Here, as with previous work, atomic layer deposition (ALD) has been used to deposit Al2O3 on positive electrode active materials, LiCoO2, to create a protective barrier layer, suppress the high potential phase transition, and thus reduce the subsequent Co dissolution. However, in this study it was found that it also resulted in the reduction of the charge transfer resistance at the positive electrode–electrolyte interface, thus enhancing the performance of the battery. Energy-dispersive X-ray spectroscopy, in conjunction with transmission electron microscopy, shows that a discrete Al2O3 shell was not formed under the selected growth conditions and that the Al diffused into the bulk LiCoO2. The resulting active oxide material, which was significantly thicker than the nominally ALD growth rate would predict, is proposed to be of the form LiCoO2:Al with amorphous and crystalline regions depending on the Al content. The cells consisting of the modified electrodes were found to have good cycling stability and discharge capacities of ∼110 mA h g–1 (0.12 mA h cm–2) and ∼35 mA h g–1 (0.04 mA h cm–2) at 50 and 100 C, respectively.

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Metal organic decomposition (MOD) using octylic acid salts was applied to synthesize a BaTiO3–LiCoO2 (BT–LC) composite powder. The Ba and Ti octylates were utilized as metal precursors, in an attempt to synthesize homogeneous BT nanoparticles on the LC matrix. The BT–LC composite, having a phase-separated composite structure without any impurity phase, was successfully obtained by optimizing the MOD procedure. The composite prepared using octylate precursors exhibited a sharper distribution and better dispersibility of decorated BT particles. Additionally, the average particle size of the decorated BTs using metal octylate was reduced to 23.3 nm, compared to 44.4 nm from conventional processes using Ba acetate as well as Ti alkoxide as precursors. The composite cathode displayed better cell performance than its conventional counterpart; the discharge capacity of the metal octylate-derived specimen was 55.6 mAh/g at a 50C rate, corresponding to 173% of the capacity of the conventional specimen (32.2 mAh/g). The notable improvement in high rate capability obtained in this study, compared with the conventional route, was attributed to the higher density of the triple junction formed by the BT–LC–electrolyte interface.