Homogeneous and Fast Ion Conduction of PEO‐Based Solid‐State Electrolyte at Low Temperature

Abstract

Poly(ethylene oxide) (PEO)‐based electrolytes are promising for all‐solid‐state batteries but can only be used above room temperature due to the high‐degree crystallization of PEO and the intimate affinity between ethylene oxide (EO) chains and lithium ions. Here, a homogeneous‐inspired design of PEO‐based solid‐state electrolytes with fast ion conduction is proposed. The homogeneous PEO‐based solid‐state electrolyte with an adjusted succinonitrile (SN) and PEO molar ratio simultaneously suppresses the PEO crystallization and mitigates the affinity between EO and Li+. By adjusting the molar ratio of SN to PEO (SN:EO ≈ 1:4), channels providing fast Li+ transport are formed within the homogeneous solid‐state polymer electrolyte, which increases the ionic conductivity by 100 times and enables their application at a low temperature (0–25 °C), together with the uniform lithium deposition. This modified PEO‐based electrolyte also enables a LiFePO4 cathode to achieve a superior Coulombic efficiency (>99%) and have a long life (>750 cycles) at room temperature. Moreover, even at a low temperature of 0 °C, 82% of its room‐temperature capacity remains, demonstrating the great potential of this electrolyte for practical solid‐state lithium battery applications.

10 μm‐Thick High‐Strength Solid Polymer Electrolytes with Excellent Interface Compatibility for Flexible All‐Solid‐State Lithium‐Metal Batteries

“…[ 15 ] However, the subsequent drawbacks in ionic conductivity, thickness, strength, and instability with lithium anode seriously hindered the application of all‐solid‐state batteries. [ 16–18 ]…”

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

“…In addition, plasticizer SN shares the same nitrile group with PAN, which makes it also unstable on lithium metal anode. The interaction among the lithium salt, polymer matrix and SN as well as the resultant formed SEI may restrain the continuous reaction between lithium anode and free SN molecule, [40,41] but extra attention should be paid when applying SN in lithium metal batteries.…”

Designing Polymer‐in‐Salt Electrolyte and Fully Infiltrated 3D Electrode for Integrated Solid‐State Lithium Batteries

“…Among all solid‐state electrolytes, solid polymer electrolytes (SPEs) comprised of lithium salt and polymer are particularly attractive by virtue of their low cost, facile preparation, high flexibility and easiness of forming intimate interface with electrode [11–13] . Unfortunately, the ionic conductivity of SPEs at room temperature (RT) is generally low [14, 15] . Considering that the ionic transport in SPEs is completed by the local relaxation and segmental motion of amorphous regions in polymer chains (Figure 1 a), [16–18] various approaches, including cross‐linking, [19, 20] forming copolymer, [21] and introducing inorganic fillers, [22] have been implemented to expand the proportion of amorphous regions to promote ionic conductivity.…”

“…In principle, the simple and effective way to gain highly conductive PISSEs is to search for polymer matrices with excellent mechanical strength. Different from other polymers such as poly(ethylene oxide) (PEO), polyacrylonitrile (PAN) and polycarbonate, [15, 28, 32b] poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) is expected to has superior comprehensive properties, as depicted in Figure 1 c. It can not only dissolve and dissociate large amounts of lithium salt to obtain high ionic conductivity at RT, but also have excellent mechanical strength, and thermal and electrochemical stability [33] .…”

“…[11][12][13] Unfortunately, the ionic conductivity of SPEs at room temperature (RT) is generally low. [14,15] Considering that the ionic transport in SPEs is completed by the local relaxation and segmental motion of amorphous regions in polymer chains (Figure 1 a), [16][17][18] various approaches, including cross-linking, [19,20] forming copolymer, [21] and introducing inorganic fillers, [22] have been implemented to expand the proportion of amorphous regions to promote ionic conductivity. Alternatively, polymer-in-salt solid electrolyte (PISSE: the content of the lithium salt exceeding 50 wt.…”