Recent advances in the research of polyanion-type cathode materials for Li-ion batteries

In the past decades, research efforts on polyanion-type cathode materials by the scientific community intensified significantly. This paper reviews the latest advances in the exploration and development of polyanion-type compounds as high performance cathode materials for Li-ion batteries. It focuses on the synthesis, structure and physicochemical (especially electrochemical) properties of several classes of polyanion compounds. The relationship between composition-structure-performance of the novel electrode materials is also summarized and analyzed. The main approaches, achievements and challenges in this field are briefly commented and discussed.National Natural Science Foundation of China[20873115, 21021002, 90606015]; National Basic Research Program of China (973 program)[2007CB209702, 2011CB935903

Sol-gel synthesis and electrochemical properties of fluorophosphates Na(2)Fe(1-x)Mn(x)PO(4)F/C (x=0, 0.1, 0.3, 0.7, 1) composite as cathode materials for lithium ion battery

Fluorophosphates Na(2)Fe(1-x)Mn(x)PO(4)F/C (x = 0, 0.1, 0.3, 0.7, 1) composite were successfully synthesized via a sol-gel method. The structure, morphology and electrochemical performance of the as prepared materials were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and charge/discharge measurements. XRD results show that, consistent with Na(2)FePO(4)F, Na(2)Fe(0.9)Mn(0.1)PO(4)F (x = 0.1) crystallize in a two-dimensional (2D) layered structure with space group Pbcn. However, increasing the content of Mn to x >= 0.3 results in a structure transition of Na(2)Fe(1-x)Mn(x)PO(4)F from the 2D layered structure of Na(2)FePO(4)F to the three-dimensional (3D) tunnel structure of Na(2)MnPO(4)F. SEM and TEM analysis indicates nanostructured primary particles (about tens of nanometres in diameter) are obtained for all samples due to uniform carbon distribution and low calcining temperature used. Na(2)FePO(4)F is able to deliver a reversible capacity of up to 182 mA h g(-1) (about 1.46 electrons exchanged per unit formula) with good cycling stability. Compared with Na(2)FePO(4)F, partial replacement of Fe by Mn in Na(2)Fe(1-x)Mn(x)PO(4)F increases the discharge voltage plateau. Similar to Na(2)FePO(4)F, iron-manganese mixed solid solution Na(2)Fe(1-x)Mn(x)PO(4)F (x 0.1, 0.3, 0.7) also show good cycling performance. Furthermore, Na(2)MnPO(4)F with high electrochemical activity was successfully prepared for the first time, which is able to deliver a discharge capacity of 98 mA h g(-1). The good electrochemical performance of Na(2)Fe(1-x)Mn(x)PO(4)F materials can be attributed to the distinctive improvement of ionic/electronic conduction of the materials by formation of nanostructure composite with carbon.National Basic Research Program of China (973 program)[2011CB935903, 2007CB209702]; National Natural Science Foundation of China[20873115, 21021002, 90606015

Promoting long-term cycling performance of high-voltage Li2CoPO4F by the stabilization of electrode/electrolyte interface

National Basic Research Program of China (973 program) [2011CB935903]; National Natural Science Foundation of China [21233004, 21021002]High-voltage Li2CoPO4F (similar to 5 V vs. Li/Li+) with double-layer surface coating has been successfully prepared for the first time. The Li3PO4-coated Li2CoPO4F shows a high reversible capacity of 154 mA h g(-1) (energy density up to 700W h kg(-1)) at 1 C current rate, and excellent rate capability (141 mA h g(-1) at 20 C). XRD and MAS NMR results show that Li2CoPO4F can be indexed as an orthorhombic structure with space group Pnma and coexists with Li3PO4. The XPS depth profiles and TEM analysis reveal that the as-prepared material has a double-layer surface coating, with a carbon outer layer and a Li3PO4 inner layer, which greatly enhances the transfer kinetics of the lithium ions and electrons in the material and stabilizes the electrode/electrolyte interface. Using LiBOB as an electrolyte additive is another way to further stabilize the electrode/electrolyte interface, and the LiBOB has a synergistic effect with the Li3PO4 coating layer. In this way, the Li2CoPO4F cathode material exhibits excellent long-term cycling stability, with 83.8% capacity retention after 150 cycles. The excellent cycling performance is attributed to the LiBOB electrolyte additive and the Li3PO4 coating layer, both of which play an important role in stabilizing the charge transfer resistance of Li2CoPO4F upon cycling

Evaluating the Potential of Leading Large Language Models in Reasoning Biology Questions

Recent advances in Large Language Models (LLMs) have presented new opportunities for integrating Artificial General Intelligence (AGI) into biological research and education. This study evaluated the capabilities of leading LLMs, including GPT-4, GPT-3.5, PaLM2, Claude2, and SenseNova, in answering conceptual biology questions. The models were tested on a 108-question multiple-choice exam covering biology topics in molecular biology, biological techniques, metabolic engineering, and synthetic biology. Among the models, GPT-4 achieved the highest average score of 90 and demonstrated the greatest consistency across trials with different prompts. The results indicated GPT-4's proficiency in logical reasoning and its potential to aid biology research through capabilities like data analysis, hypothesis generation, and knowledge integration. However, further development and validation are still required before the promise of LLMs in accelerating biological discovery can be realized

Promoting long-term cycling performance of high-voltage Li 2CoPO4F by the stabilization of electrode/electrolyte interface

High-voltage Li2CoPO4F (～5 V vs. Li/Li +) with double-layer surface coating has been successfully prepared for the first time. The Li3PO4-coated Li 2CoPO4F shows a high reversible capacity of 154 mA h g-1 (energy density up to 700 W h kg-1) at 1 C current rate, and excellent rate capability (141 mA h g-1 at 20 C). XRD and MAS NMR results show that Li2CoPO4F can be indexed as an orthorhombic structure with space group Pnma and coexists with Li 3PO4. The XPS depth profiles and TEM analysis reveal that the as-prepared material has a double-layer surface coating, with a carbon outer layer and a Li3PO4 inner layer, which greatly enhances the transfer kinetics of the lithium ions and electrons in the material and stabilizes the electrode/electrolyte interface. Using LiBOB as an electrolyte additive is another way to further stabilize the electrode/electrolyte interface, and the LiBOB has a synergistic effect with the Li3PO 4 coating layer. In this way, the Li2CoPO4F cathode material exhibits excellent long-term cycling stability, with 83.8% capacity retention after 150 cycles. The excellent cycling performance is attributed to the LiBOB electrolyte additive and the Li3PO 4 coating layer, both of which play an important role in stabilizing the charge transfer resistance of Li2CoPO4F upon cycling. ? 2014 The Royal Society of Chemistry

Integration of air separation and partial oxidation of methane in the La04Ba06Fe08Zn02O3-delta membrane reactor

Singapore National Research Foundation (NRF) [R-279-000-261-281]A disc-membrane made of the La0.4Ba0.6Fe1-xZnxO3-delta (LBFZ-x) perovskite oxide with x=0.2 was used to carry out air separation. The oxygen permeation through the membrane was driven by either He sweeping or partial oxidation of methane (POM) at the permeate side of membrane. Both operation temperature and thickness of the LBFZ-0.2 membrane impact oxygen permeation flux under a permeation gradient. Oxygen permeation flux increases with the decrease in the thickness of membrane and the trend gradually levels off. A much greater oxygen flux through the LBFZ-0.2 membrane was achieved when the POM reaction instead of the He sweeping was used to drive oxygen permeation. It could reach 12 cm(3) cm(-2) min(-1) through a 0.5 mm-thick LBFZ-0.2 membrane. The most influential property exhibited by the LBFZ-0.2 membrane lies in its chemical stability under the reducing atmosphere of POM. The membrane remains intact and supplies oxygen to maintain almost quantitative CH4 conversion and CO selectivity through a 500 h testing period at 900 degrees C. The chemical stability of LBFZ-0.2 was also verified by the retention of perovskite structure. (C) 2011 Elsevier B.V. All rights reserved

Electrochemical performance and surface properties of bare and TiO2-coated cathode materials in lithium-ion batteries

Electrochemical performance and spectroscopic characterizations of the decomposition products from electrolytes on native and TiO2-coated LiCoO2 and LiMn2O4 in different potential regions were investigated. The results showed that TiO2-coated materials exhibited better cyclic stability in different potential regions (i.e., 3.0-4.3 V and 3.0-4.6 V), and the decomposition of the electrolytes was suppressed on the coated materials surface. Results from FTIR and temperature-programmed-desorption mass spectroscopy (TPD-MS) showed that the decomposition of the electrolytes on the electrode surface is related to both the material measured and the oxidation potential. The causes for the formation of different oxidation products of electrolytes have been analyzed. An improved electrooxidation mechanism of the electrolytes was also proposed. It is shown that the different reactivity of cathode materials to the oxidation of electrolytes can well be related to their thermal stability in practical Li-ion batteries

Sol-gel synthesis of Li2CoPO4F/C nanocomposite as a high power cathode material for lithium ion batteries

Li2CoPO4F cathode materials are successfully synthesized by solid state (SS) and sol-gel (SG) methods. The XRD results show that Li2CoPO4F samples prepared by two methods are both indexed as orthorhombic structure with space group Pnma. The particles of Li2CoPO4F (SS) are micron grade. However, the particle of Li2CoPO4F (SG) is only tens of nanometers with an amorphous carbon uniformly coated. A high reversible capacity of 138 mAh g(-1) is achieved for Li2CoPO4F/C (SG) at 1 C, which is much higher than that of 106 mAh g(-1) prepared by solid state method. Also, Li2CoPO4FIC (SG) shows excellent rate performance, a capacity of 119 mAh g(-1), 86% retention of that at 1 C, is achieved at 20 C. The excellent rate capacity of the material is attributed to nanosized particles and uniform carbon coating that reduce ion diffusion length and enhance electronic conductivity. Furthermore, the preliminary performance characteristics of Li2CoPO4F/Li4Ti5O12 full cells are presented. The cell shows a high voltage plateau around 3.4 V with excellent rate capacity. The impressive electrochemical properties indicate that Li2CoPO4F can be a promising high power cathode material for lithium ion batteries. The capacity fading mechanism of Li2CoPO4F is also briefly investigated. (C) 2012 Elsevier B.V. All rights reserved.National Basic Research Program of China (973 program) [2011CB935903]; National Natural Science Foundation of China [21021002, 20873115