Enabling Electrochemical-Mechanical Robustness of Ultra-High Ni Cathode via Self-Supported Primary-Grain-Alignment Strategy.

The electrochemical-mechanical degradation of ultrahigh Ni cathode for lithium-ion batteries is a crucial aspect that limits the cycle life and safety of devices. Herein, the study reports a facile strategy involving rational design of primary grain crystallographic orientation within polycrystalline cathode, which well enhanced its electro-mechanical strength and Li+ transfer kinetics. Ex situ and in situ experiments/simulations including cross-sectional particle electron backscatter diffraction (EBSD), single-particle micro-compression, thermogravimetric analysis combined with mass spectrometry (TGA-MS), and finite element modeling reveal that, the primary-grain-alignment strategy effectively mitigates the particle pulverization, lattice oxygen release thereby enhances battery cycle life and safety. Besides the preexisting doping and coating methodologies to improve the stability of Ni-rich cathode, the primary-grain-alignment strategy, with no foreign elements or heterophase layers, is unprecedently proposed here. The results shed new light on the study of electrochemical-mechanical strain alleviation for electrode materials.

LiMn0.8Fe0.2PO4/Carbon Nanospheres@Graphene Nanoribbons Prepared by the Biomineralization Process as the Cathode for Lithium-Ion Batteries.

Biomineralization technology is a feasible and promising route to fabricate phosphate cathode materials with hierarchical nanostructure for high-performance lithium-ion batteries (LIBs). In this work, to improve the electrochemical performance of LiMn0.8Fe0.2PO4 (LMFP), hierarchical LMFP/carbon nanospheres are wrapped in situ with N-doped graphene nanoribbons (GNRs) via biomineralization by using yeast cells as the nucleating agent, self-assembly template, and carbon source. Such LMFP nanospheres are assembled by more fine nanocrystals with an average size of 18.3 nm. Moreover, the preferential crystal orientation along the [010] direction and certain antisite lattice defects can be identified in LMFP nanocrystals, which promote rapid diffusion of Li ions and generate more active sites for the electrochemical reaction. Moreover, such N-doped GNR networks, wrapped between LMFP/carbon nanospheres, are beneficial to the fast mobility of electrons and good penetration of the electrolyte. As expected, the as-prepared LMFP/carbon multicomposite presents the outstanding electrochemical performance, including the large initial discharge capacity of 168.8 mA h g-1, good rate capability, and excellent long-term cycling stability over 2000 cycles. Therefore, the biomineralization method is demonstrated here to be effective to manipulate the microstructure of multicomponent phosphate cathode materials based on the requirement of capacity, rate capability, and cycle stability for LIBs.