At a panel session at the Advanced Automotive Battery and Ultracapacitor Conference (AABC) this week in Long Beach, California, directors and managers of advanced battery systems from GM and from Ford provided some insight into automakers’ requirements for lithium-ion battery technology to enter the automotive business.
The task of displacing NiMH is not trivial, according to Ted Miller, Advanced Battery Systems Supervisor for Ford. NiMH offers excellent performance and simplified controls. In addition, from a technology adoption point of view, NiMH offers validated performance and life models; a well-established production base; and a proven track record—all very important to automakers in assessing a technology for inclusion in future products.
Nevertheless, lithium-ion chemistry has two factors strongly in its favor: first, the power and energy attributes of the chemistry make it a solid choice for advanced hybrids, plug-in hybrids and electric vehicles. Second, the price of nickel is skyrocketing.
Director of GM’s Materials and Processes Lab, Mark Verbrugge, said that bringing lithium-ion batteries into advanced vehicles
...is a question of how and when, not a question of whether it will happen. Once you recognize the need is there, and that society will demand the products, the question is when.
That “when” is bounded by a well-defined process that, while it may vary in some specifics from company to company, is essentially similar for all the automakers.
Ted Miller outlined five basic criteria that must be met before lithium-ion technologies can move into showrooms:
Basic data on the specific cells and packs, including performance (versus temperature, state of charge and life); life (cycle and calendar); cost (with a detailed bill of materials and a model); and abuse tolerance.
Design information, including packaging, electrical and thermal (the heat transfer model).
Models, models and more models. “Better modeling is really critical,” said Miller. MATLAB-based performance, life, electrochemical models, all with costs.
Performance model. This needs to be a cell-level equivalent circuit model in MATLAB that provides voltage and current response based on power demand or input; response over the full operating temperature range; thermal response during simulated usage; and degradation behavior as a function of simulated usage.
Electrochemical model. This should determine electrode-level behavior and performance limitations over the full operating range (temperature, pulse current and time, change in SOC, and cell life). Verification testing to validate the model is required.
Life model. A cell life (cycle and calendar) model must be developed in order to determine the effect of usage and stand time. The model must consider the fundamental cell performance deterioration mechanism. Again, verification testing and lab analysis is required to validate the model.
A credible battery manufacturing plan, including plant investment, timing and production design qualification. The automakers also want details regarding the suppliers and support for production materials, and an R&D plan for performance improvement and cost reduction.
Fundamental analysis of performance degradation, with validation.
More specifically, there are three stages through which a new technology program—in this case, lithium-ion batteries—need to move: concept readiness, implementation readiness, and manufacturing.
In Concept Readiness, the requirements and design concept are defined and understood. Any IP or patent issues and/or opportunities are reviewed, and safety assessments are completed. Manufacturing feasibility is assessed, a demonstration strategy is established, business case and cost targets are set, and key technology issues are identified.
In the Concept Readiness stage, batteries would be manufactured in a lab-scale operation—a low-volume production of 10's to 100's of meters of electrode per day, or several thousand cells per year. The manufacturing operation would combine automated winding and hand assembly, and have an investment level of $5-$10 million.
The Implementation Readiness stage that follows, agreement on design trade-offs is reached, and complete validation plans and a detailed safety analysis are developed. The business case is confirmed. Manufacturing would be a pilot-scale operation with moderate volume cell production of 10's to 100's of thousands per year. Small-scale automation would handle most processes. This stage requires an investment level of $20-$30 million in manufacturing.
The final stage is Volume Production. This is a high volume, fully automated operation, capable of producing tens of millions of cells per year, with high quality process controls. The necessary investment level at this manufacturing stage is $100-$150 million.
Partnerships with key suppliers and experienced battery R&D and manufacturing teams are key, especially given the process gauntlet the cells must run. Having few US producers makes this “more challenging” for the US-based automakers.
From Ford’s point of view, there are a number of remaining technical challenges for lithium-ion batteries: improved low-temperature performance, fail-safe operation, simplified battery controls and life validation.
However, Miller noted, “I call lithium-ion a PHEV enabler. It’s the obvious option for PHEVs.” Among the benefits that lithium-ion batteries offer for plug-ins—aside from the energy and storage densities—are tunability (being able to design for an application-optimized power-to-energy ratio), and a wider range of electrode material choices (thereby avoiding being captive to a single metal).
For GM, which has already announced it plans to produce a plug-in version of the upcoming two-mode Saturn VUE hybrid with 10 miles all-electric range and has shown the Volt concept with 40-mile all-electric range, plug-ins are definitely on the agenda.
We are being challenged by our leadership to get these products [plug-in hybrids] and get the energy storages systems for these products as quickly as possible.—Joe LoGrasso, Engineering Group manager for Hybrid Energy Storage Systems at GM
But, LoGrasso noted, like other automakers,
GM uses a multiphase process [for battery integration], qualifying cell and module capability, cycle life, calendar life and power. Then we develop and test the packs to evaluate performance attributes, then work through the integration. This is all a precursor to declaring a solution technically ready and then planning production. This can take on the order of 5 years—from the start of evaluation to the showroom.
That’s a long time. That’s something we have to as an industry and as a company figure out ways to improve... [figuring out] how to parallel path some of these key work streams to develop battery solutions and vehicles is very important.
OEMs need to evaluate and select the best-in-class technology; figure out a reuse strategy across platforms; and move to plug-and-play energy storage integration, LoGrasso said. Energy Storage System Suppliers—which includes battery developers, pack developers and integrators, as well as the materials and components suppliers—need quick entry into the market (revenue); to minimize OEM-specific design work; and to share risk. Everyone wants to focus on their internal strengths.
LoGrasso suggested several areas in which standards could meet both groups needs. These ares for potential standardization are:
A common battery controls interface.
A standard “battery usage” record. Currently there is no good means of determining and recording how a battery is used. Ambiguity is not good. A recorded battery history with common metrics could also be useful for the secondary battery market. This would also prove important in the extremely sensitive area of warranties.
Standard charging interfaces for PHEVs.
Battery system verification. Each OEM currently has customized verification and validation plans. Common verification could lead to earlier technology readiness assessments, and could reduce verification costs and lead time.
LoGrasso said that GM is working with its hybrid partners BMW and DaimlerChrysler to develop and bring these and other ideas forward.
Successfully bringing lithium-ion technology to market will require collaboration, said Miller:
It will require collaboration between automakers, battery makers and the government. It this is important, we have to put our money where our mouth is. If we cede this opportunity, if we cede this technology, shame on us.
The market is obviously growing but it’s not there yet. Everyone has to get involved from our side and the government side...there has to be some [mutual] assumption of risk.