Leaders must scan the internal and external environment, chart strategic and task objectives, and provide performance feedback. These instrumental leadership (IL) functions go beyond the motivational ...and quid-pro quo leader behaviors that comprise the full-range—transformational, transactional, and laissez faire—leadership model. In four studies we examined the construct validity of IL. We found evidence for a four-factor IL model that was highly prototypical of good leadership. IL predicted top-level leader emergence controlling for the full-range factors, initiating structure, and consideration. It also explained a unique variance in outcomes beyond the full-range factors; the effects of transformational leadership were vastly overstated when IL was omitted from the model. We discuss the importance of a “fuller full-range” leadership theory for theory and practice. We also showcase our methodological contributions regarding corrections for common method variance (i.e., endogeneity) bias using two-stage least squares (2SLS) regression and Monte Carlo split-sample designs.
Although researchers predominately test for linear relationships between variables, at times there may be theoretical and even empirical reasons for expecting nonlinear functions. We examined if the ...relation between intelligence (IQ) and perceived leadership might be more accurately described by a curvilinear single-peaked function. Following Simonton's (1985) theory, we tested a specific model, indicating that the optimal IQ for perceived leadership will appear at about 1.2 standard deviations above the mean IQ of the group membership. The sample consisted of midlevel leaders from multinational private-sector companies. We used the leaders' scores on the Wonderlic Personnel Test (WPT)-a measure of IQ-to predict how they would be perceived on prototypically effective leadership (i.e., transformational and instrumental leadership). Accounting for the effects of leader personality, gender, age, as well as company, country, and time fixed effects, analyses indicated that perceptions of leadership followed a curvilinear inverted-U function of intelligence. The peak of this function was at an IQ score of about 120, which did not depart significantly from the value predicted by the theory. As the first direct empirical test of a precise curvilinear model of the intelligence-leadership relation, the results have important implications for future research on how leaders are perceived in the workplace.
In the search for high energy density cathodes for next-generation lithium-ion batteries, the disordered rocksalt oxyfluorides are receiving significant attention due to their high capacity and lower ...voltage hysteresis compared with ordered Li-rich layered compounds. However, a deep understanding of these phenomena and their redox chemistry remains incomplete. Using the archetypal oxyfluoride, Li2MnO2F, we show that the oxygen redox process in such materials involves the formation of molecular O2 trapped in the bulk structure of the charged cathode, which is reduced on discharge. The molecular O2 is trapped rigidly within vacancy clusters and exhibits minimal mobility unlike free gaseous O2, making it more characteristic of a solid-like environment. The Mn redox process occurs between octahedral Mn3+ and Mn4+ with no evidence of tetrahedral Mn5+ or Mn7+. We furthermore derive the relationship between local coordination environment and redox potential; this gives rise to the observed overlap in Mn and O redox couples and reveals that the onset potential of oxide ion oxidation is determined by the degree of ionicity around oxygen, which extends models based on linear Li–O–Li configurations. This study advances our fundamental understanding of redox mechanisms in disordered rocksalt oxyfluorides, highlighting their promise as high capacity cathodes.
Abstract
Lithium-rich disordered rocksalt cathodes display high capacities arising from redox chemistry on both transition-metal ions (TM-redox) and oxygen ions (O-redox), making them promising ...candidates for next-generation lithium-ion batteries. However, the atomic-scale mechanisms governing O-redox behaviour in disordered structures are not fully understood. Here we show that, at high states of charge in the disordered rocksalt Li
2
MnO
2
F, transition metal migration is necessary for the formation of molecular O
2
trapped in the bulk. Density functional theory calculations reveal that O
2
is thermodynamically favoured over other oxidised O species, which is confirmed by resonant inelastic X-ray scattering data showing only O
2
forms. When O-redox involves irreversible Mn migration, this mechanism results in a path-dependent voltage hysteresis between charge and discharge, commensurate with the hysteresis observed electrochemically. The implications are that irreversible transition metal migration should be suppressed to reduce the voltage hysteresis that afflicts O-redox disordered rocksalt cathodes.
Lithium‐rich transition metal cathodes can deliver higher capacities than stoichiometric materials by exploiting redox reactions on oxygen. However, oxidation of O2− on charging often results in loss ...of oxygen from the lattice. In the case of Li2MnO3 all the capacity arises from oxygen loss, whereas doping with Ni and/or Co leads to the archetypal O‐redox cathodes LiLi0.2Ni0.2Mn0.6O2 and LiLi0.2Ni0.13Co0.13Mn0.54O2, which exhibit much reduced oxygen loss. Understanding the factors that determine the degree of reversible O‐redox versus irreversible O‐loss is important if Li‐rich cathodes are to be exploited in next generation lithium‐ion batteries. Here it is shown that the almost complete eradication of O‐loss with Ni substitution is due to the presence of a less Li‐rich, more Ni‐rich (nearer stoichiometric) rocksalt shell at the surface of the particles compared with the bulk, which acts as a self‐protecting layer against O‐loss. In the case of Ni and Co co‐substitution, a thinner rocksalt shell forms, and the O‐loss is more abundant. In contrast, Co doping does not result in a surface shell yet it still suppresses O‐loss, although less so than Ni and Ni/Co doping, indicating that doping without shell formation is effective and that two mechanisms exist for O‐loss suppression.
O‐loss from Li2MnO3 can be almost completely suppressed with Ni substitution due to the presence of a near stoichiometric Ni‐rich rocksalt shell, acting as a self‐protecting surface layer against O‐loss. In contrast, Co‐substitution does not result in a surface shell but still suppresses O‐loss, although less effectively than Ni and Ni/Co‐cosubstitution.
Abstract
Layered Li-rich transition metal oxides undergo O-redox, involving the oxidation of the O
2−
ions charge compensated by extraction of Li
+
ions. Recent results have shown that for 3d ...transition metal oxides the oxidized O
2−
forms molecular O
2
trapped in the bulk particles. Other forms of oxidised O
2−
such as O
2
2−
or (O–O)
n−
with long bonds have been proposed, based especially on work on 4 and 5d transition metal oxides, where TM–O bonding is more covalent. Here, we show, using high resolution RIXS that molecular O
2
is formed in the bulk particles on O
2‒
oxidation in the archetypal Li-rich ruthenates and iridate compounds, Li
2
RuO
3
, Li
2
Ru
0.5
Sn
0.5
O
3
and Li
2
Ir
0.5
Sn
0.5
O
3
. The results indicate that O-redox occurs across 3, 4, and 5d transition metal oxides, forming O
2
, i.e. the greater covalency of the 4d and 5d compounds still favours O
2
. RIXS and XAS data for Li
2
IrO
3
are consistent with a charge compensation mechanism associated primarily with Ir redox up to and beyond the 5+ oxidation state, with no evidence of O–O dimerization.
It is possible to increase the charge capacity of transition-metal (TM) oxide cathodes in alkali-ion batteries by invoking redox reactions on the oxygen. However, oxygen loss often occurs. To explore ...what affects oxygen loss in oxygen redox materials, we have compared two analogous Na-ion cathodes, P2-Na0.67Mg0.28Mn0.72O2 and P2-Na0.78Li0.25Mn0.75O2. On charging to 4.5 V, >0.4e – are removed from the oxide ions of these materials, but neither compound exhibits oxygen loss. Li is retained in P2-Na0.78Li0.25Mn0.75O2 but displaced from the TM to the alkali metal layers, showing that vacancies in the TM layers, which also occur in other oxygen redox compounds that exhibit oxygen loss such as LiLi0.2Ni0.2Mn0.6O2, are not a trigger for oxygen loss. On charging at 5 V, P2-Na0.78Li0.25Mn0.75O2 exhibits oxygen loss, whereas P2-Na0.67Mg0.28Mn0.72O2 does not. Under these conditions, both Na+ and Li+ are removed from P2-Na0.78Li0.25Mn0.75O2, resulting in underbonded oxygen (fewer than 3 cations coordinating oxygen) and surface-localized O loss. In contrast, for P2-Na0.67Mg0.28Mn0.72O2, oxygen remains coordinated by at least 2 Mn4+ and 1 Mg2+ ions, stabilizing the oxygen and avoiding oxygen loss.
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