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Anodizing

Anodizing.

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Anodizing

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  1. Anodizing Anodizing is an electrochemical process in which the part is made the anodic electrode in a suitable electrolyte. Sufficiently high voltage is deliberately applied to establish the desired polarization to deposit oxygen at the surface (O2 overvoltage). The metal surfaces or ions react with the oxygen to produce adherent , oxide coatings, distinguishing the process from electro-brightening or electropolishing processes. Industrial anodizing processes are confirmed mainly to Al, Zr and Ti alloys. Anodic coating applications include: 1. Protection : corrosion, wear and abrasion resistance. 2. Decorative : clear coatings on polished or brightened surfaces, dyed (color) coatings. 3. Base for subsequent paint or organic coating

  2. a : thin barrier layer b : rough surface localized dissolution c : formation of pores d : growth of anodic oxide film Cell wall Porous oxide Barrier layer Aluminum Barrier layer Anodic Oxide Film of Al 4Al + 6H2SO4 = 2Al2O3 + 6SO3 + 3H2 + 6H+ + 6e- + 1250 kJ Heat generation/ ↑ Al oxide film breakdown / Formation of porous oxide layer Formation of anodic oxide film of Al

  3. Template-Assisted Nanowire Fabrication

  4. Alumina Templates on Silicon Wafers (I)

  5. Alumina Templates on Silicon Wafers (II) SEM image of porous alumina anodized in 4 wt.% H2C2O4 at 45 V. The pore diameter is ~ 44 nm. 40 nm Bi nanowires deposited in the porous alumina template on a silicon wafer with a conducting adhesion layer. Aluminum

  6. Li Battery

  7. e- e- A e- e- e- e- e- e- Li+ Li Rechargeable Battery LiPF6염 + 카보네이트계 용매 LiCoO2 Graphite Discharge C + LiCoO2 LixC6 + Li(1-x)CoO2 Charge Anode Anode Cathode Cathode

  8. Electrode Materials for Future Lithium Batteries • * J.-M. Tarascon & M. Armand, NATURE,VOL 414, 15 NOVEMBER 2001, p. 362

  9. 4. Features of the lithium ion battery Lithium Ion < Energy density of secondary batteries > • Volume energy density (Wh / l) • ⇒ nickel hydride battery ≈ lithium ion battery • Weight energy density (Wh / kg) • ⇒ nickel hydride battery < lithium ion battery

  10. Production of Anode of Li-ion Battery by Electrodeposition LSA LSM-c composite (1994. SONY) Anode material : graphite Cathode : transition metal oxide (LiCoO2, LiNiO2, LiMnO2, etc.) LSM : Lithium Storage Metal, LSA : Lithium Storage Alloy LSM-based anode can be easily produced by Electrodeposition. • Slurry process Active material Dry mixing Slurry dispersion Coating on current collector Conductive agent Drying Press Binder • Electrodeposition Current collector Electrodeposition of Active material Washing Drying

  11. 5.2 Anode materials [1] Carbon (0.2 V vs. Li/Li+) 1) General features - mostly used as the negative electrode of commercial rechargeable lithium batteries - layer structure → Li ions intercalate into/ deintercalate from carbon layers. - (reversible) - the quantity of sites capable of Li depends on ▪ crystallinity ▪ microstructure ▪ micromorphology - various advantages ① more negative redox potentials (0.2 V vs. Li/Li+) ② structural stability ③ no dendrite formation of Li ④ good cyclic performance After cycling discharge charge Li Li Li Li < Dendrite formation of Li in bare Li metal anode >

  12. - layer structure with a perfect stacking order ▪ prevalent AB (hexagonal) ▪ less common ABC (rhombohedral) - Graphite ( electrode materials ) <advantage> <disadvantage> ⇒ ▪ high initial coulomb efficiency ⇒ ▪ specific charge limitation : 372mAh/g (LiC6) ▪ discharge : lower & flat potential curve ▪ lower electrolyte tolerance (exfoliation) ① graphitic carbon • - forming lithium-graphite intercalation compound (LiXC6) • maximum lithium content : one Li per six carbon • ABAB layers  AAAA layers intercalation Li+

  13. 2) charge/discharge behavior of carbon - theoretically, carbonaceous materials → Li ions intercalation (reversible) - in practice ⇒ forming irreversible specific charge → the first cycle ▪ charge : charge consume ( LiC6 : 372 mAh/g ) ▪ discharge : deintercalation of Li ions recovers only about 80~95% ⇒ charge loss → irreversible specific charge → the second cycle ▪ discharge : charge recovery ≈ 100% Irreversible Specific charge SEI film formation Li intercalation

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