Title: SUCCESSFUL RESEARCH PROJECT WITH KARLSRUHE INSTITUT OF TECHNOLOGY (KIT)
Published: 12. January 2022
Last modified: 7. February 2024

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# SUCCESSFUL RESEARCH PROJECT WITH KARLSRUHE INSTITUT OF TECHNOLOGY (KIT)

 Posted on 12. January 20227. February 2024

## **Development of a modular system for filtering toxic and flammable gases in conjunction with a suitable container for transporting damaged to non-transport-safe (critical) lithium-ion batteries**

Dr. Ing. Ilian Dinkov (FFB), M. Sc. Jan Braun (FFB), M. Sc. Mona Meyer-Hollmann (
LogBATT GmbH)

### 1. **Presentation of cooperation partners KIT and LogBATT**

The research project on which this report is based, the development of a modular
filter system integrated into battery transport boxes, was carried out jointly by
the cooperation partners of the Research Centre for Fire Protection Technology at
the Karlsruhe Institute of Technology and LogBATT GmbH.

Founded in 1950 and affiliated to the Engler-Bunte Institute, Chair of Combustion
Technology (EBI-VBT) of the University of Karlsruhe (KIT), the Research Centre for
Fire Protection Technology is engaged in research and development work in the field
of preventive and defensive fire protection.

The logistics company LogBATT GmbH, founded in 2017, specialises in the ADR-compliant
transport of critically defective lithium-ion batteries and develops and produces
its own safety containers, so-called SafetyBATTboxes for the storage and transport
of lithium-ion batteries. Such safety containers must be officially certified by
the Federal Institute for Materials Research and Testing (BAM).

Only if the following legal requirements are met during a real fire test, the containment
will receive an official approval:

 * Temperature of the outer surfaces of the complete package must not exceed 100
   °C. A short-term temperature peak of up to 200°C is permissible.
 * No flame should be allowed to form outside the package.
 * No projectiles may escape from the package.
 * The structural integrity of the package must be maintained.
 * The packaging must have a gas management system. This must be able to handle 
   pressure surges and have HF management.
 * The HF concentration in the filtered flue gas must be below the AEGL 2 limit 
   value. These limit levels correspond to concentration guide values according 
   to the Major Accidents Ordinance and are 12 ppm and 9.8 mg/m respectively.^(3)

### 2. **SafetyBATTboxes: new generation of safety containers for safe storage and hazard-free transport of lithium-ion batteries**

Lithium-ion batteries can pose a wide variety of potential hazards:

 * **Thermal, chemical, electrical and kinetic**

The SafetyBATTboxes have been designed with a wide range of safety measures to contain
all the above-mentioned potential hazards from LIBs and to shield them from the 
outside. In the event of a battery reaction, the thermal event inside the SafetyBATTbox
is contained and only the resulting flue gas is discharged to the outside via defined
venting openings.

### 3. **What happens in a battery fire**

Rechargeable batteries are booming: they can be found in virtually all mobile consumer
electronics devices, power tools, gardening tools, electric bicycles (pedelecs and
e-bikes) and electric cars.

Since lithium-ion batteries are designed to provide a large amount of electrical
energy, the chemical energy contained in these batteries is considerable. High-quality
cells available on the market from well-known manufacturers contain several safety
devices inside the cell that can “shut down” the cell as an electrical system in
an emergency. However, if the lithium-ion batteries/modules/cells are misused, e.
g. due to overcharging or discharging, overheating, mechanical damage or an internal
cell defect, a thermal reaction, the so-called _thermal runaway of _the cell, can
occur. If the _thermal runaway of _one or a few individual cells causes a thermal
runaway of the entire system (module and/or battery), this is a so-called _thermal
propagation _event. In a thermal runaway, an uncontrolled reaction occurs between
the two electrodes and the stored chemical energy is released in one fell swoop.
The dangerous thing about a _thermal runaway _is the combination of the materials
used in lithium-ion batteries in conjunction with the high energy density mentioned.
Due to the enormous heat development (sometimes > 1000°C on the surface of the cell),
one or a few individual defective cell(s) is often enough to set the entire battery
on fire. The danger of a _thermal runaway _is particularly present in accident-damaged
batteries or batteries that are generally no longer safe to operate.

During this thermal run-through of the cell, the material contained in the cell 
decomposes and gas is produced. This creates an overpressure in the cell until it
finally bursts open and the gas produced is blown off to the outside. This mostly
white-greyish gas consists mainly of evaporated electrolyte, its reaction products
and other cell components (for measured data, see chapter 4). This gas is highly
flammable and can cause a so-called oxyhydrogen explosion, flash fire and fire.

### 4. **Research project for the further development of the SafetyBATTbox filter system**

In general, the containment vessels cannot completely absorb the very large quantities
of gas that are released in the event of a _thermal runaway _and must therefore “
blow off” (so-called vents). For example, approx. 44 l of flue gas can escape from
a commercially available 18650 round cell. These emitted gases are both toxic and
usually flammable, which is why they should be filtered before leaving the transport
box and the gas outlet of the safety containers should also have a flame-retardant
effect.

During the research project, basic investigations into filter effects, material 
tests and flue gas analyses were carried out, and research and tests were carried
out on an advanced filter system as an integral part of a transport box.

The future filter system should fulfil the following tasks:

 * The filter as a component of the gas management system is the only opening of
   the transport box to the outside. It prevents a critical overpressure from building
   up in the box.
 * Preventing the spread of fire by preventing the flames from penetrating through(
   flame blocking effect).
 * Insulation effect, filter system must compensate for or prevent heat penetration
   of the transport box via the venting surfaces.
 * As extensive as possible retention/filtering of flammable and toxic substances
   from the escaping flue gas.

In order to gain basic knowledge about the composition of the escaping smoke gases,
filtering possibilities, suitable materials, etc., battery fires were started in
the SafetyBATTboxes and various measurements were carried out during this process.

First, analyses were carried out on unfiltered flue gas escaping from a lithium-
ion battery fire and then various types of SafetyBATTboxes were set up with different
filter systems and comparative measurements of the escaping flue gas were carried
out on them.

For example, in the course of the research project, various filter systems were 
tested in so-called SafetyBATTboxes type M. For each of the fire tests, a lithium-
ion cell module (12 kg, 2.14 kWh, prismatic cells, NMC cell chemistry) was (12 kg,
2.14 kWh, prismatic cells, NMC cell chemistry) was brought to _thermal runaway _by
means of overheating (ceramic radiant heater).

The modules were each charged to approx. 100 % SoC before the start of the test.
For the fire tests, the box was equipped with a variety of sensors and probes, including
temperature sensors in and on the box, pressure sensors to measure the pressure 
difference between the inside of the box and the environment, and the pressure drop
of the filter system. The outside temperature was continuously documented with a
thermal imaging camera and the weight loss with a scale. The SafetyBATTboxes are
double-walled and have an outlet on each side. Each of these is equipped with a 
flame arrester. The sampling probes for the emission measurement were positioned
at the outlets of the SafetyBATTbox, in each case after the flame arrester. In addition,
a sampling probe was placed in the box during the first test in order to obtain 
a zero measurement of the resulting flue gas. In addition to the usual flue gas 
components (O _(2), CO, CO _(2)), the measurement also included a broad flue gas
spectrum.

Figures 1, 2 and 3 show exemplary shots of the test preparation: Installation of
the module in the SafetyBATTboxes (Fig. 1), incl. the packaging of the module using
packaging material specially developed by LogBATT GmbH (Fig. 2). The lid of the 
SafetyBATTboxes has a seal and is fitted with tension locks all around. Figure 3
shows the closed box and the installation of the measuring instruments (exhaust 
gas probes, pressure sensors and thermocouples).

![Abb 1](https://www.logbatt.com/wp-content/uploads/sites/5771/2022/01/abb-1.jpg)

_Figure 1: Cell module in the SafetyBATTbox_

![Abbildung 2 Verpackungsmaterial](https://www.logbatt.com/wp-content/uploads/sites/
5771/2022/01/Abbildung-2-Verpackungsmaterial.png)

_Figure 2: Packing material_

![Abbildung 3 SafetyBATTbox vor dem Brandversuch incl. Messinstrumente](https://
www.logbatt.com/wp-content/uploads/sites/5771/2022/01/Abbildung-3-SafetyBATTbox-
vor-dem-Brandversuch-incl.-Messinstrumente.png)

_Figure 3: SafetyBATTbox before the fire test incl. measuring instruments_

Figure 4 shows an example of some sections of the real image and thermal image recordings
during the _thermal runaway _test. The images in the same row were taken at the 
same time. It can be seen (see figure 4.1) that after a certain overheating time,
the cells of the module, directly below the radiant heater, lead the _thermal runaway
_into the corridors with a relatively moderate smoke development. Subsequently, 
the thermal event continues to propagate (_thermal propagation) _until the entire
module has undergone thermal runaway. The thermal runaway in the box is characterised
by a rather high temperature, as well as a high pressure rise. The images in Figures
4.3 to 4.6 show the discharge of the reaction products in the form of a massive 
emission of flue gas. After a short time, the reaction is finished, the amount of
flue gas decreases noticeably and the module continues to smoke (see Fig. 4.7 and
4.8).

 * [⌊Abb 4.1 1⌉⌊Abb 4.1 1⌉[
 * [⌊Abb 4.2⌉⌊Abb 4.2⌉[
 * [⌊Abb 4.3⌉⌊Abb 4.3⌉[
 * [⌊Abb 4.4⌉⌊Abb 4.4⌉[
 * [⌊Abb 4.5⌉⌊Abb 4.5⌉[
 * [⌊Abb 4.6⌉⌊Abb 4.6⌉[
 * [⌊Abb 4.7⌉⌊Abb 4.7⌉[
 * [⌊Abb 4.8⌉⌊Abb 4.8⌉[

_Figure 4: Real images and thermal images during and after thermal runaway and thermal
propagation._

As mentioned above, the thermal run-through of a module in the SafetyBATTbox is 
associated with high temperature and pressure gradients. Figure 5 shows the temperature
curves inside the box during the test. Directly above the module (T1-T3) the temperatures
reach maximum values of about 800 °C. After leaving the box, the exhaust gases cool
down to values below 250 °C (T5-T8). On the outside of the box, maximum temperatures
of always below 80 °C were measured due to the double-walled construction. This 
means that the legal criteria regarding temperature are fulfilled.

![Abb 5](https://www.logbatt.com/wp-content/uploads/sites/5771/2022/01/abb-5.png)

_Figure 5Temperatures inside the SafetyBATTbox_

![Abb 6](https://www.logbatt.com/wp-content/uploads/sites/5771/2022/01/abb-6.png)

_Figure 6: Pressure difference_

The measured pressure curve in figure 6 shows maximum values above 120 mbar. The
figure also shows the thermal runaway of the individual cells (twelve individual
cells in the module).

A comparison of selected pollutants, some of which are relevant for statutory approval
(
HF emissions) with and without a filter system is shown in Table 1.

| **Fabric** | **Without filter system** | **With filter system** | **Adsorber effect** | 
| Total carbon (C) | max. approx. 21,000 ppm | max. approx. 17,144 ppm | 18,3 % | 
| Hydrogen fluoride (HF) | 13 mg/m ^(3) | 0.9 mg/m ^(3)  | 93 % | 
| Benzene | 261 mg/m ^(3)  | 142 mg/m ^(3)  | 45,6 % | 
| Dimethyl carbonate (DMC) | 13.475 mg/m ^(3)  | 5,524 mg/m ^(3)  | 59 % | 
| Ethyl methyl carbonate (EMC) | 7,411 mg/m ^(3)  | 2,394 mg/m ^(3)  | 67,7 % | 
| Main components deposits | Lead, chromium, | cobalt, copper, | manganese, nickel |

Table 1: Results of the exhaust gas analysis

The new filter system has significantly higher filtering effects compared to measurements
taken completely without a filter system. This means that the newly developed filter
system, in addition to meeting the legal requirements for pollutant limits (HF <
9.8 mg/m ^(3)), achieves an additional reduction of a wide variety of pollutants
in the escaping flue gas. During the fire tests, the following substances were detected
as main constituents in the flue gas in addition to the usual fire gases:

 * Solvent vapours of the unburnt electrolyte and its reaction products
 * Hydrocarbons as decomposition and reaction products of the organic solvents and
   the conducting salt, these include:
    - short-chain alkanes, alkenes and alkynes (C1 – C10) such as methane, ethane,
      ethene, propane, propene etc.
 *  - Carbon monoxide (CO) and dioxide (CO _(2))
 *  - Species containing fluorine and phosphorus (hydrogen fluoride (HF), hydrofluoric
      acid (HF _((aq))), phosphoric acid (H _(3)PO _(4)), hydrogen phosphide compounds
      e.g. phosphine etc.)
 *  - Hydrogen chloride
 *  - Hydrogen (H _(2))
 *  - Nitrogen oxides such as nitrogen monoxide and dioxide (NO _(x), N _(2)O)
 *  - Other hydrogen carbonates (benzoles etc.)
 *  - Oxygen (O _(2))
 *  - Released conducting salt, e.g. lithium hexafluorophosphate (LiPF _(6))
 * Graphite dust
 * Light and heavy metal particles such as aluminium, nickel, cobalt, copper, manganese,
   chromium, lead, lithium, etc.
 * Other released particles and dusts (ash, soot, etc.)

Many of these substances have one or more of the following hazards: very toxic, 
harmful, carcinogenic, dangerous for the environment, irritant, flammable, corrosive,
mutagenic, oxidising.

The results of the flue gas analysis show that a complete removal of all toxic, 
flammable or other hazardous components of the flue gas occurring in Li-ion battery
fires is hardly technically feasible (under the given framework conditions). However,
these can be greatly reduced by the filter system developed during the research 
project.

From all the investigations and analyses carried out, it can be deduced that a combination
of different filter materials can have a positive effect on the filter effect. A
mixture of different filter materials (also with regard to grain size and structure),
each of which has a targeted effect on specific gases, is superior to a universal
filter. To achieve the best possible filter effect, different materials should be
combined in future filter systems.

The knowledge generated during the research project includes:

 * Comparable gas analyses of different filter systems in real fire tests
 * Analyses Pollutant loads Filter system and deposits
 * Detection of main components of flue gas
 * Detection Influences on flue gas composition
 * Investigation and tests on various possible filter methods and different filter
   materials
 * Development of a modular filter system, accordingly scalable filter systems for
   different sizes of transport containers possible

In summary, LogBATT GmbH, together with the Research Centre for Fire Protection 
Technology at KIT, was able to create a solid basis with regard to flue gas filtration
of lithium-ion battery systems and is ready for future filter requirements in transport
boxes for lithium-ion batteries. This is because the SafetyBATTboxes, with the newly
developed filter system in the course of the research project, achieve an average
reduction of more than 55% in the emission of pollutants in the flue gas during 
a lithium-ion battery fire.

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