Lithium Ion Battery Types for Electric Vehicles

Lithium-ion-battery-type-for-electric-vehicles

Lithium and lithium-ion batteries are frequently used in consumer products, including electric vehicles.  There are many types of lithium batteries that have been developed over the past few decades, and I want to take a look at their current uses, types of lithium batteries, and how they compare to each other.  I also want to explore the differences between lithium and lead-acid batteries, as well as the limitations of lithium batteries.  Considering which lithium battery to use, can be a little overwhelming as most lithium battery types are either identified by their chemical composition or short-form abbreviation.

 

 

What are lithium ion batteries?

Lithium ion batteries contain metallic lithium ions that are inserted into compounds with layered structures, which is also called intercalation.  The lithium ions then move from the negative electrode to a positive electrode during discharge and move in the reverse direction for charging.  In a lithium-ion battery the anode is graphite and the specific metallic lithium ions are the active material in the cathode.  To get more detailed information, please refer to the lithium-based batteries article at battery university.

 

As they state in the above-noted article, Lithium is the lightest of all metals, has the greatest electrochemical potential, and specific energy per weight, thus making lithium ion batteries the best power density for their battery weight.  The closest other battery type are deep cycle lead acid batteries.

 

Research and testing has provided a stepping stone for each metal lithium battery.  Many researchers are pushing the envelope regarding higher specific energy, specific power, safety, temperature performance, life span, and lower costs.

 

Uses of Lithium-ion Batteries

 

Each type of lithium-ion battery has their own strength and weakness.  Since the first lithium-ion battery was created, they have been improved upon which has lead to the development of different chemical combinations.  One of the most popular uses of lithium-ion batteries is consumer electronics, specifically mobile phones, laptops, and digital cameras.

 

As the benefits of the first successful lithium-ion batteries were realized and used on a commercial scale, the research and development of different chemical combinations were tested.  This lead to the increasing number of battery types that are currently used.  The current typical use of lithium-ion batteries includes smartphones, laptops, electric vehicles, golf carts, and regeneration battery storage.

 

 

7 Types of Lithium-ion Batteries

 

These battery types are listed in the order of discovery, and you may notice that some batteries use the strengths of a previous lithium-ion with a new intended purpose.  The structures of the electrodes are adjusted to suit each variation to maximize its characteristics.  The six characteristics of any battery include specific energy (run time), specific power (ability to deliver high current), safety, performance (at hot and cold temperatures), lifespan (cycle life and longevity), and low cost.

 

There are actually eight characteristics called the octagon battery, which also include toxicity and fast charging.  As these two characteristics are the same for each battery variation, they have not included in this list of lithium-ion batteries.  Nickel and Lithium based batteries contain little toxic material but should be disposed of carefully as they can be hazardous.  Every lithium battery can be pierced by a sharp object, which could cause a chemical reaction with water in the air.  All lithium-ion batteries should be charged at a rate of 1C or slower.  Fast charging is charging at a rate above 1C, which can degrade the battery decreasing its lifespan.

 

1 – Lithium Cobalt Oxide (aka LCO)

Chemical Composition: LiCoO2

 

lithium cobalt oxide

 

2 – Lithium Manganese Oxide (aka LMO)

Chemical Composition: LiMn2O4 and Li2MnO3

 

lithium manganese oxide

 

3 – Lithium Nickel Manganese Cobalt Oxide (aka NMC)

Chemical Composition: LiNiMnCoO2

 

lithium nickel manganese cobalt oxide

 

4 – Lithium Iron Phosphate (aka LFP)

Chemical Composition: LiFePo4

 

lithium iron phosphate

 

5 – Lithium Nickel Cobalt Aluminum Oxide (aka NCA)

Chemical Composition: LiNiCoAlO2

 

lithium nickel cobalt aluminum oxide

 

6 – Lithium Titanate (aka LTO)

Chemical Composition: Li4Ti5O12

 

lithium titanate

 

7 – Lithium Sulphur

Chemical Composition: LiS

 

 

 

 

How do the lithium-ion batteries compare to each other?

 

Lithium cobalt oxide are used in a lot of consumer electronics as they are very stable, though they have a relatively lower capacity than other lithium batteries.  This is one of the more expensive types of lithium-ion battery on the market and is subject to overheating and outgassing.

Lithium-ion manganese oxide is an inexpensive alternative which uses a spinel structure to provide a three-dimensional framework.  This allows for a higher rate of charging compared to the other lithium-ion batteries.

Lithium iron phosphate is not a lithium-ion battery as it typically uses carbon as the anodes.  This lithium battery uses heat to extract the lithium from the lithium iron phosphate crystalline structure.  This battery has a 25% less capacity compared to other lithium batteries but does not have the same safety concerns from overheating and explosion.  Other benefits include a longer cycle life in the area of 5 times longer than other lithium batteries, although the cost is higher.

Lithium-titanate oxide is one of the quicker charging batteries when compared to other lithium-ion batteries.  Rather than using carbon as the anode surface, this battery uses lithium-titanate which acts as a barrier to the lithium-ions allowing higher currents when necessary.  The disadvantages are lower voltage and lower capacity when compared to the other lithium-ion batteries.

Lithium-sulfur is the newest type of lithium battery.  This battery is relatively light due to the low atomic weights of lithium and sulfur, with a combined weight comparable to water.  Other benefits include a higher energy density, between 2 to 3 times that of other lithium-ion, as well as lower costs.

 

 

 

 

What is the difference between a deep cycle lead acid battery and lithium-ion battery?

 

The biggest difference between lithium-ion batteries and lead acid batteries is the weight of the battery.  More important though is the difference of the power to weight ratio which is more commonly referred to the battery power density.  A lithium-ion battery pack can be put together with the same voltage of a lead-acid battery but with a higher power capacity at the same weight.  The other option is to replace the lead acid battery with the same voltage and lower capacity, but with a higher power density.  Either one would result in a increase of vehicle performance, as the energy used to move the heavy lead acid is more than accounted for with the lighter lithium-ion battery pack.

 

The liquid lithium-ion electrolyte will react to water creating a lithium hydroxide and hydrogen gas.  This would not be a good situation, which is why each lithium-ion battery cell is in a rigid and sealed container.  As you might be aware a non-sealed lead acid battery can be topped up with distilled water if the electrolyte is low.  With lead acid batteries this would be a temporary solution as battery performance would be decreased.

 

Overcharging is a concern with both lead-acid batteries or lithium-ion batteries can lead to a ruptured battery.  On a sealed lead acid battery the electrolyte is vented in the event of overcharging.  This is intended to avoid a ruptured battery but can still have a high enough internal pressure that would overpower the vent if left in the overcharging state.  For the lithium-ion battery, the luxury of venting is not possible as its reaction to water in the air would be dangerous.

 

 

battery-charging

 

Limitations of a Lithium-ion Battery

 

Charging each of the listed lithium-ion batteries must be limited to under 1C of the battery capacity.  The battery capacity is listed as amp-hours capacity, or AH, which is the most important factor to pay attention to when purchasing.  The amp-hour discharge rate is driven by C-rates.  C-rates are a standard time-based identifier with which to indicate the discharge rate with a time element involved.  The C-rating scale is based on the relation to 1C which is 1 hour.  As an example, 50 amp-hours at 1C would mean that 50 amps are discharged over 1 hour.  Using this same battery with a 5C discharge rate would be 35 amp-hours, meaning that 35 amps are discharged over 12 minutes, or 5 times faster than 1C within 1 hour.

On the other side of the C-rating, lower than 1C numbers is where most lead-acid and lithium-ion batteries are rated.  You will typically see a 20 hour rating which is the same as 1/20 C, or 0.05C discharge rating.  At the indicated discharge rate the battery will be fully discharged.

As the Battery University describes in their course, BU-402: What Is C-rate?.

A slow self-discharge is another limitation to the lithium-ion battery.  The battery self-discharge rate is dependent on the stored temperature.  The higher the ambient temperature the higher loss percentage discharge rate.  For 21 degrees Celsius the monthly loss due to self-discharge rate is 8%.  It appears that the rate of discharge is doubled at every increase of 20 degrees, which is 15% at 40 degrees Celsius, and 31% at 60 degrees Celsius per month.

Lastly, one of the limitations for a lithium-ion battery, is the reaction to being punctured.  This can happen by either being physically pierced or by prolonged overcharging, which generates excessive internal pressure.  The overcharging issue is solved by a protection circuit board (PCB) that is supplied with lithium-ion battery packs.  Depending on the size of the battery pack voltage and capacity there would be multiple PCBs as each pack would be used to protect its own cells.  A battery management system (BMS) would still be required to supply both a controlled discharge of power to the motor as well as a controlled charge to all of the battery packs.

There is still a danger when the lithium-ion batteries are disposed of after full use.  If the lithium-ion battery is put with other garbage then the casing could be punctured causing the release of unstable and flammable hydrogen gas, and this is why most landfills require lithium-ion batteries to be disposed of separately.  This is true for lead acid batteries as well as they pose an environmental threat from case punctures which would release all the lead acid.

 

There is more selection when you are looking to buy a lithium-ion battery.  It can be confusing when shopping for a lithium battery when a battery pack of the same voltage and capacity is a drastically different price.  Knowing the different types of lithium batteries that are available and their characteristics is half the battle.

 

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