Highly Elastic and Polar Block Polymer Binder Enabling Accommodation of Volume Change and Confinement of Polysulfide for High-Performance Lithium–Sulfur Batteries

Abstract

Lithium polysulfide (LiPS) shuttling and sulfur volume change causing degradation of electrodes have hindered the practical application of lithium–sulfur batteries. Here, a highly elastic and polar block polymer binder, poly­(acrylic acid)-b-((poly­(n-butyl acrylate)-co-poly­(2,2,3,4,4,4-hexafluorobutyl acrylate))-b-poly­(acrylic acid) (PAA-b-(PnBA-co-PHFBA)-b-PAA), was designed and synthesized to both accommodate sulfur volume change and confine LiPSs. The rigid–soft modulated triblock polymer combined the traditional polar binder PAA, low glass-temperature PnBA, and high-polarity PHFBA. The resultant binder can not only adjust the striking volume expansion and inhibit disintegration of a pure sulfur cathode but also strongly anchor LiPSs. The cycle stability and rate performance of lithium–sulfur batteries were significantly improved after being incorporated with the multifunctional binder. Besides, abundant F atoms can enhance ionic conductivity to improve electrochemical reaction of the sulfur cathode. This work offers a feasible and effective strategy for designing an efficient multifunctional binder toward building next-generation high energy density lithium–sulfur batteries.

Ion-Conducting Cross-Linked Polyphosphazene Binders for High-Performance Silicon Anodes in Lithium-Ion Batteries

“…In the FT-IR spectra, a broad peak originating from the carboxylic acid group appeared in the range of 2500–3500 cm –1 , and the carbonyl peak shifted from 1713 to 1689 cm –1 after the hydrolysis reaction . The molecular weight of PCPP could not be obtained because of the strong interactions between the carboxylic acid groups in PCPP forming the physically cross-linked structures . However, since the reaction under the basic conditions used in this study does not degrade the phosphazene backbone, the molecular weight (or chain length) of the resulting PCPP should be close to that of PEPP.…”

“…42 The molecular weight of PCPP could not be obtained because of the strong interactions between the carboxylic acid groups in PCPP forming the physically crosslinked structures. 45 However, since the reaction under the basic conditions used in this study does not degrade the phosphazene backbone, 46 the molecular weight (or chain length) of the resulting PCPP should be close to that of PEPP. The two carboxylic acid groups per repeating unit of PCPP can form strong hydrogen bonds with the silanol groups on the Si particles that can prevent the Si particles from being detached for some degree from the binder materials by the large volume change during the charge/discharge cycles.…”

Molecular structure-controlled synthesis of sulfur-containing polymers for rechargeable Li–S batteries

“…The natural stability of carbon chains can effectively improve the structural stability and electrochemical performance of cathode materials. Many types of organic polymers can be used for the preparation of sulfur-containing polymers with carbon chains as the main chains, such as polyacrylic acid (PAA), [80][81][82][83] polyacrylonitrile (PAN), [84][85][86] polypyrrole (PPy) [87][88][89][90] and polyaniline (PANI). 91,92 In this part, we discuss and analyze the molecular structure design of polysulfanes with carbon chains as the main chains by different methods.…”

Freestanding TiO2 Nanoparticle-Embedded High Directional Carbon Composite Host for High-Loading Low-Temperature Lithium–Sulfur Batteries

“…Nevertheless, at low temperatures, there are new issues over and above the shuttle effect, such as a strong aggregate of lithium polysulfides (LiPSs), sluggish redox conversion, and low discharge capacity. − Considering the low energy output at low temperatures, increasing the sulfur loading mass is attractive for developing high-energy low-temperature Li–S batteries. Most of the Li–S battery designs that have been disclosed so far have a sulfur content and mass below 2.0 mg cm –2 and 50 wt %. − Some works have increased the sulfur loading above 10.0 mg cm –2 . , However, the main problem of high-loading Li–S batteries is the low sulfur utilization rate due to the accumulation of insulation sulfur and LiPSs. With the increase in the sulfur content in the electrodes prepared by scraping thin slurry on the collector, the thickness of the electrode will inevitably rise, leading to an increased charge transport distance and the introduction of electrically insulating adhesive, thus suffering from mechanical instability, slow charge transfer kinetics, and increased interfacial resistance. , In summary, a decreased temperature, high sulfur mass, and increased thickness of electrodes are the triple barriers to developing low-temperature high-loading Li–S batteries.…”