2History of battery….Pioneering work for the lithium battery began in 1912 by G. N. Lewis but it was not until the early 1970’s when the first non-rechargeable lithium batteries became commercially available. Attempts to develop rechargeable lithium batteries followed in the eighties, but failed due to safety problems.the first commercial lithium-ion battery was released by Sony in The cells utilised layered oxide chemistry, specifically lithium cobalt oxide. These batteries revolutionised consumer electronics.
3Michael FaradayCharles-Augustin de Coulombdemonstrated the relation between electricity and chemical bonding,capacity (mAh/g) = [F × nLi) / ( M×3600)] × 1000Where, F = Faraday’s constant( 96,500 coulombs per gm equivalent)n Li = Number of Li per formula unit of the electrode materialM = Molecular mass of the electrode material.
4Cell – Energy storage device that converts chemical energy present in to electrical energy. Battery: Combination of one or more cell;The cell components: Cathode, Anode and Electrolyte, seperator and current collector.Primary Battery Secondary BatteryZinc- MnO2: Inexpensive, small in size, voltage ~ 1.5V, use in watches, calculators etc, use and dispose,Rechargeable cell , Ni- Cd, Li -Ion batteryEnergy storage of the battery is means that How much charge a battery can deliver to the external circuit.coulomb is defined as the quantity of electricity transported in one second by a current of one ampere. Named for the 18th–19th-century French physicist Charles-Augustin de Coulomb
5Why Li-based power sources? Li is the lightest metal (specific gravity ρ=0.53 g/cm3) high energy densityTheoretical capacity of Li : 3860 Ah/kg (Li Li+ + e-)Extremely high compared to Zn (820 Ah/kg) and Pb (200 Ah/kg).
6Salient Features of LIB High Energy density, Light weight, design flexibilityPreferred choice for portable appliancespresent world production per year is~ 300 million cells.Market value ~ US $ 200 Billionexpected growth up to ~ 40%Courtesy of Panacenia.com.
7Specification for the Commercial Battery fabricated by Panasonic. Size (DWH)3.83562 mmWeight15gNominal capacity760 mAhNominal voltage3.7 VCharge voltage4.2 VCharge time150 min.Energy density (Volumetric)375 Wh/dm3Energy density(Gravimetric)190 Wh/kgCycle performance85% at 1000th cycleTemperature range-20C to + 60CCathodeLiCoO2AnodeGraphiteCourtesy of Panasonic website
9LIB TechnologyDifferent configurations : a) cylindrical b) coin c) prismatic d) thin and flat (pLiON) [ref. Nature 2001, Tarascon et al .]
10Material Considerations AnodesCarbon anodesCapacity~372 mAh/gGraphite – layered, low capacity, high reversibilityHard Carbon- Non-layered, high capacity. Irreversible capacity lossMetal coating (Ag,Zn or Sn) of anodes tried
11Amorphous Tin Composite Oxides (ATCO) SnMxOy (x≥1), M = glass-forming elements (e.g. a mixture of B and P)Gravimetric capacity- high (>600 mAh/g)Sn2+,Sn4+/Sn redox coupleSnO + 2 (Li+ + e-) → Sn + Li2OSnO2 + 4 (Li+ + e-) → Sn + 2Li2OSn (Li+ + e-) ↔ Li4.4SnCapacity-fading need to be solved before these materials can be used commerciallyIrreversible loss of Li in Sn formationReversible capacity
12Other options Lithium metal nitrides Inter-metallics Oxides Pros: High capacity(~900 mAh/g), low average voltageCons: High moisture sensitivity, lack of economic manufacturing processesInter-metallicsCu6Sn5 – Capacity fadingInSb – In (high cost), Sb (toxic)OxidesSpinel-type oxides- Li4Ti5O12, Li4Mn5O12 and Li2Mn4O12Low voltage spinels + high-voltage cathodes= intermediate voltage Li-ion cells.Do not produce metallic Li which is a safety concern in LiC6 or metallic lithium anodes.
13Electrolytes Li salt dissolved in a solvent. LIB Operation range : V, Decomposition potential of H2O = 1.23 V Aqueous electrolyte not used4 types of non-aqueous electrolytes in use: liquid, gel, polymer and ceramic-solid electrolytes.
14Liquid electrolytesHighly ionizable Li-salts - LiPF6, LiAsF6 etc dissolved in organic carbonates - ethylene carbonate (EC), dimethyl carbonate (DMC) etcOrganic carbonates - aprotic, polar, high K, solvate Li salts at high concentration (>1M), good ionic conduction.Problems : leakage, sealing, non-flexibility of the cells, side reactions with charged electrodes
15Solid electrolytesCrystalline or glassy matrix - Li ions move through vacant/interstitial sites - high σionic (~ S/cm at 25°C)Crystalline : Nasicon framework phosphates – LiM2(PO4)3 and perovskite-based oxides, (Li,La)MO3 (M = Ge, Zr, Hf)Glasses : oxides or sulfidesAdvantages : (i) No leakage, (ii) Wide operating temperature range (iii) Better charge-discharge cycling profile (iv) Long life – little self discharge.
16Polymer electrolyteA salt dissolved in a high-molecular-weight polar polymer matrixE.g. PEO (Poly-ethylene oxide)Chemically stable – contains only C-O, C-C and C-H bonds.Cation mobility - cation-ether-oxygen co-ordination bonds, regulation - local relaxation and segmental motion of the PEO polymer chains -> high σionic of the electrolyte.Pros : ease of fabrication, flexibility, lightweight, leak proofCons: low conductivities at or below room temperatureAddressed by plasticized or gel electrolytes - polymer electrolytes with a component (solid or liquid): to enhance the ionic conductivity.
17Layered Cathodes Layered materials Facile Intercalation / deintercalation – high reversibilityα-NaFeO2 structure( sp grp R3m)LiNiO2, LixCoO2 (widely in use, 140 mAh/g) – thermally stable : High cost, toxicityLiMnO2 – cheap, substitution needed to stabilize the structure (Li1+x Mn0.5Cr0.5O2, 190 mAh/g )
18NaSICON materialsOxyanion scaffolded structures built from corner-sharing MO6 octahedra (where M is Fe, Ti, V or Nb) and XO4n tetrahedral anions (where X is S, P, As, Mo or W)Polyoxyanionic structures possess M-O-X bondsAltering the nature of X -> change (through an inductive effect) the iono-covalent character of the M-O bondingPossible to tune M redox potentials.Promising candidate - LiFePO4
19Spinels LiMn2O4 - cubic spinel structure with sp grp Fd3m Spinels - 3D hosts with Li ions occupying 8a tetrahedral sites.Capacity fading and poor recyclabilityCost, non-toxicity and availability
20Advanced Applications Mars Exploration rover” spirit”Koizumi taking a 10 minute spinEliica, Japan Speed – 90km/hr
22Preparation of Composite Electrodes ( Cathode or Anode). Fine powders of the active materials (LiCoO2, CaSnO3, etc) mixed with conducting carbon (Super PMMM) and PVDF in N-methyl pyrolidinone (NMP) solvent.PVDF acts as binder that helps the thick film coating to adhere well to the metal foil.This mixture of active material : conducting carbon :PVDF in fixed proportion ( in my case 70:15:15) was stirred to get the homogenous paste like slurry.The Slurry was coated on to a clean Al or Cu foil. Thick film was dried at 100oC in an air.Thick film coaterFurnace
235. Electrode was then pressed between spherical twin roller at about 5. Electrode was then pressed between spherical twin roller at about KPa pressure. This ensures that the film of the composite electrode adheres to the Al/Cu foil.6. Electrode was cut into circular discs (16mm). Thickness ~ 0.05 – 0.12mm7. Electrode- discs were dried in vacuum oven at 800C for ~ 12 hrs.
248. Electrode disc then transferred to the Glove Box. O2 and H2O content< 1ppmGlove Box
25Fabrication of Lithium - Ion Cell Diameter of coin cell ( 2016) ~ 16mm and height 2.0mmParts of Coin cell –Cup > 16mm diameter and plastic ring, separators ( polypropylene separators; Electronically nonconducting but solution/ion permeable) Steel spring for close packing. Finally cell was sealed using a press and transferred out the glove boxPunching MachineLi ion - coin CellMicropipette
26Electrochemical Characterization : Galvanostatic Cycling and Potentiostatic Cycling:Galvanostatic Mode: The output voltage of the cell is monitored at constant current.Potentiostatic Mode: The current is monitored at a particular voltageMulti cell analyzer BITRODE
27Specific Capacity of the cell : The capacity of the electrode material in the battery depends on the amount of Li that can be intercalated / deintercalated into the host structure.Capacity: Number of Coulombs (Charge) in (amperes-hours) delivered by a battery.Specific capacity: Amount of charge delivered per unit weight of electrode active material (Ah/g or mAh/g ).Theoretical specific capacity of a Li – containing oxide is calculated by assuming that all the Li per formula unit of the oxide participate in the electrochemical reaction and is given bySpecific Theoretical capacity (mAh/g) = [F × nLi) / ( M×3600)] × 1000Where, F = Faraday’s constant( 96,500 coulombs per gm equivalent)nLi = Number of Li per formula unit of the electrode materialM = Molecular mass of the electrode material.
28Theoretical Capacity of the Electrode Material: Weight of the active electrode material × its theoretical specific capacityExperimental Capacity: Our experimental value observed by BITRODE (mAh)Specific Capacity: Experimental capacity / weight of Electrode Material.Number of Lithium Ions de – intercalated from the cathode active material during charging process,Charging Capacity of Electrode / Theoretical CapacityWhere charging capacity = Charging current × Charging timeIn Coin – type cell the weights of electrodes ~ 8-15mg hence the current will be small.