Atomic Layer Deposition of Al2O3-Ga2O3 Alloy Coatings for Li[Ni0.5Mn0.3Co0.2]O2 Cathode to Improve Rate Performance in Li-Ion Battery.

Metal oxide coatings can improve the electrochemical stability of cathodes and hence, their cycle-life in rechargeable batteries. However, such coatings often impose an additional electrical and ionic transport resistance to cathode surfaces leading to poor charge-discharge capacity at high C-rates. Here, a mixed oxide (Al2O3)1-x(Ga2O3)x alloy coating, prepared via atomic layer deposition (ALD), on Li[Ni0.5Mn0.3Co0.2]O2 (NMC) cathodes is developed that has increased electron conductivity and demonstrated an improved rate performance in comparison to uncoated NMC. A "co-pulsing" ALD technique was used which allows intimate and controlled ternary mixing of deposited film to obtain nanometer-thick mixed oxide coatings. Co-pulsing allows for independent control over film composition and thickness in contrast to separate sequential pulsing of the metal sources. (Al2O3)1-x(Ga2O3)x alloy coatings were demonstrated to improve the cycle life of the battery. Cycle tests show that increasing Al-content in alloy coatings increases capacity retention; whereas a mixture of compositions near (Al2O3)0.5(Ga2O3)0.5 was found to produce the optimal rate performance.

Is bigger really better? Obesity among high school football players, player position, and team success.

OBJECTIVE: American football is one of the most common high school sports in the United States. We examine obesity among high school football players, and variations based on positions, team division, and team success. PATIENTS AND METHODS: We used 2 data sets from the North Carolina High School Athletic Association (n = 2026) and MaxPreps (n = 6417). We examined body mass index, calculated using coach-reported height and weight, by player position, division, and success based on win-loss percentage. RESULTS: Most players (62%) were skill players, with 35% linemen and 3% punters/kickers. Most skill players (62%) were healthy weight and 4% obese or morbidly obese. In contrast, only 8% of linemen were healthy weight, with 21% morbidly obese. Team success was correlated with size only for skill players. CONCLUSIONS: Obesity is a significant problem for high school football players. Pediatricians should consider the context of football playing in assessing long-term health risks for these young men.