The increasing demand for portable electronic devices has led to an intensive search to improve energy storage systems. By far Li-ion batteries are the most successful technology for portable devices. However, there is a necessity to increase the energy density as well as battery life for more demanding applications such as electric vehicles (EVs). In the quest for new materials for Li-ion batteries, Li and Zn metal anodes have raised as the most promising alternative to increase energy density. Nevertheless, the main obstacle for metal anodes to become practical is the dendrite growth which lead to electrical short-cut and short battery life.
Great efforts have been put in the development of new strategies to stabilize Li and Zn anodes. To do this, several materials like graphene, carbon nanotubes, porous copper, and graphite filters have been used to control de lithium ion deposition. The utilization of porous material reduces the local current densities helping to increase battery life. Another strategy is based on the use of structured electrolytes containing immobilized anions to stabilize the electrodeposition in metal anodes at large overpotentials. These structures are used between the electrode and the separator to allow a more homogeneous plating on the electrode surface.
The latter strategy was explored recently by Zhi et al, they proposed the use of collagen hydrolysate (CH) coated on an adsorbed glass mat (AGM) substrate (Zhi et al., 2020). CH-AGM is used as an interlayer to produce a phenomena called shock electrodeposition to stabilize the metal anode and suppress dendrite growth. In this case, the negative charge on the surface of the CH-AGM interlayer is caused by oxygen functional groups in the backbone of the collagen hydrolysate. The authors tested the CH-AGM interlayer in full cells with Li and Zn anodes at different scales from 5, 65, and 200 Ah. The implementation of the CH-AGM in the full cells resulted in outstanding performance, both the Li and Zn batteries delivered up to 600 cycles with a coulombic efficiency of 99.7 %. While pristine Li and Zn batteries failed after 10 and 100 cycles, respectively. According to the authors, the cells containing CH-AGM present a cation regulation mechanism which can simultaneously induce an ionization shock within the separator and spread cations on the anode surface to perform homogeneous plating.
The development of novel strategies to overcome fundamental challenges related to dendrite growth, fast metal depletion, and electrode passivation is required, especially for high loading intercalation cathodes. The use of biomaterials such as collagen can have a great impact with a relatively easy fabrication procedure like the one presented by Zhi et al. The promising results of obtained in their work indicate the possibility to increase the stability of the batteries in a simple and efficient way.
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For more details on the work of Zhi et al, please refer to the full paper available at https://advances.sciencemag.org/content/6/32/eabb1342/tab-pdf.
Zhi, J., Li, S., Han, M., & Chen, P. (2020). Biomolecule-guided cation regulation for dendrite-free metal anodes. Science Advances, 6(32), 1–15. https://doi.org/10.1126/sciadv.abb1342