In Case Studies

Boeing’s Dreamliner 787, which Boeing advertised as 20% fuel efficient, was grounded in 2013. In the same year, Tesla’s Model S came under a federal safety investigation after it caught fire at least 3 times. Last year Samsung recalled 2.5 million Galaxy Note 7 smartphone.

For all the three companies, which are top players in their domain, the problem was same – the Lithium-Ion batteries installed in heart of their product as a power source.

Problem statement from client –How to stop lithium-ion batteries explosion and are there some solutions that can be adopted?

Challenge – Why does a lithium-ion battery explode unexpectedly?

Lithium-ion batteries are the most used type of batteries across several industries but, do you know what makes them hazardous? One of the major reasons why most of the lithium-ion batteries explode is because of thermal runaway.

Solution Northstar offered

Our search team did some deep digging and returned with a set of available solutions that could solve the thermal runaway problem and R&D team can evaluate and adopt those for quick implementation. The three exemplary solutions are listed below (The actual solutions adopted by the client have been replaced because of confidentiality concerns) –

1. Introducing a Flame Retardant

Thermal runaway often occurs from punctures and improper charging. To counter such fire hazards, the inventors used a thermal fluid which contains a flame retardant.

A flame retardant is a compound that inhibits, suppresses or delays the production of flames or prevents the spread of fire.

Here they have the microencapsulated the flame retardant (usually a bromine compound) in high-density polyethylene and added water and a glycol compound to prepare the thermal fluid used. The glycol compound is used here as “antifreeze” (common glycol compounds used are ethylene glycol, diethylene glycol, and propylene glycol).

Also, the invention is mostly discussed in light of EV batteries. A battery when called upon to power an electric vehicle heats up. Thermal fluid flows through the container and over the modules of the battery.

In the event of an overcharge, or a car accident resulting in a battery puncture, the flame retardant in the thermal fluid acts to reduce the fire hazard. More precisely, bromine compound microcapsules rupture when rupture temperature is reached because of excess heat of the fire. The flame retardant is released from the microcapsules and acts to bring the fire under control.

2. Using Damage initiating Devices

The University of California researched a solution related to high elastic modulus polymer electrolytes suitable for preventing thermal runaway. Also, they have developed a thermal runaway shutdown mechanism that can be triggered either mechanically or thermally (or both), as battery damage happens (i.e., before or shortly after thermal runaway starts) and take care of the problem before it can even begin.

Such predictive or instantaneous countermeasures are especially needed when a battery is subjected to impact or high-pressure and its internal structure gets damaged, causing internal shorting.

The basic principle on which it operates is – as a mechanical load is applied to the battery, damage initiators can trigger widespread damage or destruction of the electrode so that the internal resistance increases significantly to mitigate thermal runaway even before it can happen.

Here they have talked about two types of damage initiators –

Passive damage initiators

These initiators initiate cracking or voiding in electrodes upon impact, and such cracks and/or voids increase the internal impedance of the electrode and, thus, reduce heat generation associated with possible internal shorting. Such additives are known as cracks or voids initiators (CVIs).

The electrode damages can be caused by debonding or stiffness mismatch of CVI-electrode interfaces, fracture, and rupture of CVI, etc. Examples of passive additives include solid or porous particles, solid or hollow/porous fibers, and tubes, etc. and they can be formed from carbon materials such as graphite, carbon nanotubes, activated carbons, carbon blacks, etc.

Active damage initiator

These initiators can produce a significant volume or shape change upon a mechanical or thermal loading. Active damage initiators can include solid or porous particles, solid or hollow beads, solid or hollow/porous fibers and tubes, etc. Active damage initiators can be formed from shape-memory alloys such as Ni—Ti, Ni—Ti—Pd, Ni—Ti—Pt, etc.

3. Changing the Battery Design for Minimal Impact

According to a patent filed by Tesla, the inventors discussed a battery design that provides a predictable pathway through a portion of the cell (e.g., the cell cap assembly) for the efficient release of the thermal energy that occurs during thermal runaway, thereby reducing the chances of a rupture in an undesirable location.

Furthermore, the design maintains the functionality of the cell cap as the positive terminal of the cell, thereby having minimal impact on the manufacturability and maximum use in a variety of applications.

While searching for solutions, we also found some quality solutions to other problems in LIB domain listed below.

  • How to overcome dendrite formation?
  • How to increase the life cycle of Lithium-ion batteries?
  • How to decrease viscosity and increase dispersion efficiency of anode binders?
  • How to you can make your LIB operate at high temperature?

If you are facing problems and are seeking solutions, including but not limited to above mentioned, do get in touch. We might be able to put an end to your woes. To give you an example, recently we helped Joe, senior researcher at one of the largest chemical companies in the US, find a solution to temperature resistance problem in acrylate adhesives?

Disclaimer: We have concealed the actual details due to the confidentiality reasons.

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