Amorphous Selenium and Crystalline Selenium Nanorods Graphene Composites as Cathode Materials for All-Solid-State...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Selenium (Se) possesses high theoretical capacity and electrical conductivity, making it a promising cathode material for lithium-selenium (Li-Se) batteries.
• Traditional Li-Se batteries face challenges with low active material utilization and capacity decay, hindering their practical application.
• All-solid-state batteries offer enhanced safety and potentially higher energy densities compared to their liquid electrolyte counterparts.

Purpose of the Study:

• To synthesize and evaluate novel amorphous selenium-graphene (a-Se/rGO) and selenium nanorods-graphene (b-Se/rGO) composites as cathode materials for all-solid-state Li-Se batteries.
• To investigate the electrochemical performance, including capacity, utilization rate, and cycling stability, of these composite materials.
• To understand the influence of selenium's amorphous versus crystalline structure on battery performance.

Main Methods:

• Synthesis of ultra-high dispersion amorphous selenium graphene composite (a-Se/rGO) and selenium nanorods graphene composite (b-Se/rGO) via hydrothermal methods.
• Assembly of all-solid-state Li-Se batteries utilizing a heated thawing electrolyte (2LiIHPN-LiI; HPN=3-hydroxypropionitrile).
• Electrochemical characterization including charge-discharge cycling, capacity retention, and utilization rate measurements.

Main Results:

• The a-Se/rGO composite achieved an initial utilization rate of 103% and a capacity of 697 mAh/g, retaining 281 mAh/g after 30 cycles at 0.5 C.
• At a higher rate of 2 C, a-Se/rGO demonstrated a capacity of 610 mAh/g, attributed to the high availability of amorphous Se and favorable electrolyte properties.
• The b-Se/rGO composite maintained 270.58 mAh/g after 30 cycles with a discharge capacity retention of 66.13% compared to the first cycle.

Conclusions:

• Amorphous selenium within the a-Se/rGO composite is beneficial for capacity release in all-solid-state Li-Se batteries.
• The formation of crystalline selenium during the initial charge process leads to capacity attenuation in amorphous selenium-based cathodes.
• The synthesized a-Se/rGO composite exhibits promising performance for next-generation all-solid-state energy storage applications.