1. SEC 598 – PV SYSTEMS ENGINEERING Project -1 A Brief Study on Lithium-Ion Battery Technology For Large Scale Residential Systems - GOVINDARAJASEKHAR SINGU

2. Contents  Introduction and Purpose  Battery Science & Electrochemistry  Power & Energy Density  Construction & Manufacturing Technologies  SWOT Analysis  Conclusion

3. Introduction With a tenfold increase in the market for small solar power storage systems expected over the next three years, it is important that Second Solar aggressively develop and produce battery- supported photovoltaic (PV) systems for residential applications at large deployment scales to capitalize on this opportunity. Lithium-ion batteries have been selected for a suitability analysis, and are advocated by the others to serve as the preferred battery choice for these residential systems.

4. Battery Science & Electrochemistry  The smallest working unit in a battery is the electrochemical cell, consisting of a cathode and an anode separated and connected by an electrolyte.  The electrolyte conducts ions but is an insulator to electrons. In a charged state, the anode contains a high concentration of intercalated lithium while the cathode is depleted of lithium.  During the discharge, a lithium ion leaves the anode and migrates through the electrolyte to the cathode.

5. Contd..  The chemical reaction of lithium-cobalt battery at anode and cathode is, Cathode: Anode: In a lithium-ion battery the lithium ions are transported to and from the positive or negative electrodes by oxidizing the transition metal, cobalt (Co), in Li 1-x CoO 2 from Co 3+ to Co 4+ during charge, and reduced from Co 4+ to Co 3+ during discharge.Co Cathode Materials: Cobalt, Manganese, Phosphate, Nickel-cobalt-manganese Anode Materials: Graphite and Copper foils.

6. Power & Energy Density  Power Density (W/L) – The maximum available power per unit volume P = Voltage * Ampere-hours  Energy Density (Wh/L) – The nominal battery energy per unit volume. E = Power (Wh) /mass  For residential energy storage systems Nickel-Cobalt-Manganese-Oxide and Nickel-Cobalt- Aluminum-Oxide are considered because of their higher energy and power density.

7. Contd..  Manufacturer’s specifications of NMC battery,

8. Construction & Manufacturing Tech’s  Lithium ion cells are available in three different shapes they are: cylindrical, prismatic, pouch cells. The figure is shown below,

9. Contd..  General manufacturing procedure of li-ion batteries is,

10. Contd…  Currently existing technologies to construct and manufacture a lithium ion cell, they are,  Magnetron Sputtering - a target material is bombarded with microwaves during discharge, which ionizes and vaporizes the target material.  Aerosol Deposition - an electrolyte solution is aerosolized and fed to an extremely hot oxygen- hydrogen flame which deposits a layer of “glass soot” on a chosen substrate or electrode material.

11. Contd..  Pulsed Laser Deposition – It is an accurate and reliable way to deposit extremely thin (down to 1.2 nm thick) films on top of a chosen substrate.  Assembly Techniques: Bolt Joining (Cylindrical), Ultrasonic/Tab welding(Pouch), Projected welding(Prismatic/Cylindrical)

12. SWOT Analysis  Strengths – Light weight than Lead Acid batteries - Higher Energy density - Long Lasting  Weaknesses – Need for Battery Management Systems - Expensive than other battery technologies  Opportunities – Li-ion batteries may become cheaper as electric vehicle industry matures. - Global market of PV Systems coupled with power systems is expected to increase over next three years.  Threats – Emerging battery technologies - Resource limitations (Recycling process is complicated for Li-ion batteries)

13. Conclusion  Based on the study it is concluded that Li-ion can store large amount of energy for a long time than any other existing battery technology.  It has low discharge rate and able to withstand cold weather conditions which is mainly suitable for residential energy storage systems.  It can be dispose easily and recyclable too which reduces environmental hazards.

14. Thank You