Application-MXene helps the development of lithium battery silicon anode materials-①

Research Background

Due to its unique physicochemical properties, MXene has been extensively studied and involves multiple fields . Due to the high-capacity rich, natural content, low releasing lithium potential, silicon anode material, anode material is very competitive, and there are some practical outlook, however, there are the two key issues, restricted the silicon anode materials Further development. Repeated lithiation / delithiation cycles, the larger the volume expansion and contraction can lead to instability and the pulverized material is silicon anode SEI film-forming, SEI film rupture leads to further consumption of the electrolytic solution, and a sharp attenuation capacity. Low electron conductivity and ion conductivity rate affect the rate capability of the material, therefore, the silicon negative electrode material has been studied how to better adjust the working strain without significant change in volume, a stable SEI membrane and enhance its electronic and ionic conductivity . This time sharing how MXene helps the development of lithium battery silicon anode materials is only part of the published articles, and I will share other articles later .

Literature 1 :

Enhanced reversible Li-ion storage in Si @ Ti 3 C 2 MXene nanocomposite Electrochemistry Communications 97 (2018) 16–21 .

brief introduction

By mixing commercial silicon multilayer simple and ultrasound of Ti . 3 C 2 MXene , since MXene good electrical conductivity, electrochemical performance of the composite material is improved. Graphite alkenyl compared, since MXenes manufacturing process is simple, easily throughout the composite prepared .

Literature 2 :

Enhanced cycling performance of Si-MXene nanohybrids as anode for high

performance lithium ion batteries

Chemical Engineering Journal 378 (2019) 122212 .

brief introduction

Establish a small layer after peeling MXene nanoplatelets based on, by freeze-drying method, the preparation of porous sandwich structure Si /-D of Ti . 3 C 2 composites . Compared with the exfoliated MXene , the specific surface area of the composite material is reduced, indicating that the silicon nanoparticles are successfully filled on the porous MXene matrix. The introduction of a few layers of MXene nanosheets not only buffered the volume expansion problem, so that the composite material can maintain a stable structure after multiple cycles, but also improved the electrical contact between the Si particles and the electrode, so that the polarization voltage was significantly reduced . At a current density of 500mA / g , after 200 cycles, the specific capacity can be maintained at 1130mAh / g, reflecting good electrochemical performance.

Literature 3 :

Employing MXene as a matrix for loading amorphous Si generated upon lithiation towards enhanced lithium-ion storage

Journal of Energy Chemistry 38 (2019) 50–54 .

brief introduction

Fanxiao Bin Tianjin University School of Chemical Engineering Task Force , the mixture ultrasound, followed by suction filtration deposition manner was prepared MXene & Si composite electrode, MXene as Si support the negative electrode material during charging and discharging, Si particles of amorphous edge, Amorphous Li x Si is produced . After several cycles after , S I particles are still walking MXene on the substrate, to produce 5nm core-shell structure size, the inner core is a crystalline silicon, amorphous silicon as the outer shell, so that in the late cycle appears capacity increase of the phenomenon . Compared with Si alone , the electrochemical performance of the entire composite material has improved due to the following points : ( 1 ) MXene has a good electricity Conductivity enhances the electron transport capability ; ( 2 ) MXene as a carrier can alleviate the agglomeration of Si in the process of charging and discharging ; ( 3 ) the introduction of MXene helps faster ion transmission.

Literature 4 :

Flexible and Freestanding Silicon / MXene Composite Papers for High-Performance Lithium-Ion Batteries

ACS Appl. Mater. Interfaces 2019, 11, 10004−10011 .

brief introduction

The team of Feng Jinkui of the School of Materials Science and Engineering of Shandong University prepared a flexible self-supporting Si / MXene composite paper by vacuum filtration of the mixed liquid , which can be directly used as a negative electrode material for lithium batteries, eliminating the need for conductive agents and binders. The versatility of MXene allows it to play the role of conductive agent and binder, which greatly improves the energy density of the battery system . Having a diameter of 20-60 nm of Si nanospheres may be uniformly adsorbed MXene base on. XPS tests show that MXene and Si nanospheres formed at the interface of the Si-C bond, can enhance the electron transport and kept at the phase interface in the cycle structure of the stable, this unique structure can accommodate a large volume expansion, enhancement The conductivity of the composite material prevents stacking of MXene sheets, provides more active sites and promotes effective ion migration, thus exhibiting excellent electrochemical performance , and commercial SiCompared with nanospheres , it has a very obvious performance improvement. Composites in 200 mA / G at a current density after 100 cycles, the capacity was 2118mAh / G , 1000 mA / G lower, after 200 cycles, the capacity retention at 1672 mAh / G, reflecting stable cycling performance, in 5000 The rate performance at mA / g is 890 mAh / g . This work provides more references for the development of Si anode materials.

Literature 5 :

High capacity silicon anodes enabled by MXene viscous aqueous ink

NATURE COMMUNICATIONS | (2019) 10: 849.

brief introduction

Swiss Federal Institute of Material Science Institute of Zhang Zhuanfang research group , in MXene many leading ink preparation of work reports and applications, they passed directly to the silicon powder and mixed viscous ink, the use of commercial coating process, at no extra In the case of conductive agent and binder, a high-load MXene / Si composite electrode (thickness up to 450 microns) is constructed . MXene ink has very viscous properties, and the ink is composed of most single-layer nanosheets . The high viscosity of the ink and the high mechanical strength of the nanosheets can effectively build a high-load MXene / Si composite electrode. High-quality, large-size single-layer MXene nanosheets can effectively encapsulate Si particles to form a sandwich structure . The continuous three-dimensional skeleton conductive network not only provides the possibility of rapid transmission of ions and electrons , but also provides excellent mechanical properties, resulting in a flexible, high-load MXene / silicon-based negative electrode material. The electrode has achieved a surface capacity of up to 23.3 mAh / cm 2 , far exceeding the surface capacity of the silicon electrode reported by predecessors. It is found by fitting that when micron-scale silicon is usedEven if the load capacity is further increased, the overall specific capacity improvement space on the negative electrode side is not large, indicating that the MXene ink in this study has maximized the capacity of micron silicon . And the electrode preparation process is simple, fully compatible with the commercial coating process, can be mass-produced, and has huge potential application value .

Source: mxene notes

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