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When the battery is charged a cutoff voltage up to 4.2 V, only half lithium can be extracted from LiCoO₂ to Li_0.5CoO₂. Thus, it is a well-accepted strategy to charge LiCoO₂ cathode beyond 4.2 V, in order to utilize more lithium ions from the cathode and to increase the specific capacity and the energy density of LiCoO₂. However, the charge cutoff voltage over 4.2 V incurred the dissolution of LiCoO₂ into the electrolyte, thereby causing an increased capacity fade upon cycling. In this study, ALD derived coatings were employed to mitigate the capacity fading of LiCoO₂ in order to satisfy LIB application. We will report the roles of various metal oxides on LiCoO₂ performance.

SnO₂ anode, with much higher specific capacities than commercial graphite, has been one of the more promising anode materials in LIBs. During charge/discharge processes the maximum 4.4 Li⁺ combining with Sn to form Li_4.4Sn is accompanied by the large atomic uptakes (440% rise in the number of atoms) inducing the huge volume change (259%). The repeated huge expansion/contraction of Sn lattice causes the cracking, crumbling and pulverization among Sn particles and the consequent loss of electrical contact between Sn particles and current collector, resulting in the poor cycle performance, a key issue, prohibiting SnO₂ anode from the application for high performance LIBs. In this study, using an ALD technique, we successfully uniformly deposited crystalline and amorphous SnO₂ on both sides of graphene nanosheets (GNS) to mitigate the main challenges of high volume change anodes.

Atomic layer deposition (ALD) is a surface-controlled and layer-by-layer process, relying on two sequential self terminating half-reactions, offering unmatched precision in terms of controlling the ratio and morphology of the crystalline and amorphous phases of deposited materials[1-6]. Thus, ALD shows significant promise for synthesis of anodes and cathodes and ultra-thin film coating layers on active electrodes in lithium ion batteries (LIBs). In an ALD reactor, various metal oxide thin films were directly coated on LiCoO₂ electrode, and both amorphous and crystalline SnO₂ was deposited on GNSs.

Atomic layer deposition; Lithium Ion Batteries; Cathodes; Anodes