1,100 nm.
The Cary 3500 UV-Vis is anotherrecipient of the ACT, published by
My Green Lab, and boasts a 10-year
warranty on the Xenon flash lamp.

Agilent Cary
4000/5000/6000i/7000 UV-Vis(-NIR) Spectrophotometers
The high-end UV spectrophotometers
are fitted with the ability to measurehighly absorbing samples, as well
as diffuse reflection and specularreflection, operating within the rangeof 175 to 3,300 nm.
With superb photometric performancein the 175 to 3,300 nm range using
the latest generation of detectors(PbSmart, InGaAs, and sandwich),these systems have improved
sensitivity and lowered stray lightin the NIR, making them powerfultools for materials science research.
The Agilent Cary 7000 universal
measurement spectrophotometer(UMS) will satisfy all your solid
sampling needs. The Cary 7000
instrument's multiangle specularreflectance and transmittancecapabilities allow you to design
experiments never before possible—
expanding your research—while
the automated reflectance andtransmission will save you timeand money.

Table 1. An overview of the Agilent UV-Vis and UV-Vis-NIR spectrophotometers.
SystemCary 60Sample Type

Analysis Requirements

Liquids and solids– Routine analysis of liquid samples– Remote fiber optic measurements, ideal for moisture-controlled environment (glovebox)– High-throughput with the 18-cell changer– Color measurements

Cary 3500 Multicell
and Compact

Liquids– Multiple simultaneous measurements– Temperature-controlled experiments– Fast data collection (250 data points per second)

Cary 3500 Flexible

Liquids and solids– Variable pathlengths– Fast data collection (250 data points per second)– Large sample compartment

Cary 4000
Cary 5000
Cary 6000i
Cary 7000

Liquids and solids– Small or large samples– Extended wavelength into NIR– Measurement flexibility– Color measurements

Conclusion
Agilent's range of UV-Vis/NIR spectrophotometers provide
a diverse array of functions that enable important research
involving metal-ion batteries to be conducted. From routine
battery components research on the Cary 60, material
characterization on the Cary 3500, and quantitative analysisof leach solutions on the Cary 4000/5000/6000i/7000, theCary instruments cover a wide range of research needs withflexibility and scalability. The availability of many accessories
and dynamic software make the Cary range the mostpowerful on the market for battery research.

5References
1. Liu, H.; Cheng, X-B.; Huang, J-Q.; Kaskel, S.; Chou, S.;
Park, H. S.; Zhang, Q. Alloy Anodes for Rechargeable
Alkali-Metal Batteries: Progress and Challenge.
ACS Materials Letters 2019, 1(2), 217–229.
2. Patel, M. U. M.; Dominko, R. Application of In Operando
UV-Vis Spectroscopy in Lithium–Sulfur Batteries.
ChemSusChem 2014, 7, 2167–2175.
3. Bouteau, G.; Van-Nhien, A. N.; Sliwa, M.; et al. Effect ofStandard Light Illumination on Electrolyte's Stability ofLithium-Ion Batteries Based on Ethylene and Di-Methyl
Carbonates. Sci. Rep. 2019, 9, 135.
4. Xia, T.; Zhang, W.; Murowchick, J. B.; Liu, G.; Chen, X.
A Facile Method to Improve the Photocatalytic andLithium-Ion Rechargeable Battery Performanceof TiO2 Nanocrystals. Adv. Energy Mater. 2013, 3,
1516–1523.

www.agilent.com
DE15818117
This information is subject to change without notice.
© Agilent Technologies, Inc. 2024
Printed in the USA, June 5, 2024
5994-7529EN

5. Mendes-Felipe, C.; Barbosa, J. C.; Gonçalves, R.;
Miranda, D.; Costa, C. M.; Vilas‑Vilela, J. L.;
Lanceros‑Mendez, S. Lithium Bis(Trifluoromethanesulfonyl)imide Blended in Polyurethane
Acrylate Photocurable Solid Polymer Electrolytes for
Lithium-Ion Batteries. J. Energy Chem. 2021, 62, 485–496.
6. Ma, W.; Li, W.; Jiang, J.; Xu, Y.; Li, W.; Liu, X.; Chen, Z.;
Jiang, Y.; Zhang, J.; Zhao, B. Iodine-Containing Additive
Engineering for Rejuvenating Inactive Lithium andConstructing Highly Stable Lithium Metal Anodes. Chem.
Engin. J. 2023, 477, 146890–146890.
7. Sen Zhang; Fangfang Xing; Ling Chen; Xiujuan Wang;
Xiaoming H. Chemistry of Materials 2022, 34(20),9031–9041.
8. Liu, K.; et al. Electrospun Core-Shell Microfiber Separator
with Thermal-Triggered Flame-Retardant Properties for
Lithium-Ion Batteries. Sci. Adv. 2017, 3(1).
9. Peeters, N.; Binnemans, K.; Riaño, S. Solvometallurgical
Recovery of Cobalt from Lithium-Ion Battery CathodeMaterials Using Deep-Eutectic Solvents. Green Chemistry
2020, 22(13), 4210–4221.