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Rechargeable Batteries, Old and New
John B. Goodenough
The University of Texas at Austin
Modern Society is enabled by the chemical energy
stored in fossil fuels.
Unsustainable Cost
• National vulnerabilities from uneven, finite
distribution
• Spoiled environment by extraction
• Air pollution and global warming by use
Sustainable Energy Supply
• Generation of electrical energy by wind, solar,
nuclear, and other sources
• Storage of electrical energy at an acceptable
cost
• What is the status of rechargeable batteries?
Electrochemical capacitors?
Battery Principle
Chemical Energy
(in electrodes)
I, V
Δt
Electrical Energy
(P=IV for Δt)
Rechargeable Electrochemical Cell: Pcharge > Pdischarge
Battery=Stack of cells connected in series to increase V, in parallel (or electrode area) to increase I=dq/dt and/or Δt.
 Challenges: Cost, Safety, Energy Density, Life, Rate.

Traditional Rechargeable Cells
‐
e‐
e‐
Separator
+
NiO6/3 layer
M2+
Reductant
H+
Oxidant
Anode Electrolyte Cathode
 Anode
H+
H+
NiOOH
KOH
+ 2H2O H SO Cd(OH)2 + 2 H+ + 2e‐
2
4
0
Pb + H2SO4
PbSO4 + 2H+ + 2e‐
Cd0
 Cathode
+ H+
+ e‐
KOH
NiOOH
Ni(OH)2
H2SO4
+
‐
PbO2 + H2SO4 + 2H + 2e
PbSO4 + 2H2O
TYPICAL BATTERY DISCHARGE
Vdis
Voc
dis
(i)
(ii)
(iii)
I
Vdis = Voc − ηdis(I,q)
Vch = Voc + ηch(I,q)
Relectrolyte = (dV/dI)ii
Cell Energy at Constant I = dq/dt
Energy =
∆
;
∆
Q(I)/wt or vol = specific or volumetric capacity
V(q) = VOC – η(q, I); VOC = (μA – μC)/e ≤ electrolyte Eg
VV
V
V
η
VV
VOC
η
Diffusion‐limited (end of life)
(i)
(ii)
VOC
Two Phase
(iii)
t or q
t or q
t or q
t or q
η(q, I) increases with resistance to working-ion current
Problem: Maximize VOC, Q(I) and # cycles to Q/Q0 = 0.8; minimize η
Electrolyte
 Aqueous Electrolyte: Eg = 1.23 eV
•
LUMO = H2O/H2; HOMO = O2/H2O
 Kinetic Stability
•
NiOOH/KOH/Cdo
Voc = 1.5 V
 Limited Life
•
PbO2/H2SO4/Pbo
Voc = 2.0 V
First Li-ion Battery
E
EF(Li)
LUMO
1.1 eV
2.6 eV
S2‐:3p6
4 eVoc
3.2 eV
Co4+/Co3+
0.3 eV
O2‐:2p6
HOMO
Li1‐xCoO2
Electrolyte, Separator
LixC
LiCoO2//C Cell
Separator
SEI layer
LixC6
Li1‐xCoO2
Lix[M2]O4 Spinel Electrodes
O2‐
16d
8a
Lix[Mn2]O4
16c
a0
2 quadrants of structure
Edge‐shared MO6/5 octahedra
3D Li+ insertion into close‐
packed oxygen array Note: Li1+x[Li1/3Ti5/3]O4: V=1.5 V
Li1‐x[Ni0.5Mn1.5]O4: V=4.7 V
Ni(II)  Ni(IV) with little step
NASICON Framework
Na1+3xZr2(P1-xSixO4)3
LixFe2(SO4)3: V =3.6 V
LixFe2(MO4)3: M = Mo, W: V =3.0 V
Na3-xV2(PO4)3: V = 3.4 V
c
NASICON
a
Capacity Challenge
5.0
5.0
4.5
4.5
Potential (V) vs. Li /Li
Li1‐xCoO2
4.0
3.5
+
+
Potential (V) vs. Li /Li
(Limited specific capacity further reduced by anode
SEI layer)
Li1‐xFePO4
3.0
2.5
4.0
3.5
3.0
Lix[Mn2]O4
2.5
2.0
1.5
Li1‐x[Ni0.5Mn1.5]O4
LixTiS2& Li2[Ti2]S4
0
50
100
Capacity (mAh/g)
150
200
2.0
0
50
100
150
200
Capacity (mAh/g)
250
300
ELECTRODE MATERIALS
MO2
Li
MO2
Li
MO2
Li
MO2
LUMO
Na2MnFe(CN)6 and Na3V2(PO4)3 :
V  3.4 V, Q(10C) > 100 mAh/g
Framework of Prussian Blue
Analogues
Anode Problem with Organic Liquid
Electrolyte
• An EF (Anode) > LUMO requires an SEI
• SEI on Li0 or Na0 creates dendrites, so C
anode
• Need VCh < Vplate, so C-buffered alloys
• Need SEI permeable to Li+ or Na+: if Li+,
Na+ come from cathode, get capacity loss
on initial charge.
• Reforming SEI gives capacity fade limiting
cycle life
• SEI slows Li+ or Na+ transfer
Separators
• Celgard membrane: penetrated by dendrites;
insertion-compound cathode
• Polymer-gel membranes: blocks dendrites; adds
choice of liquid flow-through cathode
• Anode/Solid-electrolyte interface: prevents
dendrites, allows choice of sulfur or liquid flowthrough and air cathode if solid electrolyte stable in
alkaline water
Al2O3/PEO Separator
(K.S. Park, J.-H. Cho, C.J. Ellison
Oxide: Dried (400C) Al2O3 Powder (300-400nm)
Polymer: DEGDVE = Di(ethyleneglycol) divnylether with ethylneoxide (EO) units
PETT = tetrathiol crosslinker
Preparation: AIBN = thermal initiator (80C, 4h)
Yield: Quantitative, homogeneous network
AIBN = Azobisisobutyrolnitrile
PEO/Al2O3 Composite-Membrane
Separator
K. Park et al.
Photographs of a PEO/Al2O3 (2/1 in weight) composite membrane (25  20 cm2)
Mechanical Stability
• Tensile test shows a good
mechanical stability,
especially after Al2O3
incorporation.
• Stability against Li dendrite
Minor surface dent by Li dendrite
After full charging
It blocks Li dendrite.
Presence of Osmosis
• Presence of concentration gradient of a redox-molecule across the PEO/Al2O3
membrane
•
Balancing the concentrations between catholyte and anolyte is necessary,
for example, with high-molecular-weight Ionic liquids and PEGDME.
Charge/Discharge Cycle Property
Anolyte: 1M LiTFSI in EC.DEC w/0.1M PEGDME 500
Catholyte: 1M LiTFSI in EC/DEC w/0.1M 6-Bromohexyl ferrocene
PVDF‐HFP: Widely used as host for gel‐polymer
electrolytes
But with unsatisfactory mechanical strength
Glass‐fiber paper: Used to enhance the mechanical properties
Polydopamine: Biomimetic polymer of mussel adhesive protein Polymerized at room temperature in aqueous solution
Modify the surface properties of PVDF‐HFP
-1
Specific Capacity (mAh g )
0.2 C
0.5 C
1C
2C
120
0.5 C
80
GF/PVDF-HFP/PDA
GF/PVDF-HFP
Glass fiber
40
0
0
10
20
30
40
50
Cycle number
The composite membranes have good thermal stability and mechanical strength.
Gel‐polymer electrolytes: Improve rate and cycle performance of air‐dried cathode of Na2MnFe(CN)6
Hongcai Gao, et al. Adv Energy Mater 2015
Strategy for an Alkali-Metal Anode
cathode
cathode
Li+/Na+
Separator membrane
Separator membrane
Current collector
Solid electrolyte
Current collector
Cost Targets
• Cycle Life N > 10,000; calendar life
10 years
• Simple processing of inexpensive
materials.
• Increased VQ(I) to reduce number of
cells.
• Simplify battery management
Lithium-Sulfur Batteries