Professor Yang Jinhu, Tongji University ACS Nano: MXene coated porous silicon nanospheres to help lithium batteries

Lithium ion batteries ( LIBs ) are the main power source for portable electronic devices and electric / hybrid vehicles. However, the current commercial graphite-based anode materials due to the lower theoretical specific capacity ( 372 mAh g ^-1 ) are insufficient to meet today‘s high energy requirements. Silicon ( Si ) has become the most promising anode material for next-generation lithium-ion batteries due to its ultra-high theoretical specific capacity ( 4200 mAh g ^-1 ), lithium insertion potential ( 0.4 V vs Li / Li ⁺ ) and abundant reserves One is getting more and more attention. However, the large volume change of silicon anode (up to 400% ), lower intrinsic conductivity (≈ 10 ^-3  S cm ^-1 ) and lithium diffusion coefficient ( 10 ^-14  ~ 10 ^-13  cm ²  s ^-1 ) Frequently cause electrode powdering / cracking and irreversible reaction, resulting in permanent capacity loss and overall performance deterioration. Exploring silicon-based anode materials with high conductivity and stability is the key to high-performance lithium-ion batteries ( LIBs ).

Achievements

      Recently, Tongji University ‘s Professor Yang Jinhu and professor of relaxation in top international journal ACS Nano published entitled " Ti 3 C 2 T the X-  MXene nanosheets AS A Robust and Conductive Tight ON Si Anodes Significantly Enhance Electrochemical Lithium Storage Performance" paper. By assembling the interface policy of Ti . 3 C 2 T X  MXene nanosheets ( TNSS ) tightly wrapped Si porous nanospheres ( Si P-NSs ), prepare a Si -based composite material. A large number of characterizations and mechanical simulations show that TNSs as Si p-NSs conductors and tight coatings can effectively improve electron transport and electrode stability. In addition, TNSs with abundant surface groups canThe Si p-NS component has a strong interface interaction and has pseudocapacitive properties, which is conducive to the rapid and stable storage of lithium. Thus, compared to Si p-NSs electrode, a silicon content of up to 85.6% of Si p-NSs @ TNSs electrode exhibits significantly enhanced cell performance, ultra-high reversible capacity ( 1154 mAh G ^-1 ), the long-term cycle stability ( 2000 cycles, capacity decay rate is 0.026% ) and rate performance. It is worth noting that the energy density of the LIBs of Si p-NSs @ TNSs is 405 Wh kg ⁻¹ , which is 4 times the LIBs of Si p-NSs . This work provides a new strategy for the development of advanced silicon-based anode materials for high-performance lithium batteries. 

Figure  1  Si p-NSs @ TNSs preparation diagram.

Figure  2 The structure of  Si p-NSs @ TNSs .

Figure  3  The electrochemical performance and stability of LIBs of Si p-NSs @ TNSs .

FIG  . 4  Si @ P-NSs TNSS of LIBs different magnifications test .

Figure  5  The finite element simulation model of Si p-NSs @ TNSs .

in conclusion

In summary, the Ti 3 C 2 T x  MXene nanosheets ( TNSs ) were tightly wrapped with Si porous nanospheres ( Si p-NSs ) through the interface assembly strategy to prepare the core-shell structure Si p-NSs @ TNSs . TNSs as Si p-NSs conductors and tight cladding layers, and strong interface interaction with Si components make the composites have higher electrical conductivity and excellent structural stability, which is the key to improving the comprehensive performance of lithium storage . In addition, the mechanical simulation also quantitatively revealed that the Si p-NSs @ TNSs composite material generated low radial stress and hoop stress after lithiation , confirming that the coating of TNSs effectively enhanced the structural stability of the silicon anode. This study provides a new strategy for energy applications using MXene as a high-performance anode material.

Original link:

https://pubs.acs.org/doi/abs/10.1021/acsnano.0c01976

Source: MXene Academic