Quaternary ammonium salt additive reconstructing the electrolyte environment and layered organic vanadium oxide assisting novel Ni-ion batteries

Ni-ion aqueous batteries (NIBs) were considered an important development direction for aqueous batteries due to the high theoretical capacity (913 mA h g⁻¹) and volume capacity (8136 mA h cm⁻³) of nickel metal. Herein, an electrolyte additive (dodecyl trimethyl ammonium chloride, DTAC) was used to improve the electrolyte environment, achieve efficient transport of Ni-ion, and combine the intercalated vanadium oxide cathodes to realize novel strategy NIBs. Firstly, the introduction of trace amounts of DTAC improved the high-concentration NiCl₂ (4.2 M) electrolyte environment and reconstructed the hydrogen bond network. Molecular dynamics (MD) calculations and electrochemical results indicated that DTAC contributed to the desolvation process of Ni²⁺ and the realization of fast dynamics. The results of Ni symmetric cells demonstrated that DTAC enhanced the rapid migration of Ni-ion and achieved longer cycling stability (1750/1500 h at 0.2/0.5 mA cm⁻² without obvious short circuits). Secondly, the insertion of organic small molecules (pyrrolidine) into vanadium oxide (V₂O₅) to expand the interlayer spacing promoted the Ni-ion storage capacity of the cathodes. The capacity retention rate of Ni full battery after 6000 cycles at 5 A g⁻¹ reached 82.17%. This work provided a novel strategy for the development of Ni-ion aqueous batteries.