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