Synthesis and electrochemical performance of 0.6Li3V2(PO4)3·0.4Li–V–O composite cathode material for lithium ion batteries

Huang

ACS Appl. Mater. Interfaces

et al. 2019

Sodium-ion batteries (SIBs) are increasingly on demand owning to their prospect as an inexpensive alternative to Li-ion batteries. However, designing electrode materials with satisfactory rate capacity performance requires high electron transport and Na+ conductivity, which is extremely challenging. Herein, we report a hexadecylamine (HDA)-mediated synthesis of NaTi2(PO4)3 (NTP) electrodes via one-step solvothermal process. The addition of HDA material (1) enables the formation of a carbon coating that improves the electron conductivity and (2) importantly serves as a structure-directing agent reducing the NTP-impurity phases in which the transport of Na+ ions are sluggish. As a result, the synthesized NTP anode delivers superior rate of capacity retention of 77.8% under the 100-fold increase in current densities. Moreover, outstanding specific capacity of 117.9 mAh g–1 at 0.5 C and capacity retention of 88.6% after 1500 cycles at 1 C can be obtained. The findings of this work provide new opportunity to design SIBs electrodes with superior electrical and ionic conductivity.

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Results and Discussionmentioning

confidence: 99%

Purifying the Phase of NaTi₂(PO₄)₃ for Enhanced Na⁺ Storage Properties

Huang

ACS Appl. Mater. Interfaces

et al. 2019

ACS Appl. Energy Mater.

“…Lithium-ion batteries (LIBs) are currently the most important energy storage devices for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and electric vehicles (EVs). , Among all cathode materials for LIBs, monoclinic lithium vanadium phosphate, Li 3 V 2 (PO 4 ) 3 (LVP), has gained intense attention because of high charge–discharge voltage, relatively high theoretical specific capacity, and thermodynamically stable structure. − Similar to other lithium transition metal phosphates, the electrochemical performance of LVP has been limited by its poor electronic conductivity due to the framework formed by VO 6 octahedra corner-sharing with PO 4 tetrahedra . Carbon coating is an economic and convenient method to enhance the electronic conductivity of electrode materials, which can also alleviate the aggregation of LVP particles during calcination. − It is usually achieved by introducing carbon sources, such as graphene, graphene oxide (GO), ,, carbon black, carbon nanoflakes, citric acid, − glucose, and humic acid, as raw materials.…”

Section: Introductionmentioning

confidence: 99%

Investigating the Structure of an Active Material–Carbon Interface in the Monoclinic Li₃V₂(PO₄)₃/C Composite Cathode

Huo

Lin

et al. 2019

A widely adopted strategy to enhance the electronic conductivity of lithium transition metal phosphates is to form a phosphate/C composite by introducing reagents (carbon sources) that can transform to carbon during calcination. In the present work, a systematic study combining X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, solid-state nuclear magnetic resonance, and electrochemical measurements was conducted to investigate how the electrostatic interaction between the functional groups (carboxyl, hydroxyl, etc.) of a carbon source and the building units of Li3V2(PO4)3 (Li+, VO2+, PO4 3–, etc.) in the original precursor affects the structure of a Li3V2(PO4)3–carbon interface in the final composite. It was demonstrated that the types and concentrations of electronegative functional groups in a carbon source play an important role in controlling not only the morphology of the product but also the composition, crystallinity and microstructure of the Li3V2(PO4)3–carbon interface and, in turn, the electrochemical behavior of the Li3V2(PO4)3/C composite. This study provides guidance on carbon–lithium transition metal phosphate interface design and control.

“…To further calculate the Li + diffusion coefficient in the electrodes, galvanostatic intermittent titration technique (GITT) measurement was performed for LVP/C and LLZO-coated LVP/C, which is considered to be a reliable method to calculate D Li+ . 51,52 Fig. 9a shows the full GITT curves of LVP/C and LLZO-coated LVP/C at the first cycle.…”

Section: Resultsmentioning

confidence: 99%

Enhanced Electrochemical Performance of Li₃V₂(PO₄)₃/C Coated with Li Fast Ion Conductive Li₇La₃Zr₂O₁₂

Cheng

et al. 2017

J. Electrochem. Soc.

Li7La3Zr2O12-coated Li3V2(PO4)3/C (LLZO-coated LVP/C) has been synthesized via a conventional sol-gel method, in which LLZO as the fast Li-ion conductor and carbon as the mixed coating with excellent electronic conductivity could enhance the transport of both electrons and Li-ions at the electrode's surface. X-ray diffraction (XRD) and transmission electron microscopy (TEM) with energy dispersive spectrometer (EDS) have been performed to prove the existence of LLZO on the surface of LVP. The valence states of the La and Zr elements are investigated by X-ray photoelectron spectroscopy (XPS). The capacity retention rates of LVP/C and LLZO-coated LVP/C after 100 cycles at 0.5C are 75.7% and 83.4%, respectively. Besides, the LLZO-coated LVP/C exhibits a specific discharge capacity of 161 mA h g−1 at 0.1C and 95 mA h g−1 at 5C at the voltage range of 3.0–4.8 V (vs Li+/Li), respectively. The superior electrochemical performance of LLZO-coated LVP/C can contribute to two aspects as follows: (1) LLZO coating provides a chemically stable layer which effectively reduces the chemical reactions between the active material and the electrolyte; (2) Compared with the uncoated LVP/C, the ionic conductivity of LLZO-coated LVP/C increases which is proved by the results of CV and GITT. Thus, we believe that the synthesis strategy of LLZO or other solid-state electrolytes and carbon hybrid coating could be employed to develop other cathode materials for their application in power lithium ion battery.