Types of Lithium
Lithium energy is an active area of study so new chemistries are being developed every year.
Some of the most popular chemistries are:
While these are all lithium batteries, there are key differences between them.
has a very long life and a wide temperature range. They are capable of handling large charge currents greater than 10C. They have one of the lowest energy densities (2.4V/Cell) of all lithium batteries and are one of the most expensive.
became very popular because of its high energy density (3.6 V/Cell). Cobalt is a very energy-dense material but is extremely volatile and expensive. It is a resource that is depleting quickly due to its recent increase in consumption. LCO has many negatives, it cannot handle large charge currents, are very sensitive to temperature, and have a short cycle life.
is a rapidly developing chemistry, at the time this is written. The blending of nickel, manganese, and cobalt produces a very well-rounded battery. With a high energy density (3.6V/Cell) and a decreased use of cobalt, it has become one of the most desired batteries in the industry. Due to its lower cobalt concentration, it is safer than LCO. Its life cycle is longer than LCO but shorter than LTO. It can handle charge currents up to 2C and a greater range in temperature. It is also important to know that batteries that contain cobalt require more safety features which make the batteries more expensive.
is popular in industries with heavy use and rough environments. While this chemistry has a slightly lower energy density (3.2V/Cell), it can withstand a lot of abuse. It has a long lifespan, it is less costly and much safer because it does not contain cobalt. It can even withstand a very wide range of temperatures. LFP can also withstand discharge currents up to 20C but typical usage patterns include 1C. Overall this is the safest and most reliable chemistry.
|Voltages||2.4 volts||3.60 volts||3.6 volts||3.2 volts|
|Thermal Runaway||280 °C||150 °C||210 °C||270 °C|
|Cost||$1,000 per kWh||$450 per kWh||$700 per kWh||$400 per kWh|
LFP vs. NMC
While higher energy li-ion chemistries are available, Lithium iron phosphate (LFP) is safest with the longest cycle life due to its stable chemical make-up. A demonstration of how much more stable the LFP chemistry is compared to the high energy Lithium Cobalt Oxide (LCO), used in consumer electronics, is to compare the thermal runaway temperatures – the high temperatures at which the chemistries begin to become unstable and volatile. LCO has a much lower thermal runaway temperature of 150°C (302°F) compared to LFP’s thermal runaway temperature of 270°C (518°F). This large difference shows LFP to be the much safer of the two lithium chemistries.
High energy density is important for battery systems which need to be smaller and lightweight. A more modern cathode chemistry than LCO is Nickel Manganese Cobalt (NMC). NMC is the result of an attempt to balance safety and performance. A version of NMC is the chemistry is utilized in automotive EV battery systems today. EV batteries utilize higher voltages and with the higher energy available, additional safety measures and control must be implemented. The cells heat up quicker, so proper charging is critical.
With larger industrial, motive power battery systems, space is available for the larger batteries, and weight is actually needed for the counterbalance systems. Fast charging is critical and LFP accommodating lead acid charging helps with systems safety. Cycle life and safety is prioritized. The lower voltage of LFP is good match for Lead Acid replacement. This and the tolerance of Lead Acid charging systems make LFP the safest backward compatible option for material handling batteries.
The physical construction of the cell also affects its safety. All lithium batteries contain a critical component called the separator, which is placed in between the anode and cathode layers in the electrode. The separator limits the chemical reaction of the electrode and helps to prevent thermal runaways by closing its porous structure at high temperatures. The safest Li-ion cells incorporate ceramic separators. The ceramic material is resilient at high temperatures and helps prevent the breakdown of the separator that occurs during a thermal runaway event.
The electronics of the Li-ion battery also provide protection against safety events, with incorporated fuses and protection against over-charge, over-discharge and high and low temperature charging. These battery “smarts,” combined with the long cycle life and short charge time seamlessly integrate with the material handling equipment. The fact that the battery is virtually maintenance free over the life-time of the truck, eliminates the possibility for user error and greatly reduces the risks in the workplace.
|Parameter||Lithium Iron Phosphate (LFP)||Nickel Manganese Cobalt (NMC)||Comparison|
|Voltage||3.2V||3.7V||NMC Batteries are lighter and more compact|
|Weight Energy Density||90-120 Wh/Kg||150-250 Wh/Kg||NMC Batteries are lighter and more compact|
|Volume Energy Density||300-350 Wh/L||500-700 Wh/L||NMC Batteries are lighter and more compact|
|Max Discharge Rate||30C||2C||LFP Batteries provide more power over a shorter period, and can be charged faster|
|Max Charge Rate||10C||0.5C||LFP Batteries provide more power over a shorter period, and can be charged faster|
|Typical Cycle Life (@80%)||3000+ Cycles||500-1000 Cycles||LFP Batteries will deliver more cycles over a longer calendar life|
|Calendar Life (@80%)||8-10 Years||500-1000 Cycles||4-5 Years **|
|Thermal Runaway Onset *||~195 °C||~170°C||NMC Batteries have lower thermal runaway thresholds and will burn hotter|
|Thermal Runaway Increase *||210°C||500°C||NMC Batteries have lower thermal runaway thresholds and will burn hotter|
|* Royal Society of Chemistry, 2014 | ** With derated charge voltage|