A Bibliometric Analysis of Doctoral Candidates' Enrollment Policies in China

As the entrance of doctoral education in China, doctoral candidates' enrollment is closely related to the quality of doctoral education. Because the policy literature truly reflects the government’s signature on the handling of related public affairs. So the study on it can help clarify the government's management thinking and motivation for the enrollment of doctoral candidates. Based on the analyzing the structural elements of the national doctoral candidates' enrollment policy literatures from 1981 to 2017, this article is aimed at exploring the characteristics and historical changes of the doctoral candidates' enrollment policy literatures in the time of promulgation, the organization of the enactment, and the types of documents. Keywords: doctoral candidates' enrollment policies, bibliometric analysis, promulgation time, issuing agency, document typ

Mechanism of Exact Transition between Cationic and Anionic Redox Activities in Cathode Material Li2FeSiO4.

The discovery of anion redox activity is promising for boosting the capacity of lithium ion battery (LIB) cathodes. However, fundamental understanding of the mechanisms that trigger the anionic redox is still lacking. Here, using hybrid density functional study combined with experimental soft X-ray absorption spectroscopy (sXAS) measurements, we unambiguously proved that Li(2- x)FeSiO4 performs sequent cationic and anionic redox activity through delithiation. Specifically, Fe2+ is oxidized to Fe3+ during the first Li ion extraction per formula unit (f.u.), while the second Li ion extraction triggered the oxygen redox exclusively. Cationic and anionic redox result in electron and hole polaron states, respectively, explaining the poor conductivity of Li(2- x)FeSiO4 noted by previous experiments. In contrast, other cathode materials in this family exhibit diversity of the redox process. Li2MnSiO4 shows double cationic redox (Mn2+-Mn4+) during the whole delithiation, while Li2CoSiO4 shows simultaneous cationic and anionic redox. The present finding not only provides new insights into the oxygen redox activity in polyanionic compounds for rechargeable batteries but also sheds light on the future design of high-capacity rechargeable batteries