The Current State of Electric Vehicles Part 3: Electric Vehicles Now Use Lithium-ion Batteries
Written on 05 October 2014
by Ruth Fisher, PhD
A copy of the full analysis can be downloaded by clicking on the link at the bottom of this blog entry.
From the beginning, the biggest problem facing all-electric vehicles has been their short range, that is, they cannot go very far without having to recharge their batteries. Since lithium-ion (Li-ion) batteries offer the greatest energy capacity and density of all the batteries, and thus the greatest potential for longer range, Tesla chose to use Li-ion batteries to power its first all-electric vehicle, the Tesla Roadster. As Tesla notes:
Tesla battery packs have the highest energy density in the industry
Nickel Metal Hydride (NiMH) batteries are commonly used in hybrid cars. However, a 56 kWh NiMH battery pack would weigh over twice as much as the Roadster battery. Instead, Tesla uses Li-ion battery cells which dramatically decrease the weight of the Roadster pack and improve acceleration, handling, and range.
As seen in Figure 1, taken from Justin Amirault, et. al. “The Electric Vehicle Battery Landscape: Opportunities and Challenges,” Li-ion batteries encompass a family of batteries, with each type being comprised of different materials.
Lithium-ion Batteries: Raw Materials
Digging a little deeper, we find that Li-ion batteries contain three primary functional components:
• Positive Electrodes, which are made from a metal oxide, generally one of three materials:
• a layered oxide, such as lithium cobalt oxide (LCO),
• a polyanion, such as lithium iron phosphate (LFP), or
• a spinel, such as lithium manganese oxide (LMO);
• Negative Electrodes, which are generally made from carbon, most popularly, graphite; and
• Electrolyte, which is composed of a lithium salt in an organic solvent.
The cost of the battery is the largest cost component of electric vehicles. And of the battery costs, the most significant contributors are the costs of the raw materials, particularly those used in the cathodes (positive electrodes).
Raw materials costs are estimated to account for 75% of the cost of a battery. Lithium itself makes up only about 3% of a battery by weight, either as salt in the electrolyte or incorporated into the cathode material. This means that costs of other materials, most importantly the cathode, will dominate the raw materials and manufacturing costs
Differences in prices of raw materials across battery types will thus contribute significantly to differences in prices across EVs that use batteries constructed from different materials. And, in fact, current prices of raw metals vary widely across types:
Ferrous Titanium $6.15/kg
Lithium-ion Batteries: Performance Characteristics
In addition to cost variations, different material constructions of Li-ion batteries also generate differences in battery performance. Figure 2 provides specific information for the different compositions of lithium ion batteries. Information from Battery University on battery chemistry and general industry use is presented in columns [A] – [E] of Figure 2. Information from Consumer Reports on performance characteristics of the different battery types in the use of EVs is presented in columns [F] and [G] of Figure 2. And information on manufacturers of both electric vehicles and EV batteries for each of the battery types is presented in columns [H] and [I] of Figure 2.
The differences in potential performance for six different characteristics – each rated on a scale of 1 (low) to 4 (high) – across Li-ion battery types are presented in Figure 3. Note that the potential performances of the various battery types are potentials. The current state of lithium-ion battery development for use in electric vehicles is still in the early stages, and manufacturers are still working to close the gap between potential battery performance and actual performance.
What Figures 2 and 3 indicate is that
• lithium cobalt oxide batteries (LCO) (first generation Li-ion batteries) and lithium manganese oxide batteries (LMO) (second generation Li-ion batteries) offer the package of characteristics with the least overall potential for EVs;
• lithium iron phosphate batteries (LFP) (third generation Li-ion batteries) and lithium nickel manganese cobalt oxide batteries (NMC) (fourth generation Li-ion batteries) provide much better over-all potential for EVs than first- and second-generation batteries;
• lithium nickel cobalt aluminum oxide batteries (NCA) and lithium titanate batteries (LTO) provide the best overall potential for EVs.
Return to Part 1: Electric Vehicle Battery Basics