Recent Development in Topological Polymer Electrolytes for Rechargeable Lithium Batteries

Abstract

Solid polymer electrolytes (SPEs) are still being considered as a candidate to replace liquid electrolytes for high‐safety and flexible lithium batteries due to their superiorities including light‐weight, good flexibility, and shape versatility. However, inefficient ion transportation of linear polymer electrolytes is still the biggest challenge. To improve ion transport capacity, developing novel polymer electrolytes are supposed to be an effective strategy. Nonlinear topological structures such as hyperbranched, star‐shaped, comb‐like, and brush‐like types have highly branched features. Compared with linear polymer electrolytes, topological polymer electrolytes possess more functional groups, lower crystallization, glass transition temperature, and better solubility. Especially, a large number of functional groups are beneficial to dissociation of lithium salt for improving the ion conductivity. Furthermore, topological polymers have strong design ability to meet the requirements of comprehensive performances of SPEs. In this review, the recent development in topological polymer electrolytes is summarized and their design thought is analyzed. Outlooks are also provided for the development of future SPEs. It is expected that this review can raise a strong interest in the structural design of advanced polymer electrolyte, which can give inspirations for future research on novel SPEs and promote the development of next‐generation high‐safety flexible energy storage devices.

Branched Polymers: Synthesis and Application

“…The application of branched polymers in biomedicine has been summarized previously, , and we will not further discuss it here. In the following, we mainly introduce the applications of branched polymers in solid polymer electrolytes for Li batteries, ,− coatings and membranes, − surfactants, − and hydrogels. − …”

“…In the recent decades, solid polymer electrolytes for Li batteries composed of polymer matrixes and alkali metal salts have received much attention due to the advantages of processability as well as the tunable physical and chemical properties. ,,− In solid polymer electrolytes, the electrostatic interaction between polymers and alkali metal salts facilitates dissociation of the alkali metal salts and then promotes ion transport through the motion of polymer chain segments. It is found that branched polymer electrolytes for Li batteries have higher ionic conductivity compared with linear polymer electrolytes, which resulted from the higher motility of branched polymer chain segments.…”

Charge–Discharge Behavior of Lithium-Ion Batteries Using a Polymer Electrolyte Bearing High-Density Functional Groups

“…Liu et al reviewed different polymer backbones (polyether, polycarbonate, polyacetal) containing polar groups facilitating lithium salt dissociation, dissolution, and ionic conduction. They emphasized that increasing the degree of branching and/or number of the functional group helps dissolve lithium salts, thereby improving ionic conductivity and promoting lithium-ion transport . Carbonyl group interactions are weaker, allowing significant enhancement of lithium transport compared with PEO. , Polyester has improved thermal stability and a low tendency for depolymerization in the presence of highly nucleophilic anions of lithium salts.…”

Regulating Conductive Copolymerization Networks in the Polymer Electrolyte for High-Performance Quasi-Solid-State Lithium–Metal Batteries

“…At present, widespread polymer electrolytes are dual-ion conductors, but the rapid movement of anions will cause the knotty problem of low cation transference numbers, and thus it will result in concentration polarization, electrochemical polarization, and eventually restricting the energy density delivery . Distinguished from the conventional dual-ion system electrolytes, single-ion system electrolytes can promote cation shuttling by inhibiting the mobility of anions in copolymerized lithium salts, thereby alleviating the aforementioned adverse issues, improving the electrochemical performance of LIBs, and enhancing energy efficiency. , 2-acrylamido-2-methylpropanesulfonic acid (AMPS), a typically inexpensive solvent resistance comonomer, possesses multifunctional groups, the unsaturated CC bond for polymerization, amide groups (−CO–NH−) with high polarity for dissociation of lithium salt and sulfonate groups (−SO 3 ) for lithiation as single-ion conductor lithium salt in polymer electrolyte. , For instance, Jia and co-workers designed a serial of intriguing elastic single-ion polymer electrolytes (SIPEs) with Pluronic and AMPSLi, which exhibited an ionic conductivity of 1.10 × 10 –4 S cm –1 at 65 °C, an extended ESW (>5 V) and a high lithium transfer number ( t Li+ > 0.93) . Nan and his co-workers employed a strategy to incorporate 1 wt % AMPS as an organic additive into the PVDF-substrate electrolyte that achieved a high ionic conductivity of 2.2 × 10 –4 S cm –1 at 26 °C, increased the number of Li + transference to 0.49, and effectively suppressed the growth of Li dendrites .…”

“…Accordingly, the multifunctional polymer electrolytes are usually designed to balance the above contradictions. Copolymerization is an efficient modification strategy for integrating and optimizing the ion conducting and functional chain segments, thus constructing the fast ionic transport paths and maintaining the interfacial stability in high-performance LIBs. , …”