Rapid social development and economic growth have been achieved by utilizing fossil fuel-based energy sources. However, fossil fuels are not sustainable, causing numerous environmental problems. Many researchers have put a lot of effort into realizing new ideas on how to develop renewable energy resources, such as wind, water, or sun, in the most efficient way, without incurrence of further ecological catastrophes. Nevertheless, since most renewable energy sources are intermittent, an Energy Storage System is necessary at any cost to store renewable energy sources with the changing power.
For the last 25 years, Li-ion rechargeable batteries (LIBs) have been most widely used as a secondary battery for energy storage, whose technological growth has also been very rapidly accomplished. As the LIBs have no higher voltage, higher energy density, and memory effects, compared to other secondary batteries and do have a long cycle life, a good conservative property, a high power output, they have been utilized as a power source for mobile electronic devices, such as mobile phones, laptops, camcorders, and power tools; in recent years, now that greenhouse gas (GHG) regulations have been globally introduced according to the climate change, the usage range has been expanding into the use for energy storage, such as electric vehicles (xEV) and ESS (energy storage system). Currently, the LIBs, which are applied as a secondary battery for electric vehicles, reveals the mileage limit due to their physical limit (maximum energy density: up to 250 Wh/kg) (Figure 1.1); in order to materialized an electric vehicle which has the mileage level similar to that of gasoline vehicles, it should be necessary to develop a next generation secondary battery having an energy density higher than that of LIBs. Furthermore, it is time to develop a next-generation secondary battery that meets the demands for the safety improvement of secondary batteries due to the increase of the energy density of the secondary battery system and for price reductions on the secondary battery system which accounts for more than half of the total price of an electric vehicle.
The Lithium-Sulfur (Li-S) secondary battery is a battery made up by utilizing sulfur as a cathode material and lithium metal as an anode material, and is a secondary battery as well with the properties of lower prices and higher energy density, where the oxidation reaction of lithium may occur in the lithium metal of an anode and the reduction reaction of sulfur in a cathode, when discharging. The Li-S secondary battery expresses a high value (500 Wh/kg or more) in the theoretical energy density, which is corresponding to about two times of the LIBs; is enabled for the high power output; and could make the mileage more than doubled compared to the conventional LIBs, when applied to electric vehicles, due to its excellent low temperature property (maintaining the capacity of up to 50% even at -70℃) (Figure 1.2). Unlike the LIBs, because domestic supply and demand for cathode materials is enabled and the price is lowered, the production cost of a battery could be reduced. According to the reports by McKinsey and Lawrence Berkeley National Laboratory (LBNL) in 2012, they suggested that the Li-S secondary battery Sulfur rechargeable batteries are the most promising as energy storage media capable of achieving $65/kWh of a raw material charge, based on 100,000 electric vehicles (Figure 1.3). In addition, as sulfur, the main material of Li-S secondary batteries, has an abundant yield and could be acquired from by-products or wastes in the oil refining process, it is easy to secure the materials for it; moreover, since it is nontoxic and eco-friendly, it has surly the limelight as a next-generation secondary battery. Therefore, it is expected that if Li-S secondary batteries are developed and applied to the energy storage system and medium- or large-sized secondary batteries for electric vehicles, they could lead the structure of market competition and play a greater role in selecting the next generation energy technologies, based on such technologies.
This report would provide a comprehensive description on the development of Li-S rechargeable batteries, including major historical advances, related technical hurdles, and component/material developments. Furthermore, it also focused on the latest emergence of cell configurations that might promise to make a leap of the research of Li-S secondary batteries. In addition to it, the advanced characterization technologies have also been introduced to better understand the chemistry-related mechanisms of Li-S secondary batteries.
The Strong Points in this report are as follows:
① Conceptual organization and historical development trend of Li-S Batteries
② Understanding the current status of technical hurdles and component/material developments on Li-S batteries
③ The latest advent trends for the development material composition of Li-S battery cells
④ Presenting application cases of Li-S batteries by major companies
⑤ Introduction of technologies and patents related to Li-S batteries
Contents
1. Outline of Li-S Secondary Battery
1-1. Need for Li-S Secondary Battery
1-2. History of Li-S Secondary Battery
1-3. Principle of Li-S Secondary Battery
1-4. Technical Issues of Li-S Secondary Battery
2. Status of Technical Development on Sulfur Cathode for Li-S Secondary Battery
2-1. Conventional Sulfur Complex Electrode
2-2. Sulfur-Porous Carbon Complex Material
2-3. Sulfur-Graphene Complex Material
2-4. Binder-Free Sulfur-Carbon Complex Electrode
2-5. Sulfur-Polymer Complex Material
2-6. Sulfur-Metal Oxide/Chalcogenide Complex Material
3. Status of Technology Development of Lithium Sulfide (Li2S) Cathode for Li-S Secondary Battery
3-1. Activation of Micronized Li2S Particles
3-2. Li2S-Carbon Complex
3-3. Chemical Synthesis of Li2S Cathode Material
3-4. Li2S Cathode-applied Entire Solid-State Secondary Battery
4. Development Status of Electrolyte and Membrane Technology for Li-S Secondary Battery
4-1. Liquid Electrolyte
4-2. Carbonate-based Electrolyte
4-3. Polymer/Solid Electrolyte
4-4. Membrane
5. Status of Anode Technology Development for Li-S secondary battery
5-1. Lithium Metal Anode
5-2. Silicon Anode
5-3. Carbon Anode
6. Status of Technology Development of Binder for Li-S Secondary Battery
7. Composition of Li-S Secondary Battery Cell
7-1. Medium Layer
7-2. Porous Collector
7-3. Sandwich Electrode
7-4. Dissolved Polysulfide Catholyte
8. Voltage Window of Li-S Secondary Battery
8-1. Upper Voltage Flat-Part
8-2. Lower Voltage Flat-Part
9. Analysis Technology and Mechanistic Understanding for Li-S secondary battery
9-1. In-Situ Analysis
9-2. Dissolution of Polysulfide
9-3. Formation of Protective Layer
9-4. Kinetics
10. Status of Developers for Li-S Secondary Battery
10-1. Status of Major Developers
10-2. Status of Major Patent Application
11. Conclusion and Future Direction of Technology Development for Li-S Secondary Battery
12. Reference