In Situ Forming Gel Polymer Electrolyte for High Energy‐Density Lithium Metal Batteries

Abstract

In situ forming gel polymer electrolyte (GPE) is one of the most feasible ways to improve the safety and cycle performances of lithium metal batteries with high energy density. However, most of the in situ formed GPEs are not compatible with high‐voltage cathode materials. Here, this work provides a novel strategy to in situ form GPE based on the mechanism of Ritter reaction. The Ritter reaction in liquid electrolyte has the advantage of appropriate reaction temperature and no additional additives. The polymer chains are cross‐linked by amide groups with the formation of GPE with superior electrochemical properties. The GPE has high ionic conductivity (1.84 mS cm−1), wide electrochemical stability window (>5.25 V) and high lithium ion transference number (≈0.78), compatible with high‐voltage cathode materials. The Li|LiNi0.6Co0.2Mn0.2O2 batteries with in situ formed GPE show excellent long‐term cycle stability (93.4%, 300 cycles). The density functional theory calculation and X‐ray photoelectron spectroscopy results verify that the amide and nitrile groups are beneficial for stabilizing cathode structure and promoting uniform Li deposition on Li anode. Furthermore, the in situ formed GPE exhibits excellent electrochemical performance in Graphite|LiMn2O4 and Graphite|LiNi0.5Co0.2Mn0.3O2 pouch batteries. This approach is adaptable to current battery technologies, which will be sure to promote the development of high energy‐density lithium‐ion batteries.

Cross-Linkable Binders for Si Anodes in High-Energy-Density Lithium-Ion Batteries

“…At the same time, the band belonging to the stretching vibration of C�O shows a blue shift from 1725 to 1717 cm −1 , and a new band at 3208 cm −1 appears, which can be attributed to the formation of −NH−. 28 The blue shift of the carbonyl group and the simultaneous occurrence of the amino group indicate the formation of amide bonds. 28 A similar phenomenon occurs in PMAH and cross-linked PMAH (c-PMAH) (Figure S3a), as well as PBAH and cross-linked PBAH (c-PBAH) (Figure S3b).…”

“…XPS characterization was employed on the disassembled Si@POAH anode to evaluate the Ritter reaction. In the N 1s and O 1s spectra of Si@POAH, the characteristic peaks for nitrile (399.5 eV) 31 and hydroxyl (532.4 eV) 28 groups are observed (Figure S4a,b). While in the N 1s spectrum of Si@c-POAH, the peak at 399.5 eV disappears and a peak at 399.8 eV attributed to the amide group occurs.…”

Tailoring the interface of lithium metal batteries with an in situ formed gel polymer electrolyte

“…Then, the Ritter reaction can occur between the hydroxyl and nitrile groups, leading to the amide group covalently cross-linked polymer matrix. 34,35 FTIR was used to characterize the chemical structure evolution during the reaction. As shown in Fig.…”

“…33 Further studies showed that the formation of PVA-CN-based GPE lies in the cross-linking reaction between the nitrile and hydroxyl groups, which is initiated by PF 5 , a strong Lewis acid decomposed from LiPF 6 . 34 It follows the mechanism of the Ritter reaction, leading to the cross-linking of various chains with amide groups. 35…”

In situ polymerization of solid-state polymer electrolytes for lithium metal batteries: a review

“…Regarding the study of other esters, Xue et al 115 synthesized the PMHA gel in situ using methyl methacrylate (MMA), hydroxypropyl acrylate (HPA), and acrylonitrile (AN) as the monomers. After that, PHMA was dissolved in the liquid electrolyte and heated for 48 hours at 60 °C.…”