lithium iron phosphate synthesis at varying hydrothermal temperatures 1
TRANSCRIPT
Lithium Iron Phosphate Synthesis at Varying Hydrothermal TemperaturesBY FARBOD MOGHADAM
Fuel Cells vs. BatteriesFuel Cells Batteries Both
Advantages External fuel source (infinite fuel from cell perspective, no charging)
Minimal degradation over time
Infrastructure for natural gas access exists
Functional at Room Temperature
Portable and stationary use
Low cost of production
Rechargeable with little degradation
Higher power density (lighter transporting ions)
Rely on chemical properties of material
Disadvantages High Operating Temperatures
Requires infrastructure for transport
Lesser research to date
High materials cost, sparsity and political implications
Lower energy density (heavier active fuel materials)
Lacks infrastructure (charging stations)
Costly for large-scale usage
Some level of infrastructure improvement necessary
Safety concerns
The State of Batteries Predominant Types
◦ Alkaline◦ Lead-Acid◦ Nickel Metal Hydride◦ Lithium-Ion
Current Usage – Cell Phones and mobile devices, small gadgets, computers, hybrids and electric cars
Prospective Usage – More extensive usage in cars, grid storage
General Issues – Cost, energy density, safety
Cathode Materials for Lithium-Ion Batteries - layered (, 3.8 V)
- layered(, 3.8 V)
- layered(, 3.7 V)
- spinel(, 4.1 V)
- olivine(, 3.5 V)
Energy Density ,
,
Power DensityCostCyclability (Capacity Retention)Chemical StabilityComments Highly ordered layered
molecular structure
Unstable when overcharged – poor cycling (degradation)
Layered oxides have highest theoretical capacities due to layered structures, practical values much lower
High energy density (20% more than LCO by weight)
Less ordered
Less stable – Ni occupies Li layer
Doped with Co at ~0.8:0.2 Ni:Co ratio alleviates ordering issue
Only non-commercialized material on this chart
High rate capability
Co as a dopant tends to increase order/structural stability and capacity, improve electronic conductivity, improve cycling, in small amounts
Ni stabilizes structure during delithiation
Rapid loss of capacity at high charging voltages
Safe
Fe doping – additional discharge plateau at high voltages
Co doping – capacity retention, stabilizes structure
Ni doping – decreases electrical conductivity, increases capacity, Co replacement reduces LiNiO; Ni as coating increases capacity retention
Rapid initial loss of capacity – loss of oxygen, dissolution of Mn, changes of morphology
Flat discharge profile
High coulombic efficiency
addition increases conductivity, sometimes created during use, or added deliberately
Low intrinsic electronic conductivity – reasoning behind carbon coating and carbon black addition
Improving Cathode Performance
Naoki Nitta, Feixiang Wu, Jung Tae Lee, Gleb Yushin, Li-ion battery materials: present and future, Materials Today, Volume 18, Issue 5, June 2015, Pages 252-264, ISSN 1369-7021, http://dx.doi.org/10.1016/j.mattod.2014.10.040.(http://www.sciencedirect.com/science/article/pii/S1369702114004118)
Experimental Objectives Assess the effect of hydrothermal temperature on particle size of LFP (goal of 10 syntheses)
Explore electrochemical properties of various samples of LFP
Create stock supply of carbon-coated LFP for other experiments
PROCEDURE
Precursors3𝐿𝑖𝑂𝐻+𝐻 3𝑃𝑂4→3𝐻2𝑂+𝐿𝑖3 𝑃𝑂4
1. Purge water supply with Nitrogen gas
2. Measure out 6 mmol (1.668 g) and place under vacuum
3. Mix 6 mmol (6.70 g of 1M solution) , 24 mL PEG, and 18 mmol (0.7553 g) LiOH in autoclave, purge with Nitrogen gas
4. Re-hydrate the with deoxygenated water and add it to the autoclave
Hydrothermal Synthesis𝐿𝑖3 𝑃𝑂4+𝐹𝑒𝑆𝑂4→𝐿𝑖𝐹𝑒𝑃𝑂4+𝐿𝑖2𝑆𝑂4
5. Prepare solution in hydrothermal oven at two temperatures
Centrifuging & Drying6. Refine LFP powder with water (centrifuge) and dry
Carbon Coating7. Anneal the LFP with sucrose for carbon-coating
Film Creation and Coin Cells8. Combine carbon-coated LFP with carbon black, PVDF, and NMP
9. Roll slurry into film and dry the film
10. Punch out sections of the film and create coin cells
Procedural/Manual Mishaps Oxygen exposure – can happen at any step before hydrothermal, resulting in potential oxidation of Fe and failed synthesis of LFP
Fineness of powder – both sucrose and LFP must be very fine for carbon coating, LFP 2 failed because of coarse sucrose
Spillage – during loading, tightening, and unloading of tube in Prometheus, there is always a chance of powder spillage: a potential for contamination
120−205℃ 135−180℃
150−205℃ 160−205℃
135−205℃
Single-Temperature Samples
Synthesis Schematic (Dual Temperature)
First Temperature Mechanism:
Second Temperature Mechanism:
High Temperature
Critical Nucleus
Precursor particles in solution Craters in surface
LFP particle
Quantitative Analysis
120/205 135 135/180 135/205 150/205 160/205 2050
0.5
1
1.5
2
2.5
3
3.5
4
4.5
LFP Particle Size
Synthesis Temperature (Celsius)
Maj
or A
xis L
engt
h (µ
m)
120/205 135/205 150/205 160/205 2050
0.5
1
1.5
2
2.5
3
3.5
4
4.5LFP Particle Size
Synthesis Temperature (Celsius)
Maj
or A
xis L
engt
h (µ
m)
Conclusions In general, particle size decreased with initial temperature as expected, falling from as large as 4 microns to as small as 200 nanometers.
The secondary temperature had a profound and clear effect on particle surface properties – smoother at higher temperatures.
The particle size more or less plateaus above at 200 – 1000 nm, then, at some point between and , rate of growth overcomes solubility in determining particle size and particle size increases with temperature.
Why what we do is importantWe must be mindful of where we get much of our oil – the politically unstable Middle East. As our country falls deeper into debt, we must also end our reliance on foreign entities and import for our basic needs.
As the population grows, the demand for energy will increase and the supply must increase accordingly.
Climate change is already an issue – the way we move forward as a society will largely decide the fate of our planet.
Renewable energies have reached grid parity with conventional fuels – economic feasibility provides further incentive for transition to renewables.
President Obama’s recent Clean Power Plan opts to cut carbon emissions by 32% in the energy sector – inevitably focus will be shifted to alternative energies (forced incentive).
In the Chueh lab, we have all bases covered: batteries for mobile use and fuel cells for stationary use, it’s just a matter of continuing research and discovering/exploring materials with commercial potential.
Thanks to…
Professor Chueh Yiyang Li
And the rest of the Chueh Group