Three-component layer double hydroxides by urea precipitation: structural stability and electrochemistry

Three-component layer double hydroxides (LDHs) with varying compositions were produced by urea precipitation, and tested for their stability and electrochemical performance. Optimum initial metal ion concentrations in the starting solutions were established. Initial Al3+ concentration in the solution needs to be at least 0.015 M for the LDH formation. From the solutions with initial Al3+ concentration of 0.025 M, higher fractions of Ni2+ and Co2+ could be recovered. Co2+ could be incorporated at various levels without disturbing the LDH structure. LDH structure proved stable once it formed. Cyanate in the LDHs was dominantly N-bonded which contributed to the stability of the structure. Highest specific discharge capacity delivered by a LDH was 336 mAh/g, which was about 30% higher than that by β-Ni(OH)2. LDHs reached their stable capacities at a lower rate than either β-Ni(OH)2 or the interstratified-Ni(OH)2 (α+β). The interstratified sample delivered the highest capacity compared to any of the tested compositions.