Summary of the latest research progress of sodium ion battery and lithium sulfur battery

This summary will bring you the latest research progress on recent sodium-ion batteries and lithium-sulfur batteries.

1. Angew. Chem. Int. Ed.: Singlet oxygen in an aprotic sodium-oxygen battery cycle

An aprotic sodium-oxygen battery requires reversible formation/dissolution of sodium superoxide (NaO2) during the cycle. The poor cycle life associated with incidental chemistry is due to the reaction of the electrolyte and the electrode with NaO2 (strong nucleophile and base). However, its reactivity cannot explain both side reactions and irreversibility. Recently, Dr. Stefan A. Freunberger (Corresponding author) of the Technical University of Graz, Austria, confirmed that singlet oxygen (1O2) is formed at all stages of the cycle and is the main driving force for incidental chemistry. In situ or ex situ detection is achieved by rapid selective formation of a stable adduct with a capture agent and 1O2. The 1O2 formation includes proton-mediated superoxide disproportionation during discharge, pause, charge below 3.3 V, and direct electrochemical generation of about 0.1 V to 1O2. Trace water required for high capacity is also a driving force with chemistry. Controlling high activity singlet oxygen is therefore the key to highly reversible battery operation.

2. Angew. Chem. Int. Ed.: Ultra-high capacity room temperature sodium ion battery organic thiocarboxylate electrode

Organic battery electrodes are expected to replace traditional metal oxide electrode materials because of their low cost, no heavy metal and easy-adjusting structure. Carboxylates and carbonyl compounds have been widely studied as organic room temperature sodium battery electrodes. Professor Du Yaping and Prof. He Gang (co-author of Xi'an Jiaotong University), for the first time, gradually replaced the oxygen atom of the carboxyl group in sodium terephthalate with a sulfur atom and used it as a sodium ion battery electrode to improve the electron delocalization, conductivity and sodium absorption capacity. . The above general strategy based on molecular engineering greatly enhances the specific capacity of organic electrodes having the same carbon skeleton. After introducing two sulfur atoms into the carboxylate skeleton, the reversible capacity of the molecular solid at a current density of 50 mA·g-1 reached 466 mAh·g-1. After the introduction of four sulfur atoms, the capacity increased to 567 mAh·g-1 at a current density of 50 mA·g-1, which is the highest capacity of the anode of the organic sodium ion battery.

3. Nano Energy: The Reaction Mechanism of SnF2@C Nanocomposites as Anode Materials for High Capacity Sodium Ion Batteries

As a rechargeable battery anode with a very high theoretical energy storage capacity, tin-based materials have attracted the attention of many researchers. Professor Kyung Yoon Chung (communication author) of Korea Science and Technology Research Institute prepared a nanocomposite based on SnF2 and acetylene black, and used it as a high performance sodium ion battery anode material to study its electrochemical performance and related storage. Energy mechanism. Compared with the reversible capacity of micron-sized pure SnF2 electrode (323 mAh·g-1), the reversible capacity of the nanocomposite electrode (563 mAh·g-1) is greatly improved. The nanocomposite electrode exhibits superior rate performance, and the reversible capacity can reach 191 mAh·g-1 at a high current density of 1 C, while the pure electrode capacity is low. The change in crystal structure was observed by in-situ XRD, and the results showed that there were two or more solid solutions in the charge/discharge process.

4. Nano Energy: In Situ Electron Microscopy Observation of Electrochemical Sodium Plating/Deplating Mechanism on Carbon Nanotube Current Collectors

As a final anode of a high energy density battery system having a sodium broad prospects for the use of sodium metal. Recently, for the relevant rational design cycle no branches sodium crystals deposited nano-dimensional current collector made some progress. However, in the key information into the body of sodium nucleation and growth behavior is still a mystery. Recently, Xiamen University professor Wang Mingsheng (corresponding author), etc. using amorphous carbon nanofiber (CNF) as a current collector, the first observation of the sodium plating / stripping dynamics at the nanoscale by in situ electron microscopy. Using solid electrolytes, the authors found that sodium metal reversibly grows and dissolves in all possible regions (even in its network) around a single CNF in the form of nanoparticles/microparticles. It is worth noting that experiments have confirmed the transport of sodium ions in the fibers, allowing more sodium to deposit uniformly inside the network without contacting the electrolyte; this is the key to electroless sodium plating, especially in all solid sodium batteries. In addition, combined with intensive in situ experimental design, CNF exhibits superior sodium capacity compared to graphitized carbon.

5. Nat. Commun. : Application of hydrogenated graphene as a carbon-rich flexible electrode in lithium and sodium

Since the first report by Williams et al in 1969, organic electrode materials have attracted the interest of many scientists due to their design diversity, flexibility, low cost and environmental friendliness. Crosslinked carbon-rich or all-carbon frameworks have exceptional thermal/chemical stability, good electrical conductivity, high strength, and unusual mechanical properties such as strong shear deformation. These superior properties make it ideal for lithium ion batteries (LIBs) and sodium ion batteries (SIBs). Recently, Li Yuliang, a researcher at the Institute of Chemistry of the Chinese Academy of Sciences, and a researcher at the Institute of Bioenergy and Processes of the Chinese Academy of Sciences, Huang Changshui (co-communication author), etc., focused on improving the conductivity, capacity, and molecular design of good bulk ion transport by in situ on copper foil. ethynylbenzene three framework carbon hydrogen-rich substituted alkynyl graphite (HsGDY) thin films cross-coupling reaction. The above organic film can be used as a flexible electrode independent of lithium ion and sodium ion batteries, the reversible capacity of the lithium ion battery can reach 1050 mAh·g-1, and the sodium ion battery can be 650 mAh·g-1. The electrodes also exhibit superior rate and cycle performance due to their extended π-conjugated system and high surface area stratified pores.

6. ACS Nano: Honeycomb Co@NC composite for high sulfur loading lithium-sulfur batteries

Lithium-sulfur batteries are expected to be an alternative to lithium-ion batteries due to their high theoretical capacity (1675 mAh·g-1), high energy density (2600 Wh·kg-1), abundant reserves, low cost and environmental friendliness. In order to realize the commercial application of high energy density lithium-sulfur batteries, in addition to increasing the sulfur content (HSC) of the composite positive electrode material, the sulfur loading (HSL) of the sulfur composite electrode is also increased. Professor Dong Quanfeng and Associate Professor Zheng Mingsen (co-communication author) of Xiamen University, based on the previous research work, constructed a new type of quasi-two-dimensional porous honeycomb Co@NC material as a lithium-sulfur battery by using the method of bionics. Contains a sulfur matrix. Scientific research has found that the honeycomb structure has the highest density, the largest available space, and the least amount of materials required. Such a special structure is used as a skeleton material for lithium-sulfur batteries, which not only allows a single surface with a high specific surface area. The honeycomb is high in content of sulfur (93.6 wt%), and it can also achieve high sulfur loading (7.5 mg·cm -2 ) through the ordered packing of multilayer honeycomb sheets while maintaining the "double" of Co-N. Catalytic and multifunctional functions have achieved excellent electrochemical performance.

7. Nano Energy: Alkenyl radicals are covalently linked to sulfur to reduce the solubility of lithium polysulfide in high-capacity lithium-sulfur batteries with high coulombic efficiency

Long-chain lithium polysulfide dissolved in a lithium-sulfur battery ether-based electrolyte is one of the reasons for low coulombic efficiency and specific capacity. Prof. Cheng Chenglin (corresponding author) of Suzhou University reported a new strategy for stabilizing sulfur cathodes, namely sulfur and alkenyl radicals covalently linked to form low solubility lithium polysulfide. The coulombic efficiency is not low at 0.2-6 C. At 99.9%, the capacity at 6 C is as high as 702 mAh·g-1. The in-situ UV/vis spectroscopy was used to determine the possible mechanism, and it was proved that the short-chain polysulfide with lower solubility was mainly produced during charge and discharge. In addition, according to the DFT calculation, it is confirmed that the breaking bond of the linear sulfur chain preferentially occurs at the center of the linear sulfane to form a short-chain polysulfide, which can effectively avoid the generation of soluble long-chain polysulfide and inhibit the shuttle effect, and is beneficial to the improvement of the lithium-sulfur battery. Coulomb efficiency and rate capacity.

8. Nano Energy: High-sulfur single-walled carbon nanotube network in high-performance lithium-sulfur batteries

Lithium-sulfur batteries (Li-S) are the most promising alternatives for next-generation energy storage systems. However, limited sulfur content and sulfur loading in the cathode region result in lower regional capacity, even better than the most advanced lithium-ion batteries , which greatly offsets the high-energy advantages of Li-S batteries, further hindering their practical application. Recently, researchers and CAS metal Li Feng Liu Chang researchers (co-author) show like electronic conductivity efficiency theoretically sulfur body for sulfur nanomaterial has a vital role, and build efficient single wall carbon nanotubes (SWCNT Conductive network for proof-of-concept studies with sulfur content up to 95 wt%. Interwoven SWCNTs not only provide abundant electron and lithium ion transport pathways, but also promote the capture of polysulfides during sulfur conversion reactions. Therefore, the lithium-sulfur battery has a high regional capacity (8.63 mAh·cm-2) and a high regional sulfur loading (7.2 mg·cm-2), which is much higher than that of a lithium ion battery (4 mAh·cm-2). . The above method provides a new design concept for the electrode material of the high energy density lithium sulfur battery, and can be extended to other electrochemical energy storage systems.

9. Nano Lett.: Preparation of S-GO-CNT nanocomposites by freeze-drying and their high sulfur loading properties

Lithium/sulfur (Li/S) cells at room temperature are among the best in energy storage devices, but some of the drawbacks of the sulfur electrode itself have largely limited its electrochemical applications. In recent years, some of the sulfur-based active materials studied in the laboratory have tried to overcome the shortcomings of the sulfur electrode through reasonable structural design and exhibited excellent electrochemical performance. Professor Elton J. Cairns of the University of California, Berkeley (corresponding author) reported a new type of sulfur electrode material - cetyltrimethylammonium bromide-sulfur modified-graphene oxide-carbon nanotube complex (S -GO-CTA-CNT). Theoretical calculations show that when the mass ratio of electrolyte to sulfur (E/S) is small and the sulfur loading is 6 mg·cm -2 or higher, the energy density of the battery is expected to reach 300 Wh·kg -1 . Tests have shown that the aluminum foam electrode exhibits a high specific capacity between 900 and 1000 mAh/gS in 80-150 cycles. For high-sulfur-loaded electrodes (11.5 mgS·cm-2), a large amount of electrode material was successfully accommodated in a foamed aluminum substrate, showing a high specific capacity of 900-1178 mAh/gS, and excellent cycle performance at high and low current densities. .