HMSC lithium sulfur full-cell performance: (a) lithium thio buckle battery (6.9mgcm-2S + 6.8mgcm-2mo6s8, electrolyte active substance ratio ~ 1.
5μlmg-1); (b) lithium sulfur soft bag full battery (electrolysis Liquid active material ratio ~ 1.2 μlmg-1, ~ 2 times metal lithium excessive); (c) Comparison of energy density of lithium sulfur battery full battery. Note: Figure C is the energy density of the buckle battery experiment parameters and the real energy density of the security-level soft bag full battery.
. Lithium sulfur batteries are considered one of the ideal choices of the next generation of high-energy density battery systems, and are highly concerned by the world’s scientific research and industry, is also one of the key research directions of future countries..
However, as the research continues to deepen, lithium sulfur batteries are also facing increasingly severe challenges.. The current important issue is that the volumetric energy density of lithium sulfur batteries is low, which leads to the loss of competitiveness in many important market applications, and the high electrolytic solution has also become a bottleneck with its weight.
. Sony Shan, Associate Researcher, Department of Clean Energy, Department of Cleaning Energy, Department of Cleaning Energy, Department of Cleaning Energy, Department of Cleaning Energy, Department of Cleaning Energy, Professor Li Ju, and Dr. Xue Weizheng, a Professor of MIT, and the solution to the solvement of common problems in lithium sulfur batteries.
New ideas, supply new possibilities for the future development of new high-energy density lithium sulfur batteries. Related research results are published in “Nature – Energy”. The size and weight of the energy density limit Lithium sulfur battery development Shan Min said to the “my country Science News” said that the next generation of high-energy density battery systems is important based on the battery system of metal lithium negative electrode, such as lithium sulfur, lithium-empty battery, etc.
. “Compared to lithium sulfur batteries, although the lithium-empty battery has a higher theoretical energy density, it is still in the basic research stage, many key issues have not been well resolved..
The lithium sulfur battery has advantages such as low cost, high energy density. After years of unremitting efforts, lithium sulfur battery technology has become increasingly mature, close to commercialization. “The results of the Papers of the University of Canada in 2009 published in” Nature-Materials “have received the reversible capacity of 80% of the theoretical capacity, igniting people’s research passion on lithium sulfur batteries.
. Currently, all countries in the world pay attention to lithium sulfur batteries. Research on basic scientific issues in many universities, research institutes, and many companies, such as Oxis, United States, have been engaged in the commercialization of lithium sulfur batteries.
. Li Ju said that in the past decade, many key technologies in the laboratory include a large breakthrough and progress in the positive and electrolyte, but in how to technically to commercialization from laboratory. It has encountered a large technical bottleneck and barrier, such as highly active material load, electrolyte system, metal lithium negative electrode, and soft bag lithium battery process.
. The current important issue is that the volume of energy is low, leading to its loss of competitiveness in many important market applications, and the high electrolytic solution has also become a bottleneck with its weight of energy density..
In addition, the safety and long cycle life of the metal lithium negative electrode have not been well solved.. Breakthrough in key technical bottlenecks, the cause of lithium sulfur battery is low in size: from the intrinsicity, theoretical density of lithium and sulfur in active material is relatively low, 0.
534 g / cm3, sulfur 2.07 g / cm3 And the theoretical density of lithium cobaltate and three yuan in the lithium-ion battery is much higher; from the electrode structure, there is a most important reason is that sulfur is electron and ion insulator, so dispersion of sulfur to a large amount. The high-specific surface area can only exert its capacity, and the problem brought by using a large amount of conductive carbon is that the entire positive electrode has a high specific surface area, high porosity is high, and the porosity of conventional carbon sulfur positivity is a lithium ion battery.
Twice the positive. Therefore, the key technical bottleneck is currently constrained in high active material load conditions, high electrode density and low non-active material content under high active substance load conditions..
For problems with high energy density of the battery device, the research team innovates the use of high electron and ion conductance embedded electrode material MO6S8 substituted into the non-active substance carbon constitutes an embedded-conversion type mixed electrode, so that the sulfur is responsible for high activity Under conditions of material load (greater than 10 mg / cm2), carbon content is reduced to less than 10% by weight, and the electrolyte active material is reduced to 1.2 μl mg-1, and the electrode porosity is less than 55%..
An hourly soft bag with this new type of mixed electrode can greatly improve the single energy density in the condition of ensuring the life of the cycle, high volume energy density (581WH / L) and weight energy density (366Wh / kg) can be achieved at the same time. For future development of new high-energy density lithium sulfur batteries, a new solution and practical commercial technology method is supplied..
According to the introduction, the comparison and theoretical estimation of lithium ion batteries, such as lithium ion batteries, the study team believes that the amount of carbon content in the positive material of the sulfur positive material is the root cause of lithium sulfur cell volume and the root cause of the electrolyte infiltration.. Therefore, there is an idea of replacing non-active conductive carbon with an electrochemically active substance.
. At the same time, alternative materials must also meet the following conditions: first high-electron and ion conductance – the use of carbon; second and lithium sulfur electrolyte compatible, can stabilize the capacity in the lithium sulfur battery voltage section – improve the overall Energy output; and high theoretical density – replace the higher electrode density after rendering of carbon; re-and polyulfide lithium has strong adsorption applications, can alleviate the “shuttle effect” of lithium sulfur batteries. “After the above screening principles, we have selected the CHEVREL phase MO6S8 in many materials to constitute a mixed electrode.
. Previous studies have tried to use TIS2 or other sulfides with capacity contribution to the positive electrode as a sulfide. However, the previous research did not seize the key to the conductive carbon content, only staying on the problem of the ‘shuttle effect’, very few studies can do high-energy density under harsh conditions of the whole battery.
. “Su Shanyi explained. The integrated energy density improves Xue Weizheng, the longest spending time is the preparation of the material and the optimization of battery performance.
Since the carbon content is lowered to 10%, how to ensure that the sulfur capacity of such low carbon content is a major challenge. At the same time, the optimization of battery performance is a system engineering. It is only possible to optimize the positive electrode.
At the same time, there is still a lot of work in electrolyte and lithium negative matches, which takes a total of approximately one year to solve these problems.. Previously, the energy density of all-batteries, especially volume energy density.
The weight energy density of the lithium sulfur-sulfur-sulfur lithium battery of the United Kingdom can reach 400Wh / kg, but the volumetric energy density is only 300Wh / L. At present, commercial lithium ion battery energy density is 260Wh / kg and 700Wh / L. The study soft bag lithium battery volume energy density (581WH / L) and weight energy density (366Wh / kg) have surpassed the above two battery systems in integrated energy density.
. The team said that the future will continue to optimize the material preparation and soft bag lithium battery assembly process, and combine new research results in the lithium negative electrode and electrolyte to seek commercialization..
In the subsequent study, it will continue to enrich the research system along the idea, and focus on solving the last obstacles for commercialization of lithium sulfur batteries – the problems in metal lithium negative poles. .