Empowering Battery Research

By Isabella Germinario, 9 minutes to read
Industry: Technology: , ,

Electrochemical cells play an essential role in keeping the clockwork of our lives turning. The demand for better batteries with heightened performance, boosted utility, and swifter production is ever rampant in many industries. But how can the challenges in battery research be surmounted?

Nanoscience Instruments provides four different solutions to researchers involved in enhancing batteries:

High Resolution Imaging in an Inert Environment Using an SEM

Argon-Compatible Phenom XL G2 Desktop SEM

The Phenom XL G2 Argon-Compatible Desktop SEM is ideal for investigating air-sensitive battery materials in an inert environment. Its compact footprint ensures that it fits inside a glovebox, offering an ideal condition for investigating energy storage devices.

Phenom SEM for battery research
  • Fits inside a glovebox, preventing degradation of air-sensitive samples
  • Inspect air sensitive materials such as solid-state lithium batteries without oxidation
  • Enhanced functionality with EDS (energy dispersive x-ray spectroscopy)
  • Automation in conjunction with element identification streamlines workflow
  • Images are 60 seconds away after loading the sample
Phenom Argon-compatible Glovebox workflow

The Argon-compatible Phenom XL G2 is ideal for battery researchers, enabling investigation of air-sensitive materials in a large sample chamber, and preventing degradation while simultaneously increasing throughput. Features of the fundamental Phenom XL G2 system remain intact and create an efficient workflow entirely inside a compact glovebox. Full-screen, crisp images are 60 seconds away from loading the sample.

EDS Point Analysis on two regions of interest and their respective spectra. Data generated on a Thermo Scientific Phenom desktop SEM.

Electrospun Battery Separators

Problem:

Separators have the important role of acting as a barrier between the cathode and anode to inhibit physical contact and short circuits. In standard separators, porous polypropylene films or polyolefin-based membranes are employed in this role. However, they exhibit unfavorable characteristics in terms of battery utility such as low electron conduction, high volume expansion, structural instability, low wettability, and inferior thermal-dimension stability. These traits lead to poor battery performance and dangerous consequences (usually in the form of explosions).

Solution:

Electrospun nanofibrous mats demonstrate great utility as potential separators with high safety and increased efficiency compared to traditional polymers or membranes. The interconnected pores and substantial surface-area-volume ratios of the fibers diminish degradation rates during discharge and charge processes. What’s more, electrospun separators favor a rapid and complete uptake of soaked electrolyte; this is particularly desirable in battery research because it simultaneously boosts ionic conductivity and the overall power response of the battery.

Fiber morphology and arrangements are completely controllable with electrospinning by taking advantage of several variable parameters: polymer melt or solution viscosity, concentration, applied voltage, collector-tip separation distance, and optional rotating disc collector angular speed.

Additionally, confirmation of desirable fiber morphology, diameter, pore-size, and other parameters that are significant for battery separators can be easily accomplished using the Phenom XL Desktop SEM‘s FiberMetric software. Automatically detect and analyze up to 1000 fibers per image, and measure diameter and orientation distributions with minimal effort.

Furthermore, electrospinning is compatible and favorable with the implementation of nanoparticles to enhance electrochemical properties (Al2O3 is one such example of nanoparticles that demonstrated improved changes).

Ultimately, electrospinning yields structures that are perfect for battery separators. Tensile strength through mechanical aptitude, high safety, an ideal piezoelectric nature, thermal stability, and impressive ionic conduction are but just a few likeable characteristics that electrospun structures boast.

Technique Description:

Electrospinning is a powerful technique used to generate small fibers that finds utility in a range of applications. The structures derive from a polymer solution (or melt) and can be attuned to fit specific dimensions in the micro or nanometer regimes. They are formed by exploiting an electrohydrodynamic phenomenon wherein an electric field drives a charged liquid jet onto a collector.

To control the liquid flow, a pump allows the solution to trickle out of the reservoir at a constant rate. The applied electric field permeates the space between the reservoir tip and collector, ensuring that the charged jet flows in a single direction

Violent whipping occurs during the solution’s flight so that the solvent evaporates and leaves behind fibers. Depending upon the concentration of the solution, one may yield particles by an identical technique called electrospraying.

Researchers have options to tailor the electrospinning process as they desire with a range of collectors, voltage strength, separation distance, polymer composition and concentration, and viscosity.

SEM image of PAN nanofibers fabricated to serve as battery separator material
SEM image of PAN nanofibers fabricated by a Fluidnatek electrospinning system. Imaged using a Phenom desktop SEM.

Fluidnatek Electrospinners

Our suite of electrospinning equipment includes the LE-50, LE-100, and LE-500, which are designed to fabricate nanofibrous material with tunable morphologies. They are capable of generating viable structures that have the potential to be employed as battery separators.

  • Electrospun separators have improved wettability and ionic conductivity due to high porosity, large surface–volume ratios, and interconnected pores
  • Improve thermal stability and electrochemical performance using sequential fabrication and multilayer techniques
  • Flexibility of materials enables fine-tuning of separator performance: monolayer or multilayer, modified, composite, and gel polymer separators
  • Study the morphology of electrospun materials in high-resolution with a desktop SEM
Fluidnatek LE-50 Electrospinning and Electrospraying system, featuring a real-time Taylor Cone camera feed and touchscreen controls

Solid Electrolyte Interphase Analysis by EQCM-D

Problem:

The SEI (solid electrolyte interphase) is a layer of solid material that accrues on anodes, composed of salt degradation and solvent reduction products. It occurs specifically at the mass exchange boundary where the electrolyte meets the anode and inherently has a puzzling nature; this is due to its dynamic time-dependent behavior and unclear progression.

A stable SEI governs reversible charging processes and overall stability in batteries, yet the layer’s complexity is only just being understood. Being able to view the SEI with necessary resolution is quite difficult without the use of an optimized instrument capable of offering in situ information.

Schematic representation of Li-Ion cell with a graphite anode and LiMO2 (M=C0, Ni, Mn…) cathode, representing the SEI's placement inside the battery, which traditionally made it difficult to observe.

EQCM-D (electrochemical quartz crystal microbalance with dissipation) enables scientists to quantitatively estimate delicate mass changes, SEI shear modulus, and SEI viscosity, among other properties relevant in battery research. It is possible to characterize passivation layer formation and its structural changes in real-time, and various parameters can be adjusted to influence the dynamics of the experiment: applied current, voltage, temperature, and additives.

Solution:

Schematic of EQCM-D Set-up used by battery researchers
Schematic diagram of QSense Electrochemistry Module setup

Viscoelastic films are relevant in flexible molecular systems like biology, biotechnology, polymers, lipids, proteins, electrochemistry (left), environmental studies, and nanoparticles. As such, a more refined method to deal with complex systems is QCM-D (dissipation); this technique principally utilizes voltage decays to glean information on the dissipation factor.

Combining dissipation with electrochemistry enables scientists in battery research to explore electropolymerization, ion intercalation, corrosion, and electrodeposition at multiple harmonics.

Technique Description:

QCM (quartz crystal microbalance) is a highly precise analysis technique capable of measuring microgram changes in mass per unit area.

At its core, the method functions by sandwiching a disc of quartz between two metal electrodes and applying a specific voltage. Due to the piezoelectric nature of quartz, the potential difference between the electrodes stimulates the disc into oscillatory motion.

The frequency of oscillations changes whenever mass – however slight – is added or removed with respect to the surface. If the resonant frequency of the quartz lies in the MHz range, then frequency variations can be measured with less than 1 Hz resolution.

Both frequency and mas changes can be linearly related with a combination of overtone number and property-dependent constant. However, for viscoelastic films, any attempts to model the relationship linearly fail to properly represent the two quantities.

Diagram of Sauerbrey's measurement mechanism, which enables real-time measurement of surface interactions for battery research
Sauerbrey’s measurement mechanism: (a) voltage is applied to the quartz crystal, causing oscillation at a constant frequency (b) molecules start to deposit, decreasing frequency of oscillation, and (c) more molecular deposition further decreases oscillation frequency.

QSense EQCM-D

QSense EQCM-D enables real-time measurements of mass and viscoelastic properties at surfaces and can be used in the analysis of SEI formation alongside potential development of new battery electrode materials.

QSense Pro Automated QCM-D
  • In situ monitoring of dynamics and mass exchange at the SEI
  • Identify conditions in which SEI is optimized for battery performance
  • Easily track and manage time evolution of electrolyte boundaries in real-time

Surface Wettability by Optical and Force Tensiometry

Problem:

The waiting time necessary for proper electrolyte uptake is the biggest inhibiting step in battery production. Oftentimes the electrolyte must soak into each component for hours in which there might not be anything to do but sit idly. While electrodes may sometimes demonstrate adequate wettability, separators are usually the most challenging components to work with. Slow absorption can only be remedied with a higher mass uptake – but how can scientists in battery research enhance the study of this process?

Solutions:

Attension Theta Flow Optical Tensiometer

The Attension Theta Flow is an automated optical tensiometry platform that leverages its advanced features to characterize surface properties of battery anodes, cathodes, and separators using contact angle and surface free energy measurements.

Image of a contact angle measurement featuring a droplet on battery material
  • Automated optical tensiometry platform with easily interchangeable modules for surface topography and picoliter-volume contact angle studies
  • Enables electrolyte wettability optimization using predictive modeling and surface free energy measurements
  • Plug-and-play modules controlled by pre-programmable recipes create an easy workflow
  • Maintains high accuracy, traceability, and reproducibility across experiments
Relevant Attension Theta measurement methods for battery research

The Attension Theta Flow is an automated optical tensiometry platform that leverages its advanced features to accelerate electrolyte wettability studies. Plug-and-play modules controlled by pre-programmable recipes support a quick and easy workflow and enable any user to conduct experiments while maintaining high accuracy, traceability, and reproducibility across experiments.


Attension Sigma 700 Force Tensiometer

The Sigma 700 automated force tensiometer accurately measures mass uptake through electrolyte imbibement, wettability properties, surface and interfacial tension, dynamic contact angle, and a host of other surface characteristics relevant to battery research.

  • Comprehensively study density, sedimentation, adhesion force, contact angles, and surface free energies
  • Tailored for in-depth analysis of porous separator substrates
  • Acquire time-dependent functions describing mass of electrolyte absorbed
  • Live analysis yields rate of absorption
  • Complete flexibility to study solids, liquids, and powders
  • Multiple measurement options on a large range of sample sizes
Relevant Attension Sigma measurement methods for battery research

The Attension Sigma 700 offers high precision interfacial measurements tailored for in-depth analysis of porous separator substrate. It is ideal for battery research as it is capable of yielding time-dependent functions describing mass of electrolyte absorbed; and furthermore, quantitative data from the instrument’s live analysis leads to kinetics for the rate of absorption in all kinds of separator and ionic or organic electrolyte combinations.


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