Mutual modulation between surface chemistry and bulk microstructure within secondary particles of nickel-rich layered oxides

Abstract

Surface lattice reconstruction is commonly observed in nickel-rich layered oxide battery cathode materials, causing unsatisfactory high-voltage cycling performance. However, the interplay of the surface chemistry and the bulk microstructure remains largely unexplored due to the intrinsic structural complexity and the lack of integrated diagnostic tools for a thorough investigation at complementary length scales. Herein, by combining nano-resolution X-ray probes in both soft and hard X-ray regimes, we demonstrate correlative surface chemical mapping and bulk microstructure imaging over a single charged LiNi0.8Mn0.1Co0.1O2 (NMC811) secondary particle. We reveal that the sub-particle regions with more micro cracks are associated with more severe surface degradation. A mechanism of mutual modulation between the surface chemistry and the bulk microstructure is formulated based on our experimental observations and finite element modeling. Such a surface-to-bulk reaction coupling effect is fundamentally important for the design of the next generation battery cathode materials.

Electrochemo‐Mechanical Effects on Structural Integrity of Ni‐Rich Cathodes with Different Microstructures in All Solid‐State Batteries

“…The fluctuating and more fast‐growing R Cathode/SE values of polycrystalline materials should come from severe interfacial side‐reactions [ 8b ] and the continuous development of microcracks inside the bulk during repeated cycling, resulting in inhomogeneous charge distribution and severe surface lattice reconstructions. [ 10 ] These results illuminate that the smaller increase in the impedance of S‐NCM811/SE interface during cycling could be responsible for its better cyclability and rate performance than LP‐NCM811 and SP‐NCM811 electrodes in ASSBs.…”

“…revealed that more severe surface degradation is positively correlated with bulk microcracks by using the full‐field transmission hard X‐ray microscopy (TXM) and finite element modeling (FEM). [ 10 ] Therefore, it is also imperative to consider other factors that may affect the electrochemical performance of ASSBs, such as reducing the microcracks and the mechanical strain during the phase transition of conventional polycrystalline nickel‐rich cathodes.…”

Guiding the Design of Heterogeneous Electrode Microstructures for Li‐Ion Batteries: Microscopic Imaging, Predictive Modeling, and Machine Learning

“…Features like surface reconstructions and lithiation heterogeneities can impact the mechanical integrity of particles and dictate the rate of degradation of electrodes. For example, consequences of surface reconstructions and lithiation heterogeneities for subparticle mechanical strain were revealed by Li et al [57] where, through the application of TXM and soft X-ray absorption spectroscopy, the surface chemistry was linked to subparticle cracking through TXM and finite element modeling (Figure 4c).…”

“…c) Renderings from a 3D tomographic reconstruction of a single NMC811 particle showing internal cracks and granular structure. Reproduced with permission [57]. Copyright 2020, Springer Nature.…”

Precise surface control of cathode materials for stable lithium-ion batteries

“…[41][42][43][44] Although enormous efforts have been devoted to these two aspects resulting in some achievements in recent years, the one which is vital or more urgent is still an elusive question that is yet to be addressed. 45,46 Surface coating can effectively protect cathode materials against aggravated side reactions at the electrode/ electrolyte interface. However, the poor electronic and ionic conductivity of most of inert coating materials signify the increase of the charge-transfer resistance (R ct ) between the cathode and electrolyte interface, which will reduce the electrode capacity and increase the polarization during the charge/discharge process.…”