3D Cube‐Maze‐Like Li‐Rich Layered Cathodes Assembled from 2D Porous Nanosheets for Enhanced Cycle Stability and Rate Capability of Lithium‐Ion Batteries

Abstract

cathode of LIBs. Recently, Li-rich cathode materials (LMNCO), x Li 2 MnO 3 ·(1 − x) LiTMO 2 (0 < x < 1, TM = Mn, Ni, Co, etc.), have received extensive attentions due to their promising reversible capacity (>250 mAh g −1 ), environmental benignity, and low cost. [3] Nevertheless, the sluggish diffusion of electrons and lithium ions within LMNCO results in electrode polarization and inferior rate capability. [4] It has been verified that the electrochemical performance of LMNCO is closely connected with the morphology and structure, thereby rational design and control of the formation process for LMNCO is considered to be an effective route to enhance the capacity retention and rate capability. [5][6][7][8][9] On the basis of this, extensive efforts have been devoted to develop nanometersized materials and great progresses have been achieved over the past several years, such as construction of nanoplates, [5] nanowires, [10] nanoparticles, [11] and nanorods, [12] which possess a short Li + diffusion pathway thanks to their diminished dimensions. However, severely undesired side reactions between nanoscale electrode/electrolyte are detrimental to structural stability. [13] In order to address these challenges of nanometer-sized materials, hierarchical micro/nano-materials have been developed recently. [14][15][16] Hierarchical LMNCO possessed stable framework of micro-materials can achieve the prolonged cycle life through reducing interfacial reaction with electrolytes. [16] However, individual hierarchical structure strategy may be not enough, as the rate capability and cycling stability of the hierarchical LMNCO still need to be further improved. [17,18] Recent reports have evidenced two-dimensional (2D) nanostructure owns the advantages of open electrons and ions transport path, high active surface area, and excellent structure stability by accommodating the drastic volume evolution, which makes it applicable for ultrahigh-rate and cycling-stable lithium storage. [19][20][21] In addition, 2D nanosheets often have large exposed surface areas and specific facets. [22,23] It has been reported that in LMNCO cathodes, if the surfaces are parallel to {010} facets (e.g., (010), (100), and (110) planes), perpendicular to (001) plane, the Li + diffusion kinetics will be substantially strengthened. [15,16,24,25] Consequently, the synergistic effect of the 2D nanosheets, hierarchical structure, and Li-rich oxide is a promising candidate for the cathodes of next-generation lithium-ion batteries. However, its utilization is restricted by cycling instability and inferior rate capability. To tackle these issues, three-dimensional (3D), hierarchical, cube-maze-like Li-rich cathodes assembled from two-dimensional (2D), thin nanosheets with exposed {010} active planes, are developed by a facile hydrothermal approach. Benefiting from their unique architecture, 3D cube-maze-like cathodes demonstrate a superior reversible capacity (285.3 mAh g −1 at 0.1 C, 133.4 mAh g −1 at 20.0 C) and a great cycle stability (capacity retention of ...

Pseudo‐Bonding and Electric‐Field Harmony for Li‐Rich Mn‐Based Oxide Cathode

“…The transformation rate (the slope) of 3% LCO is about −0.5933, much larger than that of the pristine sample (−1.1889), 1% LCO (−0.7154), and 5% LCO (−0.6056), demonstrating its optimized structure stability. [27] Consequently, these results demonstrate that the integration structure of the modified samples is more stable because of the weak undulation in its host structure and the related property of the reversible redox reaction, which are well consistent with the superior cyclic performance observed for 3% LCO ( Figure 5).…”

“…Furthermore, the Li + diffusion kinetic of all samples was investigated by galvanostatic intermittent titration technique (GITT). [27,55] The overall GITT voltage response curves and the corresponding Li + diffusion coefficients for the samples before and after the cycling are shown in Figures S10A-D and S11A,B, Supporting Information. As shown in Figure S11C, Supporting Information, a current pulse was applied to the electrode, and a linear voltage response with respect to t 1/2 is observed, indicating that the obtained diffusion value in this region of the electrode cycling curve is accurate, according to previous studies.…”

Improvement in electronic conductivity of perovskite electrolyte by variable‐valence element doping

“…Lithium batteries with higher capacities and larger cycle lifetimes are required to provide more competitive electric vehicles on the market . The electrochemical performances of lithium batteries are determined mainly by the cathode materials, such as LiCoO 2 , LiFePO 4 , LiMn 2 O 4 , LiNi 1‐x‐y Co x Mn y O 2 , and LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA), whose applications are restricted due to some technical bottlenecks . The discharge capacities of the cathode material increase with the increasing cut‐off voltage; however, the capacity fades rapidly under a high cut‐off voltage, which hinders the provision of high capacities of cathode materials .…”

Interfacial Degradation and Optimization of Li‐rich Cathode Materials†

“…In addition to the above two structural design methods, the main structure of Li‐rich particles can also be changed to form a 3D structure. Chen group [ 125 ] used a facile hydrothermal approach to get Li‐rich 2D nanosheets with {010} active planes. The formation of 3D cube‐maze‐like cathodes is illustrated in Figure 10C.…”

“…(C, D) Schematic diagrams of the formation of 3D cube-maze-like cathodes and the SEM images of SHC-LMNCO after cycling. Reproduced with permission from Ref [125]. Copyright 2020, WILEY-VCH.…”