Materials and Structural Design for Advanced Energy Storage Devices Imran Shakir Sustainable Energy Technologies Center (SET) King Saud University Saudi Arabia
Specific Power (W/kg) Introduction and Motivation Portable electronics Electrical vehicle 20-30% CO 2 emission Capacitor + - + - + - + - + - + - Thickness >1000nm E= ½ CV 2 C α 1/thickness Supercapacitor + - + - + - + - + - + - + - + - + - + - + - + - Thickness <1nm Electrolyte solution Specific Energy (Wh/kg) Important Parameters: 1. Energy and Power density 2. Cycle life and safety 3. Cost
Supercapacitors Electric Double-Layer Capacitors Hybrid Capacitors Pseudocapacitors
Electric Double Layer Capacitor EDL formed with electrode and electrolyte with solvent molecules between as dielectric. Store energy by adsorbing electrolyte ions onto the surface of the electrode Fast acting. Low energy potential, charge confined to surface
Pseudocapacitor Rely on redox reactions that take place at the electrode Electrode materials typically made up of transition metals, conducting polymers, or compound with O and N functional groups Higher Energy density but lower cycling life
Hybrid capacitor A combination of EDLC and pseudocapacitors. Optimizes power density of EDLC with energy density of pseudocapacitor One common example is the Li ion capacitor which is a current leader in the field
Design Considerations Energy Storage Materials Materials Properties Materials Properties Design & Synthesis Fundamental Properties Application Energy Conversion A balance between different materials properties is highly desirable for ultra efficient devices for energy storage and conversion devices 7
Reactions occur at the electrode surfaces Materials Challenges We want to get as high a surface area as possible Need to have ions and electrons together for reactions to occur However e.g. Nanomaterials behave differently than bulk materials Energy of the reactions also depend on the surface properties Electrons must still be able to get outside the cell 1. Electron resistance cannot be too high 2. Separator must be robust and allow rapid transfer of ions 3. Fundamental materials properties need to be understood Basic materials properties 1. Transport in porous materials 2. Interfacial properties
Materials for Supercapacitors
Double Layer Capacitors CNT S Carbon Aerogel Activated Graphene
C carboxylic E Easter P - Purified CNTS
Graphene Nanosheet for EDLC
Solution Processable Holey Graphene Oxide Nano letters 15 (7), 4605-4610 13
Graphene Sandwich between MWCNTs layers for Energy Storage Devices Imran Shakir, Electrochimica Acta 129, 396-400
Graphene Sandwich between MWCNTs layers for Energy Storage Devices Imran Shakir, Electrochimica Acta 129, 396-400 15
Pseudocapacitors Store energy using fast surface redox reactions Metal oxides: Capacity 1300 F/g (RuO 2 ) Nominal voltage 1.2 V Conducting polymers: Capacity 30 40 mah/g Nominal voltage 1.0 V
MoO 3 Nanorods for Energy Storage Applications Imran Shakir et al. Electrochimica Acta 56 (2010) 376 380 8 4 180 o C 150 o C 120 o C 20 10 I/mA 0-4 I/mA -8-1.0-0.5 0.0 0.5 1.0 Potential/V (Vs. Ag/AgCl) 0-10 -20 100 mv/s 50 mv/s 40 mv/s 30 mv/s 20 mv/s 10 mv/s 5 mv/s -1.0-0.5 0.0 0.5 1.0 Potential/V (Vs. Ag/AgCl) Maximum current was obtained from the samples synthesized at 180 0 C which was due to the increase of crystallinity and morphology.
MoO 3 Nanorods for Energy Storage Applications Specific Capacitance (F/g) 32 24 16 8 180 o C 150 o C 120 o C 0 0 30 60 90 120 Scan rate (mv/s) Specific Capacitance (F/g) 32 24 16 8 0 180 o C 150 o C 120 o C 0 20 40 60 80 100 Number of Scans The increase in ionic resistivity at higher scan rate leads to a drop in the capacitance of the nanorods. The specific capacitance of as synthesized nanorods at 180 o C was found to be higher than that of nanorods synthesized at 120 o C, and comparable to that of the 150 o C (at a scan rate of 5 mv/s). Imran Shakir et al. Electrochimica Acta 56 (2010) 376 380
Hydrogenated TiO 2 as Supercapacitors
Ultra-thin Solution-based coating of Molybdenum Oxide on Multiwall Carbon Nanotubes Imran Shakir et al. Electrochimica Acta 118 (2014) 138 142 20
Ultra-thin Solution-based coating of Molybdenum Oxide on Multiwall Carbon Nanotubes Imran Shakir et al. Electrochimica Acta 118 (2014) 138 142 21
Ultrathin Metal Oxide Sandwich between raphene layers for Energy Storage Devices Ni/Cu/Ni/Au Coated Textile Fiber Substrate Deposition of metal oxide coated MWCNTs layer Repeat the steps to obtain the desired number of layers Imran Shakir, et.al Nanoscale 6 (8), 4125-4130 Imran Shakir, Electrochimica Acta 129, 396-400 Transfer of Graphene on the Layer of metal oxide coated MWCNTs
Ultrathin Metal Oxide Sandwich between raphene layers for Energy Storage Devices The specific capacitance of metal oxide with thickness of 3 nm sandwich between graphene was found to be higher than that of higher thickness (2590F/g). Imran Shakir, et.al Nanoscale 6 (8), 4125-4130 23
Ni(OH) 2 -coated ZnO Nanowire-based Energy Storage Devices 24
Ni(OH) 2 -coated ZnO Nanowire-based Energy Storage Devices The Ni(OH) 2 coated ZnO nanowires electrodes show a nonlinear charge discharge curve, which indicates electrode have pseudocapacitive behavior with a specific 25 capacitance of 3200 F/g.
Materials for lithium Ion Battery
Design Considerations 1. Volumetric and/or gravimetric energy density 2. Cycle life 3. Safe operation 4. Energy losses in course of charge/discharge cycle 5. Power performance, needed for some applications 6. Environmentally friendly and inexpensive.
Materials Requirements Large reversible capacity reversible capacity Small irreversible capacity Desirable charge profile charge profile Desirable kinetics (rate capability) Long y g cycle and calendar life Ease of processing Safety Compatibility with electrolyte and binder systems Low cost
Major Types of Materials Layered oxides with the α-nafeo 2 -type structure Oxides with a spinel structure Poly-anion oxides with the olivine and olivine-related structures
Anode Materials 1. Current Materials 1. Carbonaceous 1. Graphite 2. Hard Carbon 3. Soft Carbon 2. Titanium Oxide 2. Future Materials 1. Silicon 2. Nanomaterials 3. Other
Structure and Designing Options Some limitations such as: 1. Low electronic conductivity 2. Low ionic conductivity 3. Charge recombination 4. Wide band gap These limitations can be overcome by: 1. Tuning shape and size 2. Composite structures 3. Doping
Impedance Analysis Zn Doped Mesoporous TiO 2 Microspheres 50 -Im Z/ 40 30 20 10 Zn doped Mesoporous TiO 2 Mesoporous TiO 2 TiO 2 nanopowder 0 0 20 40 60 80 100 Real Z/ Nyquist plots for Zn doped mesoporous TiO 2 microspheres and 20 nm anatase TiO 2 nanopowder 32
Charge-Discharge Results Zn Doped Mesoporous TiO 2 Microspheres Voltage (V) 3.5 3.0 2.5 2.0 1.5 1.0 0 50 100 150 200 Capacity (mah/g) 210 180 a) b) Capacity (mah/g) 150 120 90 60 30 Zn doped mesoporous TiO 2 Mesoporous TiO 2 TiO 2 (~20 nm) 0 0 5 10 15 20 25 30 Number of Cycles (a) Charge discharge profiles for Zn doped mesoporous TiO 2 at C/5 charge discharge rates. (b) Discharge capacity of Zn doped mesoporous TiO 2 and 20 nm anatase TiO 2 nanoparticles at different discharge rates 33
Charge-Discharge Results Zn Doped Mesoporous TiO 2 Microspheres Increase in capacity (%) 1000 800 600 400 200 0 a) 8% 23% 86% 135% 312% 981% 0.2C 1C 5C 10C 20C 30C Rate 50 Coulombic Efficiency Charge Capacity at 1C 20 Discharge Capacity at 1C 0 0 0 20 40 60 80 100 Number of Cycles (a) Percentage increase in discharge capacity of Zn doped mesoporous TiO 2 and 20 nm anatase TiO 2 nanoparticles at different discharge rates. (b) Cycling performance and Columbic efficiency of Zn doped mesoporous TiO 2 up to 100 cycles at 1C charge/discharge rates. Capacity (mah/g) 250 200 150 100 b) 100 80 60 40 34
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