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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]

LiCoO2 (LCO) with average particle distribution of 8 μm (LCO‐A) and 11 μm (LCO‐B) exhibit substantial differences in cycle performance. The half‐cells have similar first‐cycle discharge capacities of 173 and 175 mAh/g at 0.25 C, but after 100 cycles, the discharge capacities are substantially different, that is, 114 and 141 mAh/g for LCO‐A and LCO‐B, respectively. Operando neutron powder diffraction of full LCO||Li4Ti5O12 batteries show differences in the LCO reaction mechanism underpinning the electrochemical behavior. LCO‐A follows a purely solid solution reaction during cycling compared to the solid solution and two‐phase reaction mechanism in LCO‐B. The absence of the two‐phase reaction in LCO‐A is consistent with a homogeneous distribution of Li throughout the particle. The two‐phase reaction in LCO‐B reflects two distinguishable distributions of Li within the particles. The faster capacity decay in LCO‐A is correlated to an increase in electrode cracking during battery cycles. [ABSTRACT FROM AUTHOR]

The ability to directly track the charge carrier in a battery as it inserts/extracts from an electrode during charge/discharge provides unparalleled insight for researchers into the working mechanism of the device. This crystallographic-electrochemical information can be used to design new materials or modify electrochemical conditions to improve battery performance characteristics, such as lifetime. Critical to collecting operando data used to obtain such information in situ while a battery functions are X-ray and neutron diffractometers with sufficient spatial and temporal resolution to capture complex and subtle structural changes. The number of operando battery experiments has dramatically increased in recent years, particularly those involving neutron powder diffraction. Herein, the importance of structure-property relationships to understanding battery function, why in situ experimentation is critical to this, and the types of experiments and electrochemical cells required to obtain such information are described. For each battery type, selected research that showcases the power of in situ and operando diffraction experiments to understand battery function is highlighted and future opportunities for such experiments are discussed. The intention is to encourage researchers to use in situ and operando techniques and to provide a concise overview of this area of research. [ABSTRACT FROM AUTHOR]

Structure-property relations are central to understanding functional materials, and for battery research the use of neutron powder diffraction to reveal the atomistic and molecular-scale origin of battery performance characteristics is often essential. Although operando experiments of this kind are increasingly common as neutron sources and instrumentation advance, these experiments are hindered by the often large barrier presented by the preparation of whole batteries that yield a neutron diffraction signal from the electrode of interest that is sufficient to extract detailed structural information. This article presents a custom battery that is specifically designed for operando neutron powder diffraction. The battery is a pouch type and contains layers of positive and negative electrodes in a parallel-connecting stack. Importantly, the battery can be easily prepared in most laboratories, is configurable, and can be used with both lithium and sodium charge carriers. This paper provides some example operando neutron powder diffraction studies using this battery. [ABSTRACT FROM AUTHOR]