Original Article:
Magnesium ion-conducting solid polymer electrolyte based on cellulose acetate with magnesium nitrate (Mg(NO3)2·6H2O) for electrochemical studies
M. Mahalakshmi, et al.
Ionics 26.9 (2020): 4553-4565.
10.1007/s11581-020-03615-4
Compared with conventional non-degradable synthetic solid polymer electrolytes, the non-toxic and biodegradable properties of biopolymer electrolytes are promoting their research and development in electronic and energy devices. The three main classes of biopolymers are polynucleotides, polypeptides, and polysaccharides. In this work, the authors developed a magnesium conductive solid polymer electrolyte (PE) using cellulose acetate and magnesium nitrate and analyzed its electrochemical performance.
Why choose cellulose acetate and magnesium nitrate for electrolyte?
- Cellulose acetate (CA) is a typical example of a polysaccharide-based biopolymer, which has the advantages of moderate flux, cost-effectiveness, relatively easy fabrication, renewable raw materials, and nontoxicity.
- CA is a semi-crystalline polymer derived from cellulose with good film-forming properties. It is insoluble in water and has a carbonyl group (C=O) in its molecular structure.
- Magnesium-based batteries are trying to replace lithium-based rechargeable batteries due to their low cost, abundant resources, and safety. Moreover, magnesium-based batteries are adjacent to lithium in the periodic table of elements and have similar electrochemical properties to lithium. Moreover, Mg2+ has a higher theoretical volumetric capacity (3832 mAh cm-1) than Li+ (2062 mAh cm-1) due to the divalent nature.
Preparation of Electrolytes Based on Cellulose Acetate and Magnesium Nitrate
Step 1: Prepare different concentrations of cellulose acetate and stir to dissolve in DMF solvent.
Step 2: Prepare different concentrations of magnesium nitrate (Mg(NO3)2·6H2O) and stir to dissolve in DMF solvent.
Step 3: Mix the above two solutions well and keep stirring for several hours to obtain a homogeneous solution.
Step 4: The resulting mixture was transferred to a polypropylene petri dish and dried at 60 °C to evaporate the solvent. A series of mechanically stable, transparent and flexible films were thus prepared.
Step 5: Select the membrane with the highest ionic conductivity to construct the primary magnesium battery for subsequent performance analysis.
Interaction Between Cellulose Acetate and Magnesium Nitrate
- The addition of Mg(NO3)2·6H2O made the semi-crystalline nature of the CA polymer more amorphous.
- The interaction between the Mg2+ ions of Mg(NO3)2·6H2O and CA through the carbonyl group means that the ions are mobile in the system.
- High mobility of ions favors highest ionic conductivity. This confirms the potential of Mg2+ in Mg(NO3)2·6H2O to act as a charge carrier in the system.
- Weakly bound Mg2+ ions can hop across the coordination sites of the host polymer C=O and conduct.
Performance of Cellulose Acetate and Magnesium Nitrate Based Electrolytes
- The highest ionic conductivity of the 60 wt.% CA/40 wt.% Mg(NO3)2·6H2O membrane was 9.19 × 10-4 S/cm.
- Using Evan's method, the ion transport number for Mg2+ was estimated to be 0.35 for a 60 wt.% CA/40 wt.% Mg(NO3)2·6H2O electrolyte membrane.
- The electrochemical stability is estimated to be 3.65 V by LSV, which is sufficient for electrochemical applications.
Chemicals Related in the Paper:
| Catalog Number | Product Name | Structure | CAS Number | Price |
|---|---|---|---|---|
| ACM9004357 | Cellulose Acetate |  |
9004-35-7 | Price |
| ACM13446189 | Magnesium nitrate hexahydrate |  |
13446-18-9 | Price |
