Real-Time Observation of Chemomechanical Breakdown in a Layered Nickel-Rich Oxide Cathode Realized by In Situ Scanning Electron Microscopy

Abstract

It is well-accepted that massive cracks in Ni-rich cathode secondary particles are the determining factors for long-term performance degradation; however, the corresponding crack generation and the state of dynamic propagation are still unknown. In this work, we utilize in situ scanning electron microscopy to reveal the dynamical morphological evolution of a single LiNi0.8Mn0.1Co0.1O2 secondary particle embedded in a cathode blend during electrochemical cycling. These observations show that very few cracks appear in the particle when cycled at a normal cutoff voltage of 4.1 V, but when the cutoff voltage is increased to 4.7 V as an extreme working condition, several cracks were clearly initially generated in the core region and propagated radially along the grain boundaries, finally reaching the particle’s surface. Impressively, crack propagation follows a repeat “grow–stagnate–grow” phenomenon during charge–discharge cycling. Our direct in situ investigation provides a full map of crack evolution in the cathode under electrochemical cycling during early stages.

Coupling-Agent-Coordinated Uniform Polymer Coating on LiNi0.6Co0.2Mn0.2O2 for Improved Electrochemical Performance at Elevated Temperatures

“…The NCM622 and NCM622@KH570-PVEC powders were pressed into disks 14 mm in diameter at 10 MPa in advance, as shown in Figure S2b,c. Although the ultrathin polymer layer is electronically insulated and has little effect on the overall electronic conductivity, the previous study has proved that the low electronic conductivity in the core region rather than on the surface of Ni-rich cathode materials is the main reason for capacity degradation. ,, …”

Realizing Holistic Charging–Discharging for Dendrite-Free Lithium Metal Anodes via Constructing Three-Dimensional Li+ Conductive Networks

“…In situ studies were conducted in ESEM (S8000, TESCAN), which was combined with the NEWARE battery testing system. Relevant in situ battery devices were designed and applied, as reported in our previous work. , Here, the in situ asymmetric cells were assembled in a glovebox, the assembly of the in situ battery was similar to the coin cell, and splints made up of polymer and alumina were used to replace the steel battery shell to leave a space for incident and outgoing electrons. Considering the vacuum environment in the SEM chamber, the electrolyte was changed from conventional electrolyte to ionic liquid (1.2 M LiFSI in PYR 13 FSI, Aladdin) to avoid evaporation of the electrolyte and contamination to SEM devices.…”

Morphology-Dependent Battery Performance of Ni-Rich Layered Cathodes: Single-Crystal versus Refined Polycrystal

“…However, it is challenging to realize high-energy Ni-rich cathodes without sacrificing durability; simply increasing the Ni contents of NCM and NCA cathodes typically compromises their chemical and structural stability owing to the high reactivity of Ni. The main cause of the rapid capacity fading of Ni-rich cathodes is the microcracking of the cathode materials, which exponentially increases the area of the cathode interior exposed to electrolyte attack. − The exposed cathode surface rapidly transforms into electrochemically inactive NiO-like phases, further accelerating the degradation of the cathode. Therefore, suppressing the microcracking of cathodes is a prerequisite for the development of LIBs with higher energy density and durability.…”