Computational Design to Suppress Thermal Runaway of Li-Ion Batteries via Atomic Substitutions to Cathode Materials

Abstract

The cathode material of a lithium-ion battery is a key component that affects durability, capacity, and safety. Compared to the LiCoO 2 cathode material (the reference standard for these properties), LiNiO 2 can extract more Li at the same voltage and has therefore attracted considerable attention as a material that can be used to obtain higher capacity. As a trade-off, it undergoes pyrolysis relatively easily, leading to ignition and explosion hazards, which is a challenge associated with the application of this compound. Pyrolysis has been identified as a structural phase transformation of the layered rocksalt structure → spinel → cubic rocksalt. Partial substitution of Ni with various elements can reportedly suppress the transformation and, hence, the pyrolysis. It remains unclear which elemental substitutions inhibit pyrolysis and by what mechanism, leading to costly material development that relies on empirical trial and error. In this study, we developed several possible reaction models based on existing reports, estimated the enthalpy change associated with the reaction by ab initio calculations, and identified promising elemental substitutions. The possible models were narrowed down by analyzing the correlations of the predicted dependence of the reaction enthalpies on elemental substitutions, compared between different reaction models. According to this model, substitution by P and Ta affords the highest enthalpy barrier between the initial (layered rocksalt) and the final (cubic rocksalt) structures but promotes the initial transformation to spinel as a degradation. Substitution by W instead generates the barrier to the final (preventing dangerous incidents) process, as well as for the initial degradation to spinel; therefore, it is a promising strategy to suppress the predicted pyrolysis.

Toward Improving the Thermal Stability of Negative Electrode Materials: Differential Scanning Calorimetry and In Situ High-Temperature X-ray Diffraction/X-ray Absorption Spectroscopy Studies of Li2ZnTi3O8 and Related Compounds

“…However, considering the significant low a c value at ∼260 °C (Figure 4c) and shoulder diffraction peaks after the HT-XRD measurements (Figure 5), other phases such as Li 2 O are likely to be involved in the formation process of the LiF phase. Moreover, there is no evidence for the presence of P in this temperature range as for our previous study on C 6 Li y . 12 Further gas chromatography and energy dispersive X-ray spectroscopy are required to elucidate the mechanisms underlying the exothermic reactions in LZTO.…”

“…Thermal runaway in lithium-ion batteries (LIBs) is the phenomenon whereby LIBs are faced with uncontrollable and continuous heat generation. − It can cause LIBs to rupture or even explode in the worst-case scenario, which can be catastrophic for both consumers and manufacturers . To prevent or mitigate the effects of thermal runaway, commercial LIBs are usually incorporated with several built-in safety features, such as positive temperature coefficient layers and current interrupt devices .…”

“…thermal stability of discharged negative electrodes. The ΔH accum i values of C6 Li y with y = 0.45 and 0.89 are considerably larger (632.9 and 604.7 J g −1 ) than those for LZTO (= 227.7 J g −1 ) and LTO (= 153.2 J g −1 ) because of the broad exothermic reaction between ∼150 and 250 °C. The main contribution to ΔH accum i is already known to be from the decomposition of SEI films.11−14 Note that this decomposition includes the reaction of newly formed SEI films during the heating process below ∼250 °C, because solvents such as EC and DEC are unstable under low voltages below ∼1.5 V vs Li + /Li 11.…”

Effect of the oxygen vacancy electronic state on Ni migration in Li0.5(Ni0.8Mn0.1Co0.1)O2 cathode material

“…13,14 Doping or substitution of transition metals has been shown to reduce this defect and promote phase stability. [15][16][17][18][19] Another cation disordering is known to occur upon delithiation of the layered NMC cathode, wherein the Ni ions would migrate and occupy the Li site upon prolonged charge/discharge cycles. This then leads to the irreversible phase transformation of a layered structure into a disordered spinel/rock-salt structure.…”