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Cubic phase garnet-type Li 7 La 3 Zr 2 O 12 (LLZO) is a promising solid electrolyte for highly safe Li-ion batteries. Al-doped LLZO (Al-LLZO) has been widely studied due to the low cost of Al 2 O 3. The reported ionic conductivities were variable due to the complicated Al3+-Li+ substitution and Li x AlO y segregation in Al-LLZO ceramics. This work prepared Li 7−3 x Al x La 3 Zr 2 O 12 (x = 0.00~0.40) ceramics via a conventional solid-state reaction method. The AC impedance and corresponding distribution of relaxation times (DRT) were analyzed combined with phase transformation, cross-sectional microstructure evolution, and grain boundary element mapping results for these Al-LLZO ceramics to understand the various ionic transportation levels in LLZO with different Al-doping amounts. The low conductivity in low Al-doped (0.12~0.28) LLZO originates from the slow Li+ ion migration (1.4~0.25 μs) in the cubic-tetragonal mixed phase. On the other hand, LiAlO 2 and LaAlO 3 segregation occur at the grain boundaries of high Al-doped (0.40) LLZO, resulting in a gradual Li+ ion jump (6.5 μs) over grain boundaries and low ionic conductivity. The Li 6.04 Al 0.32 La 3 Zr 2 O 12 ceramic delivers the optimum Li+ ion conductivity of 1.7 × 10−4 S cm−1 at 25 °C. [ABSTRACT FROM AUTHOR]

Catalytic Pt layers are coated on the surface of the mixed proton-electron conductive membranes based on La 5.5 W 0.45 Nb 0.15 Mo 0.4 O 11.25-δ (LWNM) aiming to promote the hydrogen surface exchange, and effect of the Pt layer on the hydrogen permeation flux through the LWNM membrane has been investigated. A hydrogen permeation flux of 0.483 mL/min∙cm 2 is achieved at 1000 °C fed with a mixture of 50% H 2 − 50% He under wet condition with catalytic Pt layers on both sides of the LWNM membrane, which is twice as much as that of the uncoated membrane, indicating that the Pt layers on the membrane surface exhibit obvious positive effect on the hydrogen permeation. The increase of the hydrogen permeation flux is resulted from the enhancement of hydrogen dissociation/combination on the membrane surface by the Pt layer, which promotes the hydrogen surface exchange process. Moreover, it is more effective when the Pt layer is coated on the sweep side, which demonstrates that the hydrogen surface reaction on the sweep side of the membrane plays a predominant role compared with that on the feed side. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cryogenic engineering is first proposed to fabricate solid polymer electrolytes. • Cryogenic process can improve the ionic conductivity of SPEs. • Cryogenic SPEs animate superior performance of LiFePO 4 cells at room temperature. • Cryogenic SPEs can be used for 4 V-class all-solid-state lithium batteries. Solid polymer electrolytes (SPEs) are promising candidates for all-solid-state lithium batteries (ASSLBs) due to their advantages of good interfacial adhesion and shape flexibility. However, the low ionic conductivity at room temperature (RT) and inferior electrochemical stability at high voltages limit the practical applications of SPEs. In this work, we demonstrate a cryogenic engineering to improve PEO-based SPEs for ASSLBs operated at RT. The rapid in situ cooling process will lead to the uniform formation of PEO crystal nuclei, which can limit the PEO crystal growth in SPEs. The novel crystallization structure could promote the ionic conductivity of SPEs effectively. Such improved cryogenic SPEs display a superior ionic conductivity of 2.17 × 10−5 S cm−1 and a superior electrochemical stability at RT. A discharge capacity of 154.9 mAh g−1 can be achieved at 0.1 C and RT when LiFePO 4 (LFP) is used as the cathode. The discharge capacity can remain at ~98%, even after 100 cycles performed at 0.1 C. Notably, cryogenic SPEs can be utilized in 4 V-class ASSLBs. A high discharge capacity of 118 mAh g−1 can be achieved at 0.2 C and RT with the LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) as the cathode and can retain a 94.1% capacity even after 100 cycles. These extraordinary performances of cryogenic SPEs break new ground for the fabrication of ASSLBs operated at RT and high voltages. [ABSTRACT FROM AUTHOR]