Study on the technology of solid-state electrode-electrolyte to improve the compatibility of solid lithium ion battery

【introduction】

Lithium-ion batteries mainly rely on lithium ions to move between the positive and negative electrodes to work. During charge and discharge, Li+ is intercalated and deintercalated between the two electrodes: when charging, Li+ is deintercalated from the positive electrode, and the electrolyte is embedded in the negative electrode, and the negative electrode is in a lithium-rich state; The high energy density and long cycle life of lithium-ion batteries make them an advantage in providing energy storage in portable electronic devices. Compared with flammable liquid organic electrolytes, all-solid lithium-ion electrolytes have higher safety. However, a major challenge for solid electrolyte batteries is to form a stable ion conductive interface between the electrolyte and the active material.

[Introduction]

Recently, the team of Gary M. Koenig Jr (Corresponding author) of the University of Virginia studied and characterized the solid-state electrode for the high-pressure active cathode material LiMn1.5Ni0.5O4 (LMNO) and the electrolyte Li1+xAlxGe2-x(PO4)3 (LAGP)- Electrolyte. During the temperature increase, in situ X-ray diffraction measurements were performed on a tablet consisting of a mixture of LMNO and LAGP to determine the temperature of the product material formed at the LMNO and LAGP interfaces and their formation. It was found that at 600 ° C or higher, a material consistent with LiMnPO 4 was formed. The morphology and elemental composition of the product at the interface were imaged by scanning electron microscopy and energy dispersive X-ray spectroscopy, and the LMNO-coated LAGP electrolyte particle half-cells were electrochemically characterized. Although the voltage of the Li/LAGP/LMNO battery is high, the thickness of the interface phase is large, resulting in a higher electrochemical resistance. Related results were published in the Journal of the American Ceramic Society under the title "High temperature electrode-electrolyte interface formation between LiMn1.5Ni0.5O4 and Li.4Al0.4Ge1.6(PO4)3".

[Graphic introduction]

Figure 1 In situ XRD scan

In situ XRD scanning of LAGP and LMNO powder mixtures at room temperature and after heating to 450 ° C, 600 ° C, 700 ° C and 800 ° C

Figure 2 SEM characterization

(AC) SEM micrograph of the LAGP/LMNO interface after (A) 700 ° C for 1 hour, (B) 750 ° C for 1 hour, and (C) 800 ° C for 5 hours in air.

Figure 3 Interface between LAGP particles and deposited LMNO powder

(A) secondary electron micrograph

(B) Orange EDS map marked with manganese

(C) Yellow EDS map marked with nickel

(D) Green EDS diagram marked with é”—

(E, F) composite EDS diagram containing (E) manganese and phosphorus and (F) manganese, phosphorus and antimony

Figure 4 Cycle performance analysis

(A) Li/LAGP/LMNO all solid state battery charging/discharging cycle

(B) Charge/discharge cycle of LMNO material in composite electrode

【summary】

This study characterizes the reaction of the lithium ion active material LMNO with the solid electrolyte LAGP to verify the compatibility of these materials into an all solid state lithium ion battery . For many all-solid-state battery systems, the resistance of the electrode-electrolyte interface is a common challenge, and the complexity of the oxide-phosphate material is added to the LAGP/LMNO system and the conversion to the new phase means to the LAGP/LMNO The thickness of the interface and the clear control of the contact are critical to the electrochemical performance of the system.