Stabilizing High-Voltage Cathodes via Ball-Mill Coating with Flame-Made Nanopowder Electrolytes.

LiMn1.5Ni0.5O4 (LMNO) spinel has recently been the subject of intense research as a cathode material because it is cheap, cobalt-free, and has a high discharge voltage (4.7 V). However, the decomposition of conventional liquid electrolytes on the cathode surface at this high oxidation state and the dissolution of Mn2+ have hindered its practical utility. We report here that simply ball-mill coating LMNO using flame-made nanopowder (NPs, 5-20 wt %, e.g., LiAlO2, LATSP, LLZO) electrolytes generates coated composites that mitigate these well-recognized issues. As-synthesized composite cathodes maintain a single P4332 cubic spinel phase. Transmission electron microscopy (TEM) and X-ray photoelectron spectra (XPS) show island-type NP coatings on LMNO surfaces. Different NPs show various effects on LMNO composite cathode performance compared to pristine LMNO (120 mAh g-1, 93% capacity retention after 50 cycles at C/3, ∼67 mAh g-1 at 8C, and ∼540 Wh kg-1 energy density). For example, the LMNO + 20 wt % LiAlO2 composite cathodes exhibit Li+ diffusivities improved by two orders of magnitude over pristine LMNO and discharge capacities up to ∼136 mAh g-1 after 100 cycles at C/3 (98% retention), while 10 wt % LiAlO2 shows ∼110 mAh g-1 at 10C and an average discharge energy density of ∼640 Wh kg-1. Detailed postmortem analyses on cycled composite electrodes demonstrate that NP coatings form protective layers. In addition, preliminary studies suggest potential utility in all-solid-state batteries (ASSBs).

Peer victimization and well-being as a function of same-ethnicity classmates and classroom social norms: Revisiting person × environment mismatch theory.

Person × Environment mismatch theory has been applied to understanding how the classroom social ecology moderates associations between peer victimization and socioemotional well-being. In 2004, Bellmore et al. applied this theory to the ethnic composition and social climate of the classroom. The current study tested whether their findings replicate with a slightly younger, rural sample from the Southeastern United States, whether associations held longitudinally, and whether child ethnicity moderated effects. Participants were 4th-grade and 5th-grade students from 13 elementary schools (N = 1,448; Mage = 10.13 years; 701 girls; 37.9% Black, 4.40% Latina/o, 57.7% White). Measures included peer-reports of peer victimization, teacher-reports of loneliness, social withdrawal, and anxiety, and self-reports of prosocial peer treatment. Classroom social disorder was assessed using teacher-reports of aggressive behavior and peer victimization. Evidence that having a large percentage of same-ethnicity peers amplifies peer victimization-adjustment linkages was limited. Although the exact nature of identified interactive effects somewhat varied from Bellmore et al., findings similarly underscored the benefits of low social disorder and ethnically diverse classrooms. Together, these findings point to a need to understand the proximal sociostructural impact of ecological factors when studying the consequences of peer victimization. (PsycInfo Database Record (c) 2021 APA, all rights reserved).