Researchers in Korea have developed ultra-thin SiO₂ nanoparticle layered separators for Li-metal batteries for enhanced lithium dendrite resistance and improved thermal properties. A paper on their work is published in the journal Energy Storage Materials.

Mechanical and thermal failure of a polyolefin separator often causes the internal short-circuit of batteries, which leads to abrupt heat generation in a short time, so-called thermal runaway. For this, we introduce grafting polymer layers with cross-linking to make a superior, thin, and uniform SiO₂ layer with strong chemical binding to the surface of a polypropylene separator (PPS). The surface of the PPS was modified with i) coating of double bond-contained PVDF, ii) grafting with poly(ethylene glycol) methacrylate, 3-(trimethoxysilyl)propyl methacrylate, and ethylene glycol dimethacrylate, and iii) coating with SiO₂ nanoparticles via immersing (GDPS-SNPI) or casting (GDPS-SNPC) methods.

The pore structure and distribution, electrolyte affinity, thermal stability, and mechanical properties were progressively improved after respective modification steps.

—Park et al.

Park et al.

The GDPS-SNPC cell showed excellent capacity retention of 100% at 1 C after 100 cycles and the lowest increase in the cell impedance, whereas an LFP half-cell with PPS exhibited capacity retention of 88.32%.

Furthermore, the team found that the coating method for SiO₂ nanoparticles substantially influences the long-term cycling stability of Li-symmetric cells.

The GDPS-SNPC cell survived after cycling more than 1,000 h at a current density of 1 mA cm⁻², whereas the GDPS-SNPI cell died before 500 h.

Post-mortem analysis of the cycled Li-metal surface shows that smooth Li-plating occurred at the GDPS-SNPC cell, presumably due to a high Li-ion transference number.

This work provides a solid methodology for producing a novel and robust separator and advances the understanding of separators’ impact on electrochemical and physical phenomena within the cell.

—Park et al.

Resources

• Jaewon Park, Young Je Kwon, Jeongsik Yun, Kaiyun Zhang, Min Jeong Lee, Gyeong Min Choi, Ji woo Bae, Se Hun Kim, Joon Ha Chang, Min Wook Pin, Jin Hong Lee, Hoik Lee, Kie Yong Cho (2024) “Ultra-thin SiO₂ nanoparticle layered separators by a surface multi-functionalization strategy for Li-metal batteries: Highly enhanced Li-dendrite resistance and thermal properties,” Energy Storage Materials, Volume 65 doi: 10.1016/j.ensm.2023.103135