The composite gel electrolyte with low tortuosity ion-conducting arrays (GPE/ICAs) exhibiting high room-temperature ionic conductivity (1.08 mS cm −1 ) was successfully prepared by directionally growing ice crystals and in-situ polymerization.
The stable and rapid Li + migration through ICAs in the GPE is proved by 6 Li solid-state nuclear magnetic resonance and synchrotron radiation X-ray diffraction combined with computer simulations.
Li/LiFePO 4 full cells using GPE/ICAs exhibit excellent cycle performance and high-capacity retention at wide temperature (0–60 °C), which has the potential towards all-weather practical solid-state batteries.
Understanding the Li-ions conduction network and transport dynamics in polymer electrolyte is crucial for developing reliable all-solid-state batteries. In this work, advanced nano- X-ray computed tomography combined with Raman spectroscopy and solid state nuclear magnetic resonance are used to multi-scale qualitatively and quantitatively reveal ion conduction network of poly(ethylene) oxide (PEO)-based electrolyte (from atomic, nano to macroscopic level). With the clear mapping of the microstructural heterogeneities of the polymer segments, aluminium-oxo molecular clusters (AlOC) are used to reconstruct a high-efficient conducting network with high available Li-ions (76.7%) and continuous amorphous domains via the strong supramolecular interactions. Such superionic PEO conductor (PEO-LiTFSI-AlOC) exhibites a molten-like Li-ion conduction behaviour among the whole temperature range and delivers an ionic conductivity of 1.87 × 10 −4 S cm −1 at 35 °Ϲ. This further endows Li electrochemical plating/stripping stability under 50 μA cm −2 and 50 μAh cm −2 over 2000 h. The as-built Li|PEO-LiTFSI-AlOC|LiFePO 4 full batteries show a high rate performance and a capacity retention more than 90% over 200 cycling at 250 μA cm −2 , even enabling a high-loading LiFePO 4 cathode of 16.8 mg cm −2 with a specific capacity of 150 mAh g −1 at 50 °Ϲ.
The large scale application of solid state lithium metal batteries based on NASICON-type Li 1+x Al x Ti 2-x (PO 4 ) 3 (LATP) electrolyte has been hindered by insufficient ion conductivity and interface instability due to the spontaneous Ti 4+ reduction reaction between Li metal and LATP. To address these issues, Li 1.7 Al 0.3-x Bi x Ti 1.7 (PO 4 ) 3 (0 ≤ x ≤ 0.03) (LABTP) electrolytes were prepared, and the influence of Bi substitution on the microstructure and conductivity of LATP were investigated. Suitable amount of Bi substitution accelerates densification and improves the ionic conductivity . Furthermore, unlike commonly used polyethylene oxide (PEO) and polyvinylidene difluoride (PVDF), polyvinylbutyral (PVB)-based quasi-solid electrolytes with LABTP is first-time proposed to improve the compatibility and stability of the LATP/Li interface. The synergistic effect of Bi doping and PVB reduces the reduction reaction of Ti 4+ . Small voltage hysteresis is observed in the corresponding Li||Li symmetric cells. The solid-state Li|LABTP@PVB|LiFePO 4 full cell can deliver a high capacity of 146.2 mAh g −1 and a stable cycling performance without reduction after 200 cycles.
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