Innovative association network of new energy vehicle charging stations in China: Structural evolution and policy implications.

New energy vehicles (NEVs) can effectively reduce emissions and alleviate global climate problems, and are crucial to global sustainable development. China is the world's largest seller of NEVs, but charging stations have always been a major constraint to the development of NEVs. To clearly characterize the structural characteristics of an innovation association network of NEV charging stations, this study analyzes the structural characteristics of China's innovation association network of NEV charging stations with the patent data since 2007 in the Incopat Global Patent Database from the three perspectives of province, city and patent applicant using method of social network analysis (SNA). The findings show the following: (1) The innovation association network of NEV charging stations has been expanded constantly, with the association strength evidently increasing. (2) The innovation association network of NEV charging stations exhibits a typical core-periphery structure, with the quantity of nodes with high association strength varying little, and the quantity of nodes with low- and medium-association strengths exhibiting an evident increasing trend. (3) The effect of regional central cities is enhanced, with an evident group structure. There has been no information barrier caused by excessive small group formation in the province association network, whereas there are small group development trends in city and patent applicant cooperation networks. In addition, policy recommendations for further expanding technological innovation in charging stations to promote the development of the NEV industry are discussed based on the study results.