A Study on the Microstructure Regulation Effect of Niobium Doping on LiNi0.88Co0.05Mn0.07O2 and the Electrochemical Performance of the Composite Material under High Voltage.

High-nickel ternary materials are currently the most promising lithium battery cathode materials due to their development and application potential. Nevertheless, these materials encounter challenges like cation mixing, lattice oxygen loss, interfacial reactions, and microcracks. These issues are exacerbated at high voltages, compromising their cyclic stability and safety. In this study, we successfully prepared Nb5+-doped high-nickel ternary cathode materials via a high-temperature solid-phase method. We investigated the impact of Nb5+ doping on the microstructure and electrochemical properties of LiNi0.88Co0.05Mn0.07O2 ternary cathode materials by varying the amount of Nb2O5 added. The experimental results suggest that Nb5+ doping does not alter the crystal structure but modifies the particle morphology, yielding radially distributed, elongated, rod-like structures. This morphology effectively mitigates the anisotropic volume changes during cycling, thereby bolstering the material's cyclic stability. The material exhibits a discharge capacity of 224.4 mAh g-1 at 0.1C and 200.3 mAh g-1 at 1C, within a voltage range of 2.7 V-4.5 V. Following 100 cycles at 1C, the capacity retention rate maintains a high level of 92.9%, highlighting the material's remarkable capacity retention and cyclic stability under high-voltage conditions. The enhancement of cyclic stability is primarily due to the synergistic effects caused by Nb5+ doping. Nb5+ modifies the particle morphology, thereby mitigating the formation of microcracks. The formation of high-energy Nb-O bonds prevents oxygen precipitation at high voltages, minimizes the irreversibility of the H2-H3 phase transition, and thereby enhances the stability of the composite material at high voltages.

Alkalized MXene/carbon nanotube composite for stable Na metal anodes.

Ti3C2 MXenes are emerging 2D materials and have attracted increasing attention in sodium metal anode fabrication because of their high conductivity, multifunctional groups and excellent mechanical performances. However, the severe self-restacking of Ti3C2 MXenes is not conducive to dispersing Na+ and limits the function of regulating sodium deposition. Herein, an alkalized MXene/carbon nanotube (CNT) composite (named A-M-C) is introduced to regulate Na deposition behavior, which consists of Na3Ti5O12 microspheres, Ti3C2 MXene nanosheets and CNTs. Ti3C2 MXene nanosheets with large interlayer spaces and "sodiophilic" functional groups can provide abundant active sites for uniform nucleation and deposition of Na. Plenty of nanosheets are grown on the surface of the microsphere, thereby reducing the local current density, which can guide initial Na nucleation and promote Na dendrite-free growth. Furthermore, CNTs increase the electrical conductivity of the composite and achieve fast Na+ transport, improving the cycling stability of Na metal batteries. As a result, at a capacity of 1 mA h cm-2, the A-M-C electrode achieves a high average coulombic efficiency (CE) of 99.9% after 300 cycles at 2 mA cm-2. The symmetric cells of A-M-C/Na provide a long cycling life of more than 1400 h at 1 mA cm-2 with a minimal overpotential of 19 mV at an areal capacity of 1 mA h cm-2. The A-M-C/Na//NVP@C full cell presents a high coulombic efficiency of 98% with 100 mA g-1 in the first cycle. The strategy in this work provides new insights into fabricating novel MXene-based anode materials for dendrite-free sodium deposition.

Boron-doped three-dimensional porous carbon framework/carbon shell encapsulated silicon composites for high-performance lithium-ion battery anodes.

Deleterious volumetric expansion and poor electrical conductivity seriously hinder the application of Si-based anode materials in lithium-ion batteries (LIBs). Herein, boron-doped three-dimensional (3D) porous carbon framework/carbon shell encapsulated silicon (B-3DCF/Si@C) hybrid composites are successfully prepared by two coating and thermal treatment processes. The presence of 3D porous carbon skeleton and carbon shell effectively improves the mechanical properties of the B-3DCF/Si@C electrode during the cycling process, ensures the stability of the electrical contacts of the silicon particles and stabilizes the solid electrolyte interface (SEI) layer, thus enhancing the electronic conductivity and ion migration efficiency of the anode. The developed B-3DCF/Si@C anode has a high reversible capacity, excellent cycling stability and outstanding rate performance. A reversible capacity of 1288.5 mAh/g is maintained after 600 cycles at a current density of 400 mA g-1. The improved electrochemical performance is demonstrated in a full cell using a LiFePO4-based cathode. This study presents a novel approach that not only mitigates the large volume expansion effects in LIB anode materials, but also provides a reference model for the preparation of porous composites with various functionalities.

Tuning the Interface Stability of Nickel-Rich NCM Cathode Against Aggressive Structural Collapse via the Synergistic Effect of Additives.

Nickel-rich layered oxides are envisaged as one of the most promising alternative cathode materials for lithium-ion batteries, considering their capabilities to achieve ultrahigh energy density at an affordable cost. Nonetheless, with increasing Ni content in the cathodes comes a severe extent of Ni4+ redox side reactions on the interface, leading to fast capacity decay and structural stability fading over extended cycles. Herein, dual additives of bis(vinylsulfonyl)methane (BVM) and lithium difluorophosphate (LiDFP) are adopted to synergistically generate the F-, P-, and S-rich passivation layer on the cathode, and the Ni4+ activity and dissolution at high voltage are restricted. The sulfur-rich layer formed by the polymerization of BVM, combined with the Li3PO4 and LiF phases derived from LiDFP, alleviates the problems of increased impedance, cracks, and an irreversible H2-H3 phase transition. Consequently, the Ni-rich LiNixM1-xO2 (x > 0.95) button half-cell cycled in LiDFP + BVM electrolyte exhibits a significant discharging capacity of 181.4 mAh g-1 at 1 C (1 C = 200 mA g-1) with retention of 83.7% after 100 cycles, surpassing the performance of the commercial electrolyte (160.7 mAh g-1) with retention of 53.3%. Remarkably, the NCM95||graphite pouch cell exhibits a remarkable capacity retention of 95.5% after 200 cycles. This work inspires the rational design of electrolyte additives for ultrahigh-energy batteries with nickel-rich layered oxide cathodes.

Modification of the Ni-Rich Layered Cathode Material by Hf Addition: Synergistic Microstructural Engineering and Surface Stabilization.

The rapid decline of the reversible capacity originating from microcracks and surface structural degradation during cycling is still a serious obstacle to the practical utilization of Ni-rich LiNixCoyAl1-x-yO2 (x ≥ 0.8) cathode materials. In this research, a feasible Hf-doping method is proposed to improve the electrochemical performance of LiNi0.9Co0.08Al0.02O2 (NCA90) through microstructural optimization and structural enhancement. The addition of Hf refines the primary particles of NCA90 and develops them into a short rod shape, making them densely arranged along the radial direction, which increases the secondary particle toughness and reduces their internal porosity. Moreover, Hf-doping stabilizes the layered structure and suppresses the side reactions through the introduction of robust Hf-O bonding. Multiple advantages of Hf-doping allowed significant improvement of the cycling stability of LiNi0.895Co0.08Al0.02Hf0.005O2 (NCA90-Hf0.5), with a reversible capacity retention rate of 95.3% after 100 cycles at 1 C, as compared with only 82.0% for the pristine NCA90. The proposed synergetic strategy combining microstructural engineering and crystal structure enhancement can effectively resolve the inherent capacity fading of Ni-rich layered cathodes, promoting their practical application for next-generation lithium-ion batteries.

CI3D: Context Interaction for Dynamic Objects and Static Map Elements in 3D Driving Scenes.

Multi-view 3D visual perception including 3D object detection and Birds'-eye-view (BEV) map segmentation is essential for autonomous driving. However, there has been little discussion about 3D context attention between dynamic objects and static elements with multi-view camera inputs, due to the challenging nature of recovering the 3D spatial information from images and performing effective 3D context interaction. 3D context information is expected to provide more cues to enhance 3D visual perception for autonomous driving. We thus propose a new transformer-based framework named CI3D in an attempt to implicitly model 3D context interaction between dynamic objects and static map elements. To achieve this, we use dynamic object queries and static map queries to gather information from multi-view image features, which are represented sparsely in 3D space. Moreover, a dynamic 3D position encoder is utilized to precisely generate queries' positional embeddings. With accurate positional embeddings, the queries effectively aggregate 3D context information via a multi-head attention mechanism to model 3D context interaction. We further reveal that sparse supervision signals from the limited number of queries result in the issue of rough and vague image features. To overcome this challenge, we introduce a panoptic segmentation head as an auxiliary task and a 3D-to-2D deformable cross-attention module, greatly enhancing the robustness of spatial feature learning and sampling. Our approach has been extensively evaluated on two large-scale datasets, nuScenes and Waymo, and significantly outperforms the baseline method on both benchmarks.

Synthesis of Porous Ni-Doped CoSe2 /C Nanospheres towards High-Rate and Long-Term Sodium-Ion Half/Full Batteries.

Carbon-layer-coated porous Ni-doped CoSe2 (Ni-CoSe2 /C) nanospheres have been fabricated by a facile hydrothermal method followed by a new selenization strategy. The porous structure of Ni-CoSe2 /C is formed by the aggregation of many small particles (20-40 nm), which are not tightly packed together, but are interspersed with gaps. Moreover, the surfaces of these small particles are covered with a thin carbon layer. Ni-CoSe2 /C delivers superior rate performance (314.0 mA h g-1 at 20 A g-1 ), ultra-long cycle life (316.1 mA h g-1 at 10 A g-1 after 8000 cycles), and excellent full-cell performance (208.3 mA h g-1 at 0.5 A g-1 after 70 cycles) when used as an anode material for half/full sodium-ion batteries. The Na storage mechanism and kinetics have been confirmed by ex situ X-ray diffraction analysis, assessment of capacitance performance, and a galvanostatic intermittent titration technique (GITT). GITT shows that Na+ diffusion in the electrode material is a dynamic change process, which is associated with a phase transition during charge and discharge. The excellent electrochemical performance suggests that the porous Ni-CoSe2 /C nanospheres have great potential to serve as an electrode material for sodium-ion batteries.