EV Battery Technology,part 3
This course is presented as part of Evannex Universitya free, open learning environment that presents concise, video-based mini-courses for those who have interest in electric vehicles (EVs)
A look backthe basic elements of an EV batterythe battery production process the metrics by which we compare one battery chemistry to anotherthe cost drivers for EV batteries
In the preceding parts of this EVU mini-course you learned about:>> the basic elements of an EV battery>> the battery production process >> the technological characteristics by which we compare one battery chemistry to another>> the cost drivers for EV batteries
Now it time to look at Battery trends going forward.
Is it reasonable to expect lower cost?Technical advances in the design and fabrication of anodes, cathodes and electrolytes are likelycell capacity improvements of 40%overall increase in battery capacity by 80 to 110 percent
No one has a crystal ball, but recent trends indicate a few key facts:>> Technical advances in the design and fabrication of anodes, cathodes and electrolytes are likelyThese will result in: >> cell capacity improvements of 40%>> overall increase in battery capacity by 80 to 110 percent in the 2020 - 2025 timeframe
The graph on the right of your screen shows battery cost projections of 10 different studies of battery cost. Youll note that all converge on 200/kWh in the time range of 2020 to 2030. In the last few decades, technology has tended to progress more rapidly that most projections indicate, so the $200/kWh projection in the 2020 to 2025 timeframe seems reasonable and achievable.
The Battery Landscape
Source: Electric Vehicle Integration into Modern Power Networks,Electric Vehicle Battery Technologies (Ch. 2), Young, K. et al,Springer, 2013
This graph of specific energy (a measure of battery capacity) and specific power (a measure of power to weight of a battery) provides yet another view of the current status and future outlook for EV batteries.
The graph shown on your screen provides a compact view of the existing battery landscape, represented in terms of specific energy and specific powerterms we discussed in part 2 of this mini-course.
As you can see, Li-Ion batteries offer distinct advantages over lead acid and Nickel-metal-hydride batteries, with super capacitorsa technology well discuss briefly in a few momentsoffering significant potential in high power applications.
The stars on the graph indicate goals established by the United States Advanced Battery Consortium. Note that goals for Hybrid electrics and PHEVs have already been met, but the goal for BEVs has yet to be achieved with production battery technology.
The dashed diagonal lines indicate the time to discharge at various specific energy and specific power configurations. From the plot, as power demand increases, the battery discharges more rapidly and the battery will not offer as much total energy.
Batteries vs. Gasoline
Source: McKinsey&Co from DoE data, http://www.mckinsey.com/insights/energy_resources_materials/battery_technology_charges_ahead
In 2012, McKinsey & Co. developed a graph that compares the cost of gasoline with the cost of EV batteries in $ / kWh and then depicts the regions in which EV variants and ICE vehicles are competitive. In this case competitive means that any electric vehicle price premium associated with battery costs will be offset over a reasonable period of ownership.
The mid-blue shaded region of the graph shows that as battery costs falls below about $350/KwH, BEVs and PHEVs become fully competitive at a gasoline price of about $3.50 a gallon. When battery cost is reduced to $150 /kWh BEVs are competitive regardless of the cost of gasoline.
By 2020, it is likely that batteries will cost about $200 -$300 / kWh, meaning that a gasoline cost of $3.00 per gallon makes BEV fully competitive with ICE vehicles.
But all of this assumes incremental improvements in battery tech. What if there are disruptive improvements? Lets take a quick look at a few research directions.
Battery ResearchComponentsGraphene and carbon nanotubes for supercapacitors that would reduce charging time to minutes, rather than hoursproblem: fabrication and costproblem: relatively low energy densitylithium rather than graphite electrodes have the potential to increase capacity by 100 - 300% problem: left cycle and safety concernssuper-thin batteries can be spread over then entire vehicle surfaceproblem: early stages
There are a number of major national research programs, such as the Joint Center for Energy Storage Research, dedicated to the improvement of energy story technology.
In the domain of batteries, this research is focused on a number of important areas including:
>> Graphene and carbon nanotubes that can be used for supercapacitors that would reduce charging time to minutes, rather than hours>> the problem: fabrication and cost>> and another problem: relatively low energy densityAnother research area is in new electrode materials>> lithium rather than graphite electrodes have the potential to increase capacity by 100 - 300% >> problem: life cycle and safety concernsFinally, >> super-thin batteries can be spread over the entire vehicle surface>> problem: research is in its early stages with potential for success uncertain.
Battery ResearchChemistryLithium-Vanadium-Phosphate (LVP)faster charging and longer life expectancy than Li-Ion.Lithium sulphurincrease energy density by a factor of 4Lithium airpotential to achieve energy density of gasoline, but is not suitable for the heavy loads of automotive applications, possibly could supplement a Li-Ion battery
Understanding advances in battery chemistry demands a highly technical background and is beyond the scope of this EVU mini-course. For our discussion, suffice it to say that a variety of Lithium based chemistries offer potential:>> Lithium-Vanadium-Phosphate (LVP) offers faster charging and longer life expectancy than Li-Ion.>> Lithium sulphur is claimed to increase energy density by a factor of 4>> Lithium air has the potential to achieve energy density of gasoline, but is not suitable for the heavy loads of automotive applications, but possibly could be used to supplement a Li-Ion battery
Supercapacitorstwo carbon electrodes sandwich and electrolyte to for the super capacitorthin film, with high power density, but lower specific energyable to charge very quickly, very thin (body panel applications)supplement EV batterydoes not replace itprovides burst of power for acceleration, allowing battery to provide steady state power
Source: IEEE Spectrum, http://spectrum.ieee.org/nanoclast/transportation/advanced-cars/graphenebased-supercapacitors-take-another-crack-at-allelectric-vehicles
Finally, a word about supercapacitors.If you read about the future of EVs, youll often encounter the term and along with it, statements about supercacitors as a breakthrough technology for EVs. The future impact of supercacitors is unclear, but its worth exploring this energy storage technology briefly,
>> two carbon electrodes sandwich an electrolyte to form the super capacitor that holds an electrical charge
The characteristics of this device are that it can be implemented as a:>> thin film, with high power density, but lower specific energy>> it can be charged very quickly, >> and because it is very thin, it has potential for body panel applications, that is, the supercapacitor would become part of the vehicle body panels, thereby accommodating the geometric constraint we discussed earlier in this mini-course
Given the current state of the technology and the immutable laws of physics, a supercacitor would>> supplement EV batterybut does not replace it
>> It provides burst of power for acceleration, allowing battery to provide steady state poweror alternatively, might be used to supplement a Li-Ion battery to extend its capacity
Summarybattery components form cells, organized into modules, and built as a packbuilding higher capacity batteries is constrained by geometry, weight, and technology six characteristics must be considered when evaluating a battery packspecific energy, specific power, life span, cost, safety and performancenew technology may enable improvements in all six characteristics
Weve covered a lot of ground in this EVU mini-course. Lets summarize:>> battery components form cells, organized into modules, and built as a pack>> building higher capacity EV batteries is constrained by geometry. weight, and technology >> six metrics must be considered when evaluating a battery packspecific energy, specific power, life span, cost, safety, and performance>> new technology may enable improvements in all six characteristics
If these improvements are significant (and only time will tell if they are), EVs will provide the range and performance that will rival ICE vehicles.
a free study guide for all EVU mini-courses is available for download from our website For a complete list of mini-courses and the study guide, visit: www.evannex.com
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