beta-Ni(OH)(2) hexagonal plates were synthesized from the high specific surface area nickel hydroxide by adopting the solvothermal treatment, i.e., heat-treatment of nickel hydroxide in a closed vessel in the presence of the disperse phase. An aqueous ammonia solution was chosen as the disperse phase, and it was effective for producing unit cell derived hexagonal particles even at a relatively low temperature of around 80 degrees C. A wide variety of sizes and specific surface areas of the hexagonal beta-Ni(OH)(2) could be available by choosing the solvothermal conditions such as amount and concentration of ammonia solution as the disperse phase as well as treatment temperature. The solvothermally synthesized hexagonal plates showed stable discharging behavior without serious deterioration in the discharging capacity when relatively high charge/discharge rates were adopted. It was speculated that there is a suitable specific surface area for the hexagonal particles to achieve a higher discharging capacity at high charge/discharge rates. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3446847] All rights reserved.