The document describes research into developing porous carbon-germanium nanoparticle composites for use as anode materials in lithium-ion batteries. Key points include:
- The composite, called 3D-Ge/C, was synthesized and shown through characterization to have a 3D nanostructure with large pore volume and surface area for lithium ion accessibility.
- Electrochemical testing found the material exhibited excellent performance as an anode, including high specific capacity close to the theoretical maximum, superior cyclability retaining 99.6% of capacity over 100 cycles, and ability to charge and discharge rapidly even at ultrahigh rates.
- When used in full cells paired with a lithium cobalt oxide cathode, the 3
2. Index
• Introduction
• Types of batteries
• Applications of batteries
• Anodic materials
• Paper presentation
• Summary
2
3. What is a battery?
3https://www.google.co.in/search?q=battery
4. Primary batteries are non rechargeable
Because their electrochemical reaction cannot be
reversed.
Ex. alkaline battery
Types of batteries
Secondary batteries are re-chargeable
Because their electrochemical reaction can be reversed.
By applying a certain voltage to the battery in the opposite
direction of the discharge.
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Ex. lithium ion batteries
5. 5
Zn + 2 MnO2 + 2NH4Cl Zn(NH3)2Cl2 + Mn2O3 + H2O+electrical energy
Primary battery - Example
https://www.google.co.in/search?q=battery
6. Secondary batteries - Rechargeable Li ion
batteries
ANODE
Commercial anode materials: Hard Carbon, Graphite etc..
CATHODE
Common cathode materials of LIBs are the transition
metal oxides such as
LiCoO2, LiMn2O4, LiNiO2, LiFePO4
ELECTROLYTE (solvent + salt)
Role of electrolyte is ion conductor between cathode and
anode. Ex: LiPF6 , LiBF4 in an Organic solvents .
6https://www.google.co.in/search?q=battery
8. The mobile world depends on lithium ion batteries (LIBs), which provide portable
power for a variety of applications.
Due to their high energy density, low self-discharge, and long cycle life they form
ideal candidates for Secondary Batteries.
Li is lightest metal and has one of the highest standard reduction potentials (-3.0 V)
Theoretical specific capacity of Li is 3860 Ah/kg in comparison with 820 Ah/kg
for Zn and 260 Ah/kg for Pb
The first commercial lithium-ion battery was released by Sony in 1991
Lithium ion Secondary Batteries
8
9. Electrochemical Reactions in a LIB
• Cathode
LiCoO2 Li1-xCoO2 + xLi+
+ x e-c
d
Cn + xLi+
+ x e-
CnLix
c
d
• Anode
• Overall
LiCoO2 + Cn Li1-xCoO2 + CnLix
c
d
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13. What is the requirement of a
good anode material?
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14. Requirements
1) Large capability of Lithium adsorption
2) High efficiency of charge/discharge
3) Excellent cyclability
4) Low reactivity against electrolyte
5) Fast reaction rate
6) Low cost
7) Environmental friendly and non-toxic
Anode materials
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15. 15
Graphite cannot meet the batteries demand for simultaneous high energy and
power densities.
Replacing the graphite anode with other Advanced Porous Materials having
higher reversible capacity and rate capabilities as well as long-term cyclability is
required.
Ragone plot showing Energy Density v/s Power Density for storage device
16. Commercially available LIBs are made of graphite
anode, which has a specific capacity of
372 mA h g-1
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This is the value to beat!
Benchmarking Li ion Battery based on graphitic electrodes
17. Large pore volume
High surface area
Shortened solid-phase lithium
diffusion distance
Full lithium ion accessibility
Efficient ionic and electronic transport between the
electrode-electrolyte interfaces
17
3D Mesoporous Structures
https://www.google.co.in/search?q=mof
18. Si has the highest specific capacity
(4200 mA h g-1)
But the poorest electrical conductivity
and poor lithium diffusivity.
Si anode can only cycle at slow rate.
Sn has good electrical conductivity due to its
metallic nature
low lithium diffusion rate in Sn still limits
them from being good electrode materials
In contrast, Ge exhibits good electrical
conductivity
Good lithium diffusivity
low charge/discharge potential
Higher Energy density and Power densities
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Thus, Ge could be an ideal candidate as anode material for LIBs
Among the lithium alloy-based anode materials
Nano Lett. 2014, 14, 1005−1010
19. Department of Materials Science and Engineering,
Chonnam National University, South Korea
Energy Environ. Sci. 13th Aug 2015.
10.1039/C5EE02183A 19
Duc Tung Ngo, Hang T. T. Le, Chanhoon Kim, Jae-Young Lee, John G. Fisher,
Il-Doo Kim and Chan-Jin Park
20. Fig. 1 Schematic diagram illustrating the procedure to synthesize 3D-Ge/C. 20
21. Powder X-Ray Diffraction (PXRD) patterns
of 3D-Ge/C and diamond cubic Germanium
Ge
Raman scattering spectrum
21
Characterizations of 3D-Ge/C
22. Pore size = 20-100 nm
The surface area = 124.9 m2/g
Pore volume = 0.298 cm3/g
22
N2 adsorption isotherms at 77k and Inset shows the pore size distribution
24. (d) TEM image and SAED pattern (inset) (e) HR-TEM image and compositional line
scanning profiles.
24
The d-spacing for (111) plane = 0.33 nm
(220) Plane = 0.2 nm
25. (a) XPS general survey spectrum of 3D-Ge/C; high resolution XPS spectra of
(b) Ge 3d, (c) C 1s, and (d) O 1s of 3D-Ge/C composite . 25
Ge 3d
C 1s O 1s
26. 26
Electrochemical studies
Fast charging and slow discharging
Fast charging and fast discharging
High Efficiency and good Cyclability
Specific Capacity
The amount of charge that can be stored in a material
per unit of volume or unit of mass.
Charge Rate(C)
The current is applied or drained from the battery
to complete charge or discharge it in one hour
27. Charge/discharge curves of the Ge/C electrode was measured at a rate of
C/10 in the potential range 0.01–1.5 V
In the 1st cycle, The charge capacity is = 1604 mA h g-1
Discharge capacity was = 2286 mA h g-1
After 100th cycles, the reversible capacity was =1598 mA h g-1(99.6%)
Almost reached the theoretical capacity of Ge =1620 mA h g-1
Half cell studies
27
Charging
discharging
29. Cyclic Voltammograms of 3D-Ge/C corresponding to the first three cycles
The Cathodic peaks are observed at 0.15, 0.37 and 0.51 V.
In the anodic sweep, the peaks are observed at 0.55 and 0.64 V.
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30. • At 100C (26sec) ,The specific capacity of electrode = 1122 mA h g-1
• After 200 cycles, the reversible capacities were tested and found to be
almost 100% for different charging rates.
These results reveal the superior cyclability of the Ge/C electrode under
high charge rates
Potential profile at different charge rates and discharge rate was fixed at C/2
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31. The Potential profile of Ge/C electrode at charge/discharge rates same .
Specific Capacity of the electrode = 697 mA h g-1 at charge/discharge rate is 50 C
Specific capacity = 1366 mA h g-1 at charged at 50C & discharged at C/2 rate
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These results demonstrate that, the specific capacity of electrode was greatly
affected by the discharge process
33. Charge potential vs time at different charge rates and discharge rate was fixed at C/2
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Ultrahigh Charge Rates
Even at an ultrahigh charge rates high specific capacity could be achieved in just
few seconds
Higher Energy density and Power densities
34. 34
Cyclability and Coulmbic efficiency for 1000 cycles at a charge/discharge rates of 2C
long-term Cyclability and High Efficiency
35. Full cell is connected by using 3D-Ge/C anode and LiCoO2 cathode
and capacities measured at a rate of C/10 and voltage profile (inset)
At 1st cycle , The charge and discharge capacities were 1901 and 1561 mA h g-1
Reversible capacity of the full cell (1491 mA h g-1) was slightly lower than half-cell
(1604 mAh g-1) at the same rate of C/10
Ultra-high rate cathode materials LiFe0.9P0.95O4-d, modified LiFePO4 and
Li1.2Ni0.2Mn0.6O2 instead of LiCoO2
35
Full Cell studies
36. Fabricated the full cell LIB by using 3D-Ge/C anode and LiCoO2 cathode .
Up to 50-LED bulbs connected in parallel were successfully lit.
36
37. Summary
Successfully synthesized a Ge/C composite electrode with a 3D Nano architecture.
The 3D-Ge/C electrode exhibits excellent electrochemical performance: high
specific capacity, superior cyclability, and ultrahigh charge rate.
3D-Ge/C electrode offers high Energy density like batteries as well as a high Power
density like super capacitors.
The lithium diffusivity in 3D-Ge/C was ten fold higher than that of pure Ge .
3D-Ge/C electrode can be used in wide range of electrochemical devices. Such as
medical instruments, portable devices and then extended to electric vehicles.
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