Advanced Lithium Sulfur Batteries

Advanced Lithium Sulfur Batteries

Research Team Led by Associate Professor Sheng-Heng Chong

Department of Materials Science and Engineering, National Cheng Kung University

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Since their advent in 1990, first and second generation lithium ion battery technology has effectively realized long life cycle, rechargeable batteries through the intercalation reaction, which enables the reversible filling and releasing of lithium ions between layered oxide positive electrodes and graphite negative electrodes. This technology enables lithium ion batteries to achieve an energy density of 100-350 W·h Kg-1, which is much higher than that of other commercial rechargeable batteries, and maintain extremely high, long cycle capacity during battery use, reaching 1,000+ cycles. Furthermore, when these batteries are at rest, they exhibit an extremely low self discharge effect of less than 5% a month [1-3]. Due to the lithium ion battery’s high energy density, which far exceeded that of other rechargeable batteries of its time, as well as its long cycle life and shelf life. Lithium ion batteries will be the main force in the rapidly growing energy storage market in the next 30 years, and continued research and improvement have pushed the energy storage capacity of the corresponding electrode active materials very close to the theoretical limit of 200-300 mA·h g-1. As such, this ongoing optimization of this technology and its advantages is approaching the insurmountable theoretical energy density threshold limit. In addition, when it comes to component costs, the cost of cathode materials accounts for the largest proportion in batteries and is continuing to rise, simultaneously driving up the overall material and manufacturing costs of lithium ion batteries [4,5]. Faced with the dual pressures of performance limitations and rising costs, the energy density growth rate of the lithium ion battery market has dropped from 7% a year to a mere 2%. The popularity of this research proves that further improving the performance and reducing the cost of lithium ion batteries will be the key to achieving sustainable development and meeting the ever growing demands of the energy storage market [1-6].

In order to realize the key developments needed by energy storage technology, the energy storage market and next generation battery modules can be expected to develop mainly in the following two directions. Electrochemical cells will be developed based on the reaction mechanism of batteries. The plan is to use the electrochemical conversion reactions of these cells，to fully convert material chemical energy into electrical energy while simultaneously achieving highly reversible energy storage and discharge. By carefully selecting the active materials for electrochemical reactions, we can also achieve higher capacities and better capacity utilization, endowing batteries with excellent energy densities and making them more competitive in the market. In terms of battery composition, the research and development of solid electrolytes will likely be actively promoted. By making the most of their excellent mechanical, physical and electrochemical stability, we can achieve highly stable physical and chemical battery reactions that are both safe and have long-term electrochemical stability. These are the two main directions of development for next generation battery modules. The key is to realize rechargeable batteries with high energy densities by improving their energy storage capacity and stability through various means, thereby achieving new generation batteries with energy densities of as high as 300-500 W·h Kg-1 and 700-800 W·h L-1 [4-9]. These batteries will enable electric vehicles to exceed the driving range of conventional gasoline and diesel vehicles for the first time. At the same time, they are expected to reduce the cost of battery cores.

Derived from the lithium ion insertion and release reaction proposed by Stanley Whittingham, lithium ion batteries have high energy densities and excellent cycle and self discharge stability. The reaction allows lithium ions in the circuit to move quickly through the electrolyte. This allows the external electrons to be charged and discharged quickly. The lithium ions in the internal circuit can also be stably stored in the layered channel structures of the electrode’s active material, and the corresponding external electrons can achieve a low self discharge. Structural design is then used to achieve large capacity storage. By combining the positive electrode active material developed by John Goodenough and the carbon-containing negative electrode material developed by Akira Yoshino, a system can be created that suppresses the potential instability issues associated with lithium dendrite growth, thus successfully overcoming the safety concerns that arose in early commercial lithium ion batteries due to the use of lithium metal negative electrodes [1-6].   The energy storage and discharge functions of lithium ion batteries are based on the redox reactions of intercalation electrodes. When charging, an external system provides energy to drive the flow of electrons from the positive electrode to the negative electrode. This causes lithium ions to migrate from the positive electrode to the negative electrode to compensate for the difference in charge. It also completes the storage of lithium ions in the carbon negative electrode and the overall energy storage of the battery. When discharging, the working potential difference of an external device is used to drive the flow of electrons. This then drives the lithium ions inside the battery away from their temporary storage in the negative electrode and back into the crystal structure of the active material in the positive electrode from which they originated. This process is accompanied by the release of energy (as shown in Figure 1) [1-3].

Figure 1. Schematic Diagram of a Lithium Ion Battery and the Redox Reactions of its Intercalation Electrodes During Storage and Discharge

The basic structure of the lithium ion battery is comprised of two electrodes, one positive and one negative, with a separator soaked in electrolyte in between. In theory, existing commercial positive and negative electrodes are composed of corresponding active substances, conductive materials and polymer binders attached to a metal current collector. The positive and negative electrode active materials are responsible for the two key performance factors: high capacity stability and efficient, reversible charge and discharge. The positive electrode’s active material is the main supplier of lithium ions and requires a high standard redox potential. Common materials chosen include metal oxides, such as the high performance LiCoO₂, high potential LiMnO₂, LiFePO₄, and high energy density LiNi_xMn_yCo_zO₂, etc.. The positive electrode’s high potential is maintained by the interaction between the oxygen atoms and the transition metals [3-5]. The negative electrode active material must have a high lithium ion storage capacity and a low standard redox potential. With these parameters in mind, they are matched with the positive electrode to achieve a high working voltage difference and realize a high energy density. Common negative electrode materials include carbon-based and silicon-based materials and their derivatives. Conductive materials are added to increase the electrodes’ overall conductivity and reduce ohmic polarization to achieve high electrochemical utilization and high speed charging and discharging. Adhesives are added to connect conductive materials and build conductive pathways, which are wrapped around a relatively nonconductive active material and then attached to a metal current collector, ensuring electrode structure consistency and conductive network integrity. Current collectors are made from sheets of differing metals based on their positive and negative electrode characteristics. As the electrode substrate, the current collector contributes to the stability of battery conductivity and potential. The separator is a porous polymer film placed between the two electrodes to prevent physical contact, thereby preventing short circuits. It can also slightly block the rapid penetration of lithium dendrites. The porous separator must be fully soaked in electrolyte to maintain lithium ion conduction and ionic conductivity within the battery circuit. Common lithium ion battery separators are mostly comprised of polyethylene, polypropylene and polyvinylidene fluoride, etc.. The lithium salt-containing electrolytes are absorbed by cyclic and chain carbonates [1-6].

Electrochemical lithium sulfur batteries were first developed in 2009 by Linda Zazar using porous carbon as the substrate for positive electrode active materials. In 2014, Arumugam Manthiram introduced the use of porous carbon as an actual battery component. Both the practicality and stability of these batteries’ energy storage functions have since improved. It has become the main driving force in the research and development of next generation commercial lithium ion batteries and maintaining their market advantage. Lithium sulfur batteries can employ battery configurations similar to that of lithium ion batteries using low-cost sulfur, with its high theoretical capacity of 1675 mA·h g^-1, for positive electrochemical electrodes. This is the highest capacitance among existing solid state electrodes. Assisted by a lithium metal negative electrode, which has the lowest standard redox potential, the electrochemical lithium sulfur battery can achieve an outstanding theoretical energy density of 2600 W·h Kg^-1. According to their basic electrochemical characteristics, lithium sulfur batteries can potentially be made from highly abundant, low cost and low toxicity active substances and achieve high specific energy densities of 300-500 W·h Kg^-1 and 700W·h L^-1[8,10-14].

The remarkable properties of lithium sulfur batteries are based on their unique conversion-type electrode redox reaction. When discharging, the sulfur cathode reacts chemically with the lithium ions in the electrolyte to form lithium sulfide. The reaction involves the conversion of two lithium ions and is equivalent to the transfer of two electrons in  an external circuit. With the low atomic weight of sulfur, it is possible to achieve a tenfold increase in electrode discharge capacity. In addition, the conversion battery reaction of the sulfur electrode is not restricted by the oxide structure in the positive electrode active material of current lithium ion batteries. It is thus able to realize full electrochemical utilization and complete reversible reactions. During the power storage process, the lithium sulfur battery can be charged by an external system to oxidize the lithium sulfide into sulfur as two lithium ions and two electrons return to the negative electrode through the internal and external circuits respectively (as shown in Figure 2) [10-12].

The basic components of lithium sulfur batteries are the same as that of commercial lithium ion batteries. Both conform to the basic voltaic battery discharging and electrolytic battery charging structures. The battery is comprised of two electrodes, positive and negative, and a separator immersed in electrolyte. However, the conversion reaction of lithium sulfur batteries and the physicochemical characteristics and redox reaction of its sulfur electrode are very unique (as shown in Figure 3) [10-12]. Although the sulfur cathode of the lithium sulfur battery has the highest theoretical capacity among solid electrode active materials, it also has an extremely high electrical resistance of 10⁻³⁰ S cm⁻¹. This results in low electrochemical utilization of the active material and low reversible capacity during the cycle (as shown in Figure 3a). When the solid sulfur (S₈) in the cathode reacts with the lithium ions in the electrolyte, liquid polysulfides (Li₂S_x，4 ≤ x ≤ 8) are gradually formed. The liquid polysulfides are easily dissolved from the sulfur cathode due to its high solubility in the electrolyte. It then diffuses irreversibly throughout the battery through the electrolyte. Upon spreading to the lithium anode, it contaminates the lithium metal, forming insulating deposits of lithium sulfide. The process of polysulfide formation, dissolution and diffusion and electrode contamination causes irreversible loss of active substances and electrode degradation. This is the main reason behind rapid capacity loss and short cycle life in lithium sulfur batteries (as shown in Figure 3b). Some of the liquid polysulfide remaining in the positive electrode will form solid lithium sulfide as the discharging continues. The resulting insulating substance produced also has a low conductivity of 10⁻¹⁴ S cm⁻¹, resulting in a high internal resistance that causes the charging reaction to face severe polarization and limiting its reversible charging reaction (as shown in Figure 3c). During the subsequent charging process, the solid lithium sulfide will be oxidized, forming liquid polysulfide and solid sulfur. However, the liquid polysulfide lost during the charging process will form high-order polysulfide or even sulfur through oxidation during the reaction. The lost liquid polysulfide will also accept lithium ions at the negative lithium metal electrode, undergoing redox and producing low-order polysulfide or lithium sulfide. The conflict between the electrochemical and chemical reactions leads to a low Coulomb Effect, or battery overcharging (as shown in Figure 3d). However, the conversion battery reaction removes the restrictions of the active material structure on the capacity and its utilization rate. As such, active materials are expected to see many structural changes. Considering sulfur has a density of 2.07 g cm^-3 and lithium sulfide has a density of 1.66 g cm^-3, the sulfur in the cathode will see an 80% change in volume during each charge and discharge cycle accompanied by a solid-liquid phase change. These volume and state changes will gradually destroy the electrode structure over the course of repeated cycles, causing cathode failure (as shown in Figure 3) [12-15].

Figure 2. Schematic Diagram of a Lithium Sulfur Battery and its Conversion Electrode Redox Reaction During Energy Storage and Discharge

Figure 3. Redox reactions in lithium sulfur battery conversion electrodes face several potential challenges: (a) solid sulfur has high insulation properties, (b) liquid polysulfides diffuse easily, (c) solid lithium sulfide has high insulation properties, and (d) polysulfide diffusion causes active electrode degradation.

Over the past 10 years of development, electrochemical batteries have seen the introduction of various additives and components one after another. Widely used functional materials include polymers, ceramics and metals in order of the volume of research published. Over the years, several materials have entered and exited the research scope as times and trends in research changed. However, numerous types of materials still rely heavily on carbon substrates for integration with lithium sulfur batteries. When the burgeoning lithium sulfur battery industry entered the energy storage market in 2020, however, it was discovered that its unique battery conversion reaction and the solid-liquid phase change of its positive electrodes were greatly influenced by battery process parameters. The impact was not limited to the simple issues of large-scale and mass production cost differences typical to transitioning from academic research to industrial application. Instead, there were issues rooted in the very fundamentals of battery electrical performance and reaction electrochemistry. Even the research and development findings related to the material limitations of electrochemical lithium sulfur batteries mentioned above only show advantages in terms of data. Most of the actual, practical challenges still need to be overcome [10-19].

A close examination of the electrochemical reaction of lithium sulfur batteries shows that the active materials of the positive electrode has high insulation properties in both the solid sulfur form of the fully charged state and the solid lithium sulfide form of the fully discharged state. To compensate for both the low electrochemical utilization caused by the high resistance of the insulating material and the low electrochemical stability and efficiency caused by the high polarization phenomenon of the reaction process, large amounts of conductive porous carbon and various functional materials are added to the synthesis of the active material composites. They are additionally mixed with large amounts of conductive carbon. As a result, the active material in the electrode that actually participates in the energy storage and discharge reaction has a sulfur content of less than 60 wt%. This leads to a low specific capacity and overestimated battery performance [10-13]. The addition of a large amount of inactive materials, such as porous carbon materials and functional materials, is intended to inhibit the loss of polysulfides through the use of the high specific surface area and large pore volume of aforementioned porous materials and the surface adsorption properties of the functional materials. However, it has been pointed out that this line of research will cause even greater electrolyte consumption by porous carbon and functional materials. This will lead the battery manufacturing process to require the addition of excess electrolytes to keep components adequately soaked. The large amount of surplus electrolyte will be needed to replenish the electrolyte consumed by the adsorbed material and electrode during the reaction process. This results in high electrolyte to sulfur ratios of more than 20 µL mg^-1. An excess of electrolyte leads to low energy densities and overestimated polysulfide stability. It can also cover up the polarization problem and interfere with the reaction kinetic calculation of solid sulfur and lithium sulfide at the beginning of reduction and oxidation reactions. During positive electrode production, most lithium sulfur batteries also use a very low sulfur loading of about 1-2 mg cm^-2 to demonstrate various battery electrochemistry processes and performance. However, the low-sulfur cathode cannot truly reflect the insulation and polarization phenomena brought about by solid sulfur and lithium sulfide. It also cannot truly show the loss of liquid polysulfides or the effectiveness of their retention. In contrast, most lithium sulfur batteries then use excessive amounts of lithium metal electrodes to accommodate the large amounts of electrolyte. This masks the irreversible lithium consumption in the battery due to the conversion battery reaction and the solid-liquid phase change of the positive electrode [8,13-19].

In lieu of the disparity between apparent performance data and actual application value, the research and development direction of next generation lithium sulfur batteries has begun to be revised. The research of advanced lithium sulfur batteries needs to be based on the improvement of basic battery process parameters and strive to present real, useable electrochemical analysis for future reference or further explore battery performance and practicality. The indicators and parameters of advanced lithium sulfur batteries should focus on compliance with technical battery parameters. The greatest priority should be to increase the amount of active substances in the positive electrode and reduce the excess electrolyte and negative electrode materials in the battery, as well as to integrate the various technical battery process parameters into a single battery [8,13-19].

Advanced lithium sulfur batteries were first proposed in 2021, offering significant battery performance improvements that led to the improvement and adjustment of research to be based on industry parameters, thus enabling the acquisition of realistic battery electrochemistry data. The first step is to demonstrate the statistics and performance reliability of the key cathode component of lithium sulfur batteries. In regards to the process technology, it is required that the total active material content and loading of the sulfur cathode reach a minimum of 60-80 wt% sulfur content and 4 mg cm^-2 sulfur loading in order to demonstrate the effectiveness of cathode material or component structure modifications. This is mainly because the thick film of high capacity electrodes can directly reflect the ion transport and diffusion within the electrode as well as the electron transfer impedance, making it possible to study the utilization and reversibility of active substances. High capacity electrodes can also demonstrate the situations that may arise from the occurrence and diffusion of large quantities of polysulfide in real environments during the charging and discharging processes. In addition, because the formation of liquid polysulfides differs from the lithium ion battery reaction, most research tends towards inhibiting its production or production amount. However, liquid polysulfides are necessary intermediate substances for the charge and discharge reactions of lithium sulfur batteries. Therefore, more realistic test conditions are needed to analyze the diffusion and corrosion behavior of polysulfides in batteries. This area of research also needs to consider how to maintain the electrolyte dosage and enable the process technology to attain an electrolyte to sulfur ratio of 5-10 µL mg^-1. Under these conditions, lithium sulfur batteries are a branch of solid state batteries, oligo-electrolyte lithium sulfur batteries, that are mostly semi-dry batteries during the manufacturing process. Because oligo-electrolyte  lithium sulfur batteries can demonstrate a large number of more realistic battery reactions, they have rapidly become a popular area of lithium sulfur battery research that pursues data science authenticity and the correction of outdated information. Its influence has also spread to mainstream journals. More and more of these journals are beginning to require the proposal of a number of battery process technology and industry parameters for use as the basis upon which literature publications are evaluated. Others may adopt these parameters as review criteria in the future [13-20].

The development of oligo-electrolyte lithium sulfur batteries is comparable to that of early lithium sulfur batteries. In the early stages of the research, it is necessary to determine the electrochemical characteristics of high loading sulfur cathodes during the electrolyte reduction process. Then the sulfur content, loading capacity and optimal electrolyte dosage can be gradually balanced based on those electrochemical characteristics [18-21]. In recent years, research has found that cathode composite materials or battery components composed of low specific surface area and highly conductive materials and additives can effectively improve the conductivity of sulfur cathodes while simultaneously reducing electrolyte usage and consumption during the reaction process. This design allows the conductive structure to accommodate a large number of active materials. The cycling capability of the high loading sulfur cathode in oligo-electrolyte lithium sulfur batteries can be maintained through a fast electron transfer network under low electrolyte consumption. Conductive carbon fiber substrates and composite non-porous conductive carbon substrates made via electrospinning can realize high sulfur loading electrodes of 5-20 mg cm-2 which, based on a high sulfur content of about 70 wt%, can demonstrate an electrode specific capacitance of 10 mAh cm-2 and a high energy density of more than 20 mWh cm-2  in a 4-10 µL mg-1 oligo-electrolyte battery. By suppressing the loss of electrolyte, the battery can achieve  a long cycle life of 200 weeks and a long shelf life of more than 3 months (as shown in Figure 4a) [16,17,21]. Subsequent research and development of battery manufacturing processes and cell components have also proposed suitable phase separation membranes, hot pressing processes, selective adsorption, shell core electrodes, combined electrodes and other novel methods for continuing to optimize the characteristics of oligo-electrolyte lithium sulfur batteries [19,22-25].

Figure 4. Schematic Diagram of an Oligo-Electrolyte Lithium Sulfur Battery; (a) Conductive Carbon Substrate and (b) Conductive Metal Coating

On the other hand, when functional adsorbent materials are develop into substrates with low specific areas and limited pores, polysulfides can be captured via surface chemical adsorption, this inhibiting the loss of active substances as well as the addition and consumption of excess electrolyte in oligo-electrolyte batteries. When these materials also have high electrical conductivity, they can enable the trapped polysulfides to continue to react with the lithium ions being conducted stably through the electrolyte and the electrons being transmitted rapidly through the substrate. Through the adsorption of polysulfides by metal atoms and lithium by oxygen atoms, most oxide materials, when polarized, can stably adsorb polysulfides [22,26-28]. Furthermore, in the rare cases where these materials have been successfully developed into conductive metals, such as metal-plated metals and sulfur energy storage materials, they have been able to stabilize polysulfides in composites and maintain stable electron and ion transport, achieving electrodes with the high sulfur loading of 5-20 mg cm^-2 and sulfur contents of 70-75wt%. This results in oligo-electrolyte batteries that demonstrate excellent high energy densities of 10-30 mWh cm^-2 and a long cycle life of 200-500 cycles (as shown in Figure 4b) [18,20,29].

Advanced lithium sulfur batteries can also combine new reaction mechanism and composition structure technologies. For instance, electrochemical lithium sulfur batteries can be combined with solid electrolytes to form solid electrolyte lithium sulfur batteries. This new lithium sulfur battery system uses a solid electrolyte as a key component that can serve as an isolation layer to prevent electronic short circuits. It also acts as an ion channel to stabilize the transfer of lithium ions between the two electrodes and their distribution at electrode interfaces. Therefore, solid electrolytes need to possess high electronic insulation, a high ionic conductivity of ~10⁻⁴ S cm^-1, a high lithium ion transport value close to 1, a low interfacial resistance with positive and negative electrodes and high electrochemical stability [30,31]. Introducing solid electrolytes into the development of lithium sulfur batteries enables the design of solid electrolyte lithium sulfur batteries that can effectively block polysulfide diffusion or inhibit polysulfide formation in all-solid lithium sulfur batteries. However, new research has shown that lithium sulfur batteries using solid electrolytes face challenges in regards to the interface between the electrodes and the electrolyte. At the negative electrode, they have to deal with the low electrochemical stability of and compatibility with lithium metal, which promotes irregular lithium deposition that leads to local stress increases and lithium metal degradation. At the positive electrode, they must contend with the solid-solid interface separation and high interface impedance of the sulfur cathode, which can cause the active material, solid electrolyte and conductive agent to separate permanently during the cycle. This chemical-mechanical failure causes rapid capacity loss and a short cycle life. In this regard, different solid electrolytes have advantages and disadvantages based on their raw materials. This has gradually led to the development of different adaptive optimizations. Common solid electrolytes can be roughly divided into organic polymer solid electrolytes and inorganic oxide and sulfide solid electrolytes [9-11,30,31].

Polymer solid electrolytes are organic solid electrolytes. They often consist of a lithium salt dissolved in a polymer matrix. They have the advantages of being flexible, lightweight, chemically stable and very safe. Moreover, they are easy to prepare and have low manufacturing costs. Polyethylene oxide is one polymer commonly used in polymer solid electrolytes. The lithium ions are generally provided by lithium fluoride salts. The lithium salt is dissolved via –CH₂CH₂O– group polyethylene oxide. Subsequently, the lithium ions are transported via the oxygen provided by the ether groups in the polymer main chain and the formation and breaking of Li-O bonds and segment movements. Another approach is to improve the ionic conductivity of polymer solid electrolytes by incorporating polyacrylonitrile, polyvinylidene fluoride, or polymethyl methacrylate, etc.. Organic solid electrolytes based on polyethylene oxide,  polyacrylonitrile and polymethyl methacrylate can be used to form solid electrolyte gel coatings or textile electrolyte films which can then be combined with polysulfide positive electrodes to form interfaces with low electrochemical impedance. This method can increase the sulfur loading of solid electrolyte lithium sulfur batteries to 4-16 mg cm^-2 and make it possible for the battery to reach 200 cycles and rapid charge and discharge speeds of C/20-1C (as shown in Figure 5a) [32-34].

Oxide solid electrolytes are a branch of inorganic solid electrolytes. Most use structural oxide ceramics such as lithium superionic conductors, calcium titanium, and garnet, etc. to form stable crystal structures and lithium ion transport channels. Lithium superionic conductor electrolytes are based mainly on the Li2+2xZn1−xGeO4 structure. The [Li11Zn(GeO4)4]3- crystal structure network of the ceramic body accommodates 3 lithium ions which can be transmitted through the vacancy channel. Derivative materials, such as Li(4-x)Si(1-x)PxO4 and Li(3+x)GexV(1-x)O4, have demonstrated good ionic conductivity and partially improved material physicochemical stability. The calcium titanium structure electrolyte is comprised mainly of Li3xLa(2/3)-x□(1/3)-2xTiO3. It has a high lithium ion conductivity of 10−3 S cm-1 and the abovementioned electrochemical and physicochemical stability. Subsequent research is focusing on ceramic grain boundary resistance and lithium metal interface stability. Garnet electrolytes are comprised mainly of Li7La3Zr2O12 and Li6.4La3Zr1.4Ta0.6O12 structures, both of which have high lithium ion conductivity, being able to reach 10−4-10-3 S cm-1. Sulfide solid electrolytes are another branch of inorganic solid electrolytes. They can make use of Li10GeP2S12 crystalline sulfide ceramic lithium superionic conductors. The lithium ion channel formed by its crystal vacancies can achieve a conductivity of 10-3-10-2 S cm-1. This type of electrolyte can also be comprised of amorphous sulfur ceramics such as Li2S–SiS2 or Li2S–P2S5, which can also achieve an ionic conductivity of 10-4-10-3 S cm-1. Inorganic solid electrolytes can also be combined with polysulfide cathodes to eliminate excessive solid-solid interface resistance and enable oxide and sulfide solid electrolytes to stabilize the long cycle and rapid charge and discharge capacities of polysulfide cathodes in solid electrolyte lithium sulfur batteries (as shown in Figure 5b and c) [35-37].

Figure 5. Schematic Diagram of a Solid Electrolyte Lithium Sulfur Battery: (a) Polymer, (b) Oxide and (c) Sulfide Solid Electrolyte

The development of lithium sulfur batteries is aimed at breaking through the energy density bottleneck and high cost limitations of existing commercial lithium ion batteries. The research on advanced lithium sulfur batteries corrects the outdated assumption that lithium sulfur batteries should be developed from lithium ion batteries and dispells old misunderstandings about the overestimation of lithium sulfur battery performance. By incorporating the solid electrolytes of the next generation of batteries, the oligo-electrolyte and solid electrolyte batteries of advanced lithium sulfur batteries are revolutionizing the reaction mechanisms of lithium sulfur batteries. High energy density lithium sulfur batteries can be achieved by combining high power, low cost  sulfur electrodes with lithium electrodes. Furthermore, by taking battery process parameters and composition into consideration, advanced lithium sulfur batteries can be made more academically and industrially practical, thus enabling the realization of high energy density batteries with excellent cycle and battery stability.

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