Electrospining Machine:Prof. Peng Zhang, Zhengzhou University, et al: Functional gel polymer electrolyte based on PVDF-HFP/gelatin for dendrite-free lithium metal batteries

Background

Leakage of liquid electrolytes and formation of lithium dendrites challenge the safety and stability of lithium metal batteries (LMBs). The emergence of gel polymer electrolytes (GPEs) has significantly improved the safety of conventional LMBs. However, the limited inhibition of lithium dendrites by GPE is detrimental to the safety of LMB.

In view of this, a polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP)/gelatin (GN) GPE with high ionic conductivity, high-temperature resistance, and flame-retardant properties was prepared by using an electrospinnig machine and immersion method at Zhengzhou University by Prof. Peng Zhang and Guosheng Shao, et al. This study presents a promising solution to address traditional LMBs facing the safety and stability challenges faced by conventional LMB. The research results were published as “A functional gel polymer electrolyte based on PVDF-HFP/gelatin toward dendrite-free lithium metal batteries” in the journal Nano. The research results were published in the journal Nano Research.

The main points of this paper

1. This study presents a functional gel polymer electrolyte based on PVDF-HFP/gelatin for inhibiting lithium dendrite generation in lithium-metal batteries, which solves the safety and stability challenges existing in conventional lithium-metal batteries.

2. A polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP)/gelatin (GN) GPE with high ionic conductivity, high temperature resistance, and flame-retardant properties was prepared by using an electrospinnig machine and immersion method.

3. HFP-GN GPE was applied to LMB with LiFePO4 and LiCoO2 as cathodes, and excellent electrochemical performance was obtained:, LiFePO4/HFP-GN GPE/Li batteries maintained a low capacity decay rate of 0.09% after 300 cycles at 5C; and after 400 cycles at 2C, the capacity retention rate of LiCoO2/HFP-GN GPE/ Li battery capacity retention rate of up to 74%.

4. The electrolyte has excellent ion transport performance and mechanical stability, providing a potential solution for long cycle time and high safety of lithium metal batteries.

Preparation of composite gel polymer electrolytes:

1. PVDF-HFP was dissolved in a mixture of dimethylacetamide (DMAc) and acetone to prepare Nanofiber Membrane.

2. Then GN was added to hot water until it was completely dissolved. After wetting the PVDF-HFP fibers with ethanol, the PVDF-HFP fibers were immersed in the hot GN solution for a period of time.

3. The composite gel polymer membrane was prepared by cooling the HFP-GN membrane to room temperature and drying it. The gel polymer membrane absorbed a certain amount of liquid electrolyte to obtain the composite GPE.

PVDF-HFP/GN GPE becomes a safer and more stable alternative to traditional LMB with several key features:

1. PVDF-HFP Electrospun Nanofbers network has excellent ionic conductivity and affinity for liquid electrolyte, which is favorable for ion transfer and gel formation.

2. GN with sol-gel property enhances the mechanical stability of GPE and can avoid the puncture of lithium dendrites.

3. GN's amide, amino, carboxyl and other polar groups can inhibit the growth of lithium dendrites and protect the surface of lithium anode.

4. GPE is flame retardant, which can improve the safety of LMB.

5. GN's three-dimensional network structure and the synergistic effect of polar groups make GPE a potential solution for long-term cycling stability and high safety of LMB

Originallink: https://doi.org/10.1007/s12274-023-6230-0