Porous amorphous nickel phosphate electrode increases supercapattery capacity

A recent study highlights the potential of amorphous nickel phosphate as an electrode material for supercapatteries, emphasizing the importance of its internal structure over traditional metrics like surface area. Researchers have found that the presence of intraparticle pores and the inherent disorder of the amorphous framework significantly influence the electrode's performance.

The research team synthesized nickel phosphate using ethylene glycol, which served dual purposes. It acted as a capping agent to limit particle growth and as a templating agent to create a porous structure within the particles. Increasing the concentration of ethylene glycol led to a shift from dense blocks to smaller, irregular spheres with intraparticle pores.

This study stands out by isolating the effects of interparticle mesopores, intraparticle pores, particle size, and structural disorder on electrochemical behavior, moving beyond the traditional focus on surface area or particle size. Electrochemical tests revealed that nickel phosphate with an 18.75 percent ethylene glycol concentration achieved optimal performance, with a specific capacity of 386.7 C g⁻¹ at 0.8 A g⁻¹.

A complete supercapattery device using the optimized electrode achieved a maximum specific capacity of 13 C g⁻¹ at 0.8 A g⁻¹ and maintained about 75 percent of its capacity after 5000 cycles. The study suggests that the best electrode performance does not necessarily come from maximizing surface area or minimizing particle size. Instead, an intermediate concentration of ethylene glycol provided a balance between pore accessibility, hydroxide ion transport, internal active-site utilization, and electronic connectivity.

The findings propose a shift in electrode engineering for supercapatteries, advocating for a focus on the internal architecture of amorphous materials rather than solely on nanoscale particle engineering and interparticle porosity. This approach could enhance electrolyte-ion transport and overall device performance.