Developing an abnormal high-Na-content P2-type layered oxide cathode with near-zero-strain for high-performance sodium-ion batteries

Layered transition metal oxides (NaxTMO2) possess attractive features such as large specific capacity, high ionic conductivity, and a scalable synthesis process, making them a promising cathode candidate for sodium-ion batteries (SIBs). However, NaxTMO2 suffer from multiple phase transitions and Na+/vacancy ordering upon Na+ insertion/extraction, which is detrimental to their electrochemical performance. Herein, we developed a novel cathode material that exhibits an abnormal P2-type structure at a stoichiometric content of Na up to 1. The cathode material delivers a reversible capacity of 108 mA h g-1 at 0.2C and 97 mA h g-1 at 2C, retaining a capacity retention of 76.15% after 200 cycles within 2.0-4.3 V. In situ diffraction studies demonstrated that this material exhibits an absolute solid-solution reaction with a low volume change of 0.8% during cycling. This near-zero-strain characteristic enables a highly stabilized crystal structure for Na+ storage, contributing to a significant improvement in battery performance. Overall, this work presents a simple yet effective approach to realizing high Na content in P2-type layered oxides, offering new opportunities for high-performance SIB cathode materials.

An Intrinsic Stable Layered Oxide Cathode for Practical Sodium-Ion Battery: Solid Solution Reaction, Near-Zero-Strain and Marvelous Water Stability

Non-aqueous solvents, in particular N,N-dimethylaniline (NMP), are widely applied for electrode fabrication since most sodium layered oxide cathode materials are readily damaged by water molecules. However, the expensive price and poisonousness of NMP unquestionably increase the cost of preparation and post-processing. Therefore, developing an intrinsically stable cathode material that can implement the water-soluble binder to fabricate an electrode is urgent. Herein, a stable nanosheet-like Mn-based cathode material is synthesized as a prototype to verify its practical applicability in sodium-ion batteries (SIBs). The as-prepared material displays excellent electrochemical performance and remarkable water stability, and it still maintains a satisfactory performance of 79.6% capacity retention after 500 cycles even after water treatment. The in situ X-ray diffraction (XRD) demonstrates that the synthesized material shows an absolute solid-solution reaction mechanism and near-zero-strain. Moreover, the electrochemical performance of the electrode fabricated with a water-soluble binder shows excellent long-cycling stability (67.9% capacity retention after 500 cycles). This work may offer new insights into the rational design of marvelous water stability cathode materials for practical SIBs.

Psychometric properties of the risk, pain, and injury questionnaire in Chinese collegiate athletes and its relationship with locus of control

PURPOSE

This study aimed to adapt the Risk, Pain, and Injury Questionnaire (RPIQ) to Chinese collegiate athletes and examine its reliability and validity.

METHODS

Six hundred thirty collegiate athletes aged 17 to 24 years agreed to complete the RPIQ, the Chinese version of the SIAS and an LOC scale. Exploratory factor analysis (EFA, n = 300) and confirmatory factor analysis (CFA, n = 330) were conducted to explore its structure, and convergent and construct validity were investigated by examining the relationships between various factors of the RPIQ, LOC, SIAS and injury risk.

RESULTS

The results of EFA show the Chinese version of the RPIQ contained 12 items and was divided into three factors: tough, pressed and rational choice. CFA confirmed its factorial structure (CMIN/DF = 2.61, CFI = 0.93, TLI = 0.91, RMSEA = 0.07). The reliability of the scale was satisfactory (Cronbach's alpha = 0.75). Significant associations between the RPIQ factors and LOC and SIAS were found, suggesting the construct validity of the scale was acceptable. Additionally, significant gender differences were found in the RPIQ factors and athletes who participated in individual sports scored higher on tough and rational choice factors than those who participated in team sports.

CONCLUSIONS

The Chinese version of the RPIQ has sufficient psychometric properties and can be used as a reliable and effective tool for measuring attitudes of the risk, pain and injury of collegiate athletes.