Chen Yongchong, leader and researcher of the energy storage technology
research group of the Institute of Electrical Engineering, Chinese Academy of
Sciences, shared the keynote report "Battery Energy Storage Technology Issues
and Development Suggestions" during the meeting. The following is the original
text of his speech: I am very happy to have such an opportunity to discuss with
you. Four aspects of the problem. First, the diversification of energy storage
battery technology application scenarios; second, the diversification of battery
types; third, the diversification of technical connotations; fourth, the
diversification of development goals. Let’s first look at the general industrial
development background. First of all, 2017 was the year of consensus on the
development of energy storage in China. Before this, there was a lot of
controversy about whether to develop energy storage. The issuance of the
"Guiding Opinions on Promoting the Development of Energy Storage Technology and
Industry" in 2017 is a sign that the spring of energy storage in China is
coming. In 2018, global and Chinese energy storage projects developed rapidly.
Secondly, the core of developing energy storage is to promote the consumption of
renewable energy. In the past five years, the cost of photovoltaic and wind
power generation has dropped rapidly, and the cost of power batteries has
dropped due to new energy vehicles. Energy storage has begun to be used in some
previously uncompetitive fields. With competitiveness, the multiple values of
energy storage are gradually reflected. Third, the spring of energy storage has
arrived. Spring is the season of budding and flowering, but the summer of
vigorous development of energy storage has not yet arrived. Nowadays, various
types of energy storage technologies, including physical energy storage,
electrochemical energy storage, chemical energy storage, and thermal and cold
storage, have been demonstrated and commercially applied. The advantages of
energy storage have been demonstrated in the applications, but many problems
have also been discovered. Especially electrochemical energy storage technology,
it should be said that there is still a considerable gap from the overall goal
of "low cost, long life, high safety, and easy recycling", and technological
innovation and breakthroughs are needed. Energy storage has six major
application scenarios, renewable energy grid connection, grid auxiliary
services, grid transmission and distribution, distributed and microgrid, user
side, and a very special user side: the energy supply system of electric vehicle
VEG mode. There are many energy storage application scenarios, and the three
major functions of energy storage can be roughly classified: first, to smooth
intermittent power supply power fluctuations, such a scenario requires
power-based energy storage technology; second, to reduce peak-valley
differences, improve power system efficiency and Equipment utilization, most of
this scenario requires capacity-based energy storage technology; third, to
increase backup capacity and improve grid security, stability and power supply
quality, this requires UPS backup-type energy storage technology. Of course,
there is also a fourth type of composite application, especially grid-side
applications that participate in peak regulation, frequency regulation and
emergency backup. We call it composite or energy-based energy storage
technology. Therefore, the application scenarios of energy storage are diverse.
Therefore, we can infer from the application requirements that the types of
energy storage batteries can also be divided into four major categories:
capacity energy storage batteries, power energy storage batteries, energy energy
storage batteries, and backup energy storage batteries. Making a distinction
based on the power capacity ratio used by the battery will help us develop
different types of energy storage battery technologies. Especially backup energy
storage batteries. At present, it seems that the cascade utilization of power
batteries from large to small is completely possible, but it still faces great
difficulty from small to large. Its consistency, safety issues, and cost face
very big challenges. However, it is still possible to use power battery cascades
in some backup energy storage scenarios. The so-called backup energy storage may
be charged and discharged only a few times a year, instead of charging and
discharging every day. We often talk about energy storage technology, especially
energy storage battery technology. So, what exactly is energy storage battery
technology and what is its technical connotation? I summarized that energy
storage battery technology should include six major connotations.
The first is material technology, which is the foundation. But for energy
storage batteries, I particularly want to emphasize the material properties,
especially the material properties studied in the laboratory. There is still a
very big difference between the actual performance of batteries that will be
made into large batteries and used for energy storage applications in the
future, so you must not The performance of laboratory materials is equated with
the performance of energy storage batteries, let alone the performance of energy
storage battery systems.
The second is structural technology. Compared with small consumer
batteries, energy storage scenarios require high power and large capacity.
Therefore, the research and development of future energy storage batteries must
fully consider the integrated design of the internal structure and external
structure of the battery, and reduce the cost and safety pressure faced by the
external system through the innovative development of some internal structures.
This is the research on future energy storage battery structure technology.
important direction. We hope that our energy storage batteries can change from
"petite and rich" to strong and durable "silly, big and chunky" to meet the
actual scene needs of the power system.
Third, manufacturing technology.
Especially for lithium-ion batteries, its manufacturing technology is
derived from the previous magnetic tape technology, using an adhesive film
electrolytic structure, which requires high-precision, very complex, and
hundreds of manufacturing processes. If you want to reduce manufacturing costs
in the future, you will need to combine structural technology innovations in
batteries to make the entire manufacturing process simple and not complicated.
The fourth application technology. Energy storage battery application technology
is battery energy storage technology in a narrow sense that is often mentioned
in power systems, including system integration technology, BMS, PCS and EMS.
Application technology is very important. It is necessary to develop
corresponding application technology for different application scenarios,
accumulate application data, discover application problems, and evaluate
application economics. In the future, there should be independent energy storage
battery system application service providers with application technology
development as the core. They will be responsible for the design and planning,
leasing, operation and maintenance, and scrap recycling of the energy storage
system. They will also cooperate with insurance companies and promise to be
responsible for the service life and operation of the system. Safety. Fifth
regeneration technology. Our consumer batteries only have a lifespan of three to
five years, because our mobile phones have to be replaced in three to five
years, so it doesn’t make much sense no matter how long the battery life is.
However, the power system requires a life span of ten or even more than twenty
years for battery energy storage systems, and ten years is almost a ceiling for
our batteries with existing technology. Therefore, during the operation of
energy storage systems in the future, new battery regeneration technologies may
need to be developed to extend the service life of energy storage batteries.
After the battery has been used for a period of time, the battery performance
can be re-activated through in-situ repair of the SEI film on the surface of the
positive and negative electrode materials, and the replenishment and replacement
of the electrolyte to extend the actual calendar service life of the energy
storage lithium battery. For example, the slurry-thick electrode morphology of
lithium slurry batteries gives them the possibility of online regeneration
during their lifetime. The last one, recycling technology, is very important.
Including waste battery replacement technology, safe transportation technology,
recycling technology and resource reuse technology. The recycling process and
technology of lithium batteries are not yet mature. It needs to be combined with
material technology and structural technology to develop new energy storage
battery technology that is convenient for recycling and regeneration. Innovative
improvements should be made in product design and battery recycling and
processing should be considered in advance from the production end. , in order
to realize the sustainable development of resources in the energy storage
lithium battery industry, which is of important strategic significance. In the
past two days, the association is taking experts from the World Bank to inspect
the existing battery recycling situation. Including replacement processing, safe
transportation, end-of-life recycling and resource reuse. We know that scrapped
batteries are more dangerous than new batteries. How will the batteries be
transported back to the base after they are scrapped? Is it possible to develop
innovative technologies? Safely handle the batteries before they are scrapped so
that they are absolutely impossible to burn and explode. This is storage New
issues facing energy batteries. Therefore, the technical connotation of energy
storage batteries is very rich. These six technical connotations require us to
make breakthroughs from all aspects, not just breakthroughs in material
technology.
Industry pain points. There are four major comprehensive problems with
energy storage batteries: high cost, short life, poor safety, and difficult
recycling. For lithium-ion batteries, it is a core design idea of a
bonded-coated thin-film electrode structure and the parallel connection of
internal pole pieces followed by the tabs, which brings fundamental problems to
the consistent design of battery cells and battery systems. Yesterday we went to
Kehua. Mr. Chen from Kehua said that the application of nanoparticle materials
in batteries requires nanoscale mechanical control and power control. This makes
sense. This requires the existing battery manufacturing control accuracy to be
very high. Why? Because its electrode layer is only a very thin thickness of
more than 100 microns and contains nano-micron particles, it requires
high-precision control, which makes it very difficult to reduce battery
manufacturing costs. Therefore, innovative technologies are needed, such as the
development of capacity-type ultra-thick electrode technology, to reduce the
absolute requirements for manufacturing precision and reduce the manufacturing
cost of energy storage batteries. Therefore, we say that the development of
energy storage batteries has gradually changed from the original primary
requirement of high energy density of consumer batteries to the core requirement
of low cost. The use of batteries in mobile phones is a necessity. Mobile phones
cannot do without batteries. Therefore, whether the battery is cheap or
expensive, it must be used. However, if energy storage batteries are too
expensive, the power system can be used without them, and non-energy storage
methods can even be used to solve some of the problems faced by energy storage.
Therefore, "low cost" has become our primary goal in the development of energy
storage batteries.
Let me briefly explain the development goals. The cost of energy storage
batteries in a narrow sense only includes primary (purchase) costs, while the
cost of energy storage batteries in a broad sense also includes secondary
(operation and maintenance) costs and tertiary (recycling) costs. Among them,
the primary cost includes the material cost and manufacturing cost of the
battery. In the case of limited room for material cost reduction, simplifying
the battery production process and reducing manufacturing costs and labor costs
through subversive design of battery structure technology will be an important
cost reduction direction for new energy storage batteries. Secondary costs are
closely related to battery life. It is necessary to combine material technology
and structural technology to develop new repair and regeneration technology to
extend the service life of batteries and reduce the cost per kilowatt-hour of
capacity batteries and the frequency cost of power batteries. The third cost
mainly refers to the recycling cost of the battery. At present, if the recycling
and regeneration process of energy storage batteries is to fully comply with the
requirements of environmental protection standards, the cost is still very high.
Innovative battery design ideas and recycling ideas are needed to reduce the
tertiary costs of batteries. At present, the cost of energy storage batteries is
relatively high, so it can be applied in some complementary scenarios first. In
the future, as the cost drops, it can gradually be applied in competitive
scenarios.
The second long life, battery cycle life is the basis of calendar service
life, but it is not equivalent to the actual calendar service life of the
battery. Currently, there is a lack of suitable accelerated aging experimental
standards that can correspond to the actual calendar decay changes of batteries.
In the future, in addition to establishing relevant testing standards, it is
also necessary to develop innovative online repair and regeneration technology
to increase the calendar service life of energy storage batteries and meet
actual energy storage working conditions. If the battery cycle life tested in
the laboratory is 3650 times, even if it is charged and discharged once a day,
365 times in 365 days a year, which is exactly 3650 times in ten years, we
cannot say that the battery has a calendar life of ten years. Because the
battery is a highly non-equilibrium chemical system, even if it is not charged
or discharged, its performance will be attenuated when placed somewhere, which
is very important. Therefore, regeneration technology must be developed in the
future, and here are the reasons.
Moreover, the direction of application development will change from passive
operation and maintenance now to active operation and maintenance in the future.
We need active operation and maintenance. The annual operation and maintenance
cost of our pumped storage power station is about 70 million to 80 million yuan.
Why does the electrochemical energy storage system not require operation and
maintenance? it's out of the question. The third goal is high security. The
safety of energy storage batteries is very important. Relatively speaking,
aqueous batteries such as flow batteries and lead-acid batteries are safer and
can meet the safety requirements of energy storage power stations. However, the
charging cut-off voltage of the battery also needs to be strictly controlled to
prevent the aqueous solution from overvoltage electrolysis. Hydrogen evolution
and explosion; the safety issues of organic lithium-ion batteries are more
prominent. Currently, they are generally at a safety passing line of around 60
points, waiting for technological breakthroughs; solid-state batteries do not
contain flammable electrolytes, so they have the highest safety. After mass
production is achieved in the future, it may first be applied to certain special
scenarios with high safety requirements.
However, if solid-state batteries are to be applied to power energy storage
on a large scale, there are still considerable difficulties that need to be
overcome in terms of cost reduction, longevity and system consistency. In
addition, the recycling and processing of solid-state batteries is also a big
problem. Safety prevention technology to avoid battery (internal or external)
short circuit and emergency maintenance technology after battery short circuit
occurs are important directions for the development of energy storage battery
safety technology. It is not enough to simply protect the safety of lithium
energy storage batteries through external fire extinguishing devices. In the
future, disruptive battery structure technology and safety maintenance
technology must be developed to completely solve battery safety issues from
within the battery and ensure the safety of energy storage batteries. Safe
operation of transportation and energy storage power stations. The fourth goal
is easy recycling. The recycling and utilization of resources will be the
biggest challenge facing the future large-scale application of energy storage
batteries. There are three basic requirements for energy storage batteries to
achieve the goal of easy recycling:
1. The battery recycling process complies with safety and environmental
standards;
2. Rare and precious metal elements can be recycled nearly 100%;
3. The battery has a certain residual value.
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