Atomistic understanding of the LiNiO₂–NiO₂ phase diagram from experimentally guided lattice models

Abstract

The compositional phase diagram of LiNiO2 as a function of lithium content has been the object of numerous experimental and computational studies over the last two decades. Even between experimental...

Single-Crystal-like Durable LiNiO2 Positive Electrode Materials for Lithium-Ion Batteries

“…The (101) H1 peak of PC-LNO split into the (201) M and (110) M peaks originating from the M phase in the 3.5 to 3.9 V region. The (003) H1 peak of PC-LNO shifted continuously toward lower angle from 3.5 to 3.9 V, and then shifted to the higher angles with the appearance of the distinct (003) H3 peak at above 4.0 V. This behavior of PC-LNO was consistent with the behavior of stoichiometric LiNO 2 in previous studies ,, and corresponded to the behavior of the d Q /d V curves. The overall behavior of SC-LNO was similar to that of PC-LNO, but the split of the (101) H1 peak was obscure.…”

Single step synthesis of W-modified LiNiO2 using an ammonium tungstate flux

“…52,86,87 In particular, the minimum in the d q /d V plot corresponding to the stable composition x = 2/5 (at ≈3.98 V in charge) is readily destabilised by variations of W content or synthesis temperature, confirming that this feature is only visible in highly stoichiometric LNO samples. 88,89 The reduction in intensity is also accompanied by a shift in the average voltage of each of the features, highlighted in the zoomed plots of the 4.1 to 4.3 V region. Fig.…”

“…The structural evolution of LNO upon delithiation has been reported previously, and transitions through several hexagonal and monoclinic structures are expected, conventionally denoted as H1 > M > H2 > H3. 85,88,90 Visual comparison of the operando XRD data suggests that the introduction of W into the structure does not change the observed phase evolution. During the operando experiment, the undoped material delivered an initial specific charge capacity of 228.0 mA h g −1 , compared to 212.6 mA h g −1 and 204.3 mA h g −1 for the 1 mol% W samples prepared at 700 °C and 800 °C, respectively.…”

Investigation of Structural and Electronic Changes Induced by Postsynthesis Thermal Treatment of LiNiO2

“…Moreover, with increasing heat treatment temperature, an increasing peak width is observed in the voltage range of 4.15–4.27 V. This peak corresponds to the phase transition from the second hexagonal phase (H2) to the third hexagonal phase (H3) . The cation off-stoichiometry (Li 1– z Ni 1+ z O 2 ) has been shown to disrupt Li ordering, thus establishing the behavior of solid solution and eliminating phase transitions . The H2-to-H3 phase transition is crucial to the performance since it always entails large volume changes and the coexistence of two phases induces interfacial strain .…”

“…38 The cation off-stoichiometry (Li 1−z Ni 1+z O 2 ) has been shown to disrupt Li ordering, thus establishing the behavior of solid solution and eliminating phase transitions. 39 The H2-to-H3 phase transition is crucial to the performance since it always entails large volume changes and the coexistence of two phases induces interfacial strain. 40 The release of the strain further induces cracking in electrode particles.…”