Imperfect Battery Materials: A Closer Look at the Role of Defects in Electrochemical Performance

Abstract

Structural and compositional defects in crystalline materials are unavoidable. Accurately disentangling their role in composition−structure−property correlations is therefore essential but has long been hindered by our inability to precisely identify and quantify certain microstructural features. As a result, deviations from ideal structures have frequently been disregarded or assumed to be detrimental. Nonetheless, today's structural disorder characterization advancements offer unprecedented insights into defect architectures. Recent models and tools applied to scattering and spectroscopic techniques provide an accessible window for observing and accurately parametrizing microstructural complexity and, if understood and mastered, offer the utmost control for designing better materials. One important field that can greatly benefit from advancement in the understanding and control of structural defects is the development of battery materials, whose performance and cycle life are closely related to structural aspects, including defects. This perspective offers an overview of the progress achieved in this field, with a special focus on cathode materials, and a discussion about opportunities for future developments.

Carbon quantum dots modified and Y3+ doped Ni3(NO3)2(OH)4 nanospheres with excellent battery‐like supercapacitor performance

“…[35] (2) The hierarchical porous structure and large specific surface area increase the exposure of electroactive centers and accelerate the migration of ions through the electrolyte to the electrode. [36] Figure 7a shows the CV curve of the AC electrode at 10-100 mV s À 1 , from which the potential range of AC can be obtained to be À 1.0-0 V. The activated carbon has a quasirectangular CV curve (Figure 7a) and a quasi-triangular GCD curve (Figure 7b), both of which indicate that the energy storage mechanism of the activated carbon is double-layer energy storage. The electronic double-layer capacitor is related to the adsorption/desorption energy storage of electrolyte ions at the interface between the electrode material and the electrolyte.…”

“…The high specific capacitance and good coulombic efficiency of NiY@CQDs might come from two aspects: (1) The abundant valence distribution promotes the electron transfer between the electrode and the collector and improves the charge transfer efficiency [35] . (2) The hierarchical porous structure and large specific surface area increase the exposure of electroactive centers and accelerate the migration of ions through the electrolyte to the electrode [36] …”

Stacking Fault Formation in LiNi0.6Co0.2Mn0.2O2 during Cycling: Fundamental Insights into the Direct Recycling of Spent Lithium-Ion Batteries

“…Figure 6 i illustrates a stacking fault included in the ABCAB··· packing sequence of the FCC structure, which corresponds to the direction of the c h -axis in the rhombohedral structure. There are several types of stacking faults; 35 for instance, AB(A)BCABC···, AB(A)CABCA···, and AB(A)CBACB···, which are classified as deformation (intrinsic), extrinsic, and growth (twin) stacking faults, respectively (see Figure S7 ). When α is the probability of a fault occurring at any layer, 1 – α is the probability of the regular stacking sequence, i.e.…”

“…Figure 6i illustrates a stacking fault included in the ABCAB••• packing sequence of the FCC structure, which corresponds to the direction of the c h -axis in the rhombohedral structure. There are several types of stacking faults; 35 for instance, AB(A)-BCABC•••, AB(A)CABCA•••, and AB(A)CBACB•••, which are classified as deformation (intrinsic), extrinsic, and growth (twin) stacking faults, respectively (see Figure S7). When α is the probability of a fault occurring at any layer, 1 − α is the probability of the regular stacking sequence, i.e., the probability of A being followed by C, B being followed by A, and C being followed by C. According to the Paterson's model 32,33 on scattering amplitudes for layers including α, the normalized peak profile (I) at the peak position of (l H ) is represented by…”

Dynamic Study of Intercalation/Deintercalation of Ionic Liquids in Multilayer Graphene Using an Alternating Current Raman Spectroscopy Technique

“…There have been many studies investigating intercalation into bulk graphite, mostly focused on group I metal ions, including lithium, sodium, and potassium. − In addition, several groups have investigated intercalation of other ions, including nitrates (from HNO 3 ), large fluoroanions (including perfluoroalkylimides, perfluoroalkylsulfonates, and perfluoroalkylborate esters), and ionic liquids. These investigations have mainly looked at HOPG and have used a wide range of characterization techniques/methods, including the combination of Fourier transform infrared (FTIR) and Raman spectroscopy, by X-ray diffraction, thermogravimetry, and the above structural characterizing techniques .…”