Lithium‐ and manganese‐rich layered oxides (LMLOs, ≥ 250 mAh g−1) with polycrystalline morphology always suffer from severe voltage decay upon cycling because of the anisotropic lattice strain and ...oxygen release induced chemo‐mechanical breakdown. Herein, a Co‐free single‐crystalline LMLO, that is, LiLi0.2Ni0.2Mn0.6O2 (LLNMO‐SC), is prepared via a Li+/Na+ ion‐exchange reaction. In situ synchrotron‐based X‐ray diffraction (sXRD) results demonstrate that relatively small changes in lattice parameters and reduced average micro‐strain are observed in LLNMO‐SC compared to its polycrystalline counterpart (LLNMO‐PC) during the charge–discharge process. Specifically, the as‐synthesized LLNMO‐SC exhibits a unit cell volume change as low as 1.1% during electrochemical cycling. Such low strain characteristics ensure a stable framework for Li‐ion insertion/extraction, which considerably enhances the structural stability of LLNMO during long‐term cycling. Due to these peculiar benefits, the average discharge voltage of LLNMO‐SC decreases by only ≈0.2 V after 100 cycles at 28 mA g‐1 between 2.0 and 4.8 V, which is much lower than that of LLNMO‐PC (≈0.5 V). Such a single‐crystalline strategy offers a promising solution to constructing stable high‐energy lithium‐ion batteries (LIBs).
Lattice thermal expansion (LTE) has been investigated in double perovskites LaPbMSbO6 (M = Mn, Co, Ni). Ordinary LTE behavior with good thermal stability is identified for the Mn sample, whereas ...unusual LTE with a preferably expanded interplanar distance of (040) is revealed for Co and Ni samples. Temperature-dependent X-ray diffraction patterns (T-XRD), Raman spectra (T-Raman), and specific heat capacities (T-C p) consistently indicate that a rare isostructural displacive phase transition (IDPT) with a second-order phase transition nature is predominant near the critical temperature. Refinements of neutron powder diffraction (NPD) and in situ T-XRD data present temperature-sensitive bond parameters which are relevant to planar oxygen O1. X-ray photoelectron spectra (XPS) further confirm the Jahn–Teller (J-T) activated Co2+ (HS) or Ni3+ (HS/LS) cations at the B-site sublattice. This unusual LTE behavior could be understood by the cooperative J-T effect contributed by a Pb2+ ion and Co2+/Ni3+ ion from A- and B-site sublattices, respectively. The importance of 6s(Pb)-2p(O)-3d(Co/Ni) extended orbital hybridization on affecting thermal expansion behavior is highlighted on the basis of temperature-induced phonon mode softening. This study presents a microscopic description of connection between anisotropic thermal expansion and a cooperative J-T effect, which inspired exploration of thermal–mechanical coupled functional materials based on LaPbMSbO6 double perovskites.
Lithium‐Ion Batteries
In article number 2201652, Anatoliy Senyshyn and co‐workers investigate the degradation mechanisms of real life 18650‐type lithium‐ion batteries using a combination of neutron ...diffraction, calorimetry, infrared measurements, and chemical analytics of battery electrolytes. In addition to the increase of internal cell resistance, loss of movable lithium and “drying out” of the cell, they reveal decomposition of conducting salts to be the main driving factor in the electrolyte degradation.
A comprehensive understanding of the nexus of diffusion mechanisms on the atomic scale as well as structural influences on the ionic motion in solid electrolytes is key for further development of ...high-performing all-solid-state batteries. Therefore, current research not only focuses on the search for innovative materials, but also on the study of diffusion pathways and ion dynamics in ionic conductors. In this context, we report on the extended characterization of the ionic electrolyte Li
La
Zr
Nb
(LLZO-Nb). The commercially available material is analyzed by a combination of powder X-ray (either lab- or synchrotron-based) and neutron diffraction. Details of lithium disorder were obtained from high-resolution neutron diffraction data, from which the ionic transport of Li ions was determined by applying the maximum entropy method in combination with the one-particle potential formalism.
A series of low‐temperature studies on LiNi0.80Co0.15Al0.05O2 18650‐type batteries of high‐energy type with different stabilized states of fatigue is carried out using spatially resolved neutron ...powder diffraction, infrared/thermal imaging, and quasi‐adiabatic calorimetry. In‐plane distribution of lithium in the graphite anode and frozen electrolyte in fully charged state is determined non‐destructively with neutron diffraction and correlated to the introduced state of fatigue. An independent electrolyte characterization is performed via calorimetry studies on variously aged 18650‐type lithium‐ion batteries, where the shape of the thermodynamic signal is evolving with the state of fatigue of the cells. Analyzing the liquid electrolyte extracted/harvested from the studied cells reveals the decomposition of conducting salt to be the main driving factor for fatigue in the electrolyte degradation.
A series of non‐invasive experimental techniques is employed to characterize the state‐of‐health in a batch of differently aged cylinder‐type lithium‐ion batteries along with a simple and fast method to define the state‐of‐health of the electrolyte using its thermal response on freezing.
We investigated why commercial Li
7
La
3
Zr
2
O
12
(LLZO) with Nb- and Ta substitution shows very low mobility on a local scale, as observed with temperature-dependent NMR techniques, compared to Al ...and W substituted samples, although impedance spectroscopy on sintered pellets suggests something else: conductivity values do not show a strong dependence on the type of substituting cation. We observed that mechanical treatment of these materials causes a symmetry reduction from garnet to hydrogarnet structure. To understand the impact of this lower symmetric structure in detail and its effect on the Li ion conductivity, neutron powder diffraction and
6
Li NMR were utilized. Despite the finding that, in some materials, disorder can be beneficial with respect to ionic conductivity, pulsed-field gradient NMR measurements of the long-range transport indicate a higher Li
+
diffusion barrier in the lower symmetric hydrogarnet structure. The symmetry reduction can be reversed back to the higher symmetric garnet structure by annealing at 1100 °C. This unintended phase transition and thus a reduction in conductivity is crucial for the processing of LLZO materials in the fabrication of all-solid state batteries.
Investigation of commercial Li
7
La
3
Zr
2
O
12
(LLZO) with various substituents. Although impedance spectroscopy suggests something else: the ion conductivity does not show a strong dependence on the substituting cation, but rather on the sample treatment.
The Li
ion conductor Li
P
O
N
O
(x≈1.9) has been synthesized from P
N
, Li
N and Li
O in a Ta ampoule at 800 °C under Ar atmosphere. The cubic compound crystallizes in space group
with a=12.0106(14) ...Å and Z=4. It contains both non-condensed PO
N
and PO
N
tetrahedra as well as O
ions, surrounded by Li
ions. Charge neutrality is achieved by partial occupancy of Li positions, which was refined with neutron powder diffraction data. Measurements of the partial ionic and electronic conductivity show a total ionic conductivity of 6.6×10
S cm
with an activation energy of 0.46±0.02 eV and a bulk ionic conductivity of 4×10
S cm
at 25 °C, which is close to the ionic conductivity of amorphous lithium nitridophosphate. This makes Li
P
O
N
O
an interesting candidate for investigation of structural factors affecting ionic conductivity in lithium oxonitridophosphates.
Lattice thermal expansion (LTE) has been investigated in double perovskites LaPbMSbO
(M = Mn, Co, Ni). Ordinary LTE behavior with good thermal stability is identified for the Mn sample, whereas ...unusual LTE with a preferably expanded interplanar distance of (040) is revealed for Co and Ni samples. Temperature-dependent X-ray diffraction patterns ( T-XRD), Raman spectra ( T-Raman), and specific heat capacities ( T- C
) consistently indicate that a rare isostructural displacive phase transition (IDPT) with a second-order phase transition nature is predominant near the critical temperature. Refinements of neutron powder diffraction (NPD) and in situ T-XRD data present temperature-sensitive bond parameters which are relevant to planar oxygen O1. X-ray photoelectron spectra (XPS) further confirm the Jahn-Teller (J-T) activated Co
(HS) or Ni
(HS/LS) cations at the B-site sublattice. This unusual LTE behavior could be understood by the cooperative J-T effect contributed by a Pb
ion and Co
/Ni
ion from A- and B-site sublattices, respectively. The importance of 6s(Pb)-2p(O)-3d(Co/Ni) extended orbital hybridization on affecting thermal expansion behavior is highlighted on the basis of temperature-induced phonon mode softening. This study presents a microscopic description of connection between anisotropic thermal expansion and a cooperative J-T effect, which inspired exploration of thermal-mechanical coupled functional materials based on LaPbMSbO
double perovskites.
Binary lithium silicides play a crucial role in high energy density anode materials for rechargeable batteries. During charging processes of Si anodes Li
Si
is formed as a metastable phase which has ...been stabilized through Li by Mg, Zn and Al substitution. Here we investigate Li by Zn substitution in the lithium-richest phase Li
Si
and report on the particular site preference of Zn atoms since Zn is substituting Li atoms only on one out of 13 possible lithium sites. This site preference shows an interesting relation to the closely related phase Li
Si
and thus Li
Zn
Si
with
= 0.025(1) and
= 0.033(1) can be considered as the missing link between the structures of Li
Si
(= Li
Si) and Li
Si
(= Li
Si).
Cation doping is an effective strategy for improving the cyclability of layered oxide cathode materials through suppression of phase transitions in the high voltage region. In this study, Mg and Sc ...are chosen as dopants in P2‐Na0.67Ni0.33Mn0.67O2, and both have found to positively impact the cycling stability, but influence the high voltage regime in different ways. Through a combination of synchrotron‐based methods and theoretical calculations it is shown that it is more than just suppression of the P2 to O2 phase transition that is critical for promoting the favorable properties, and that the interplay between Ni and O activity is also a critical aspect that dictates the performance. With Mg doping, the Ni activity can be enhanced while simultaneously suppressing the O activity. This is surprising because it is in contrast to what has been reported in other Mn‐based layered oxides where Mg is known to trigger oxygen redox. This contradiction is addressed by proposing a competing mechanism between Ni and Mg that impacts differences in O activity in Na0.67MgxNi0.33‐xMn0.67O2 (x < 0 < 0.33). These findings provide a new direction in understanding the effects of cation doping on the electrochemical behavior of layered oxides.
Beyond the well‐known P2 to O2 phase transition, oxygen redox is a main bottleneck for capacity retention. Using synchrotron‐based methods, it is revealed that competing mechanisms between Ni and Mg (or Li, Zn, and Cu) are critical for controlling the degree of oxygen redox in doped Ni–Mn based layered oxides in Na‐ion batteries.
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