Analyzing O/N and C/S in Battery Components

Modern life relies on the (mobile) electrical power that batteries provide. No cellular phone, tablet, notebook, or car could be used without a functioning battery.

Since the first primary battery was created and utilized by Allesandro Volta, many batteries of various chemical compositions and sizes have been developed and employed in a wide range of applications, including flashlights or storage of excess electrical power from a power plant or the grid.1

Regardless of the application of a battery, its configuration as a primary (not rechargeable) or secondary battery (rechargeable), or its dimensions, a chemical analysis for sulfur, carbon, nitrogen, or oxygen concentrations may be required for single components.

Elemental analyzers such as the ELEMENTRAC CS-i and ELEMENTRAC ONH-p2 make it possible to accurately measure C/S and O/N in selected samples over a wide concentration range.

Unlike spectrometric techniques such as spark OES or XRF that only measure the element concentrations on surface, the ELEMENTRAC series analyzers use combustion or inert gas fusion to examine the complete sample.

This allows for safe and reliable analysis from the lower ppm to the high percentage range. This article presents the working principle of the analyzers and applications.

ELEMENTRAC ONH-p2 with optional autocleaner.

Figure 1. ELEMENTRAC ONH-p2 with optional autocleaner. Image Credit: Eltra

The ELEMENTRAC ONH-p2 Analyzer

The ELEMENTRAC ONH-p2, as displayed in Figure 1, is a powerful inert gas fusion analyzer that comes equipped with two infrared cells, an 8.5 kW electrode furnace, and a wide-range thermal conductivity cell for the safe and reliable analysis of nitrogen, oxygen, and hydrogen.

Conducting analysis is simple and convenient for trained and untrained users. The sample is logged with its weight in the ELEMENTS software, followed by the application to the sample port and starting the measurement in the software. All subsequent steps are carried out automatically.

Once the analysis starts in the software, the sample port closes, and the sample is flushed with a carrier gas, preventing atmospheric gas (nitrogen and oxygen) from entering the furnace.

A graphite crucible is outgassed in the analyzer’s impulse furnace to remove possible contamination. Following a short stabilization phase, the sample is dropped into the crucible and melts.

As a result of the vertical sample transfer to the crucible (as shown in Figure 2) and the effective flushing, capsules containing a powdered sample don't need to be sealed, simplifying the entire process of analyzing any powdered samples.

Sample port of the ELEMENTRAC ONH-p2.

Figure 2. Sample port of the ELEMENTRAC ONH-p2. Image Credit: Eltra

The reaction of carbon in the graphite crucible and oxygen in the sample produces carbon monoxide. Hydrogen and nitrogen are emitted in their elemental form. The sample gases and the carrier gas (helium) pass through a filter before entering a copper oxide catalyst, where the conversion of CO to CO2 takes place.

The infrared cells measure the CO2 to assess the oxygen content. Water and CO2 are removed chemically, and the nitrogen content is measured in the thermal conductivity cell.

For hydrogen analysis, a nitrogen carrier gas and the sample gas pass through a Schuetze reagent, rather than a copper oxide catalyst. Alternatively, Argon can establish the nitrogen and oxygen content during analysis.

The ELEMENTRAC CS-i Analyzer

The elemental analyzer ELEMENTRAC CS-i is presented in Figure 3.

This instrument measures the sulfur and carbon concentration in largely inorganic samples using combustion in an induction furnace and the following analysis of the gaseous combustion products, sulfur dioxide, and carbon dioxide, in up to four infrared cells.

Complete sample combustion is ensured using a high temperature greater than 2000 °C. This enables accurate and reliable elemental analysis over a wide concentration range.

After a sample is weighed using a ceramic crucible and logged in the ELEMENTS software, addition of an accelerator such as tungsten (approximately 1.7 g) is required.

Once the sample is placed on the pedestal and the analysis starts, all subsequent steps are processed automatically.

The accelerator and the sample are melted in a pure oxygen atmosphere in the analyzer's induction furnace. This leads to the reaction of carbon to a mixture of carbon monoxide (CO) and carbon dioxide (CO2) and sulfur to sulfur dioxide (SO2). The combustion gases pass through a dust filter and moisture absorber for purification.

Following this, the detection of sulfur dioxide takes place in infrared cells. In the CS-i infrared cells with varying sensitivities (low/high) may be adjusted according to the requirements of the user.

Following the sulfur measurement, the oxidation of carbon monoxide to carbon dioxide and sulfur dioxide to sulfur trioxide occurs. Cellulose wool is then used to remove the SO3 gas, and infrared cells detect the carbon content.

ELEMENTRAC CS-i.

Figure 3. ELEMENTRAC CS-i. Image Credit: Eltra

Sample Preparation

Elemental analyzers can measure C/S or O/N/H concentrations in practically any inorganic sample.

Despite the relatively simple analysis process for C/S and O/N/H measurement, some considerations must be made, such as the required analysis, sample shape, and sample composition (see diagram below). The typical applicable sample weights for C/S and O/N/H analysis range from 20 mg to 1000 mg.

Sample-Related Settings and Preparation for ONH Analysis

For each battery component (such as Si3N4), an individual application must first be developed that considers the chemical nature of the sample, the available sample amount, and the particle shape and size.

These specifications determine the appropriate maximum amount of sample for a single analysis, the required sample preparation, and the applied analysis power.

The following diagram presents the general procedure for powdered samples. Solid samples such as pins or wires like drillings or granulates may be processed.

Analyzing O/N and C/S in Battery Components

Image Credit: Eltra

Application of a powdered sample in a nickel capsule.

Figure 4. Application of a powdered sample in a nickel capsule. Image Credit: Eltra

Typically, (battery component) samples that undergo an O/N/H analysis are in the shape of fine powders. Such samples require a nickel capsule before application to an elemental analyzer (as shown in Figure 4). The samples may cause blockages without this capsule, making the complete transfer to the graphite crucible unsafe.

Depending on the chemical nature of the powder, additional sample preparation steps are required for a reliable nitrogen and oxygen analysis.

Refractories and precious metals, including palladium, titanium, and platinum, have a high melting point. Further flux must be provided to ensure a complete release of the embedded gases.

The high-melting sample and the nickel capsule are placed in an additional nickel basket to reduce the melting point of the subsequent alloy in the crucible. The sample amount is typically limited to 50-100 mg for nitrogen and oxygen measurement to ensure that the analysis is reliable.

Since hydrogen is released more readily from the sample during hydrogen analysis, the sample amount may be increased, and a nickel basket is not required. ELTRA advises the application of tin flux to the graphite crucible to ensure a smooth release of the embedded hydrogen.

Analyzing solid metal samples is restricted to inert materials vs. atmospheric gases. Applying metals such as lithium is not feasible because of the severe reactions with atmospheric oxygen and water.

Other samples unsuitable for ON or H analysis include lithium products such as LiOH or LiS. These products react chemically with the upper electrode, affecting the repeatability of measurements and leading to maintenance issues.

Application of accelerator to a crucible with sample.

Figure 5. Application of accelerator to a crucible with sample. Image Credit: Eltra

Sample-Related Settings and Preparation for CS Analysis

Unlike O/N/H analysis, fewer parameters must be considered for a reliable C/S measurement. Generally, the particle size distribution is negligible, but because of the severe combustion, potential sample loss due to swirling must be accounted for.

With typical sample weights of 250 - 500 mg, the sample is completely covered with an accelerator, and swirling is negligible, as shown in Figure 5.

The ELEMENTRAC CS-i provides unique solutions for higher sample weights, such as induction power control and intelligent oxygen supply, to assure smooth and complete combustion without sample dust because of sputtering or swirling.

Depending on the wide base of appropriate samples, accelerators must be utilized to ensure complete oxidation of the embedded sulfur and carbon. The following table presents a summary of typical sample weights and recommended accelerators:

Source: Eltra

Typical samples Recommended sample weight for C/S analysis (mg) Recommended accelerator
Iron, nickel, cobalt, lead 250-1000 mg Tungsten (1.7 g)
Copper 1000 mg Copper (2 g)
Metaloxides, carbonates, slags, refractories, precious metals Up to 250 mg Tungsten/Tin (2 g); alternatively Iron (0.7 g) + Tungsten (1.7 g)

 

Application of a prepared sample to the CS-i analyzer.

Figure 6. Application of a prepared sample to the CS-i analyzer. Image Credit: Eltra

Application Examples

Some typical applications for batteries are presented in the following.

  • O/N analysis of Si3N4 (described in the ELTRA application note 1099)
  • C/S analysis of lead slag, sulfate, and carbonate (described in the ELTRA application note 1100).

A) O/N Analysis of Silicon Nitride (Si3N4):

The analysis of oxygen and nitrogen using ELEMENTRAC ONH-p2, with the sample of silicon nitride (reference material CRM ED 101). The sample was used directly from the bottle and filled in nickel capsules. The settings utilized were 6000 W analysis power with a helium carrier gas.

Silicon nitride (CRM ED 101).

Silicon nitride (CRM ED 101). Image Credit: Eltra

Note

Lithium-based batteries may integrate silicon nitride as part of an electrode. The nitrogen content is measured to reveal the purity of the silicon nitride, while the oxygen content is determined to assess electrical properties. 

The ELEMENTRAC ONH-p 2 is ideal for precise measurements of both elements. The extremely sensitive detectors utilized in ELTRA elemental analyzers enable the element concentrations to be accurately determined, ranging from low parts per million content to high percentages.

Source: Eltra

ERM – ED 101 (Silicon nitride)*
Weight (mg) Oxygen (%) Nitrogen (%)
12.7 1.96 37.83
14.0 2.10 38.23
18.8 2.02 38.08
15.2 2.06 38.01
18.0 2.02 38.27
16.7 2.10 38.07
17.1 2.05 37.88
18.0 2.11 38.38
18.2 2.11 38.10
15.9 2.13 37.99
Mean value
  2.07 38.08
Deviation / Relative deviation (%)
  0.05 /2.6% 0.17/0.5 %

* Certified values: Oxygen (not certified); Nitrogen: 38.1% +-0.2

Analyzing O/N and C/S in Battery Components

Image Credit: Eltra

B) Analysis from Lead Sulfate Samples (Customer Samples from Battery Production):

The analysis of sulfur and carbon with ELEMENTRAC CS-i using lead sulfate from battery production as the sample. This sample was in the form of a powder and was applied as it is.

The settings used included an iron/tungsten analysis power of 90%, a generator time of 40 seconds, a gas flow chamber of 5 seconds, and a gas flow chamber/lance of 5 seconds. 

Silicon nitride (CRM ED 101).

Silicon nitride (CRM ED 101). Image Credit: Eltra

Note 

Sulfur measurement using combustion analysis is employed for the final quality control of charged lead-based batteries. The electrodes comprise lead and lead oxide and must be free of sulfur. 

The properties of the battery paste affect the performance and life span of the battery, and the contained lead sulfate determines its qualities. ELTRA’s C/S analyzers deliver the rapid and reliable measurement of sulfur and carbon concentration from the low ppm range up to 100%.

Source: Eltra

Lead sulfate (customer sample from battery production)
Weight (mg) Carbon (%) Sulfur (%)
70.4 0.139 5.60
71.8 0.163 5.91
70.0 0.138 5.64
70.9 0.140 5.52
76.9 0.163 5.85
73.4 0.152 5.62
71.8 0.162 6.15
89.3 0.144 5.81
66.9 0.146 5.62
71.0 0.136 6.07
Average values
  0.148 5.78
Deviation / Relative deviation (%)
  0.01 (7.4%) 0.21 (3.8%)

 

Analyzing O/N and C/S in Battery Components

Image Credit: Eltra

C) Analysis of Lead Carbonate Samples (Customer Samples From Battery Production):

The analysis of sulfur and carbon with ELEMENTRAC CS-i using a sample of lead carbonate from battery production. This sample came in the form of a powder and was applied as it is. 

Lead carbonate (customer sample from battery production).

Lead carbonate (customer sample from battery production). Image Credit: Eltra

The settings used include the use of an accelerator of iron/tungsten with an analysis power of 90%, a generator time of 40 seconds, a gas flow chamber of 5 seconds, and a gas flow chamber/lance of 5 seconds.

Source: Eltra

Lead carbonate (customer sample from battery production)
Weight (mg) Carbon (%) Sulfur (%)
68.6 3.17 1.23
74.6 3.21 1.13
69.9 3.34 1.13
72.1 3.23 1.06
75.4 3.36 1.20
72.6 3.21 1.14
92.8 3.13 1.15
68.3 3.29 1.17
89.8 3.22 1.12
72.3 3.20 1.17
Average values
  3.23 1.15
Deviation / Relative deviation (%)
  0.069 (2.1%) 0.046 (4%)

 

Analyzing O/N and C/S in Battery Components

Image Credit: Eltra

D) Analysis of Lead Slag Samples (Customer Samples From Battery Production):

The analysis of sulfur and carbon with ELEMENTRAC CS-i using a sample of lead slag from battery production. The sample came in the form of a powder and was used as it is. 

The settings used were an accelerator of iron/tungsten with analysis power of 90%, generator time of 40 seconds, gas flow chamber of 5 seconds, and gas flow chamber/lance of 5 seconds.

Lead slag (customer samples form battery production).

Lead slag (customer samples form battery production). Image Credit: Eltra

Note 

The lead content of batteries may be recycled and used in new batteries in an environmentally friendly way. Lead is present as lead sulfate in exhausted batteries and slags, with the latter being a byproduct of the production and recycling of batteries. 

The precise measurement of sulfate can be carried out using ELTRA’s C/S combustion analyzers, enabling the rapid and straightforward determination of the present lead. 

Lead slag is a very heterogeneous sample. While the other lead samples can be measured within reliable repeatability, the precision for sulfur and carbon measurements in slag is low. 

However, it is possible to use this application for the C/S determination in slag and obtain a summary of its carbon and sulfur content. 
An RSD and average were not calculated due to the significant deviation. The repeatability may be improved by using a laboratory ball mill for sample homogenization, but the safety of the laboratory personnel must be considered.

Source: Eltra

Lead slag (customer sample from battery production)
Weight (mg) Carbon (%) Sulfur (%)
72.8 4.5 7.7
58.4 8.7 13.4
60.2 9.4 13.1
62.5 7.0 12.3
61.3 14.3 11.3
69.0 16.5 11.1
68.6 9.8 8.9
53.1 8.6 9.9
64.9 8.1 12.7
72.0 9.9 8.8

 

Analyzing O/N and C/S in Battery Components

Image Credit: Eltra

Reference

  1. Wikipedia.org

Eltra

This information has been sourced, reviewed and adapted from materials provided by ELTRA GmbH.

For more information on this source, please visit ELTRA GmbH.

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