battery related research

1. Lithium based rechargeable cells: Recent advances and challenges
Dr.S.Jayalekshmi,
Professor (Emeritus),
Department of Physics,
Cochin University of Science and Technology.

2. Global Energy Consumption
Renewables 3% Hydroelectric 7%
Nuclear Plants 4% Fossil Fuels 86%
Transportation
Industry
Commercial and
Residential
Electricity
Energy Consumption
by Sectors
2

3. Greenhouse gas
emissions
Land pollution and
waste generation
Acid Rain
Oil Spills
Adverse Effects of Non-Renewable
Resources
Motivation

4. 7.3 million people died in
South-East Asia and
Western Pacific Regions
mostly due to air pollution
related diseases.
 Unhealthy environmental effects were
responsible for 12.6 million deaths in
2012, nearly one in four of total global
deaths.
 Around 19% of all types of cancers, now
leading cause of death worldwide, is
estimated to be attributable to
environmental factors, by the WHO
Environment should be clean, not harmful to health.
4

5. Need of cleaner and renewable energy sources
Move Fast
5
 Renewable energy output from sun and wind is intermittent since it is affected by weather conditions.
 It makes the development of advanced energy storage systems mandatory.
 Store energy when it is available in excess and release back to grid on demand.
Why Energy Storage?

6. BATTERIES AND
SUPERCAPACITORS
6

7. Carbon nanostructures
7

8. 8
Anode (Negative Electrode)
Graphite, Silicon
Cathode (Positive Electrode)
LiCoO2, LiMn2O4, LiFePO4
Electrolyte: Example: Lithium hexafluorophosphate
Main components of Li ion cells
 Transports ions from the anode to the cathode or vice-versa
 Porous membrane which is a good electronic insulator
 Keeps positive and negative electrodes apart to prevent electrical short circuits.
Separator: Example: Polypropylene (Celgard)

9. 9
Li-ion cells
 Lithium is the lightest and the most electropositive metal
 Li-ion cells- First commercialised by Sony in 1991
 Technology of choice for portable electronics
 Highest energy densities and longer life time
 Convert chemical energy into electrical energy
Li-ion cell
 The cell consists of three major components,
Anode, Cathode, Electrolyte and a Separator

10. Working of Li ion cells
 Imagine a never ending rally
 Lithium ion is as light as a shuttle cork
 Both electrodes allow lithium ions to
move in and out of their structures
Intercalation
10

11. 11
Terminology used in electrochemical technology
Specific
capacitance :
C-rate :
Coulombic
efficiency :
Specific charge : Charge obtained in one discharge cycle from unit mass of the active
material of the cell. Specific charge capacity is expressed in mA h g-1
Ability of a supercapacitor cell to store electric charge for a unit
mass of the active material and is expressed in F g-1
Duration of one full charge or discharge of a cell expressed in h-1.
Ratio of energy output on discharge to the input energy upon charging
of a rechargeable cell.
Energy density is expressed in Wh L-1 or Wh Kg-1
Power density is expressed in W L-1 or W Kg-1

12. Portable Electronics Transportation
Applications of Li ion cells
Batteries comparison  Coin cells
 AA
 AAA
 C
 D
 9V
Laptop
Powerbank Trimmer
12
 Can be charged faster
 Last longer
 High energy density

13. Research areas for discussion
• 1.Development of the next generation Li ion cells
using eco-friendly, cathodes and anodes with high
capacity, energy density and excellent electrochemical
performance characteristics
• 2.Realization of stable Li-S cells with high capacity,
energy density and excellent cycling stability
13

14. Cathode materials
14
LiCoO2 – The most successful cathode material when Li-ion cells
were commercialized in 1991
 Cathode materials such as, LiNiO2, LiMn2O4, and LiFePO4 have
also been developed
 LiCoO2 is costly and toxic, and its resources are no longer
abundant
LiFePO4:
 Olivine structure, low cost and non toxic nature
 High thermal stability, high theoretical specific capacity of
170 mA h g−1.
 Can be reversibly charged and discharged at a stable voltage of
3.2 V vs Li+/Li with negligible changes in the unit cell
parameters during LiFePO to FePO phase transition

15. Synthesis of nano-sized LiFePO4 using sol-gel technique
15
Lithium Nitrate
Iron Oxalate dihydrate
Ammonium dihydrogen
phosphate
Dried at 80 oC and fired at
700 oC in argon atmosphere
HNO3 + Citric Acid
(1 M) at 50 oC
LiFePO4
All of the reflections can be attributed to the
orthorhombic phase of LiFePO4 and the carbon
coating from the citric acid enhances the electrical
conductivity to the required range
LiFePO4
(020)
(011)
(120)
(111)
(121)
(031)
(131)
(211)
(140)
(221)
(112)

16. Anode materials
Graphite: The most commonly used anode material for Li ion cells
Layered structure: Li ions can be intercalated and de-intercalated
easily.
Abundant, relatively low-cost and long cycle life.
Low theoretical capacity of 375 mA h g-1 which is insufficient to meet
large scale applications
 Novel anode materials to be developed to achieve higher capacity in the
range 600- 1000 mAh/g
16

17. • Transition metal oxides (TMOs): Possible replacement for graphite
• Conversion-type reaction with Li
• Mn3O4.
 High theoretical capacity (936 mA h g-1)
 Earth abundance and environmentally benign
 Limitations
o Poor electrical conductivity (~10-7 to 10-8 S cm-1)
o Volume expansion and solid electrolyte interface (SEI) layer formation
 Mesoporous carbon: Excellent substrate to host anode materials
 Short diffusion path of lithium ions
 Easy electrolyte penetration through mesopores.
 High surface area and high electrical conductivity around 1 to 10 S/cm
17

18. 18
Synthesis of Mn3O4- MC composite.
Hexadecyltrime-
thylammonium
bromide
(CTAB) in water
Hydrazine Hydrate
Solvothermal process
at 180 ℃ for 12 hours
Mesoporous carbon
Filtration and
washing
Mn3O4 rods
Ultra sonication
Acetone
Drying
Mn3O4-MC composite
Stirring
Mn3O4: MC
1 : 1
Manganese acetate tetra
hydrate (MATH)
dissolved in water

19. 19
 FESEM images of composite establish the
dispersion of Mn3O4 nano flakes within MC
upon physical mixing.
 EDX mapping displays a uniform
distribution of the elements carbon,
manganese and oxygen in the composite.
EDX analysis
FESEM images of (a-b) Bare Mn3O4
(c) MC and (d) Mn3O4-MC composite
200 nm
200 nm 200 nm
100 nm
(a) (b)
(c) (d)

20. 20
Process Material
Electrode making
Slurry Mixing
Coating
Drying
Cutting
+ Active Material (80%)
+ Conductive Agent (10%)
+ Solvents
+ Binder (10%)
+ Al foil/Cu foil
- Solvents
Cell assembling process

21. Cell Assembling
21
Swagelok Cell

22. 22
Manufacturing Process Material
Cell Assembly
Stacking
Sealing
+ Electrolyte
+ Separator
Cell assembling and
characterizing processes
Cell testing

23. Half cell fabrication to assess the performance of the
nanocomposite anode, Mn3O4-MC composite
23
Li-ion test cells : Coin type cells
Anode : Mn3O4-MC composite on Cu foil
Cathode : Li foil
Separator : Celgard
Electrolyte : 1M LiPF6 in mixed ethylene carbonate and diethyl carbonate (1:1)
Voltage window : 0.01 - 3V
Mass loading ~ 1.5 mg
CV curve of Mn3O4-MC composite
at 0.1 mV s-1
Cathodic peak
 1. 03 V and 0.6 V : Solid electrolyte interface
(SEI) layer formation – electrolyte
decomposition on the electrode surface and
some irreversible
reactions.
[during the initial discharge ].
 0.02 V: Decomposition of MnO to metallic Mn.
Anodic peak
 1.3 V: Oxidation of Mn to MnO.

24. 24
 Loss in capacity is due to the SEI layer formation and the irreversible reaction of
the samples.
 Discharge profile in the first cycle differs from the subsequent cycles and is in
congruence with the results from studies.
GCD curves of Mn3O4 and Mn3O4-
MC composite at 100 mA g-1
 Bare Mn3O4
:
 First discharge capacity : 1301 mA h g-1
 First charge capacity : 650 mA h g-1
 Mn3O4-MC composite
 First discharge capacity : 1601 mA h g-1
 First charge capacity : 894 mA h g-1.
 Coulombic efficiency- 55.8 %
 Second discharge capacity : 920 mA h g-1
 Second charge capacity : 882 mA h g-1
 Coulombic efficiency- 95 %

25. 25
 Loss in capacity is due to the SEI layer formation and the irreversible reaction of
the samples.
 Discharge profile in the first cycle differs from the subsequent cycles and is in
congruence with the results from cv studies.
GCD curve Mn3O4 and Mn3O4-MC
composite at 100 mA g-1
 Bare Mn3O4
:
 First discharge capacity : 1301 mA h g-1
 First charge capacity : 650 mA h g-1
 Mn3O4-MC composite
 First discharge capacity : 1601 mA h g-1
 First charge capacity : 894 mA h g-1.
 Coulombic efficiency- 55.8 %
 Second discharge capacity : 920 mA h g-1
 Second charge capacity : 882 mA h g-1
 Coulombic efficiency- 95 %

26. 26
Rate capability of Mn3O4 and
Mn3O4-MC composite
Current density
(mA g-1)
Specific capacity (mA h g-1)
Mn3O4- MC Bare Mn3O4
Discharge Charge Discharge Charge
100 1601 894 1390 640
200 780 723 533 504
500 627 610 334 306
1000 488 469 204 189
2000 378 356 126 118
100 810 725 380 340
Cycling stability of Mn3O4-MC
composite
After 100cycles
730 mA h g-1
CE: 92%

27. Conclusions
27
 Mn3O4-MC composite could be explored as a high-capacity, low-cost and eco-friendly
anode material for Li-ion battery applications.
 FESEM and Raman studies confirm the formation of Mn3O4-MC composite by
incorporation of Mn3O4 on the surface of MC.
 After the first discharge/charge cycle, coulombic efficiency is increased to 95%.
 Discharge and charge capacities of 920 mA h g-1 and 882 mA h g-1, respectively, are
obtained by reversible electrochemical reaction.

28. Li-ion full cells using LiFePO4 cathode and
Mn3O4-mesoporous carbon nanocomposite
anode
28

29. 29

30. Silicon- carbon (Si-C) composite based anode materials
• Li ion full cell with LiFePO4 cathode and graphite anode is reported to offer a
total cell capacity of 150-160 mAh/g.
• With improved anode capacity using transition metal oxides based anodes, the
total cell capacity can be increased up to 250 mAh/g with enhanced cycling life.
• Silicon based materials of theoretical capacity of 3500 mAh/g against Li in half
cell configuration are promising anode materials
• Their low intrinsic electronic conductivity and volume expansion issues ( up to
300% volume expansion for Si) leading to structural destruction during multiple
lithiation/delithiation cycles limit practical applications
30

31. • Making the composite of nanostructured silicon with carbon is beneficial
for achieving high lithium storage capacity and having a medium which
accommodates the volume changes during Li intake.
• Si/C composite anodes can be synthesized in a cost effective way, by
coating nanostructured silicon with organic carbon.
• For carbon coating, fructose is dissolved in an ethanol/water mixture
(ratio 9:1). Silicon nanopowder is then uniformly dispersed in the solution
of fructose by ultrasonicating/mixing.
• Solvent will be evaporated and the carbonization can be done by
pyrolysing at elevated temperatures under argon atmosphere
31

32. • Carbon-rich Si based composites like SiOC and SiCN are potential
anode materials for the next generation, high energy density Li ion
cells.
• These materials can deliver well conducting and stress
accommodating carbon network
• They can store lithium with a capacity of more than 600 mAh/g.
• Ceramic structure allows easy breathing of the system during
repeated lithiation/delithiation providing mechanical compliancy of
the system.
32

33. Next generation Li on full cells with high capacity
• Synthesis of nanostructured LiFePO4 cathode active material with
electrical conductivity in the 10-3 to 10-2 S/cm range and particle size
in the 15-10 nm range employing sol-gel method in the presence of
citric acid.
• Development of nanostructured, transition metal oxides based and
silicon-carbon nano-composites based anodes as alternative anode
materials to replace graphite, with specific capacity in the range
600-1000mAh/g
33

34.  Synthesized cathode and anode materials will be initially tested
against Li metal by assembling half cells in the Ar filled glove box.
 Assembled half cells can be completely characterized using cyclic
voltammetry and charge –discharge cycling test to assess the specific
capacity, Coulombic efficiency and cycling stability of the cells.
 Various parameters can be optimized to get specific capacity close to
160-165mAh/g for the cathode active material LiFePO4 and in the
range of 600-1000mAh/g for the Si/C nano-composite anode
materials and transition metal oxides based anode materials.
34

35. Novel Energy Storage Systems – Lithium- Sulfur cells
35
Li-ion technology, though highly advanced, faces limitations when applied to electric
vehicles
Comparison of theoretical gravimetric/volumetric
energy densities of Li-ion (Graphite/LiCoO2) and
Li-S cells
Theoretical energy density
5 times greater than Li-ion

36. Advantages of Li-S cells
36
Eco-friendly
Lightweight
Cost Effectiveness
Full discharge
Maintenance free
Temperature and Pressure tolerance

37. Working of Li-S cells
37
S Li
Li
Sulfur can host two ions of lithium
Co
Li
Compared to one in Li-ion technology
Lithium interacts directly with sulfur
Discharge
Charge
Anode : Li Li+ + e-
Cathode : S8 + 16Li+ + 16e- 8Li2S
Anode : Li+ + e- Li
Cathode : 8Li2S S8 + 16Li+ + 16e-

38. Mechanism
38
 Charge/Discharge process is more complicated
 Sulfur becomes lithiated during discharge process to form polysulfide species
Long-chain lithium
polysulfides
S8 Li2S8 Li2S6 Li2S4 Li2S2 Li2S
Short-chain lithium
polysulfides
Contributes 25% of the
theoretical capacity of S
Contributes 75% of the
theoretical capacity of S
 Opposite process occurs during charging , although intermediate species might
be different.

39. Major challenges
39
 Dissolution of intermediate lithium polysulfide species in the electrolyte
Long-chain lithium polysulfide species (Li2S4 to Li2S8) dissolve readily in the
electrolyte. This leads to continuous loss of the active material ,sulfur.
 Low conductivity of sulfur and lithium sulfide
Insulating nature of sulfur and lithium sulfide, both electronically and ionically,
results in poor utilization of the active material.
 Polysulfide shuttle effect
Higher-order polysulfides migrate towards the anode, react with lithium metal,
get reduced to lower-order polysulfides, migrate back to the cathode, form
higher-order polysulfides again, and so on.
How do they have adverse effects?
 Internal shorting
 Self-discharging
 Low Coulombic efficiency

40. • During lithium intake, sulfur cathode may undergo enormous volume
expansion, which can adversely affect the discharge capacity and the
cycling stability of Li-S cells
• In order to get rid of these drawbacks, modifications of the sulfur cathode,
using various carbonaceous materials and conducting polymers have been
attempted.
• Above approaches help in improving electrical conductivity of the sulfur
cathode and in preventing shuttling phenomenon of polysulfides and the
volume expansion of sulfur.
• Addition of lithium nitrate as an electrolyte additive is also effective to
hinder polysulfide shuttle mechanism, since the direct reaction of lithium
metal with polysulfides is passivated.
40

41. • Novel type of Li-S cell architecture with the concept of inserting an “interlayer”
between the modified sulfur cathode and separator was primarily proposed by
Arumugam Manthiram and his co-workers in 2012
• In their work, free-standing interlayer film of multi-walled carbon nanotubes
(MWCNTs) obtained by vacuum filtration functions as a pseudo-upper current
collector and helps in improving the overall cell performance.
• Performance of Li-S cell is found to be significantly improved by incorporating
MWCNTs interlayer without any complex surface modifications and this has
opened a new research area in the field of Li-S cells
• . Afterwards, many types of interlayers based on different nano-structures have
come up for enhancing the electrochemical performance of Li-S cells.
41

42. • In order to overcome the adverse effects of shuttling phenomenon of
the polysulfides, the fruitful approach is to trap the polysulfides in the
cathode region and obstruct them from reaching the anode.
• Suitable interlayers inserted between the cathode and the separator
are found to be effective to achieve trapping of the polysulfides in the
cathode region .
• Interlayers with appreciable electrical conductivity also help to
reduce charge transfer resistance of the sulfur cathode.
42

43. • Various strategies have been adopted to address the drawbacks of
Li-S cell technology which mainly include the encapsulation of sulfur
in an electrically conducting matrix to improve conductivity of sulfur
cathode and the use of protective coating over sulfur to minimize its
volume expansion.
• Various carbonaceous materials such as mesoporous carbon,
activated carbon, carbon nanotubes, graphene , reduced graphene
oxide and various conducting polymers including polyaniline , PEDOT-
PSS and polypyrrole have been used as the encapsulating conducting
matrices and as the protective coating layers for sulfur cathode.
43

44. Realization of Li-S cells using SPMC cathode
44
 Mesoporous Carbon (MC).
 An inexpensive and highly conductive carbon material.
 High surface area and pore volume facilitates effective confining of
sulfur particles within its pores
 Polyaniline (PANI)
 High electrical conductivity.
 Ease of synthesis
 Highly stable and eco-friendly.
 Sulfur-Polyaniline coated Mesoporous Carbon (SPMC)
Sulfur-polyaniline coated
mesoporous carbon composite
(SPMC)-Cathode
CNTs interlayer
Li-S cells of excellent
performance
characteristics
 Sulfur.
 High theoretical specific capacity of 1675 mA h g-1
 Low electrical conductivity

45. 45
(Ammonium peroxydisulfate)
APS Solution
Aniline monomer +
Mesoporous Carbon in
HCl solution
Sulfur
6 hours stirring
Ice bath
Filtration and
washing
PANI Coated
Mesoporous Carbon
(PMC)
Sulfur with PANI Coated
Mesoporous Carbon (SPMC)
Solvothermal process
at 120 ℃ for 4 hours
Synthesis of Sulfur-PANI coated Mesoporous Carbon (SPMC) composite.
Sulfur : PMC
80 : 20
Ultrasonication
and stirring
3 hours

46. Synthesis of free-standing and flexible film of acid-functionalized carbon
nanotubes (CNTF interlayer).
46
PVDF in NMP solution
Ultra-sonicated for
2 hours
Pristine CNT
H2SO4 : HNO3 (6M)
in 3:1 volume ratio
Refluxed at 120 ℃
for 12 hours Acid-functionalized CNT
Dried at 60 ℃ in
vacuum
Ultra-sonicated for
3 hours

47. Cell fabrication
47
Li-S test cells : Coin type cells.
Cathode : SPMC composite
Anode : Li foil,
Separator : Celgard
Electrolyte : 1M lithium perchlorate in a mixed solvent of 1, 3 dioxolane (DOL)
and 1, 2 dimethoxymethane (DME) at a volume ratio of 1:1 including 0.5 M LiNO3 .
Voltage window : 1.5 V - 3V
Sulfur loading ~ 1.3 mg cm-2

48. Electrochemical studies
48
 Increase in redox currents observed for Li-S cells with CNT interlayer, which
indicates better utilization of sulfur cathode material.
 Slight over potential observed in the initial cathodic and anodic peaks in the cells
with interlayer disappears after the first cycle, perhaps due to the rearrangement of
the active material to electrochemically favorable positions
Cyclic voltammograms of the Li-S cell (a) without and (b) with CNT interlayer

49. 49
 Cells without CNT interlayer show rapid capacity fading (one-forth of the initial
values on cycling at 0.2 C and 0.5 C rates) after 50 cycles.
 Li-S cell without interlayer: 315 mA h g-1 at 0.5 C
 Li-S cell with interlayer: 1093 mA h g-1 at 0.5 C and 968 mA h g-1 at 1 C
Initial Discharge-charge profiles of the Li-S cell (a) without and (b) with CNT
interlayer

50. 50
 Li-S cells with the interlayer
 Specific capacity : 360 mA h g-1 at 2 C after 200
cycles.
 Capacity retention : 67% at 2 C and 72.3% at 1 C
 Coulombic efficiency : 98% at 2 C
 Rate capability of the Li-S cells: Capacity of
890 mA h g-1 obtained after the C-rate was
reverted back to 0.5 C from 2 C.

51. Role of CNTF interlayer
51
 Functions of the CNTF interlayer
 It facilitates localization of the polysulfides within the cathode region
 Acts as a pseudo-upper current collector and enhances the performance
efficiency of the Li-S cells

52. Role of CNTF interlayer
52
Before cycling
After cycling
(a) Conventional and (b) modified
structure of Li-S cell Trapped Polysulfides
Importance of the porosity of CNTF interlayer.
 Helps in the localization of polysulfides
and acts as a pseudo current collector.
 Facilitates penetration of the electrolyte
for electrochemical reaction.

53. Electrochemical Impedance Spectroscopy (EIS)
Analysis
• EIS measurements of the cells are carried out from 200 KHz to 50 mHz with
an ac amplitude of 10 mVpp.
• The X axis intercept of the Nyquist plot at the high frequency region gives
the equivalent series resistance (ESR)
• The charge transfer resistance (RCT) is obtained by extrapolating the semi-
circular portion of the Nyquist plot.
• The real and imaginary parts of the capacitance are calculated using the
equations
• 𝐶′
𝜔 =
−𝑍′′(𝜔)
𝜔 𝑍(𝜔) 2 𝐶′
′ 𝜔 =
−𝑍′(𝜔)
𝜔 𝑍(𝜔) 2
• Complex power (S (ω)) is determined using the relation
S(ω) = P (ω) + j Q (ω)
where 𝑃 𝜔 = 𝜔 𝐶′′
𝜔 ∆𝑉
𝑟𝑚𝑠
2
𝑎𝑛𝑑 𝑄 𝜔 = − 𝜔 𝐶′
𝜔 ∆𝑉
𝑟𝑚𝑠
2
53

54. 54
 In Nyquist plots, semicircular loop at high to medium frequency region is
related to the charge transfer resistance.
 The Li-S cell with the CNT interlayer shows a drastic decrease in Rct from
1073 Ω to 150 Ω.
FESEM images of CNTF interlayer after
200 cycles
Nyquist plots of Li-S cell
Before cycling
After cycling
Trapped Polysulfides

55. Conclusions
55
 SPMC composite cathode with the CNTF interlayer significantly improves the
performance of the assembled Li-S cells
 Presence of the conducting PMC network facilitates good electrical contact for
sulfur particles
 Polyaniline coating over sulfur particles also limits the enormous volume expansion
of sulfur during lithium intake.
 Network of carbon nanotubes of the interlayer acts as a “storeroom” of the
polysulfides by holding back the migrating polysulfides.
 Conducting network of the interlayer helps in lowering the charge transfer resistance
and subsequently ensures better utilization of sulfur composite cathode material
during the cycling process.
 The Li-S cells with the CNTF interlayer delivers high discharge capacity of
968 mA h g-1 at 1 C and 700 mA h g-1 after 200 cycles corresponding to an extremely
low capacity decay of 0.14% per cycle

56. Milestones to be covered regarding Li-S cells technology
• 1. Achieve excellent cycling stability with minimum capacity fading, for the
Li-S cells over 500 cycles with the retention of 80 to 85% of the initial
discharge capacity
• 2.Enhance the stable discharge capacity to around 1200 mAh/g in order
to achieve enough energy density to power electric vehicles
• 3. Modification of sulfur cathode using different combinations of
conducting polymer-carbon composites and the use of interlayers of
carbon nanostructures including graphene, functionalized graphene and
composites of graphene can be attempted to achieve these targets
56

57. Recent advances in Li-S cell technology
Cell architecture modification by choosing cathode active material as Li2S instead
of S
 Li2S will be confined in the pore channels of nitrogen doped, hollow porous
carbon spheres (NHPCS), followed by graphene wrapping.
Graphene wrapped, Li2S incorporated, NHPCS, (G- Li2S @NHPCS) composite
film with improved electronic conductivity and pore connectivity will serve as
cathode.
This approach eliminates the use of inactive binders, conductive additives and
current collectors and improves the energy density of resulting Li-S cells.
 Solid polymer electrolyte films based on polymer blends of PEO will be used as
solid electrolyte cum separator, instead of liquid electrolytes
 Silicon with theoretical capacity of 3500 mAh/g is an excellent choice as anode
and nanostructured Si-C composite with improved electrical conductivity will be
used as anode.
57

58. Advantages of this approach in the selection
of electrode and electrolyte materials
• Inherent drawbacks of Li-S technology like, low electronic conductivity of
sulfur, volume expansion of sulfur during Li intake and polysulfide
shuttling can be completely avoided.
• Use of Li2S instead of metallic Li in assembled cells and the replacement of
liquid electrolyte by solid electrolyte minimize safety concerns.
• High energy density in the range 600- 800 Whkg-1 and excellent cycling
stability are expected to be achieved with the proposed novel approaches in
• material selection and cell design
58

59. Looking forward
Fossil fuels are getting exhausted at alarmingly high rate and the next 15 years
will witness their complete extinction
Changing over to renewable energy sources is mandatory to meet the increasing
energy demands
Development of electric vehicles powered by rechargeable batteries
is the solution to meet the challenges due to fossil fuel extinction
with the added advantages of minimizing pollution effects
 Central ministry of our country has initiated many visionary
approaches to revolutionize automobile industry by completely
switching over to electric vehicles within the next ten years 59

60. Acknowledgements:
• UGC –Government of India for funding in the form of BSR fellowships
• Dr.Anilkumar, Dr.Manoj. M,Abhilash.A, my research students for their
contributions for enriching Li-S cell technology
• Dr. Jinisha, another research student for contributions to Li ion cell
research
• Members of my research laboratory in CUSAT, termed as the DREAM
lab for their research contributions
60

61. Lighting of an LED using Li ion cell assembled
in our lab
•Thank You
61

62. 62
For example: LiFePO4 → FePO4 + 1Li+ + 1e-
In this case we have:
Molecular weight of LiFePO4 is 157.7×10-3 kg mol-1 = 157.7 g mol-1
n=1Li+=1
F=96 485.3329 sA mol-1
So finally we obtain: Q=170 mA h g-1
Theoretical capacity calculation by Faraday’s law:
Qtheoretical = (nF) / (3600*Mw) A h g-1
Where,
n is the number of charge carrier,
F is the Faraday constant and
Mw is the molecular weight of the active material.

63. 63
C-rate calculation
Suppose if current density 60 mA g-1
1 g 60 mA
1 mg 60 µA
If mass is 1.5 mg
60 µA * 1.5 = 0.09 mA
If 0.09 mA is given to the sample with mass 1.5 mg, then the current density is 60 mA g-1