Hyperbranched PCL/PS Copolymer-Based Solid Polymer Electrolytes Enable Long Cycle Life of Lithium Metal Batteries

Abstract

Solid polymer electrolytes (SPE) are of great importance for developing the next-generation all-solid-state lithium metal batteries, which are featured by their high safety and extraordinary energy density. Herein, by using the highly efficient azide-alkyne click chemistry, a series of long-subchain hyperbranched copolymers from various compositions of AB 2 macromonomers of PCL-2N 3 (polycaprolactone) and PS-2N 3 (polystyrene) were synthesized and employed as SPE polymer host. Taking advantage of the hyperbranched structure, the crystallization of PCL was successfully suppressed, and endows the SPE with high ionic conductivity and high mechanical properties simultaneously. By doping with LiFSI, the SPEs thereof exhibit high ionic conductivity (1.59 × 10 −4 S cm −1 at 80 °C), broad electrochemical stability window (>4.6 V) and high lithium-ion transference number (>0.40). The electrolyte film based on the HB-II (the hyperbranched PCL/PS copolymer with 70 wt% PCL and 30 wt% PS) shows an ionic conductivity of 1.36 × 10 −5 S•cm −1 at 80 °C and a high lithium transference number of 0.49. The all-solid-state LiFePO 4 //Li cell with HB-II-based SPE delivers a high and stable discharge capacity (133 mAh•g −1 at 1 C, with 90% capacity retention after 300 cycles) and exhibits long lifetime up to over 1200 cycles, owing to its relatively high ionic conductivity and good interfacial stability.

High‐performance sodium ion conducting gel polymer electrolyte based on a biodegradable polymer polycaprolactone

“…The obtained value of t Na + is higher than the reported values for PCL‐based electrolytes (Table 2). 56‐62 Since the t Na + denotes the proportion of the effective cation transport (Na + ) in the electrolyte, a high t Na + is expected to reduce polarization of the electrode and enhance the electrochemical performance of the device 46 . Furthermore, large transport number is reported to overcome the problems of dendrite formation by avoiding the buildup of large electric fields in the space‐charge region 46,68 .…”

One-Pot Synthesis of Polyester-Based Linear and Graft Copolymers for Solid Polymer Electrolytes

“…83 Moreover, the brush-shaped structure destroys the regularity of the PCL segment, and the coordination between Li + and the carbonyl group of PCL is improved, thereby increasing the t Li + value. It is also worth noting that PESPE possesses higher ionic conductivity and transference number than traditional polyester-based solid polymer electrolytes (Figure 7f), 41,43,[45][46][47]49,50 indicating that PESPE has a good application prospect and is expected to be used in LIBs.…”

“…[43][44][45] Building linear block copolymers or graft copolymers and polymers with various topological structures to destroy the crystallinity of polyester has proved to be a good way to meet the practical application requirements of LIBs. [46][47][48][49][50][51] With the development of polymer synthesis technology, various living polymerizations including atom transfer radical polymerization (ATRP), [52][53][54][55][56] and reversible addition fragmentation chain transfer (RAFT) polymerization, [57][58][59][60] nitroxide-mediated radical polymerization (NMP), [61][62][63][64] and ring-opening polymerization system in the system. Moreover, the carboxylic acid group exists in a large number of commercially available chemical products, and its catalytic effect has always been easily overlooked.…”

Room-temperature all-solid-state lithium metal batteries based on ultrathin polymeric electrolytes

“…For instance, the use of hyperbranched polymers instead of linear chain polymers has been an effective strategy as the steric effect can hinder the regular packing of polymer chains mitigating crystal formation. 11,12 But the synthesis of these polymers is quite complex, making their scalable production costly. Introducing organic solvents to form a gel polymer electrolyte is also effective to reduce chain-chain interactions for lowering the crystallinity of solid polymer electrolytes.…”