Recently, the team of academician Qiao Shizhang of the University of Adelaide, Australia, successfully made the lithium-sulfur battery complete single-turn charging or single-cycle discharge within 5 minutes, which solved the key bottleneck problem of lithium-sulfur batteries.
图 | 乔世璋（来源：乔世璋）
Specifically, using a series of carbon-based transition metal catalysts as examples, they proposed for the first time the kinetic trend of sulfur reduction reactions (SRRs) based on the principle of Le Chatletle.
This trend describes the kinetics of SRRs increasing with increasing lithium polysulfide concentrations. That is, there is a mathematical relationship between the two.
This trend shows that the concentration of lithium polysulfide can be increased by designing relevant catalysts, which in turn can improve the dynamics of SRR.
In the study, the research group proved through synchrotron radiation X-ray absorption spectroscopy and molecular orbital theory calculations that the occupancy of the antibond orbital of the catalyst determines the concentration of polysulfides.
Therefore, the concentration of lithium polysulfide can be increased by adjusting the orbital occupancy of the catalyst, which in turn improves the SRR reaction kinetics.
Taking advantage of the kinetic trends established in this project, the team designed a nanocomposite CoZn/carbon catalyst and used it in the cathode of lithium-sulfur batteries.
At this time, under the conditions of high sulfur surface load (5mgcm-2), poor electrolyte (E/S=4.8), high current density (8.0C), etc., the lithium-sulfur battery achieves stable cycling, with a power density of up to 26120W kgS-1, which allows the lithium-sulfur battery to complete charging and discharging within 5 minutes.
Overall, this work proposes a novel concept that enables both in-depth mechanistic analysis and extremely excellent electrochemical performance.
It is expected that the high-power lithium-sulfur battery created this time will have broad application prospects in portable electronic products and grid energy storage systems.
Specifically, it can be used in a variety of devices, such as mobile phones, laptops, electric vehicles, large-scale power stations, etc.
Due to the high power of this lithium-sulfur battery, it is ideal for fast charging and discharging. For example, when the phone is out of battery, use this lithium-sulfur battery to fully charge the phone in a few minutes.
Another example is when an electric car is running out of power, you can drive the car into a charging station. At this point, the charging station can fully charge an electric vehicle equipped with this lithium-sulfur battery in a matter of minutes.
In general, the fast charging and discharging characteristics of this lithium-sulfur battery will greatly facilitate the daily life of human beings.
In fact, the reason why the relevant papers of this research were published in the large sub-journal Nature is also because it solves a long-standing problem in the field.
Prior to the start of this study, lithium-sulfur batteries had been in development for about 20 years, and they had a high energy density, 2-3 times higher than commercial lithium-ion batteries.
However, the power density of lithium-sulfur batteries is still very low, that is, the charging and discharging speed is very slow. In the 20 years of development of lithium-sulfur batteries, this problem has not been solved.
At present, it still takes several hours for lithium-sulfur batteries to complete charging and discharging, which limits their application in rapid charging and discharging scenarios.
In 2021, Qiao Shizhang began to ask students to study the problem of fast charging of lithium-sulfur batteries, that is, how to improve the power density of batteries.
Since the research group has a deep foundation in catalyst design, they began to think: can catalysts be used to achieve rapid charging and discharging of lithium-sulfur batteries?
Because the root cause: the reason for the slow charging and discharging of lithium-sulfur batteries lies in the slow conversion reaction of sulfur. The essence of the catalyst is that it can reduce the activation energy of the reaction, thereby improving the kinetics of the reaction.
It can be seen that the combination of lithium-sulfur battery and catalyst can effectively solve the bottleneck problem of slow charge-discharge rate of lithium-sulfur battery.
Therefore, they set this goal: to use catalysts to achieve rapid charging and discharging of lithium-sulfur batteries.
The charge-discharge rate of lithium-sulfur batteries is related to the kinetics of sulfur reduction reactions. So the question is: what parameter is the kinetics of the sulfur reduction reaction related to, and how can the kinetics of the sulfur reduction be regulated and optimized?
In order to solve the above problems, it is necessary to establish a kinetic trend of sulfur reduction.
Concentration is the most basic parameter to describe kinetics. However, for sulfur reduction reactions, it was previously difficult to detect the concentration change of lithium polysulfide on the catalyst surface by in-situ monitoring.
After long-term exploration, the team developed a set of in-situ ultraviolet spectroscopy equipment to achieve in-situ monitoring of the concentration of lithium polysulfide on the surface of the catalyst with voltage.
Taking a series of carbon-based transition metal catalysts such as Fe, Co, Ni, Cu, and Zn as examples, they found that the kinetics of the sulfur reduction reaction are related to the concentration of lithium polysulfide on the catalyst surface, that is, the kinetics will increase with the increase of lithium polysulfide concentration.
This means that the kinetics of the sulfur reduction reaction need to be accelerated by increasing the concentration of lithium polysulfide on the catalyst surface.
So, what are the properties of the catalyst that determine the concentration of lithium polysulfide, and what kind of catalyst is the most effective to design?
Through theoretical calculations combined with synchrotron radiation, the research group verified this law from both theoretical and experimental aspects: that is, the electron occupancy of the antibond orbital of the catalyst determines the concentration of lithium polysulfide on the catalyst surface. However, the EG/T2G values of different catalyst electron orbitals are linearly correlated with the concentration of lithium polysulfide.
To this end, they designed nanocomposite CoZn/carbon catalysts with higher eg/t2g values and higher lithium polysulfide concentrations. As a bimetallic catalyst, its SRR performance is significantly better than that of other monometallic catalysts.
When used in lithium-sulfur batteries, the power density of the battery is greatly improved, so that it can complete rapid charging and discharging under the premise of high sulfur load and poor electrolyte.
（来源：Nature Nanotechnology）
最终，相关论文以《通过过渡金属/碳纳米复合电催化剂工程开发大功率电池》（Developing high-power Li||S batteries via transition metal/carbon nanocomposite electrocatalyst engineering）为题发在 Nature Nanotechnology（IF 38.3）。
Huan Li is the first author, and Shizhang Qiao serves as the corresponding author[1].
图 | 相关论文（来源：Nature Nanotechnology）
It is also reported that the research of the research group is mainly based on "new materials", "new reactions", "new methods" and "new mechanisms".
In each study, Qiao Shizhang will guide the students in the macro direction. When students work on a specific topic, they ask, "What are the innovations and highlights of your topic, how is your work different from the work reported before, and what is the significance of your work for practical application?"
"Generally speaking, our team's work is mainly based on the word 'new', striving to innovate the previous research, do something different, and make the reader's eyes shine, while taking into account the performance improvement and realize the move to practical application. Qiao Shizhang said.
（来源：Nature Nanotechnology）
In fact, the team has also opened up many other directions in battery research, such as aqueous batteries, solid-state batteries, metal-sulfur batteries, and battery recycling.
Qiao Shizhang said that he believes that the fast charging concept and method proposed in this work can also be applied to other battery systems, and the team is also conducting relevant research.
In addition, the research group is also conducting relevant research on the design of high-safety aqueous batteries, the development of electrolytes in solid-state batteries, the recycling of electrode materials for lithium-ion batteries, and the metal-sulfur batteries with high energy density and fast charging.
In addition to battery-related research, the team has done a lot of research work in electrocatalysis, photocatalysis, and theoretical computation and machine learning.
"Our overall thinking is based on an innovative topic, combined with cutting-edge characterization methods, such as synchrotron radiation, in-situ spectroscopy, theoretical calculations and machine learning, to develop new materials and reactions, propose new methods, and explore new mechanisms of chemical reactions," Qiao said. ”
With many years of experience in the field of electrocatalysis, they have proposed E-Refinery, Correlated Single-atom Catalyst, the influence of local environment on catalysis, and Direct Seawater Electrocatalysis for Hydrogen production) and other new concepts are believed to bring certain guiding significance to the storage and conversion of electrochemical energy.
Resources:
1.Li， H.， Meng， R.， Ye， C.et al. Developing high-power Li||S batteries via transition metal/carbon nanocomposite electrocatalyst engineering. Nat. Nanotechnol. (2024). https://doi.org/10.1038/s41565-024-01614-4
Operation/Typesetting: He Chenlong
Support: Zou Mingzhi, Dayi (chronological)