Human society is now moving from informatization to intelligence, in which artificial intelligence (AI) is the key. In many fields, AI has demonstrated the ability to surpass the human brain, due to the continuous innovation of AI algorithms and rapidly increasing computing powers of super-computers. Considering the current data volume, it is particularly important to improve the computing power. In this aspect, innovative AI chips are critical.In the pursuit of high performance and low power consumption, AI chips face two bottlenecks. (1) The memory wall: The access speed of memories cannot keep up with the speed of data consuming by computing units, which perplexes the computer architecture for a long time. (2) The failure of the Moore's law, due to the limitation of basic physical principles. It becomes more and more difficult to improve the integration density and reduce the power consumption of chips by reducing the transistor size.A memristor is a kind of circuit device with memory effect. Under the action of external electric fields, the device can change reversibly between high and low conductance states.The different conductance states are controlled by the migration of various ionic defects, e.g., oxygen vacancies, proton defects, cations, etc. Memristors have the characteristics of simple sandwich structure, fast operation speed, low energy consumption, and rich performances. In addition, memristor arrays with crossbar structure can achieve the integration of the data storage and computing by the vector-matrix multiplication. Therefore, memristor-based neuromorphic computing, with its ability to perform computation where data are generated and the advantages of convenient realization of brain-inspired algorithms, is very promising to crack the memory wall and the failure of the Moore's law. Ionic defects are electrically