Enhancing rate capability of amorphous nickel phosphate supercapattery electrode via composition with crystalline silver phosphate by Omar, Fatin Saiha, Numan, Arshid, Bashir, Shahid, Duraisamy, Navaneethan, Vikneswaran, Rajamuthy, Loo, Yueh Lin, Ramesh, Kasi, Ramesh, Subramaniam