To Download visit https://seminarlinks.blogspot.com/. The PPT discusses the introduction of Lithium-Air Battery a type of metal-air electrochemical cell which combines the features from both lithium and oxygen, The studies show nearly 5 to 15 times of specific energy and almost 3 times of power as compared to the traditional lithium-ion batteries and they could possibly the power sources for future electric vehicles (EVs).

1. Lithium–Air Battery

2. Why Lithium–Air Batteries?
High specific energy density
batteries are attracting growing
attention as possible power sources
for electric vehicles (EVs).
Lithium–air batteries are the most
promising system, because of their
far higher theoretical specific
energy density than conventional
batteries.

3. Introduction
• The lithium-air battery (Li-air) is a metal–air
electrochemical cell.
• It works by oxidation of lithium at the anode
and reduction of oxygen at the cathode to
induce a current flow.
• A metal–air electrochemical cell is an
electrochemical cell that uses an anode made
from pure metal and an external cathode of
ambient air, typically with an aqueous or
aprotic electrolyte.
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4. Types Of Lithium Air Batteries
Lithium air batteries based
on the electrolyte used can
be classified into four types:
a) Fully Aprotic (Non-
aqueous electrolytes)
b) Aqueous electrolytes
c) Hybrid electrolytes
[Combination of (a) & (b)
or (d) ]
d) Solid state electrolytes

5. Working
• In general lithium ions move between the anode and
the cathode across the electrolyte.
• Under discharge, electrons follow the external circuit
to do electric work and the lithium ions migrate to the
cathode.
• During charge the lithium metal plates onto the
anode, freeing O2 at the cathode.
• Both non-aqueous (with Li2O2 or LiO2 as the discharge
products) and aqueous (LiOH as the discharge
product) Li-O2 batteries have been considered.
• The aqueous battery requires a protective layer on
the negative electrode to keep the Li metal from
reacting with water.

6. • Lithium metal is the typical anode choice.
• At the anode, electrochemical potential forces the lithium metal to release
electrons via oxidation (without involving the cathodic oxygen).
• The half-reaction is
Li ↔ Li+ + e−
• Upon charging/discharging in aprotic cells, layers of lithium salts
precipitate onto the anode, eventually covering it and creating a barrier
between the lithium and electrolyte.
• This barrier initially prevents corrosion, but eventually inhibits the reaction
kinetics between the anode and the electrolyte.
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7. Cathode
• At the cathode during charge, oxygen donates electrons to the lithium via
reduction.
• Mesoporous carbon has been used as a cathode substrate with metal catalysts
that enhance reduction kinetics and increase the cathode's specific capacity.
• Manganese, cobalt, ruthenium, platinum, silver, or a mixture of cobalt and
manganese are potential metal catalysts.
• In a cell with an aprotic electrolyte lithium oxides are produced through
reduction at the cathode:
Li+ + e− +O2 + * → LiO2*
Li+ + e− +LiO2* →Li2O2*
• where "*" denotes a surface site on Li2O2 where growth proceeds, which is
essentially a neutral Li vacancy in the Li2O2 surface.

8. In a cell with an aqueous electrolyte the reduction at the cathode can also produce lithium
hydroxide:
• Acidic electrolyte
2Li +
𝟏
𝟐
O2 + 2H+ → 2Li++ H2O
• A conjugate base is involved in the reaction.
• The theoretical maximal Li-air cell specific energy and energy density are 1400 W·h/kg and 1680 W·h/l,
respectively.
• Alkaline aqueous electrolyte
2Li +
𝟏
𝟐
O2 + H2O → 2LiOH
• Water molecules are involved in the redox reactions at the air cathode.
• The theoretical maximal Li-air cell specific energy and energy density are 1300 W·h/kg and 1520 W·h/l,
respectively
Electrolyte

9. Effect of Catalysts
• The electro catalysts for Oxygen reduction reaction play a key role in improving the
power density, cyclability and energy efficiency of the battery.
• Various experimental results show that Pd/ MnO2 and α-MnO2/Pd based catalysts
might have some significant effect and increase the discharge capacity of the
lithium air cell.
• It is reported that with Pd mixed with MnO2 the charge potential can be reduced to
3.7 V and the energy efficiency is increased from 60 to 89%.
• Charging potential can be further decreased to 3.6 V by the use of α-MnO2/Pd
catalyst.)

10. Aprotic (Non-aqueous)Li-Air Battery)
• Several chemical products may result from the reaction of Li with O2, depending on the chemical
environment and mode of operation.
• Most effort involved aprotic materials, which consist of a lithium metal anode, a liquid organic
electrolyte and a porous carbon cathode.
• The electrolyte can be made of any organic liquid able to solvate lithium salts such as LiPF6, LiAsF6 ,
LiN(SO2CF3)2, and LiSO3CF3), but typically consisted of carbonates, ethers and esters.
• Most studies agree that Li2O2 is the final discharge product of non-aqueous Li-O2 batteries.
• In nonaqueous Li/air batteries there are two principal electrode reactions of interest:
2Li+
𝟏
𝟐
O2 ↔Li2O & 2Li+O2 ↔Li2O2
• In the absence of practical considerations the full reduction of O2 to Li2O is desired because of its
higher specific energy and energy density, but it appears that Li2O2 is a product that forms more
readily than Li2O.
• In addition, when Li2O2 is formed full cleavage of the O-O bond may not be necessary, which is
important from a kinetic point of view.

11. • The open circuit voltage (OCV) of 2.96 V,
are 3460 Wh kg1 and 6940 Wh L1 for the
discharge state.
• For the charged state, oxygen is excluded
and the specific energy density is 11,680
Wh kg1 which is close to the energy
density of gasoline (ca. 13,000 Wh kg1).
• The energy density per unit mass and per
unit volume of non-aqueous lithium–air
batteries is about 10 times and 6 times
higher than those of lithium-ion
batteries, respectively, with a carbon
anode and LiCoO2 cathode.
Aprotic (Non-aqueous)Li-Air Battery
Schematic of aprotic type Li-Air battery design

12. Aprotic (Non-aqueous)Li-Air battery)
• Although rechargeable, the Li2O2 produced at the cathode is
generally insoluble in the organic electrolyte, leading to buildup
along the cathode/electrolyte interface.
• This makes cathodes in aprotic batteries prone to clogging and
volume expansion that progressively reduces conductivity and
degrades battery performance.
• Another issue is that organic electrolytes are flammable and can
ignite if the cell is damaged.

13. Aqueous Li-Air Battery
• An aqueous Li-air battery consists of a lithium metal anode, an aqueous electrolyte and a
porous carbon cathode.
• The aqueous electrolyte combines lithium salts dissolved in water.
• It avoids the issue of cathode clogging because the reaction products are water-soluble.
• The aqueous design has a higher practical discharge potential than its aprotic
counterpart.
• However, lithium metal reacts violently with water and thus the aqueous design requires
a solid electrolyte interface between the lithium and electrolyte.
• Commonly, a lithium-conducting ceramic or glass is used, but conductivity are generally
low (on the order of 10−3 S/cm at ambient temperatures).

14. Schematic of aqueous type Li-Air battery design

15. • Reactions involving Li and O2 in an aqueous medium depend on the pH.
• In a basic aqueous environment O2 reduction includes H2O as a reactant and
results in the formation of LiOH
2Li +
𝟏
𝟐
O2 + H2O ↔ 2LiOH (1)
• The product of this reaction is aqueous LiOH, which has a solubility limit of about
5.25 M at standard temperature and pressure.
• If LiOH exceeds its solubility limit it will precipitate out of the solution as a
monohydrate, LiOH.H2O, rather than LiOH.
4Li+6H2O+O2 = 4(LiOH.H2O) (2)
• This is a critical point for calculating the specific energy and energy density of
aqueous Li/air batteries.
Aqueous Li-Air Battery

16. • An example of the reaction of Li with O2 in a mildly acidic environment is the formation
of LiCl
2Li+
𝟏
𝟐
O2 +2NH4Cl ↔ 2LiCl+2NH3 +H2O
• The OCV with a LiCl and LiOH saturated aqueous solution was around 3.0 V
• where LiCl is saturated to prevent the reaction of LiOH and the lithium protective layer of
a water stable lithium ion conductor.
• The specific energy density of the aqueous system calculated from reaction (2) and OCV
of 3.0 V is 1910 Wh kg-1 for the charged state and 2004 Wh kg-1 for the discharge state.
• The mass specific energy density is five times higher than that of a conventional lithium-
ion battery.
Aqueous Li-Air Battery

17. Mixed Aqueous–Aprotic Li-Air Battery
• The aqueous–aprotic or mixed Li-air battery design attempts to unite
advantages of the aprotic and aqueous battery designs.
• The common feature of hybrid designs is a two-part (one part aqueous and
one part aprotic) electrolyte connected by a lithium-conducting
membrane.
• The anode abuts the aprotic side while the cathode is in contact with the
aqueous side.
• A lithium-conducting ceramic is typically employed as the membrane
joining the two electrolytes.
• The use of a solid electrolyte is one such alternative approaches that allows
for a combination of a lithium metal anode with an aqueous cathode.

19. Mixed Aqueous–Aprotic Li-Air Battery
• In 2015 researchers announced a design that used highly porous graphene
for the anode, an electrolyte of lithium bis(trifluoromethyl)
sulfonylimide/dimethoxyethane with added water and lithium iodide for
use as a "mediator".
• The electrolyte produces lithium hydroxide (LiOH) at the cathode instead of
lithium peroxide (Li2O2).
• The result offered energy efficiency of 93 percent (voltage gap of .2) and
cycled more than 2,000 times with little impact on output.
• However, the design required pure oxygen, rather than ambient air

20. Solid-State Li-Air Battery
• A solid-state battery design is attractive for its safety, eliminating the chance of ignition from
rupture.
• Current solid-state Li-air batteries use a lithium anode, a ceramic, glass, or glass-ceramic
electrolyte, and a porous carbon cathode.
• The anode and cathode are typically separated from the electrolyte by polymer-ceramic
composites that enhance charge transfer at the anode and electrochemically couple the cathode
to the electrolyte.
• The polymer-ceramic composites reduce overall impedance.
• The main drawback of the solid-state battery design is the low conductivity of most glass-ceramic
electrolytes.
• The ionic conductivity of current lithium fast ion conductors is lower than liquid electrolyte
alternatives.

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22. Challenges
Cathode
• Incomplete discharge due to blockage of the porous carbon cathode with
discharge products such as lithium peroxide (in aprotic designs) is the most
serious.
• The effects of pore size and pore size distribution remain poorly
understood.
• Catalysts have shown promise in creating preferential nucleation of Li2O2
over Li2O, which is irreversible with respect to lithium.
• Atmospheric oxygen must be present at the cathode, but contaminants
such as water vapor can damage it.

23. Challenges
Electrochemistry
• In 2017 cell designs, the charge overpotential is much higher than the discharge
overpotential.
• Significant charge overpotential indicates the presence of secondary reactions.
Thus, electric efficiency is only around 65%.
• The decrease in cell capacity is attributed to kinetic charge transfer limits.
• Since the anodic reaction occurs very quickly, the charge transfer limits are
thought to occur at the cathode.
• Catalysts such MnO2, Co, Pt and Au can potentially reduce the overpotentials, but
the effect is poorly understood.
• It is also reported that catalysts may alter the structure of oxide deposits.
• Significant drops in cell capacity with increasing discharge rates are another issue.
• The decrease in cell capacity is attributed to kinetic charge transfer limits.
• Since the anodic reaction occurs very quickly, the charge transfer limits are
thought to occur at the cathode.

24. Challenges
Stability
• Long-term battery operation requires chemical stability of all cell
components.
• Current cell designs show poor resistance to oxidation by reaction products
and intermediates.
• Many aqueous electrolytes are volatile and can evaporate over time.
• Stability is hampered in general by parasitic chemical reactions, for
instance those involving reactive oxygen.

25. Future Research
Future research should emphasize on the following:
• Understanding the electrochemical reaction mechanisms of Li air batteries.
• Development of Li ion conducting membrane to protect Lithium from directly reacting
with water.
• Development of protective coating for Lithium to minimize dendrite formation.
• Development of additives for electrolytes to increase the intercalation and not produce
any decomposition products.
• Development of porous Carbon cathodes which are not contaminated by discharge
products or moisturized due to the atmospheric gases etc.
• Development of a new catalyst for long cycle life, cycle efficiency and to control the
redox process.

26. Applications
Vehicles
• Li-air cells are of interest for electric vehicles, because of their high
theoretical specific and volumetric energy density, comparable to petrol.
• Electric motors provide high efficiency (95% compared to 35% for an
internal combustion engine).
• Li-air cells could offer range equivalent to today's vehicles with a battery
pack ⅓ the size of standard fuel tanks assuming the balance of plant
required to maintain the battery was of negligible mass or volume.

27. Applications
Grid backup
• In 2014, researchers announced a hybrid solar cell-battery.
• Up to 20% of the energy produced by conventional solar cells is lost as it
travels to and charges a battery.
• The hybrid stores nearly 100% of the energy produced.
• One version of the hybrid used a potassium-ion battery using
potassium-air.
• It offered higher energy density than conventional li-ion batteries, cost
less and avoided toxic byproducts.
• The latest device essentially substituted lithium for potassium.

28. Conclusion
• Lithium-Air batteries will primarily remain a research topic for at least
the next five years. Even if the challenges are successfully addressed
in that time period, the stringent requirements of durable and safe
operation in an automotive environment will further delay
commercialization.
• As a long-term solution to the daunting challenge of low-cost, high-
range electromobility, Li-air batteries remain one of the few and most
promising, and funding of research to accelerate their introduction
into the marketplace should be a top priority for government,
academic, and industrial research institutions.

29. References
Based on
• https://en.wikipedia.org/wiki/Lithium%E2%80%93air_battery
• Lithium Air Battery: Alternate Energy Resource for the Future :
ResearchGate
• Rechargeable lithium–air batteries: characteristics and prospects
• A Critical Review of Li/Air Batteries : ResearchGate
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