DESIGN OF NEW CATHODEMATERIALS FOR SECONDARYLITHIUM BATTERIESE. Sivanagi Reddy
Index Introduction Battery – Timeline Applications of batteries Secondary Lithium ion battery Structure of battery Cathode materials Advances in cathode materials Promising cathode materials conclusion
Introduction Beginning with the ‘frog-leg experiment’ by Galvani (1786), followed by the demonstrations of Volta pile by Volta (1792) and lead-acid accumulator by Plante (1859), several battery chemistries have been developed and realized commercially
Battery A battery is a transducer that converts chemical energy into electrical energy and vice versa. It contains An anode - source A cathode - sink An electrolyte - the separation of ionic transport and electronic transport
Timeline for the major events in the history of batteries
Types of batteries Primary batteries are disposable because their electrochemical reaction cannot be reversed. ΔG negative (irreversible) Secondary batteries are rechargeable, because their electrochemical reaction can be reversed by applying a certain voltage to the battery in the opposite direction of the discharge. ΔG negative, discharge ΔG positive, charge
Comparison of the volumetric andgravimetric energy density with otherbatteries
Lithium ion batteries The name of “lithium ion battery” was given by T. Nagaura and K. Tozawa The concept of “lithium ion battery” was firstly introduced by Asahi Kasei Co. Ltd Lithium ion batteries were first proposed by M. S. Whittingham in the 1970’s. Whittingham used TiS2 as the cathode and Lithium metal as the anode.
Lithium ion secondaryBatteries The lithium ion battery (LIB) system has been most successful in recent development of battery. Li is lightest metal and has one of the highest standard reduction potentials (-3.0 V) Theoretical specific capacity of 3860 Ah/kg in comparison with 820 Ah/kg for Zn and 260 Ah/kg for Pb
Lithium ion secondary batteries The first commercial lithium-ion battery was released by Sony in 1991 Battery performance is related not only capacity but also to how fast current can be drawn from it: specific energy (Wh/Kg), energy density (Wh/cm3) and power density (W/Kg)
Schematic representation of a Lithium-ion cell
Upon charging, lithium ions are released by the cathode andintercalated at the anode.When the cell is discharged, lithium ions are extracted by thecathode and inserted into the anode.
Advantages of Lithium-ion batteries POWER – High energy density means greater power in a smaller package. ◦ 160% greater than NiMH ◦ 220% greater than NiCd HIGHER VOLTAGE – a strong current allows it to power complex mechanical devices. LONG SHELF-LIFE – only 5% discharge loss per month. 10% for NiMH, 20% for NiCd
Disadvantages of Lithium-ion batteries EXPENSIVE -- 40% more than NiCd DELICATE -- battery temperature must be monitored from within (which raises the price), and sealed particularly well REGULATIONS -- when shipping Lithium-ion batteries in bulk (which also raises the price) ◦ Class 9 miscellaneous hazardous material ◦ UN Manual of Tests and Criteria
Electrolytes Role 1) ion conductor between cathode and anode 2) generally, Lithium salt dissolved in organic solvent 3) solid electrolyte is also possible if the ion conductivity is high at operating temperature. Requirement 1) Inert 2) High ionic conductivity, low viscosity 3) low melting point 4) Appropriate concentration of Lithium salt 5) Chemical/thermal stability 6) Low cost 7) Environmental -friendly, non-toxic Commercial electrolytes: LiPF6 in Carbonate solvent
Anode materials Requirements1) Large capability of Lithium adsorption2) High efficiency of charge/discharge3) Excellent cyclability4) Low reactivity against electrolyte5) Fast reaction rate6) Low cost8) Environmental -friendly, non-toxic Commercial anode materials: Hard Carbon, Graphite
cathodematerials One facet of battery research in which there have been many interesting discoveries is the area of cathodes A cathode is the electrode of an electrochemical cell at which reduction occurs Common cathode materials of Lithium-ion batteries are the transition metal oxide based compounds such as LiCoO2, LiMn2O4, LiNiO2, LiFePO4
Desired characteristics of cathodematerials A high discharge voltage Li A high energy capacity Co c O A long cycle life A high power density Light weight a Low self-discharge LiCoO2 Absence of environmentally hazardous elements
Parameters effecting Cathode behavior Method of preparation Particle size Morphology Oxygen Deficiency Temperature
CATHODE MATERIALS Layered oxide cathodes Spinel oxide cathodes Zigzag layered LiMnO2 compound Olivine structure of LiMPO4 Other compounds
Structures of cathode materialsStructures of different cathode materials for lithium ion batteries:a) LiCoO 2 layered structureb) LiMn2O4 spinel structure andc)LiFePO4 olivine structure.The green circles are lithium ions, Li+
LiFePO4 Advantages 1.Good Structural Stability--Safety, long life 2 . Fe and Phosphates are abundant-Low cost 3 . Environmentally friendly-non toxic elements Disadvantages a. LiFePO4 Structure 1.Slow Lithium-ion diffusion 2.Low electronic conductivitySymmetry : 3.Lower power capabilityOrthorhombic
Capacity ranges with respect tovarious cathode materials
Ways to Improve Cathode Performance• Increasing Energy Density • Investigate high voltage cathodes that can deliver all the Lithium in the structure will improve energy density• Thin nano-plate materials seem to offer more energy at higher rate • 30 nm LiFePO4 nano-plates performed better than thick material• Meso porous LiMn2O4 is another material where there is reduced manganese dissolution• Surface Coating of cathodes with either ionically or electronically conductive material • AlF3 coating on oxide materials is shown to improve performance
Recent advances in lithium ion battery cathode materials Composite Cathode Material for Lithium-ion Batteries Based on LiFePO4 System Some transition metal (oxy)phosphates and vanadium oxides for lithium batteries Nanostructured cathode materials
Problems in the usage of Cathode materials Raw material cost and environmental impact of large-scale cells and mass production Production cost of solid-state synthesis using high and long heating process Oxygen release and heat generation from the cathode in a fully charged state Sensitivity of safety for charge cutoff voltages Sensitivity of cathode performance for stoichiometry Low practical capacity of the cathode being half that of a carbonaceous anode
Next generation cathodes Most abundant is iron, with stable trivalent state Second most abundant is titanium, with stable tetravalent state Vanadium, with wide valence change (V 2+ –V 5+ ) Molybdenum, with wide valence change (Mo 4+ – Mo 6+ )
Potential Cathode Materials1. Olivine based phosphates systems (LiMPO4 where M = Mn, Ni) that can deliver more Lithium as compared to the conventional material LiCoO22. Only very few groups have synthesized LiMnPO4 successfully and this system has a potential around 4.3 V3. LiNiPO4 has a potential around 5.5V. It is believed that Li+ diffusion coefficient is quite high in nickel phosphate in the range 10-5 m2/s at around room temperature. It should have high thermal stability because the oxygen is covalently bound in the structure4. Novel approaches for synthesis of nanostructured olivines are required to enhance both ionic and electronic conductivity5. LiMn2O4 may be another potential candidate material if the Mn dissolution can be suppressed ◦ Mesoporous oxide with coating may stabilize Mn oxide
Structures of some promising materialsStructures of LiFePO4 and FePO4, quartz-likeFePO4, Li3Fe2(PO4)3, LipscombiteFe1.33FePO4(OH), LiFePO4(OH), H2VOPO4 and H2MnOPO4, e-VOPO4 andLi2VOPO4. PO4 tetrahedra are golden, FeO6 and VO6 octahedra areblue, FeO4 tetrahedra are green and lithium atoms are green
Conclusions and what does the future hold In present day common Lithium transition compounds such as LiCoO2, LiNiO2, LiMn2O4 and LiFePO4 are used as cathode material in battery cell production, and they have shown a good performance during charge and discharge cycling For the future there are still a number of actions of interest to further develop the performance of derived LiFePO4/C cathode material We expect upcoming researches on this new framework will lead to better cathode materials for lithium-ion batteries
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