Permeable void-free interface for all-solid-state alkali-ion polymer batteries

Abstract

All-solid-state batteries suffer from a loss of contact between the electrode and electrolyte particles, leading to poor cyclability. Here, a void-free ion-permeable interface between the solid-state polymer electrolyte and electrode is constructed in situ during cycling using charge/discharge voltage as the stimulus. During the charge-discharge, the permeation phase fills the voids at the interface and penetrates the electrode, forming strong bonds with the cathode and effectively mitigating the contact problem. Our all-solid-state potassium ion polymer batteries maintain high Coulombic efficiency more than 2000 cycles at a high operating voltage of 4.5 volt and stably cycle more than 500 cycles even at 4.6 volt. Our rational design for mitigating the contact problem is versatile, as demonstrated by the scalability of all-solid-state graphite-based polymer potassium-ion pouch cells and all-solid-state lithium-ion polymer batteries.

Fig. 1.. Conventional solid-state batteries exhibit voids at the cathode-SSE interface and the loss of contact between the electrode particles and SSE during cycling, making it difficult or impossible for ions to migrate.

A permeable 3D SSE with excellent bonding with the cathode is constructed by creating an SPP in situ from a PGSPE to fill the voids for a void-free interfacial contact.

Fig. 2.. Electrochemical test performance.

(A) Ionic conductivity for PEO-KFSI polymer electrolyte and the PGSPE electrolyte with different mass fractions of PVPI (wt % = 5, 10, 15, and 20). (B) Temperature dependence of ionic conductivities for PEO-KFSI polymer electrolyte and the PGSPE. (C) CV curves of the PEO-KFSI polymer electrolyte and PGSPE. (D) Cycling performance of the symmetric potassium cells. (E) Charge/discharge voltage profiles of PEO-KFSI electrolyte and PGSPE. (F) Cycling performance of PEO-KFSI polymer electrolyte and PGSPE at 0.5 C. (G) Cycling performance and median cell voltage at 4.6-V cut-off voltage using PGSPE. (H) Cycling performance of the solid-state potassium metal polymer pouch cell. (I and J) Safety verification of liquid and solid-state polymer pouch cells.

Fig. 3.. In situ formation of SPP 3D ion transporting networks.

(A) 3D presentation of solid permeable phase ion networks based on visual fluorescent labeling. (B) Different subdivided regions were imaged in 3D with isometric selections along the transverse and longitudinal cross-section planes. (C) Fluorescent labeling of three views of area 1 is shown in (B). (D) Fluorescence intensity distribution of different regions of the cathode surface. (E and F) Surface morphology of permeable cathodes and corresponding 3D reconstructions. (G) Cross-sectional SEM images of permeable cathodes. (H) Corresponding 3D reconstructions area labeled as 1 in (G). (I) Comparison of permeable cathode surface morphology and cathode bottom morphology. (J) Cross-sectional SEM morphology of the cathode-electrolyte interface. (K) Focused ion beam–TEM imaging and EDS chromatography of the permeable cathodes. (L) 3D distribution of different segments of the elements Fe and S.

Fig. 4.. High stability voltage study.

(A) Electrochemical stabilization voltages of PEO-KFSI electrolyte (pristine) and PGSPE. (B) Surface potential distribution of the electrolytes. (C) Spatial charge layer determination device. (D) Spatial charge layer testing of the corresponding voltage and time distribution variations. (E) Surface potential distribution for the original and cycled cathodes. (F and G) Representative quasi-static nanoindentation curve for the original and cycled cathodes and the corresponding indentation displacements. (H) Representative creep displacement time curves for the original and cycled cathodes.

Fig. 5.. Construction of a solid-state potassium-ion polymer pouch full cell.

(A) Schematic showing the fabrication of pre-potassiated graphite. (B) Photograph of the pre-potassiation system and the potassiated graphite anode. (C) Voltage profiles of the PB || potassiated graphite anode polymer pouch full cells. (D) Cycling performance (0.5 C) of a PB || potassiated graphite anode pouch cell. (E) Voltage profiles of the high-load cathode all-solid-state lithium-ion polymer pouch cell. (F). Safety verification of all-solid-state polymer pouch cell.