Li-CO 2 batteries are regarded as next-generation high-energy-density electrochemical devices. However, the greatest challenge arises from the formation of the discharge product, Li 2 CO 3 , which would accumulate and deactivate heterogenous catalysts to cause huge polarization. Herein, Ru(bpy) 3 Cl 2 was employed as a solution-phase catalyst for Li-CO 2 batteries and proved to be the most effective one screened so far. Spectroscopy and electrochemical analyses elucidate that the Ru II center could interact with both CO 2 and amorphous Li 2 C 2 O 4 intermediate, thus promoting electroreduction process and delaying carbonate transformation. As a result, the charge potential is reduced to 3.86 V and over 60 discharge/charge cycles are achieved with a fixed capacity of 1000 mAh g À1 at a current density of 300 mA g À1 . Our work provides a new avenue to improve the electrochemical performance of Li-CO 2 batteries with efficient mobile catalysts.

Green recycle and reuse of copper ions in saccharin sodium wastewater have been proved to be practically applicable, and the most difficult electrodeposition step of [CuCl4]2– to Cu0, much more difficult than normal Cu2+ to Cu0, has been successfully overcome by the rotating copper disk method. The developed method was precisely targeted at the demand of saccharin sodium wastewater and met the quality standard of reused copper product for original manufacturing process in Kaifeng Xinghua Special Chemical Ltd., the largest saccharin sodium salt manufacturer. Experimental data show that the rotating disk electrode significantly increased the reaction current in both lab scale and pilot scale, indicating that the disadvantages of the slight increase in the reaction current and low reaction rate in conventional copper electrodeposition have been successfully overcome. Impedance analysis revealed a huge reduction of dissociative electron-transfer capacitance and double-layer capacitance simultaneously. The overall pilot-scale performance of a maximal current increase of 575% compared to conventional copper electrodeposition and the residual copper ion concentration less than 50 mg/L within 90 min of treatment had been attained at 1600 rpm under −1.2 V versus Ag/AgCl. The purity of element copper in CuSO4 after overall copper recycle was attained at larger than 99.9%.

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Li-CO 2 batteries are regarded as next-generation high-energy-density electrochemical devices. However, the greatest challenge arises from the formation of the discharge product, Li 2 CO 3 , which would accumulate and deactivate heterogenous catalysts to cause huge polarization. Herein, Ru(bpy) 3 Cl 2 was employed as a solution-phase catalyst for Li-CO 2 batteries and proved to be the most effective one screened so far. Spectroscopy and electrochemical analyses elucidate that the Ru II center could interact with both CO 2 and amorphous Li 2 C 2 O 4 intermediate, thus promoting electroreduction process and delaying carbonate transformation. As a result, the charge potential is reduced to 3.86 V and over 60 discharge/charge cycles are achieved with a fixed capacity of 1000 mAh g À1 at a current density of 300 mA g À1 . Our work provides a new avenue to improve the electrochemical performance of Li-CO 2 batteries with efficient mobile catalysts.