As the "heart" of electric vehicles, power batteries have attracted as much
attention as the currently popular new energy vehicles. Among them, lithium-ion
batteries are favored by the new energy automobile industry because of their
high energy density, low self-discharge rate, high cycle efficiency, and long
cycle life, and have huge market development potential. However, the current
lithium-ion battery technology is not yet mature, and the problem of unstable
safety still exists. In addition, the frequent accidents of battery "irregular
fire" have been stimulating the nerves of consumers, and the development of
solid-state battery technology may become a breakthrough. New options for
electric vehicle safety issues.
Solid electrolytes become a trend
"The cost of lithium-ion batteries used now is relatively high and the
technology is immature. There are many potential safety hazards in the
lithium-ion batteries produced." said Wang Zhenbo, a professor at Harbin
Institute of Technology.
According to the reporter's understanding, large power battery accidents
have occurred frequently in recent years, largely due to the use of liquid
electrolytes inside the batteries. "Safety is very critical for lithium-ion
battery energy storage." Li Liangliang, associate professor at the School of
Materials, Tsinghua University, emphasized, "Currently commercial lithium-ion
batteries on the market generally use organic liquid electrolytes. Its
disadvantages are that it is easy to burn and may leak. Liquid leakage causes
environmental pollution.”
The lithium-ion battery equipment fire that occurred in Yeongam, South
Korea two months ago seemed to confirm this statement.
"The liquid organic electrolyte currently used is flammable and explosive.
Replacing the liquid electrolyte with a solid electrolyte is recognized as one
of the most effective ways to improve the safety performance of lithium
batteries." Associate researcher at the Qingdao Institute of Bioenergy and
Processes, Chinese Academy of Sciences Dong Shanmu said.
Li Liangliang told reporters: "Solid electrolyte is not flammable and does
not produce liquid electrolyte, so it is non-corrosive. It is an effective way
to solve battery safety problems and is in line with the future battery
development trend."
Technical bottlenecks are difficult to break through
"High safety is the basis and premise for the application of energy storage
batteries, and solid-state is the best way to solve the safety of secondary
batteries. Solid-state lithium batteries have entered the stage of accelerating
global layout and research and development, and many well-known institutions are
developing solid-state lithium batteries ." Wen Zhaowei said.
The reporter learned that many battery and automobile manufacturers,
including South Korea's Samsung, Japan's Toyota and my country's CATL, have
increased their investment in solid-state battery research and development, and
some batteries have now entered the vehicle testing stage. Although the
prospects are promising, the road to developing solid-state batteries is by no
means smooth sailing due to various technical and process problems.
First, there is a lack of efficient electrolyte material systems. Wen
Zhaowei pointed out that solid-state battery materials are currently developing
rapidly, but comprehensive applications are lacking. "As the core material of
solid-state batteries, there has been a breakthrough in the single indicator of
solid lithium-ion conductors, but the comprehensive performance cannot yet meet
the needs of large-scale energy storage." In this regard, Dong Shanmu also
believes that "Today's solid-state batteries use Solid-state electrolytes
generally have performance shortcomings, and there is still a big gap between
the requirements of high-performance lithium-ion battery systems."
Secondly, the interface treatment between solid electrolyte and electrode
is also a major problem currently faced by solid-state batteries. "In solid
electrolytes, the transmission impedance of lithium ions is very large, and the
contact area of the rigid interface with the electrode is small. Changes in the
volume of the electrolyte during the charge and discharge process can easily
destroy the stability of the interface." Li Liangliang pointed out. In addition,
in solid-state lithium batteries, in addition to the interface between the
electrolyte and the electrode, there are also complex multi-level interfaces
inside the electrode. Factors such as electrochemistry and deformation will
cause contact failure and affect battery performance.
Thirdly, unsatisfactory stability during long-term use is also a bottleneck
in the development of long-life energy storage solid-state batteries. "The
structure and interface of solid-state batteries will degrade over time during
service, but the impact of degradation on the overall performance of the battery
is still unclear, making it difficult to achieve long-term application." Wen
Zhaowei said.
"The failure behavior of the solid battery contact interface and the
failure mechanism behind it need to be clarified urgently." Dong Shanmu also
said, "I believe that building high-performance solid-state batteries requires
starting from two aspects. One is to build a high-performance solid-state
electrolyte, and the other is to improve Interface compatibility and
stability.
New technologies emerge one after another
"For solid-state batteries, we need to conduct research from the most basic
materials, interfaces, and monomers to the final system modules. Only by
fundamentally solving the key material and interface issues can we carry out
systematic process research to meet the needs of single cells. performance
requirements." Wen Zhaowei told reporters.
In the face of continuous challenges in the development process, various
new technologies are "contesting". Reporters recently learned about some of the
latest breakthroughs in solid-state battery technology.
For example, in terms of solid electrolyte materials, the industry has
found that solid-state batteries based on the garnet-structured lithium
lanthanum zirconium oxygen (LLZO) solid electrolyte system have excellent cycle
performance and rate performance, and it has therefore become a major technical
hotspot. "LLZO is a filler with excellent performance that can improve the
performance of polymer-based composite solid-state electrolytes. Solid-state
batteries based on LLZO can still maintain 81% capacity after 1,000 cycles." Li
Liangliang introduced.
Dong Shanmu told reporters about another idea for electrolyte materials -
"rigid and soft", using rigid polymer skeletons and inorganic particles to fuse
with flexible polymer ion transport materials. "Through the Lewis acid-base
interactions between polymers and polymers and between polymers and inorganic
particles, new channels can be created for lithium ion transport and the overall
performance of the electrolyte can be greatly improved."
The research focus on interface treatment mainly focuses on interface
design and modification layers. At present, good results have been achieved in
gelled interface design. Wen Zhaowei said: "The interface is modified by
gel-state polymers, which not only increases the contact area but also buffers
the volume effect during cycling. After 300 cycles at room temperature, there is
basically no degradation. This kind of structural design is better Improved
battery performance."
"In addition to solid-state electrolytes and interfaces, the integrated
design of solid-state batteries is also very important." Li Liangliang said when
talking about the future development of solid-state batteries, "Because for
different fields such as energy storage and new energy vehicles, targeted
battery development is required. Structural design.”
“In general, research on solid-state batteries is currently more academic.
In terms of industrialization, some key technologies cannot be obtained because
they involve the core technologies of various enterprises. As a result,
technologies based on engineering applications still need to be further
developed. Explore." Wen Zhaowei said.
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