Lithium-ion battery technology has enabled mobile devices and electric vehicles, but further cost reductions are needed for large-scale energy storage applications. Performance, safety, and cost are interdependent and improvements require an integrated approach across material development, cell manufacturing, and energy storage system design. Early design choices strongly influence the manufacturing process and overall system integration. Optimizing these factors will depend on greater collaboration between academia, manufacturers, and system integrators through cross-training and a more vertically integrated approach to design and production.

1. Performance Safety and Cost Dependencies of Large Energy Storage
Systems Page 1
By Antonio Reis.
Antonio Reis is a professional in manufacturing, equipment design and industrial maintenance for more
than 25 years. Antonio Reis has provided management, manufacturing development, maintenance
services and personnel training to various types of industries such as Metallurgical, Meat Packing, Food
& Beverage, Petrochemical, Automotive, Battery, Converting and Semiconductor. December 2016
Performance Safety and Cost Dependencies of Large Energy Storage
Systems
Background-
Never before was energy storage so visible, as a principal component of the fundamentals
for economic development. Because energy storage enables dispatchable power with relative
ease and predictability, its value proposition applies anywhere in the world.
Energy Storage Systems (ESS) capable of working as energy ballasts between generation
and point of use are particularly useful since it allows efficient integration of intermittent power
generation. Solar, wind, and wave technologies provide alternate solutions for energy
production. These methods of power generation collect and aggregate energy rather than
transforming some stored fuel.
Overall cost and fitness to the application dictate the worthiness and value of a storage
system. Electrochemistry based energy storage systems (batteries and capacitors) provide
an efficient solution for integration of energy collectors (i.e. solar panels) because they
efficiently store and dispatch generated/collected energy. In a sense, the highly reversible
charge/discharge process provides a very low “operation cost” storage.
Electrochemistry energy storage systems cover a broad range of technologies. Each
technology has advantages and challenges depending on operational requirements,
portability, life-cycle, and cost.
Lithium-Ion Technologies-
Lithium-ion battery technology has enabled the mobile revolution from the Sony Walkman to
cell phones, laptops, and tablets. The same technology is now enabling EV and PHEV cars
like Tesla, Nissan Leaf, and, GM Volt.
Lithium-ion battery technology may be the key enabling technology allowing integration of
more variable renewable resources to the electric grid. However, to become a large scale
enabler, the lithium-ion ESS must develop further to reach the $200-$250 per kWh (system
level) cost, which by many is seen as the crucial price point.
There are three ways to improve the lithium-ion cell performance: chemistries, the format and
size of the cells, and the manufacturing process. There are several approaches to improve
the performance of an energy storage system such as system sizing optimization, integration
approach, and control methodology.

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The Knowledge Spectrum-
Three main sectors participate in the development through manufacturing of large energy
storage system. (1) The Academia is responsible for the development of raw materials and
development of knowledge around materials and components, theoretical potential of future
products, modes of failure for the various operational scenarios, etc. (2) The Cell
Manufacturing is responsible for the cell design and development of manufacturing
processes to produce the cells. (3) The Energy Storage Systems Integrators are
responsible for the design development and production of systems; some application-
specific, others can be adapted to fit the requirements of a group of applications
(standardized).
Each of these sectors has particular skill set and knowledge. In my opinion, the cross craft
training in both the Academia and “practitioners” and even between practitioners in related
subjects is very low, and specialization becomes an issue.
Specialization becomes a more significant issue when it resides in organizations that are not
dedicated to the integration of the final product and not responsible for its performance.

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Systems Page 3
Such an example is often found in the development of battery management systems. Often
these systems are developed by experts in electronic design, data acquisition, and data
manipulation but lack understanding of the variations of cell performance parameters.
Implementation of temperature management with a weak knowledge of the systems Ampacity
is also an occurrence.
Organizations in the lithium-ion ESS manufacturing that have a high degree of vertical
integration, both in the design and manufacturing, could have an easier path to success due
to the inter-organization learning and collaboration.
Early Choices-
Lithium-ion cell performance is based on a multitude of dependencies related to raw
materials, manufacturing processes, cell design and operating conditions.
In a particular application, the ESS’s performance depends on the integration design, control
methodology and the variation of the cell’s performance indicators.
The cell characteristics resulting from a particular design can optimize the ESS overall design
to achieve the requirements for the application.
In the development of large prismatic cells, the complete definition of product requirements
including the final integration is critical to achieving high adoption (commodity status). It may
determine the chemistry to be used, the cell stack construction, terminal connections,
enclosure and other deterministic characteristics that define the manufacturing development
roadmap.
The importance of making “robust” design choices early on in the design process, allows the
correct influence in the manufacturing development processes and optimization of the
approaches to the systems’ integration.
Once a particular design path is chosen, and the procurement of production equipment
commences, it is difficult to make substantial changes related systems integration. A simple
example is a decision between electrode stacking or paralleling of flat-wound stacks. Two
entirely different manufacturing methodologies with the significant impact of system’s
performance.
Looking Forward-
The future acceptance of lithium-ion large ESS will depend on the development
improvements in Performance, Safety, and Cost.
The Performance component will certainly include the ability to increase the ESS charge
rate, improve control and reach the optimum balance between energy density and power
capability.

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Systems Page 4
The development/improvement of cathode materials, a better understanding of mix, coating
and calendering processes, optimization of electrode balancing will lead to an optimum
distribution of current densities across the electrodes, therefore, improving performance.
In my opinion, these developments will occur in the optimization of the manufacturing function
for the various battery components and materials along with small improvements in materials
and formulations.
While many aspects of the ESS integration are related to Performance, Safety, and Cost,
there are design dependencies that are significant making a case for the need for a vertically
integrated design approach. From a Safety perspective, an Ampacity minded cell and system
electrical bus design can lead to better thermal control of the system improving the probability
of lithium plating, limiting electrode corrosion and electrolyte degradation. At the same time,
such Ampacity minded design also aids Performance and can have an impact on the ESS’s
Cost.
The integration of battery management systems that are designed with application-specific
references and objectives can approach adaptive control methods and robust State of Health
functions that can have a huge impact on the functionality of the ESS, offer a more robust
safety layer and improve the system’s life.
For the most part, lithium-ion ESS are considered commodities. With few exceptions, the
materials and components used in large ESS are commodities. The increase in adoption will
not have a significant impact on the system’s Cost. The energy density of the individual cell
will increase somewhat but not significant.
A significant improvement in cycle life, increased operational efficiency and cost savings from
the vertical integration of the ESS design and manufacturing processes are the main areas
for great Cost of Ownership reductions.
As an example, ESS in vehicle applications should have life cycles comparative to that of the
vehicles.
Conclusions-
Lithium-ion based large ESS have tremendous potential to transform the current
electrochemical energy storage market.
The optimization of Performance, Safety, and Cost will most likely come from vertical
integration of the design and manufacturing of the overall system.
The optimization effort would gain tremendous by aggressive cross-training of the
stakeholders on the various sectors and discipline matters.