Reducing crystallinity in solid polymer electrolytes for lithium-metal batteries via statistical copolymerization

Abstract

The discovery that polyethylene oxide promotes ionic conductivity led to the development of solid polymer electrolytes. However, their conductivity is severely reduced by crystallinity. Here, statistical copolymerization is used to design macromolecular architectures where crystallinity is disrupted by a minimal amount of non-ethylene oxide comonomer units. Using the Flory exclusion model, we demonstrate that polymers containing 18 mol% comonomer and 18 wt% LiTFSI are devoid of crystallinity. A 10 mol% comonomer content is sufficient to reach a conductivity of 0.3 × 10−4 S cm−1 at 25 °C. The Li+ transference number is 0.6, indicating that the comonomer units not only limit the crystallinity but also weaken the strength of the Li+ coordination to the polymer. The resulting solid polymer electrolyte is effective in an all-solid LFP|Li-metal battery operating at 25 °C, demonstrating that statistical copolymerization is an efficient tool for polymer electrolyte design.

Improved Performance of Solid Polymer Electrolyte for Lithium-Metal Batteries via Hot Press Rolling

“…At room temperature, the transference numbers for the SPE and R-SPE were calculated as 0.12 and 0.18, respectively, which are close to the literature values [ 21 ]. The for the R-SPE was higher than the transference number of the SPE.…”

“…Crystallinity is a fundamental characteristic of polymeric systems which defines mechanical, thermal, optical, electronic, and transport properties [ 17 , 18 , 19 ]. A high crystallinity limits the movement of lithium ions [ 20 , 21 ] and, hence, enhances the ionic conductivity of SPEs. Several approaches, such as adding plasticizer and incorporating ceramic filler, have been widely explored [ 22 , 23 , 24 , 25 , 26 ] and demonstrated to successfully disrupt this crystallinity.…”

Highly ionic conductive, self-healable solid polymer electrolyte based on reversibly interlocked macromolecule networks for lithium metal batteries workable at room temperature

“…5c and d). In particular, the ionic conductivity of RILNs-3/1-LiPF 6 at 25 C is up to 6.97 Â 10 À4 S cm À1 , which is one of the best among the reported values at ambient temperature 18,22,24,[39][40][41][44][45][46][47][48][49][50][51][52][53][54] (Fig. 5e).…”

“…5b), which coincides with the reported results of crystalline PEO-based electrolytes. 38,39 As for the amorphous RILN-based electrolytes, their ionic conductivities linearly increase with temperature in the entire temperature range of interest (25-70 C, Fig. 5a), showing an almost identical E a,t of about 0.035-0.039 eV (i.e.…”

In Situ Dendrimer-Crosslinked Gel Polymer Electrolytes for Lithium-Ion Batteries with High Ionic Conductivity and Excellent Electrochemical Performance

“…So, a lower crystallinity improves the Li-ion conductivity. 32 On the other hand, in a semicrystalline polymer such as PEO with a T g under room temperature, the polymer gets its good mechanical strength from the crystalline structure. Therefore, destroying the crystalline phase risks mechanical properties and hinders its applicability as a polymer electrolyte.…”