A Crosslinked Polyethyleneglycol Solid Electrolyte Dissolving Lithium Bis(trifluoromethylsulfonyl)imide for Rechargeable Lithium Batteries

Abstract

Replacing liquid electrolytes with solid ones can provide advantages in safety, and all‐solid‐state batteries with solid electrolytes are proposed to solve the issue of the formation of lithium dendrites. In this study, a crosslinked polymer composite solid electrolyte was presented, which enabled the construction of lithium batteries with outstanding electrochemical behavior over long‐term cycling. The crosslinked polymeric host was synthesized through polymerization of the terminal amines of O,O‐bis(2‐aminopropyl) polypropylene glycol‐block‐polyethylene glycol‐block‐polypropylene glycol and terminal epoxy groups of bisphenol A diglycidyl ether at 90 °C and provided an amorphous matrix for Li+ dissolution. This composite solid electrolyte containing Li+ salt and garnet filler exhibited high flexibility, which supported the formation of favorable interfaces with the active materials, and possessed enough mechanical strength to suppress the penetration of lithium dendrites. Ionic conductivities higher than 5.0×10−4 S cm−1 above 45 °C were obtained as well as a wide electrochemical stability window (>4.51 V vs. Li/Li+) and a high Li+ diffusion coefficient (≈16.6×10−13 m2 s−1). High cycling stability (>500 cycles or 1000 h) was demonstrated.

Status and prospect of garnet/polymer solid composite electrolytes for all-solid-state lithium batteries

“…Meanwhile, PEO shows high viscosity, poor filmforming ability as well as narrow electrochemical window, which further hinder the LLZO-based/PEO SCEs for large scale application in real batteries. To explore LLZO-based/polymer SCEs with better properties, other novel types of polymers, such as poly(propylene carbonate) (PPC) [125][126][127][128] , poly(vinylidene fluoride) (PVDF) [129][130][131][132] , poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) [133][134][135][136][137] , poly(ethylene carbonate) (PEC) [138] , polyacrylonitrile (PAN) [139] , poly(methyl methacrylate) (PMMA) [140] , cross-linked polyethyleneglycol [141] , poly(ethylene glycol) diacrylate (PEGDA) [142] and mixed polymers [143][144][145] have been developed as the substrate for constructing novel LLZObased/polymer SCEs. Table 4 summarizes the intrinsic properties of the typical LLZO-based/novel polymer SCEs and the electrochemical performances of ASSLBs assembled by these novel SCEs.…”

“…To obtain efficient Li + movement at the micro-scale and enough mechanical strength at the macro-scale simultaneously, Tian et al prepared a cross-linked polyethyleneglycol by the polymerization of terminal active groups and then used it as the polymer matrix to construct the SCE with LLZO fillers (LLZ-BEPEO) [141] . This SCE delivers ionic conductivity above 5.0 × 10 −4 S cm −1 at 45 °C, a stable electrochemical window above 4.51 V, and smaller interfacial resistance and superior wettability than the LLZO-PEO electrolyte.…”

Toward High Performance All‐Solid‐State Lithium Batteries with High‐Voltage Cathode Materials: Design Strategies for Solid Electrolytes, Cathode Interfaces, and Composite Electrodes

“…[ 48 ] Among them, introducing inorganic fillers into polymer‐based SEs to increase the ionic conductivity has been extensively studied. [ 18,49 ] Both inert fillers and Li + conductor fillers, such as SiO 2 , [ 50 ] Y 2 O 3 ‐doped ZrO 2 , [ 51 ] Li 7 La 3 Zr 2 O 12 , [ 52 ] Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 , [ 53 ] Li 6.75 La 3 Zr 1.75 Ta 0.25 O 12 , [ 54 ] Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP), [ 55 ] Li 1+ x Al x Ti 2− x (PO 4 ) 3 (LATP), [ 56 ] Li 0.33 La 0.557 TiO 3 (LLTO), [ 57 ] Li 0.35 La 0.55 TiO 3 , [ 58 ] Li 10 GeP 2 S 12 (LGPS), [ 59 ] 3Li 2 S‐2MoS 2 , [ 60 ] and Li 6 PS 5 Cl [ 61 ] have been successfully incorporated into polymer matrices to form CSEs with improved ionic conductivities. These increased ionic conductivities generally can be attributed to the: 1) significantly decreased crystallinity of the polymer matrix, which facilitates polymer segmental motion; 2) increased active Li + concentration because fillers with Lewis acid–base characteristics can disrupt the ion pair and result in enhanced Li salt dissociation, and 3) percolating interfacial effect between the fillers and polymer SEs, leading to the formation of high‐speed Li + conductive networks.…”

“…A summary of the review of high‐voltage ASSLBs presented above is provided as follows: In terms of anodes paired with sulfide‐based SEs, many studies utilized In/In‐Li instead of a Li metal anode to avoid the decomposition of sulfide‐based SEs due to the elevated redox potential of In metal (0.62 V vs Li + /Li). [ 32c,34,39a,105b,135b,136,138e ] However, the high cost and toxicity of In‐based anodes limit their wide application in practical ASSLBs. Concerning organic–inorganic CSEs, oxide‐based SEs, garnet‐type LLZO in particular, [ 18,52 ] are encouraged as the common inorganic ceramic fillers for constructing stable CSEs with high performance, while sulfide‐based SEs as the fillers are rarely reported because most sulfide‐based SEs deliver poor chemical stability. Considering cathode AMs used in high‐voltage ASSLBs, most extensively studied cathode AMs are 4 V‐class cathodes such as LCO, NCM, and NCA, and there are relatively few reports on other cathode AMs that require higher cut‐off voltages, such as LMFP and LNMO. Possible reasons for this discrepancy are that a) 4 V‐class cathodes have been intensively studied in LLBs and achieved encouraging results and b) the overestimated electrochemical stability windows of SEs generally cannot ensure ASSLBs assembled with LMFP and LNMO to work stably for a long time.…”

Macromolecular Design of Lithium Conductive Polymer as Electrolyte for Solid‐State Lithium Batteries

“…Oligomer PEG with ether groups is often employed as ionic conducting segment in copolymerization, especially those with allylic end groups. [ 49–51 ] However, ether group increases crystallinity of the polymer matrix, which lowers the ionic conductivity of the SPE at the ambient temperature. Therefore, different segments are introduced to copolymerize with ether group to decrease the crystallinity and simultaneously increase amorphous domain of the polymer matrix in order to promote the ionic conductivity of SPE.…”