A critical review on nickel-based cathodes in rechargeable batteries

The 3d transition-metal nickel (Ni)-based cathodes have long been widely used in rechargeable batteries for over 100 years, from Ni-based alkaline rechargeable batteries, such as nickel-cadmium (Ni-Cd) and nickel-metal hydride (Ni-MH) batteries, to the Ni-rich cathode featured in lithium-ion batteries (LIBs). Ni-based alkaline batteries were first invented in the 1900s, and the well-developed Ni-MH batteries were used on a large scale in Toyota Prius vehicles in the mid-1990s. Around the same time, however, Sony Corporation commercialized the first LIBs in camcorders. After temporally fading as LiCoO2 dominated the cathode in LIBs, nickel oxide-based cathodes eventually found their way back to the mainstreaming battery industry. The uniqueness of Ni in batteries is that it helps to deliver high energy density and great storage capacity at a low cost. This review mainly provides a comprehensive overview of the key role of Ni-based cathodes in rechargeable batteries. After presenting the physical and chemical properties of the 3d transition-metal Ni, which make it an optimal cationic redox center in the cathode of batteries, we introduce the structure, reaction mechanism, and modification of nickel hydroxide electrode in Ni-Cd and Ni-MH rechargeable batteries. We then move on to the Ni-based layered oxide cathode in LIBs, with a focus on the structure, issues, and challenges of layered oxides, LiNiO2, and LiNi1−x−yCoxMnyO2. The role of Ni in the electrochemical performance and thermal stability of the Ni-rich cathode is highlighted. By bridging the “old” Ni-based batteries and the “modern” Ni-rich cathode in the LIBs, this review is committed to providing insights into the Ni-based electrochemistry and material design, which have been under research and development for over 100 years. This overview would shed new light on the development of advanced Ni-containing batteries with high energy density and long cycle life.