Lecture #2

Lithium-ion batteries

T Prem Kumar
premlibatt@yahoo.com
 Common battery anodes
Zn Zn2+ + 2 e– 65.39 / 2 = F 820 mAh.g–1
Pb Pb2+ + 2 e– 207.20 / 2 = F 259 mAh.g–1
Li Li+ + e– 6.94 / 1 =F 3862 mAh.g–1

Zn: –0.76 V vs. Li: –3.045 V

1 F = charge on one mole of electrons

= 1.6 x 10–19 C x 6.023 x 1023 = 96487 C
= 96487 A.s
= 96487 A.s x h/3600 s
= 26.8 Ah
 N
Lithium as an anode material
Thermodynamic potential: –3.045 V
Equivalent weight: 6.941 g
Charge density: 3862 mAh/g
(1 eqvt. = 1 F = 26.8 Ah.
Therefore, charge delivered per gram of metal: 26800 mAh/6.941 g = 3862 mAh/g.)

Arguably, the most attractive of anode materials.

A variety of lithium primary battery chemistries have been commercialized.

But rechargeable batteries based on lithium are yet to take off!

Primary systems: > 160

Secondary/rechargeable systems: ~ two dozens
 Increasing the energy density of batteries

POTENTIAL CAPACITY
(DE, Volts) (Q, Coulomb, Faraday, Ah)

- Nature of the redox couples - Nature of the redox couples

- State of advancement of the reaction - Quantity of material

ENERGY
POTENTIAL
ENERGY
ENERGY

Number of exchanged electric charges (Coulombs)

Specific energy Specific power
(Wh/litre, Wh/kg) CAPACITY (W/litre, W/kg)
 LITHIUM-ION: the beginnings
1912: G.N. Lewis

1956: W.R. Harris

Plating and stripping of lithium in PC

1962: J.E. Chilton Jr. and G.M. Cook

Lithium cycling in LiCl–AlCl3–PC (limited by
soluble CuCl2– species from cathode)

1970s: Marriage of electrochemistry & solid state chemistry

Intercalation materials
Li–TiS2 and Li–MoS2 cells
MoLi cell explosion in a Kodak camera
Scientists tacitly agreed that lithium was not a safe anode.
 Lithium dendrites
Dendrites on lithium metal anode. Lithium is intrinsically unstable in
R.R. Chianelli, J. Cryst. Growth 34 (1976) 239.
any known electrolyte.

This layer (solid electrolyte

interphase) prevents further
reaction of the metal with the
It is possible to plate lithium from electrolyte.
aprotic organic electrolytes at The SEI bestows long shelf-lives to
100% efficiency (Harris, 1956). lithium primary systems.
The plated lithium is dendritic
But it eats into the efficiency of
(needle-like). It reacts with the
electrolyte, covering itself with a rechargeable batteries and leads
layer of the products. to safety problems.
Dreamliner 787

Jan. 16, 2013: GS Yuasa Li-ion

batteries in Dreamliner 787 of
All Nippon Airways overheats.

Likely cause:
Formation of lithium dendrites
due to rapid/non-uniform charging.
Deamliner fleets grounded.
 Growth of lithium dendrites

• (a) Bare lithium in contact with the electrolyte (SEI) on Li

• (b) Lithium dendrite on first charge
• (c) SEI on dendrite
• (d) & (e) more dendrites with SEI on them
• (f) Lithium micronization
• (islands of lithium particles: thermally reactive; electrochemically inactive)
 Circumventing the impasse

•Therefore, lithium battery scientists tacitly agree

that it is difficult to assemble rechargeable cells
with lithium metal as the anode.
• So, what is the way out? (Goals: retain properties of Li; ensure safety.)
•Use less aggressive electrolytes such as polymer electrolytes.
•Use alternative materials that can be lithiated and delithiated
at potentials close to that of lithium metal.
Lithium to lithium-ion:
a tactical move
Search for alternatives to lithium

Lithium alloys such as Li–Al were the first to be considered.

Inordinate volume changes; Zintl phases.

Li-GICs were known since 1955.

So carbon began to be investigated.

1976: J.O. Besenhard—electrochemical intercalation of

lithium in graphite.

1978: M. Armand proposed graphite as an anode material.

1983: S. Basu patented LiC6 as an anode material.

 Enter Goodenough

Exfoliation of graphite in PC put paid to hopes of exploiting

graphite as an anode.

Graphite had to be pre-lithiated as the cathodes of that

time (TiS2, V6O13 and NbSe3) did not have lithium in them.

1979: J.B. Goodenough

Proposed LiCoO2 as a lithium-laden cathode material.

1980: M. Lazzari & B. Scrosati

The first rocking chair cell as we know it today.
LixWO2–TiS2 cell (1.8 V): poor e.d.
 Carbon as a lithium insertion anode

1982: R. Yazami & P. Touzain

Reversible intercalation of lithium in graphite.
(solid electrolyte)

1983: A. Yoshino & K. Sanechika

Polyacetylene–LiCoO2 test tube lithium-ion cell.
(non-aqueous liquid electrolyte;
low capacity; poor chemical stability of PAc)

Mid-1980s: Improved carbon forms (no exfoliation with PC);

EC as a co-solvent.

1991: Sony Energytec

First commercial lithium-ion battery.
THE REST IS HISTORY.
 Lithium-ion cell
•Now, if a lithium insertion anode (such as
carbon) is coupled with a lithium insertion
cathode (say, LiCoO2), the combination will
be a lithium concentration cell.
•The working of such a cell will involve a
cyclic transfer of lithium ions between the
anode and the cathode.
•Such a configuration is called a lithium-ion
cell. (Earlier nomenclatures: rocking chair
cell, shuttlecock cell, swing cell, etc.)

•Thus, lithium-ion batteries are

lithium metal-free lithium batteries!
Assembled in the Must be charged
discharged state. before use.

Electrolyte

Cu Al Current
Current
Collector
Collector

Graphite LiMO2

6C + xLi+ + xe– SEI SEI LiCoO2 →

→ LixC6 Li1–xCoO2 + xLi+ + xe–
 Discharge
reaction

Electrolyte

Cu Current Al Current

Collector Collector

Graphite LiMO2

LixC6 → SEI SEI Li1–xCoO2 + xLi+ + xe–

xLi+ + xe– + 6C → LiCoO2
 Lithium-ion cell: improved safety
• The potentials of the anodes are 50–500 mV
more positive than that of lithium.
They are thus less taxing on the electrolyte.

• Thermodynamically, both Li and LiC6

have similar reactivities.
• But the reactivity of LiC6 is limited by
the diffusion of lithium from
the insertion sites to the surface.
• In other words, the host (carbon) ‘shields’
the lithium (guest) from the electrolyte.
 Versatile chemistry
LiFePO4 3.4 V

LixC6 0.1 V
LiCoO2 3.7 V

LiNi1/3Co1/3Mn1/3O2 4V
Li4Ti5O12 1.5 V

LiMn2O4 4.1 V c
a

TiO2(B) 1.8 V
LiNi0.5Mn1.5O4 5V
Types of anode processes
(a) Lithium metal anode and intercalation cathode.
DISCHARGE: Lithium stripped from the anode gets
intercalated into the cathode.
CHARGE: Lithium is deintercalated from the cathode and
is deposited on the metal anode.
(Li-LiCoO2)

(b) Lithium metal anode and anion-exchanging electro-

active polymer cathode.
DISCHARGE: Lithium is stripped from the anode and an
equal amount of anions leave the polymer.
CHARGE: Equal amounts of lithium ions and anions from
the electrolyte move back to the anode and cathode,
respectively.
(Li-PANI)
Types of anode processes

(c) Lithium alloying anode and intercalation cathode.

DISCHARGE: The alloy is delithiated, and the lithium
intercalates into the cathode.
CHARGE: Lithium deintercalated from the cathode forms
alloy phases with the host anode element (reconstitution
reaction).
(Sn-LiCoO2)

(d) Lithium intercalating anode and cathode.

DISCHARGE: Lithium deintercalates from the
anode and intercalates into the cathode.
CHARGE: Lithium deintercalates from the
cathode and intercalates into the anode.
(C-LiCoO2)
Material MW Density Lithiated Potential Specific Charge DV
(g/mol) (g/cc) phase vs. Li+/Li charge density (%)
(V) mAh/g* mAh/cc**
Li (primary) 6.94 0.53 Li 0 3,862 2,047 ---
Li4 (rechargeable) 27.76 0.53 Li 0 965 511 0
C6 72.06 2.25 LiC6 0.05 372 837 10.6
Al 26.98 2.70 LiAl 0.3 993 2,681 96
Sn 118.69 7.29 Li4.4Sn 0.6 994 7,246 260
Si 28.09 2.33 Li4.4Si 0.4 4,198 9,786 320
Sb 121.76 6.70 Li3Sb 0.9 660 4,422 200
Bi 208.98 9.78 Li3Bi 0.8 385 3,765 215
Li4Ti5O12 459.04 3.50 Li7Ti5O12 1.55 175 613 0.2
TiO2 79.86 3.89 LiTiO2 1.5 336 1307 ---
MoO2 127.94 6.47 LiMoO2 0.8 209 1,352 --

*Gravimetric charge density; **Volumetric charge density.

Carbon as an alternative anode material

• Lithium intercalation: 50–500 mV vs. Li+/Li.

• LiC6 (fully intercalated form): 372 mA/g.
• Conducting in its charged (lithiated) and
discharged (delithiated) states.
• Chemically and thermally tolerant.
• Electrochemical stability in the voltage
window of the cell.
• Insoluble in the electrolyte.
• Mechanically robust.
• Abundant, cheap, non-toxic, easy to handle.
Carbonaceous anodes
Cost
Availability
Desirable electrochemical properties
372 mAh/g (LiC6) (compare: 3862 mAh/g for Li)

Disord. carbons (1000+ mAh/g): stable SEIs—large hysteresis (>1 V)

Kish graphites (400+ mAh/g)
Mesophase pitch-based carbons
Templated carbons
Polyacenic semiconductors
Polyaromatic hydrocarbons
Nanostructured carbons: CNTs, ACNTs

T. Prem Kumar, T.S.D. Kumari and A.M. Stephan, J. Ind. Inst. Sci. 89 (2009) 393.
 Kish graphite

T.S.D. Kumari, A.J.J. Jebaraj, T.A. Raj, D. Jeyakumar and T. Prem Kumar, Energy 95 (2016) 483.
 Kish graphite

A smorgasbord of nanocarbon structures observed in kish graphites

Y.H. Lee, K.C. Pan, Y.Y. Lin, T. Prem Kumar and G.T.K. Fey, Mater. Chem. Phys. 82 (2003) 750.
 PVC-kish graphite–morphology

100 nm 100 nm 50 nm 0.1 µm

SEM (top) and TEM (bottom) images of PVC-derived kish graphite.

Y.H. Lee, K.C. Pan, Y.Y. Lin, V. Subramanian, T. Prem Kumar, G.T.K. Fey, Mater. Lett. 57 (2003) 1113.
 PVC kish graphite–voltage profiles

T.S.D. Kumari, A.J.J. Jebaraj, T.A. Raj, D. Jeyakumar and T. Prem Kumar, Energy 95 (2016) 483.
 Li alloy-based electrodes
M° + xLi + xe- LixM

Poor cycle life owing to large Li-driven

Staggering capacity gains over C? volume swings (up to 300%)
Capacity (mAh/g)
4500 0 1000 2000 3000 4000
Décomposition
4000

i5
del’électrolyte

Potential (V) vs Li /Li

2S
300
2

2
Capacity (mAh/g)

Li

+
4i →
i4
13 S
Expansion (%)

13 S
3500
Li

Li

1.5
3i →

200
7S

3000
Li

3i
7S

1
Li
7→
Si

2500 100
12
7i
12 S

Li

0.5
Li
→
Si

2000 0
0 0 1000 2000 3000
0 1 2 3 4 5
1500 x in LixSi Capacity (mAh/g)

1000
500

0
In C Bi Zn Te Pb Sb Ga Sn Al As Ge Si
Alloy anodes
Electrochemical lithium alloying (1971)

Li–Al:
α-Li–Al (up to ~7 at.% Li) and β-Li–Al (~47–56 at.% Li; cycled)
∆V: 97% (graphite: 10.3%)—Zintl phases (Li+Al–)xAl0

Active–inactive alloy matrices

Nanocomposite alloy anodes (Nexelion)
Silicon
Li22Si5 (4.4 Li per Si) 4199 mAh/g
∆V: 280%
[<50 mV: Li15Si4 (3,578 mAh/g)]

Silicon nanopartilces
Si@C core-shell structures
Thin silicon films
Silicon nanotubes (3000+ mAhg; 6000+ cycles)
Silicon as an anode material
 Positives
highest-known capacity: 4200 mAh/g (Li22Si5)*
2nd most abundant element on the earth’s crust
environmentally friendly.

 Problem areas
inordinate volume expansion: ~400%**
poor electronic conductivity (1.2x10–5 S/cm).

 Solutions
use of nano-sized silicon
use of conductive coating
*graphite: 372 mAh/g
**leads to electrochemical pulverization and cell failure
 Nano SiC as a game-changer

No resemblance with the profiles of Si or C.

T.S.D. Kumari, D. Jeyakumar and T. Prem Kumar, RSC Adv. 3 (2013) 15028.
Oxides
•TiO2 (2-D) and Li4Ti5O12 (1.0–2.8 V)

•SnO2 (Sn in Li2O) (0.005–1.0 V)

• Tin-based composite oxide (TCO, Sn1.0B0.56P0.40Al0.42O3.6)

•Fujifilm Celltec; 600 mAh/g

Li4Ti5O12 (175 mAh/g; 1.55 V)

– inserts up to 3 Li per molecule to form Li7Ti5O12
(∆V: 0.2%: zero strain material)
 Li4Ti5O12

• Very stable (zero-strain material).

•Voltage is high for a negative electrode
(1.5 V as against 0.2 V for graphite).
•Lower cell voltage results in lower energy.
•Lower voltage means higher stability
with the electrolyte (safer).
 Amorphous tin composite oxides (ATCO)

 SnMxOy (M = glass-forming elements: B, P)

 Gravimetric capacity: >600 mAh/g

SnO + 2 (Li+ + e-) → Sn + Li2O Irreversible

SnO2 + 4 (Li+ + e-) → Sn + 2Li2O loss of Li in Sn
formation
Sn + 4.4 (Li+ + e-) ↔ Li4.4Sn

▪ Problem: capacity fading

Nexelion Sb-MOx-C (M = Al, Ti,
Mo) nanocomposite

Tin anode

Patented: 12 elements
Sn, C, Si, Co, Mg, Al, B, P

20–30 % gain in volumetric

energy density
Nitrides

LiMoN2, Li2.6Co0.4N (480–760 mAh/g), Li2.7Fe0.3N (550 mAhg)

The metal M exist as M+ ions; upon delithiation forms M2+.

Good reversibility; potentials close to Li+/Li; flat voltage profiles.

 Conversion electrodes
Capacities as large as 1,000 mAh/g
Oxides: Co3O4, Cu2O, Fe2O3, Fe3O4, Mn2O3, MoO2, NiO, RuO2
Sulfides: Co9S8, CrS, Cu2S, FeS, MnS, MoS2, Ni3S2, WS2
Fluorides: CoF, CuF2, CrF3, FeF3, NiF, TiF3, VF3
Nitrides: Co3N, CrN, InN, Mn4N, Ni3N, Sn3N4, VN, Zn3N2
Phosphides: CoP, Cu3P3, CuP2, FeP, FeP2, MnP4, NiP2, NiP3

As many as four electrons per 3d metal (0.5–1.0 V)

Fluorides: at potentials close to 3 V (not conversion anodes)
MxOy + 2yLi+ → xM + yLi2O
An SEI and a polymeric gel-type film (50–100 nm) are formed
on full discharge. Polymeric film: PEO-type oligomers
 Potential and chemistry
 Playing with the nature of the anion
1.2

Potential (V) vs Li+/Li

CoF3
1
CoO
0.8 CoS
Cu3N

Hydrides
0.6
CoP2
0.4
0.2 ?
0
H P N S O F
Polarization

H
H?<P<N<S<O<F
Energy efficiency
 New Li-reactivity mechanisms:
Conversion reactions

CoO: Rocksalt Structure

3.5
 No Interstitial voids for guest ions
Voltage (V vs Li/Li )
+

2.5

1.5
CoO Co-Nano
particles
1
discharge 30 to
0.5
50Å
0
0 0.5 1 1.5 2 2.5 3
charge
x in 'LixCoO' 500Å
CoO + 2 e− + 2 Li+  Co0 + Li20
2 e- per Co
Today’s Li-ion cells Mn+ to M0 “Conversion reactions”

LixCoO2+ 0.5Li+ + 0.5e- <=> LiCoO2

0.5-0.6 e- per Co factor 3
A.K. Shukla and T. Prem Kumar, Curr. Sci. 94 (2008) 314.
Cathodes
Present chemistry: LiNi0.80Co0.15Al0.05O2
Good performance (capacity: >160 mAh/g; >1000 cycles)
Ni and Co expensive; high Ni content materials tend to release oxygen –
safety concern.
(180 mAh/g)

(130 mAh/g)

(150 mAh/g)
Cathode active materials
LiMn2O4
Cheaper, safety better than for Co & Ni

LiNiO2
Highest safety risk, good performance

LiCoO2
Good lifetime high safety risk

LiCo1/3Ni1/3Mn1/3O2
Popular material, wide range of variability for optimizing properties

LiFePO4
3.3 V material, cheap and safe
 LiCoO2
LiCoIIIO2 → xLi+ + xe– + Li1–xCoIII1–xCoIVxO2
John B. Goodenough
First lithiated cathode
Theor. cap.: 274 mAh/g
Pract. cap: 140 mAh/g
3.6 V Co toxicity
 LiMn2O4

Theor. cap.: 148 mAh/g

Pract. cap.: 120 mAh/g
4.1 V
Mn dissolution
Used in Nissan Leaf
 LiFePO4
John B. Goodenough Conductivity: 10–9 S/cm
Theor. cap.: 170 mAh/g 2% carbon coating
Pract. cap: 169 mAh/g High-rate capability
3.45 V Safety
Low-cost, abundant & environmentally benign elements
Lithium-ion cathode materials
Li/Si anodes & S8/O2 cathodes

C 372
Si 3575
Li 3862

LC 140
S 1675
O 3350
Porous FeS: >500 mAh/g

With Li
1.0 – 3.0 V
894 mAh/g (theor: for Fe + Li2S)
Li/FeS Nanocubes
1C: 439; 2.5C: 340; 5C: 256 mAh/g

With Na
0.02 – 2.5 V
530 mAh/g
J. Liu et al., Adv. Mater. 26 (2014) 6025. >20,000 cycles @ 200 mAh/g
Iron-based (oxy/hydroxy)sulfates
 Li2Cu2O(SO4)2 (Cu3+/Cu2+: 4.7 V)

CuSO4＋Li2SO4+CuO

Ar/500C
5 days

Li2Cu2O(SO4)2

208.6 mAh/g
M. Sun et al., Chem. Mater. 27 (2015) 3077. for the high-voltage plateau
 Organic radical batteries

aminoxyl anion nitroxide radical oxoaminium cation

(n-type) (p-type)

PTMA
poly[2,2,6,6-tetramethylpiperidinyloxy- TEMPO
4-yl methacrylate] 2,2,6,6-tetramethyl-N-oxyl]
Organic Li/Na batteries

Tetrasodium salt of 2,5-dihydroxyterephthalic acid

1.6–2.8 V vs. Na+/Na (enolate group)

0.1 – 1.8 V Vs. Na+/Na (carboxylate group)

180 mAh/g (at each potential)

carbon

Much hope and hype too!

 Potential scales of electrode materials
vs. Li+/Li and H+/H2

LiF
6V
E (V) vs Li+/Li
LiNiVO4
E (V) vs H+/H2
5V
Li1-xNiO2, Li1-xCoO2
1.6
O2
4V 1.2
0.8
O2
H2O
LixMn2O’4 0.4
3V H2O
H2 0
LixTiS2 -0.4
2V LixMoO2 -0.8 H2
LixWO3
1V
pH
LixCoke 0 4 8 12
LixGraphite
0V Metal Li
Electrolytes

Key to success!

Lithium is a reactive metal.

Therefore, water cannot be used in the electrolyte.

Only an aprotic organic solvent can be used.

Protic Aprotic
Ethanol, phenol Benzene, propylene carbonate
The ideal electrolyte
Low cost, good transport properties,
large electrochemical stability window, low flammability.

Aprotic organic electrolytes

wide voltage window (~ 4.5V)

Gel polymers
flexible packaging, lower cost, improved abuse tolerance.
BUT little progress towards gel cells! Syneresis.

Ionic liquids: projected as a panacea for electrolyte problems.

AGAIN, there have been no clear indications of their usability.
They are also very costly.

1M LiPF6 in a 1:1 (v/v) ethylene carbonate + diethyl carbonate

 Common solvents and salts

Three families of solvents:

Ethers: 2-methyl tetrahydofuran
Esters: ethyl acetate
Alkyl carbonates: ethylene carbonate, propylene carbonate

Salts:
LiPF6, LiBF4, LiN(SO2CF2CF3)2 (LiBETI), LiBC4O8 (LiBOB),
LiPF3(CF2CF3)3 (LiFAP), LiN(SO2CF3)2 (LiTFSI).
 Solvents
High boiling point
Low viscosity
High dielectric constant

Low viscous solvents also have low dielectric constants.

Solvents with high dielectric constants also have high viscosities.
Therefore, need for mixed solvents.

High dielectric constant solvents promote high dissociability of

the salt.
This ensures large concentrations of salts to be used.
 Polymer electrolytes

A salt (LiPF6, LiClO4) dissolved in a

high MW polymer (with a heteroatom)

Poly(ethylene oxide) PEO

􀂉 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 -> ionic conductivity of the electrolyte.
 Ionic liquids
Wide liquid range (allows cell operation in a wide temperature range),
Low volatility (makes for easy handling and also prevents electrolyte
drying)
Non-flammability (improves device safety)
Decomposition temperatures above 300°C (aids in high temperature
operation)
Wide electrochemical window (enhances power and energy densities)
Low heat of reaction with active materials (leads to improved cell safety)

Several ionic liquids are oxidatively stable even at 5 V, though their

reductive stability could be poor.

Two major types of ionic liquids

imidazolium cation-based ones
quaternary ammonium (or phosphonium) cation-based ones

Ionic liquids based on the EMI (1-ethyl-3-methylimidazolium) cation are

attractive because of their low viscosities, but they react with lithium
and even dissolve intercalated lithium out of graphite.
Existing electrolytes

ss
Rs 6,000,000,000
ss
Solid electrolyte interphase (SEI)
Key to success of the Li-ion technology: electrolyte

These batteries operate outside the ECal stability window of

electrolytes. Anodes and cathodes react with the electrolyte as
charging proceeds).

Cell characteristics are influenced by SEI.

SEI growth is the main ageing process in Li-ion batteries.

SEI can protect the electrode from solvent co-intercalation;

SEI is a necessary evil.

SEI consists of an inorganic inner layer and a porous organic outer

layer (thickness: a few tens of nm).
 Separators

Insulating
Prevents shorting between anode and cathode inside the cell.

Porous
Allows transport of ions between the electrodes.
Wettable.

Stable
Thermally, chemically & electrochemically stable.
Flexible and dimensionally stable.
Shutdown separators

PP: 165C
PE: 135C

Softening of PE by heat
generated on cell abuse
blocks pores in the separator.

Irreversible
Tri-layer PP-PE-PP membrane
PE: polyethylene; PP: polypropylene
Conducting current collectors

 Lightweight, typically metallic

 Chemically resistant

 Stable at cell voltages

 Current collectors …
 Conductivity, cost, chemical stability, weight, malleability

 Silver, copper, aluminium, nickel, stainless steel

 Copper for anode
 Aluminium for cathode

 Aluminium for anode: alloys with Li upon charging;

copper does not alloy with lithium.
 Copper for cathode: gets oxidized upon charging;
copper dissolution into electrolyte leads to shuttle.
 Aluminium for cathode: protective oxide film prevents further
damage.
 Binder requirements
➢ Good retention of active materials
➢ Excellent adhesion to metal electrodes
➢ Electrochemical stability over a wide potential range
➢ High melting point
➢ Low swelling in electrolyte
➢ Good lithium-ion & electron conductivity

For production
• Slurry viscosity must remain constant over long periods
• Very high solubility in the slurry solvent
• Easily shaped in a roll press without spring back
• Resistant to chipping during electrode slitting
Binders

Expansion/contraction of active particles:

loss in electrical contact with other particles and with current
collector

PVdF: poly(vinylidene fluoride–tetrafluoroethylene–propylene)

Na-CMC: sodium carboxymethyl cellulose
PAA: poly(acrylic acid)
Alginate (a polysaccharide from brown algae)
Polyvinylidene difluoride (PVdF)

A highly non-reactive thermolplastic fluoroploymer

Density: 1.78 g/cm3, m.p.: 177°C, water insoluble

Sold under a variety of brand names:

KF (Kureha), Hylar (Solvay), Kynar (Arkema), Solef (Solvay)

PVdF is used as a binder as it is chemically inert over the potential

range used and does not react with the electrolyte or lithium.
Water-soluble binders
PVdF has been the mainstream binder.

There are reports that aqueous

binders can sometimes make a
battery perform better.

Water soluble binders are cheaper,

greener and easier to use for
electrode fabrication.
Silicon anode with alginate binder

Kovalenko et al., Science 334 (2011) 75.

Cell casing
Aluminum

Laminated aluminm pouch

(coffee bag configuration)
Stainless steel
 Cell designs
Round cells
A lot of experience in cell design
High life-time
Problem: Complex cooling

Pouch cells
Good cooling character
High energy density
Problem: Tightness of the film

Prismatic cells
Easy stacking in battery packs
Combines characteristics of the other cell designs
High energy/power designs
High-energy cell design:
thick electrodes; less passive components.
anode

cathode

High-power cell design:

thin electrodes; more passive components.

separator
 Electrode preparation

QC: Viscosity, QC: thickness QC: thickness, QC: thickness, QC: burr and
dispersion adhesion roller gap, tension control,
Control Risks: non- porosity cutting wheel
uniform Risks: blisters, condition
Risks: shorts, coating, shorts, poor adhesion, Risk: poor cell
lumps, dryout dryout lithium plating performance Risk: shorts
 Cell assembly, formation & testing

Winding/Stacking QC: electrolyte QC: OCV, IR, QC: OCV, IR,

QC: alignment quantity, moisture weight, dimension weight, dimension,
Risk: shorts control check before qualification tests
formation, time for
Tab welding Risk: dryout, electrolyte wetting,
QC: burr/weld, swelling due to formation
height control moisture
Risk: shorts

http://w3.siemens.com/markets/global/en/batterymanufacturing/applications/process/pages/default.aspx
 O2 and H2O
content
< 1 ppm

oDry room / glove box: (dew point at least -40C).

oDew point expresses moisture content (RH) at any temperature.
NANOMATERIALS IN LiBs

A.K. Shukla, T.S.D. Kumari and T. Prem Kumar, in Nanotechnology for Energy Sustainability,
Vol. 2, Baldev Raj, M.H. Van de Voorde and Y.R. Mahajan (eds.), Wiley-VCH, Weinheim, Germany
(2017) p. 353.

A.K. Shukla and T. Prem Kumar, Wiley Interdisc. Rev. Energy Environ. 2 (2013) 14.
 Nanomaterials give new lease of life
to lithium-ion batteries
Improved electrode kinetics
Small particle size: short diffusion paths for ions and electrons.
Large surface areas: high contact area with electrolyte.
→ high lithium-ion flux across the interface.
. Therefore, higher capacity and power.

Better resilience to strains due to volume changes during

insertion/deinsertion
Possibility of using alloy electrodes (Sn: 259%; Si: 400%)

New lithium storage mechanisms

Conversion electrodes
Lower cost (?) and materials sustainability
Improvement in electrode kinetics
Small particle sizes: short diffusion paths for ions and electrons
Lower diffusion times mean higher rate capability.
The mean diffusion time, τ, is related to the diffusion
coefficient, D, and the diffusion length, L, by τ = L2/2D. A
reduction of L from 10 μm to 100 nm reduces τ from 5000
to 0.5 s (for a D value of 10–10 cm2.s–1).

High surface area

High contact area with electrolyte → high lithium-ion flux
across the interface

But particle-to-particle conductivity in nanomaterials is poor

Problem circumvented by ‘nano-painting’ particles with
carbon
[N. Ravet et al. Electrochemical Society Meeting, Hawaii (1999)]
Disadvantages of nanomaterials

Poor packing density of electrodes

Diminished volumetric energy density; diminished gravimetric
energy density (due to presence of ‘inert’ components such as
current collectors and electrolyte)

Secondary reactions involving electrolyte decomposition

Large irreversibility (low columbic efficiency)
Poor cycle life

Increased reactivity
(Chemical potential at the nanoscale has an extra contribution
from surface free energy: μ0(r) = μ0(r=∞) + 2(γ/r)V, where γ is
the effective surface tension, V is the partial molar volume, and r
is the effective grain radius. The excess surface free energy
(2(γ/r)V) contributes to the high electro-activity toward Li storage
and surface reactions).
Nanocomposite polymer electrolytes

Among the first use of nanomaterials was as fillers in

polymer electrolytes.

Incorporation of ‘nano’ filler particles (Al2O3, LiAlO2, TiO2) in

a polymer electrolyte matrix increases the conductivity.

Additionally, the embedded particles improve mechanical

stability of the solid polymer membrane.
 From micro to nano-materials
Turn insulating LiFePO4 into Make possible the use of Si and Sn
attractive insertion materials as negative electrodes
Capacity (mAh/g)
Capacité en mAh/g
160 140 120 100 80 60 40 20 00

Voltage (V vs. Li/Li+)

120 80 40 2.5
4.5 160
4.5 m
11µµm
Micro Si/C Si
4.0
Pot. vs. Li (V)

2
Potentiel vs. Li (V)

3.5
3.5
3.0 1.5
2.5
2.5
500 nm 1
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
4.0 x dans LixFePO4
Pot. vs. Li (V)

0.5
3.53.5
3.0 0
0 400 800 1200 1600
2.52.5 50 nm
Nano Q (mAh/g)
2.0
00.0 0.2 0.3 0.4
0.1 0.2 0.6 0.7
0.4 0.5 0.6 0.8 0.9 1.01
0.8
x in xLi FePO4
in LixFePO 50 nm LiCoO2/Sn-C
x 4

Saving in cost and safety 15% gain in Wh/l

Commercialized by
SONY 2005
 Micro to nano: new reactions
Conversion reactions

Compact Structures
3.5 Universality of the mechanism
Voltage (V vs Li/Li )
+

0.2 V NiP2 + 6 Li ⇌ Ni° + 2 Li3P

3

2.5

2
CoS + 2 Li ⇌ Co° + Li2S
CoO + 2 Li ⇌ Co° + Li2O
1.5

0.5
RuO2 + 4 Li ⇌ Ru° + 2 Li2O
CoCl2 + 2 Li ⇌ Co° + 2 LiCl
0
0 0.5 1 1.5 2 2.5 3

CoF3 + 3 Li ⇌ Co° + 3 LiF

x in 'LixCoO'

CoO Co-Nano 30 to 50Å 3.5 V FeF3 + 3 Li ⇌ Fe° + 3 LiF

particles
2 to 6 e- par metal 3d
discharge

charge
500Å

2–3 x capacity gain
CoO + 2 e− + 2 Li+  Co + Li2O 0

2 e- per Co
Conversion anodes
Common belief: interstitial-free
3d metal oxides are unsuitable
for intercalation chemistry.

BUT several borides, nitrides,

fluorides, phosfides, and
sulfides of 3d metals have been
shown to give capacities as
large as 1000 mAh/g.

(Tarascon et al. Nature, 407, 496 (2000))

Initial products: metal particles

(less than 4 nm) dispersed in
amorphous Li2O.
Conversion anodes – problems

Conversion reactions are accompanied by significant electrolyte degradation.

These reactions form an inorganic/organic layer around the material.
This layer is a jelly-like film, thicker than SEI
and composed of ethylene oxide oligomers [(CH2–CH2–O)n ] (n = 1–10).
Large capacities.
BUT
High levels of electrolyte decomposition
Large hysteresis in their charge–discharge curves
Particle-to-particle electronic conductivity is poor.
Improvement in electronic conductivity achieved with composites
(*Co3O4-graphene: 820 mAh/g; **Co3O4-CNT: 1250 mAh/g).

*J. Mater. Chem., 2012, 22, 17278; **J. Mater. Chem. A, 2013,1, 1141-1147
Impossible yesterday,
possible today!
QUARTZ:
a lithium-insertion anode material

Discharge reaction (lithiation)

0.27 V a-SiO2 + (4/5)Li+ + (4/5)e– → (2/5)Li2Si2O5 + (1/5)Si
0.24 V a-SiO2 + 2Li+ + 2e– → (1/2)Li4SiO4 + (1/2)Si
0.00 V Si + (15/4)Li+ + (15/4)e– → (1/4)Li15Si4
Charge reaction (delithiation)
0.34 V Li15Si4 → 15Li+ + 4Si + 15e–
0.39 V Li2Si2O5 + (1/2)Si → (5/2)SiO2 + 2Li+ + 2e–
Lithiation-delithiation of SiO2

Ball and stick depiction of

Li2Si2O5 and Li4SiO4
(red: Li; green: Si; purple: O).
Li2Si2O5 – Orthorhombic
Li4SiO4 – Monoclinic

Cycling behavior of ball-milled

SiO2. (Inset): Coulombic efficiency
plot.

Average capacity over 200 cycles:

~800 mAh/g.
Emerging lithium chemistries
 Bottlenecks: electrolyte and cathode

Electrolyte: key to success! (at least 5 V tolerance)

Cathodes: LiCoO2 (1979) & LiFePO4 (1997)—courtesy: J.B. Goodenough
Cathodes in the offing: oxygen and sulfur
New anodes: new carbons (~400 mAh/g), conversion electrodes (>1,000 mAh/g),
alloy anodes (~1000 mAh/g) and silicon (>3,000 mAh/g).

Advancements in anodes without a parallel

progress in cathodes set a limit on the capacity
at the device level. Total capacity of a cell,
Ccell, in terms of the capacities of the anode,
CA, and cathode: Ccell = (CA x CC) / (CA + CC).

A recent development: 500 mAh/g with carbon-

encapsulated FeS2 nano octahedra.
With this earth-abundant naturally occurring
Cell capacity vs. anode capacity at material, anodes with capacities of about 2,000
fixed values of cathode capacity mAh/g can be meaningfully exploited.
Lithium batteries:
power sources of the millennium?
Features
• High energy density (> 160 Wh/kg)

• Good cycling stability (> 1000 cycles)

• High cell voltage (4 V)
• Flat discharge profile
• Low self-discharge (< 5% per month)
• No memory or lazy battery effect
• 100% DOD possible
• Affordable price (ca. 1 USD/Ah)

The most advanced battery technology today.

Thank you for your attention!