Are you mixing your binder correctly for optimal Li-ion battery pe

ASI Tech Brief:Are you mixing your binder

correctly for optimal

Li-ion battery performance?Key words: Binder distribution, binder concentration,

Li-ion battery electrodesBinder is one of the critical Li-ion battery materials

used for fabricating electrodes. The binder is mixed

with an active material (AM) along with a conductive

agent (Figure 1). The binder holds the AM particles

together and further bonds the AM-based electrode

film to its substrate – the current collector. During

the battery charge and discharge cycle, the elec-trode AM particles may experience immense volume

change, as large as 300%, in high-capacity Li-ion

anode materials such as silicon. For reliable and

Figure 1. Binder, active materials, and conductive agent on an electrodeoptimal battery performance, the binder must be dis-tributed evenly throughout the electrode to hold AM particles together, to secure the electrode film to the substrate,

and to allow the volume change of the active material. Inhomogeneous distribution of the binder is likely to lead to

local contact failure to the substrate. It can also cause critical binder performance parameter changes, such as the

binder to conductive-carbon ratio to deviate from the ideal value, thus leading to inferior battery performance.

One of the most commonly used binders in Li-ion battery manufacturing is Polyvinylidene Fluoride, also known

as PVDF. For PVDF, it is possible to monitor the binder distribution in the electrode by tracking the variation of the

fluorine content. However, due to its high ionization

potential, fluorine has been a difficult element for

traditional analysis techniques, involving ICP excita-tion Induced Breakdown Spectroscopy (LIBS) has

received significant attention in recent years for rapid

measurement of F without the need for any sample

preparation. Figure 2 shows the J200 LIBS instru-ment manufactured by Applied Spectra, Inc. With

LIBS, the laser beam is focused on the electrode

surface to ionize a minute amount of sample in order

to generate a plasma emission. The emitted light

can be subsequently analyzed for chemical content.

Figure 2. Applied Spectra Inc.'s J200 LIBS Instrument

ABSTRACT for CASE STUDY (≤ 600 words)

Key words: Binder distribution, binder concentration, Li-ion battery electrodes2 of 2Additionally, the laser targeting can be spatially controlled, allowing for mapping of binder distribution in the this case study, the J200 LIBS instrument was used to perform high lateral resolution for Li-ion battery anode

samples. The analyzed anodes were based on graphite active material on copper substrate. Two anodes, labeled

A and B, were prepared using two different mixing times of 4 and 60 minutes. The samples were mapped for F in

comparably sized areas (2x2 mm2). The selected areas were analyzed using a software-generated grid pattern,

with a 40 µm laser spot size. Within the grid pattern, one laser shot per location was applied, and multiple passes

over the entire grid were made until the substrate (Cu) was reached. At the selected laser energy, 2 passes were

required to reach the Cu substrate. The laser energy can be varied to change the profiling resolution. Furthermore,

the laser spot size can be adjusted to vary the spatial resolution for the mapping. The F LIBS data was analyzed

using Applied Spectra’s data analysis software.

Figure 2 shows the comparison of the

binder distribution for fluorine between

anodes A and B. In the mapping

results for the first pass, the F distri-bution resulted in a RSD of 34% for

sample A, and 27% for sample B, with

a noticeably higher intensity for F in

sample B compared to sample A. For

the second pass, the RSD obtained for

sample A is 42% compared to 51% for

sample B. Also for the second pass,

sample A showed higher F intensity

compared to sample B in the mapped

region. It can be seen that different

mixing times for the anode material

have led to different distribution of the

binder in the anode.

Anode A: Fluorine55.455.255.054.854.654.454.254.053.853.654.654.855.055.255.455.655.856.056.256.4Anode B: Fluorine1.0000.87500.75000.62500.50000.37500.25000.12500.000Color Scale Title55.455.255.054.8Color Scale TitleY

Axis

Title54.654.454.254.053.853.654.654.855.055.255.455.655.856.056.256.4X Axis Title55.455.255.054.854.654.454.254.053.853.654.054.254.454.654.855.055.255.455.655.8Color Scale Title55.455.255.054.854.654.454.254.053.853.654.054.254.454.654.855.055.255.455.655.8Color Scale TitleApplied Spectra’s J200 LIBS instru-Figure 2. F distribution between anodes A and B. Maps based on a 18x18 grid with a 40µm spot can provide rapid feedback on

binder distribution resulting from different processing conditions. With fast measurement times the J200 LIBS

instrument can also enable rapid inline QC of binder distribution on the production more information please contact Lucille East, at marketing@, or

visit /technology/.