Capacitive deionization (CDI) is an emerging technology for energy-efficient water desalination, and attracts more and more attention in recent years. It has been concluded that CDI technology shows competitiveness and perspectives on seawater desalination and wastewater treatment. The ionic adsorption mechanism can be clarified by electric double-layer capacitive adsorption and pseudocapacitive adsorption. The performance of CDI depends on both device and materials. The adsorption capacity and energy efficiency was improved significantly with fast growth of researches on material and novel energy storage techniques. This review summarizes researches on CDI technologies with an emphasis on electrode material design and improved adsorption performance. This review outlines the ion storage mechanisms and electrode materials of capacitive deionization. Display omitted •Electrochemical extraction of ions from seawater/brine was reviewed systematically.•An emphasis on electrode material design thought has been analyzed.•The performance of various extraction devices has been summarized and compared.•Future challenge on this technology has been clarified.