应用-MXene在磷负极材料中的应用

Research Background

P negative electrode material having the advantages of high capacity, with Si , of Sn and other comparable negative electrode, the theoretical specific capacity of up to 2596  mAh / G , involving 3 shift reaction electrons, and is suitable for a lithium, sodium, potassium and other cell systems , having more Safe lithium insertion, sodium insertion potential ( LIB/SIB averages about 0.8 and 0.3 V ). Of the three allotropes of phosphorus, due to the toxicity of white phosphorus and easy spontaneous combustion, only red phosphorus and black phosphorus are used in the battery system, but both red phosphorus and black phosphoric acid have serious volume expansion problems. In addition, there are problems such as poor conductivity of red phosphorus and relatively high preparation cost of black phosphorus . MXene having good conductivity ( has achieved the highest reported 10 . 4 S / cm & lt) , the interlayer spacing is adjustable flexibility, good mechanical properties, and good dispersibility in water , but there are disadvantages agglomerate easily stacked, if MXeneAnd P binding, preparing a composite material, in theory, can give full play two advantages‘s, but the disadvantage also can be improved , the introduced MXene improve conductivity , buffer volume expansion , the introduction of P prevents MXene agglomerated nano-sheet, and therefore, the preparation of P And MXenes composite material is an effective method to solve the problem of P anode material . This time, we will introduce the relevant work of the red phosphorus part .

Literature 1 :

A Red-Phosphorous-Assisted Ball-Milling Synthesis of Few-Layered Ti 3 C 2 T x  (MXene) Nanodot Composite

ChemNanoMat  2018, 4, 56 .

brief introduction

In this paper, through the red phosphorus-assisted ball milling method, the oxygen-containing functional groups on the surface of MXenes interact with P to overcome the van der Waals force between the layers and the Ti-C chemical bond in the layer, which makes the multilayer MXenes peeled off and the particle size Reduced, prepared TNDs/P composite material (Ti 3 C 2 T x  nanodots/P) , in which the theoretically designed P content is 40% , in the process of ball milling, micron- sized MXenes nanosheets become nano dots, ball milling After that, the layered structure of MXenes disappeared, and agglomerates of particles with a size of several hundred nanometers appeared , indicating that MXenes nanosheets with micron-sized particle diameters became MXenes nanodots. By this method, the effective two -dimensional material is converted to zero-dimensional material , because MXenes similar surface containing functional groups, this method is expected to be applied to other MXene. The conductivity of the prepared composite material is 10 -4  S/cm , which is 10 orders of magnitude higher than that of the red phosphorus material alone . Used as a negative electrode material for sodium ion batteries ,  at a current density of 100 mA/g , after 150 cycles, the specific capacity can be maintained at 600 mAh/g . 

Literature 2 :

Novel Synthesis of Red Phosphorus Nanodot/Ti 3 C 2 T x  MXenes from Low-Cost Ti 3 SiC 2  MAX Phases for Superior Lithium- and Sodium-Ion Batteries

ACS Applied Materials & Interfaces 2019, 11, 45, 42086-42093 .

brief introduction

Most MXenes materials are obtained by etching Al -based MAX phase. Among them, Ti 3 C 2 T x  MXenes materials prepared by etching Ti 3 AlC 2 are the most widely used MXenes system at present. By ultrasonic peeling, you can Furthermore, Ti 3 C 2 T x  MXenes with few layers has also been widely used. In this paper, high-energy cell crushing ( 1800W ) -assisted HF acid etching method was used to prepare the MXenes material from the Si -based MAX phase . The Si -based MAX was converted into multi-layered MXenes in the etchantMaterials, the entire preparation process is simple and efficient. This work provides a novel and promising production strategies, including the use of low-cost Si -based MAX as preparation MXene parent material. Followed by preparation of a multilayer MXenes and red phosphorus particles as a raw material, by means of high-energy ball milling, was prepared having a PO-Ti bond cooperation phosphorus nanodots with / of Ti . 3 C 2 T X composite materials , the ball milling process so that both Raw material nanometerization, in the structure of this composite material, high-capacity red phosphorus nanodots are strongly adsorbed on the Ti 3 C 2 T x  MXenes matrix, and the layered Ti 3 C 2 T x  MXenes promote the alkali metal ion The transportation makes it have good electrochemical performance in LIB /SIB when used as the negative electrode material of the battery .

Literature 3 :

An MXene/CNTs@P nanohybrid with stable Ti–O–P bonds for enhanced lithium ion storage

J. Mater. Chem. A, 2019, 7, 21766-21773 .

brief introduction

In this paper, the CNT aqueous solution is mixed with the MXene solution , and the CNT is introduced into the MXenes matrix to construct a composite conductive network material by suction filtration and freeze-drying , and then Ti 3 C 2 T x /CNTs and P are combined by ball milling . Under the action of the ball milling shear force, the oxygen-containing functional groups on the surface Ti 3 C 2 T x interact with P to form a Ti-OP bond, which helps to maintain the good relationship between the P negative electrode and the conductive substrate during the cycle contact, thereby improving the cycle stability of the system, since P high capacity negative electrode material advantages, of Ti . 3 C 2 T X / of CNTs conductive mesh network structure and the buffer, of Ti-the OP chemicalThe bond ensures good contact between the P anode and the conductive matrix in the nanocomposite . Ti . 3 C 2 T X / P @ of CNTs nanocomposites 0.05 C exhibits superior reversible capacity in the case of 2598 mAh / G , excellent cycle stability ( 500 after cycles was 2078 mAh / G ) and rate capability ( at 30 C under of 454 mAh / G ) , it showed a of Ti . 3 C 2 T X / P of CNTs @ nano composite material for high-performance lithium ion battery negative electrode potential of possibilities.

Literature 4 :

Vapor Deposition Red Phosphorus to Prepare Nitrogen-Doped Ti 3 C 2 T x  MXenes Composites for Lithium-Ion Batteries

J. Phys. Chem. Lett. 2019, 10, 6446−6454 .

brief introduction

Although the ball milling method is a very common method of preparing composite materials, in the process of ball milling the MXenes matrix and the red phosphorus negative electrode, although the multiple layers of MXenes will become a few layers, to achieve the preparation of composite materials. But for the two -dimensional material concerned, ab & plane is reduced, the ball milling process of generation of defects, is detrimental to the electrochemical performance . Herein by containing N of carbon dispersed in a small layer MXenes aqueous solution by spray drying, preparation of N -doped three-dimensional porous MXenes matrix, subsequent method by vapor deposition, was prepared N -doped the MXenes / P composite (N- of Ti . 3 C 2 T X / P) , the porous structure contributes to the electrolyte solution and infiltration buffer charging and discharging process P a volume expansion of the negative electrode material, the method TGA test compound to determine its The P content in the material , in the electrochemical performance test, the more obvious prominent point is that during the circulation of large current ,The discharge specific capacity increased obviously, corresponding to the increase in the interlayer distance of MXenes matrix . Electrochemical tests showed that this composite material is a good anode material for lithium batteries. Later , the electrochemical performance of the composite material can be further improved by increasing the P content and designing the microstructure of MXenes matrix.

Source: MXene notes 

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