Electrospinning Machine | Stabilizing the dual electrode interface via a crosslinked gelatin nonwoven separator for durable lithium metal batteries

The uncontrollable dendrite growth of the lithium metal anode greatly hinders the development of lithium metal batteries, while the problem of manganese dissolution from active materials into the electrolyte also largely affects the application prospects of manganese-based electrode materials. The separator, as a component connecting the positive and negative electrodes, has direct contact with both. Therefore, by developing functional separators, the interfaces of the positive and negative electrodes can be simultaneously regulated to address the problems of dendrite growth and manganese dissolution, improving the battery's cycle capacity and usage safety.

Recently, Associate Researcher Chen Min's team at Dongguan University of Technology published their latest research results "Stabilizing the dual electrode interface via a crosslinked gelatin nonwoven separator for durable lithium metal batteries" in the journal Chinese Chemical Letters. The first authors are Cai Weijie, an undergraduate, and Han Xinxin, a master's student, from the School of Materials Science and Engineering at Dongguan University of Technology. The researchers prepared a gelatin-based nanofiber fabric separator (CGN) through electrospinning and in-situ vapor cross-linking processes.

Graphical abstract: Schematic diagram of the preparation process of the CGN separator and its role in the battery.

Benefiting from the unique chemical composition of gelatin, the high specific surface area and high porosity imparted by electrospinning, and the enhanced mechanical properties from the cross-linking process, this separator exhibits good electrolyte wettability, low interfacial impedance, a high lithium-ion transference number, and high ionic conductivity. When applied in lithium manganate/lithium metal batteries, it can capture dissolved manganese ions and regulate the uniform deposition of lithium ions, significantly improving electrochemical performance.

Figure 1: Physical and chemical characterization of the CGN separator.

The fabric (GN) obtained after spinning gelatin is easily soluble in water and its mechanical properties are less than ideal. Placing it in an environment containing glutaraldehyde vapor causes the gelatin to undergo a cross-linking reaction, improving its mechanical properties. The cross-linked CGN fabric still maintains a fibrous structure, and its porosity, ionic conductivity, wettability, and lithium-ion transference number all show significant advantages compared to the Celgard separator.

Figure 2: Performance of the CGN separator in Li/Li symmetric cells.

Because the backbone oxygen on the gelatin peptide chain molecules has good affinity for lithium ions, it can promote lithium ion transport. Simultaneously, the side chains contain positively charged amino acid residues, which can fix the anions in the electrolyte and stabilize the electric field. Therefore, the CGN separator enables uniform deposition of lithium ions, suppressing the formation and growth of dendrites.

Figure 3: Electrochemical performance of the CGN separator in lithium manganate/lithium metal batteries.

Gelatin can capture manganese ions dissolved in the electrolyte, and the fibrous structure fabric prepared by electrospinning can provide a large number of adsorption sites. Therefore, the CGN separator can effectively capture dissolved manganese ions and improve the cycle capacity of lithium manganate/lithium metal batteries.

Figure 4: Further verification of the CGN separator's ability to adsorb manganese ions and regulate the lithium metal interface.

XPS results indicate that the primary interaction in CGN with manganese ions involves oxygen atoms. The surface of the CGN separator cycled in a lithium manganate/lithium metal battery adsorbs a large amount of manganese-containing substances, confirming CGN's ability to adsorb manganese ions. Comparison of the surface morphology and composition of the lithium metal after cycling also demonstrates that CGN can regulate the uniform deposition of lithium ions and induce the formation of a more uniform SEI film rich in inorganic Li-F components, which is beneficial for the rapid transport of lithium ions. Furthermore, this CGN separator can also be adapted to other cathodes with active material dissolution (such as sulfur cathodes), consistently exhibiting good adsorption effects and enabling higher cycle capacity.

In summary, the team utilized gelatin electrospinning combined with an in-situ cross-linking process to prepare a functional separator that stabilizes the dual electrode interfaces. At the anode interface, the CGN separator can fix anions via the amino acid residues on the gelatin side chains, stabilize the electric field, and promote lithium ion transport, resulting in stable and uniform lithium ion deposition. At the cathode interface, CGN can adsorb manganese ions via the backbone oxygen atoms of gelatin, and its large specific surface area can effectively block their diffusion to the anode side, leading to stable cycling and increased capacity. This separator also has potential application value in other battery systems suffering from active material dissolution and metal anode dendrite issues.

Paper link: https://doi.org/10.1016/j.cclet.2025.111809