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Spinel LiNi0.5Mn1.5O4 (LNMO) is a promising cathode candidate for the next‐generation high energy‐density lithium‐ion batteries (LIBs). Unfortunately, the application of LNMO is hindered by its poor cycle stability. Now, site‐selectively doped LNMO electrode is prepared with exceptional durability. In this work, Mg is selectively doped onto both tetrahedral (8a) and octahedral (16c) sites in the Fd3‾ m structure. This site‐selective doping not only suppresses unfavorable two‐phase reactions and stabilizes the LNMO structure against structural deformation, but also mitigates the dissolution of Mn during cycling. Mg‐doped LNMOs exhibit extraordinarily stable electrochemical performance in both half‐cells and prototype full‐batteries with novel TiNb2O7 counter‐electrodes. This work pioneers an atomic‐doping engineering strategy for electrode materials that could be extended to other energy materials to create high‐performance devices. [ABSTRACT FROM AUTHOR]

Given its wide application ranges, dielectric capacitors have garnered extensive attentions. However, due to the excessive premature agglomeration of free electrons, capacitors with nanocomposites as dielectrics fail to attain high breakdown strength (E b), and thereby constrain their ability to achieve superior energy storage performances. To alleviate the effects of free electrons and secondary impact-ionized electrons (SIE) on E b and leakage currents, here, a novel organic-inorganic core–shell Ni(OH) 2 @PDI (N@P) nanofiller with opposite double-PN-junction was well-designed and successfully synthesized by coating p-typed Ni(OH) 2 nanosheets with n-typed perylene diimide (PDI). It could reduce free electron kinetic energy and mitigate SIE amounts regardless of the applied electric field direction. Furthermore, PDI, as an organic compound, can uniformly and densely coat onto surfaces of 2D Ni(OH) 2 , as well as enhance compatibilities between Ni(OH) 2 and matrix, and thereby reducing structure defects at their interfaces. Last but not the least, Ni(OH) 2 nanosheets also contribute to E b improvement via acting as scattering centers. Experimental and simulation results concurrently affirmed positive influences of organic-inorganic N@P nanofillers on discharge energy density (U d) and efficiency (η) of P(VDF-HFP)-based (PVH-based) nanocomposites. Remarkably, 1.3 vol% N@P/PVH achieves a high U d of 21.7 J/cm3 and η of 81.2 % under 569.0 MV/m. More importantly, it maintains an excellent energy storage performance throughout 104 cyclic tests. This study presents a valid strategy for concurrently improving U d and η of polymer-based nanocomposites. [ABSTRACT FROM AUTHOR]