Enabling All‐Solid‐State Li Metal Batteries Operated at 30 °C by Molecular Regulation of Polymer Electrolyte

Abstract

charge-transfer resistance at Li|PEO interface, and high stability against lithium metal. [3] However, PEO electrolytes exhibit a poor Li + conductivity (≈10 −8 -10 −6 S cm −1 ), inferior Li + transference number (≈0.2), and unstable electrolyte/electrode interface, all of which deteriorate the electrochemical performances of ASSLMBs.Extensive studies have focused on the introduction of second-phase ceramic fillers into PEO matrix to enhance the Li + conductivity. Ionic insulating ceramic fillers raise the conductivity of electrolytes via Lewis acid-base chemistry to lower the polymer crystallinity, [4,5] while lithium conducting ceramics increase the Li + conductivity by lowering PEO crystallinity and providing an extra Li + transport path at ceramic/polymer interface. [6] However, the weak bonding of ceramic fillers with PEO matrix causes severe aggregation to disconnect Li + conducting channels and impede Li + transport at the interface between PEO and ceramic fillers. [6,7] Thus, the Li + conductivity of PEO-based polymer is still lower than 10 −4 S cm −1 at near room temperature, making the batteries have to be operated over 50 °C. At this high temperature, the PEO electrolyte suffers from poor mechanical strength; and thus, Li dendrites easily pierce it to cause short-circuit at a current density less than 0.3 mA cm −2 . Up to now, it is still a big challenge to simultaneously achieve both a high Li + conductivity (>0.1 mS cm −1 ) and a high critical current density (CCD) at near room temperature for PEO-based electrolytes.Copper ions, as a Lewis acid, exhibit a rich coordination chemistry by bonding with Lewis basic organic ligands and TFSI − anion, making copper coordination polymer a tailored molecular structure; and thus, a modified functionality. [8] Meanwhile, fluorides have a high interfacial energy to Li metal at the Li/electrolyte interface, which is effective in suppressing the formation of dendrites. [9] In this work, we introduce CuF 2 with an ultralow content (<0.5 wt%) into PEO electrolyte to improve the ionic conductivity through the strong coordination effect between Cu 2+ and O atoms from PEO/LiTFSI matrix. As TFSI − is immobilized by Cu 2+ , more Li + ions are released and migrate rapidly due to the weakened interaction between Li + and ether O of PEO chain. Therefore, the coordinated electrolyte presents both a high ionic conductivity of 0.2 mS cm −1 and a transference number of 0.42 at 30 °C. Moreover, the in situ formed F/Li-rich interphase reacting from CuF 2 and lithium metal can effectively accelerateThe low ionic conductivity of poly(ethylene oxide) (PEO)-based polymer electrolytes at room temperature and the undesired lithium-dendrite growth at Li|PEO interface impede their further application. Herein, a PEO polymer is regulated at the molecular level through a copper ion (Cu 2+ ) coordination effect with both PEO and Li salts to achieve a high Li + conductivity of 0.2 mS cm −1 and a transference number of 0.42 at 30 °C. Moreover, the Cu-coordinated PEO electrolyte is neither st...

Polyurethane/Li10GeP2S12 composite electrolyte with high ions transfer number and ions capture for all-solid-state lithium batteries

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High-Entropy Laminates with High Ion Conductivities for High-Power All-Solid-State Lithium Metal Batteries

“…As shown in Figure c, S 2p XPS spectra demonstrate the formation of C–S bonding owing to chemical cross-linking between HE-Li x MPS 3 and NBR during vulcanization. Compared with pristine HE-Li x MPS 3 and other reported electrolytes, − the composite electrolyte exhibits rubber-like mechanical properties with high elasticity and durability, showing a high mechanical strength of 6.0 MPa and a maximum strain of ∼310%, which is ∼60 times that of HE-Li x MPS 3 (Figures d and S20). To explore the ionic transport behavior of the HE-Li x MPS 3 /NBR electrolyte, temperature-dependent conductivities and EIS plots were measured (Figures e and S21).…”

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