Safety on Lithium-Ion Batteries

Safety on Lithium-Ion Batteries 

Lithium-ion batteries were developed in the 1970s and first commercialized by Sony in 1991 for the company’s handheld video recorder. Today everything you see is powered by batteries from smartphones, laptops, scooters, e-cigarettes, smoke alarms, toys even the International Space Station, which makes increased battery safety all the more crucial.

In 2008, Tesla unveiled the Roadster making it the first car company to commercialize a battery-powered electric vehicle. By 2025, the global lithium-ion (Li-ion) battery market is expected to reach USD 100.4 billion, over 50% of which will be used for the automotive market.

NFPA 704 rating of a lithium ion batteries marked 010. Other battery chemistries may have 000 or different designations.

NFPA 704 fire diamond for Li-ion batteries

Flammability
Red 0	Material does no burn under normal conditions
Red 1	Material needs considerable preheating before ignition or combustion occurs
Red 2	Material needs moderate heat before ignition or combustion occurs
Red 3	Liquids and solids can be ignited under ambient temperature
Red 4	Vaporizes under atmospheric pressure; burns easily
Health
Blue 0	Poses no health hazard
Blue 1	Exposure causes irritation
Blue 2	Intense and continued use cause injury
Blue 3	Short exposure causes injury
Blue 4	Short exposure causes major injury or death
Reactivity
Yellow 0	Stable
Yellow 1	Becomes unstable at elevated temperature
Yellow 2	Violent changes at high temperature, reacts with water
Yellow 3	Can detonate with trigger
Yellow 4	Can detonate at normal temperature

Lithium-Ion refers to a family of Lithium-based battery technology. This family includes several sub-families or technologies, such as:

·        LCO: Lithium Cobalt Oxide

·        NCA: Nickel Cobalt Aluminium

·        NMC: Nickel Manganese Cobalt

·        LiFePO4 or LFP: Lithium Iron Phosphate

·        LTO: Lithium Titanate Oxide, etc…………..

Often, we can hear that a product is equipped with “Lithium-Ion” batteries, this does not really have any meaning on the technology used. However, out of habit, the technology referred to as Lithium-Ion is usually LCO, NCA or NMC

Each of these technologies has very different characteristics, particularly in terms of safety.

Lithium-ion batteries are popular because of how much power they can put out at a given size and weight. A typical lithium-ion battery stores 150 watt-hours of electricity in 1 kilogram of battery, compared to NiMH Battery pack (100 watt-hours per kg) or Lead Acid Battery (25 watt-hours per kg). It takes 6 kilograms to store the same amount of energy in a lead-acid battery that a 1-kilogram lithium-ion battery can handle.

However, lithium-ion batteries are extremely sensitive to high temperatures and inherently flammable. These battery packs tend to degrade much faster than they normally would, due to heat. If a lithium-ion battery pack fails, it will burst into flames and can cause widespread damage. This calls for immediate measures and guidelines for battery safety. LCO and NCA are the most dangerous chemicals from a thermal runaway point of view with a temperature rise of about 470°C per minute. In addition, it can be seen that LiFePO4 – LFP technology is slightly subject to thermal runaway phenomena, with a temperature rise of barely 1.5°C per minute.

A lithium-ion battery pack consists of lithium-ion cells stacked together in modules, temperature sensors, voltage tap and an on-board computer (Battery Management System) to manage the individual cells. Like any other cell, the lithium-ion cell has a positive electrode (cathode), a negative electrode (anode) and a chemical called an electrolyte in between them. While the anode is generally made from graphite (carbon), different lithium materials are used for the cathode – Lithium Cobalt Oxide (LCO), Lithium Nickel Manganese Cobalt (or NMC), etc.

When a charging current is provided to the cell, lithium ions move from the cathode to the anode through the electrolyte. Electrons also flow but take the longer path outside the circuit. The opposite movement takes place during discharge with the result that the electrons power up the application that the cell has been connected to.

When all the ions have moved back to the cathode, the cell has been completely discharged and will need charging.

Now need to know why lithium-ion batteries catch fire

A. Manufacturing Defects

Flaws in production can cause metallic particles (impurities) to seep into the lithium-ion cell during the manufacturing process. Battery manufacturers need to ensure stringently controlled cleanrooms for manufacturing batteries.

Another defect could be the thinning of separators which could prove detrimental in actual use. Cells should undergo strict quality-control tests and validation before being sold.

B. Design Flaws

Car companies want to design their cars as sleek and slim while giving the maximum range and performance. These requirements push battery pack manufacturers to come up with compact designs by packing high-capacity cells into a smaller body, messing with an otherwise well-built battery.

Compromising on the design can cause damage to the electrodes or the separator. Either of which could result in a short circuit. Further, the absence of a proper cooling system or vent can cause battery temperatures to rise as the flammable electrolyte heats up.

If uncontrolled, it could result in a chain reaction of cell failures, causing the battery to heat up even more and spiral out of control.

C. Abnormal or Improper Usage

External factors like keeping the battery very close to a heat source or near a fire can cause it to explode. Penetrating the battery pack either deliberately or through an accident is bound to cause a short circuit and the battery to catch fire. That’s why unauthorized disassembly of the battery pack in electric vehicles leads to the lapse of warranty.

Users are advised to only get the batteries checked and repaired from the car maker’s authorized service centers. Even high-voltage charging or excessive discharging of the battery could damage it.

D. Charger Issues

Using poorly insulated chargers can damage the battery. If the charger shorts or generates heat near the battery, it can do enough damage to cause failure.

While lithium-ion batteries have built-in protections to stop them from overcharging, using unofficial chargers can damage the battery in the long term.

Do not charge a device under your pillow, on your bed or on a couch.

E. Low-quality components

In addition to manufacturing defects, using low-quality components is one of the highest causes of battery failures. Increasing competition is driving the prices of batteries down, causing battery manufacturers to cut corners where they shouldn’t. By skimping on poor quality electronics like the battery management system, the risk of battery failure increases.

What to do when a battery catches fire?

If you notice the lithium-ion battery overheat, try moving the device away from flammable materials and cutting of the current supply. If you’re in an electric vehicle, you should immediately evacuate and never attempt to extinguish lithium battery fires yourself. Your health and safety are far more important, call the emergency services instead.

In case of fire,  a standard ABC or BC dry chemical fire extinguisher must be used since these are considered Class B fire. A common misconception is that lithium-ion batteries contain any actual lithium metal. They don’t and that’s why you shouldn’t use a Class D Fire Extinguisher. 

There are new and improved methods to douse lithium fires as well. The Aqueous Vermiculite Dispersion (AVD) is a fire extinguishing agent that disperses chemically exfoliated vermiculite in the form of a mist. However, larger lithium-ion fires as that of EVs or ESS may need to burn out. Using water with copper material is effective but is costly.

Like thermal runaway, Lithium-ion cells have a different level of safety depending on the shocks or mechanical treatments they may undergo during their lifetime.

The nail penetration test is the most revealing way to qualify the safety of a cell technology.

The test presented below is performed by perforating a Lithium Ion NMC cell and a Lithium Ion LiFePO4 cell.

We find here the same extremely stable behavior of Lithium Iron Phosphate cells while the NMC cell ignites almost immediately.

Battery Safety experts advise using water even for large lithium-ion fires. Fires like these may burn for days and it’s important to isolate them from flammable materials and prevent them from expanding.

Purchase and use devices that are listed by a qualified testing laboratory. Always follow the manufacturer’s instructions.

Do not put Lithium Iron batteries in the trash. — recycling is always the best option. — take them to a battery recycling location or contact your community for disposal instructions.