In Situ Precipitated Organic Nanorod Electrodes for Sodium Ion Batteries

Organic electroactive materials derived from biomasses are promising candidates for next generation rechargeable batteries due to low cost, sustainability and environmental benignity. However, the organic electrodes still suffer from low power density and poor cycling stability, caused by low electronic conductivity and high solubility in liquid organic electrolytes. Herein, we firstly reported a unique in situ organic electrode fabrication technology for Na-ion batteries. Using the 2,5-Dihydroxy-1,4-benzoquinone disodium salt (DHBQDS) as an organic anode, the DHBQDS nanorod electrode is in situ formed during electrode fabrication process by precipitating DHBQDS from DHBQDS-sodium alginate-carbon black aqueous slurry film on a Cu current collector during drying process. In the slurry film, the sodium alginate binder and carbon black play a critical role in the formation of DHBQDS nanorods. Integrating the synthesis of nano-electrode materials into electrode fabrication process greatly simplifies the electrode preparation process and will significantly reduce the battery cost. Due to the fast ionic and electronic conduction of DHBQDS-carbon nanocomposite, the DHBQDS nanorod electrodes deliver a reversible capacity of 167 mAh g-1 at a high current density of 200 mA g-1 after 300 cycles, which is 87% of its initial capacity (capacity decay rate of 0.051% per cycle). To reduce the dissolution of DHBQDS in the electrolyte upon cycling, a thin layer of Al2O3 with thickness of 1nm or 2 nm was coated on the DHBQDS nanorod electrodes using atomic layer deposition (ALD). The Al2O3 coating remarkably suppresses the dissolution of DHBQDS nanorods as evidenced by the increased Coulombic efficiency from 94% to ~100% at a low current density of 50 mA g-1 after initial few activation cycles. The reversible capacity of Al2O3 coated DHBQDS nanorod electrodes remains at 212 mAh g-1 after 300 cycles with a very low capacity decay rate of 0.049% per cycle. The ALD enhanced organic nanorods exhibit the best reversible capacity and cycle life among the organic electrodes reported for Na-ion batteries.