Test Flashcards
What is the role of batteries in the green shift?
Key ways:
Energy storage
Grid stabilisation
Electrification of transportation
Distributed energy systems
Support for off grid and microgrid solutions
Circular economy and sustainability
What is the history of batteries?
1800- The Voltaic Pile
1836 - Daniell Cell
1859 - Lead-Acid Battery
1899 - Nickel-Cadmium Batteries (NiCd)
1950 - Alkaline Batteries
1970 - Lithium Batteries
What are the most common battery types?
- Lead - Acid Batteries (Automotive Starters)
- Nickel - Cadmium Batteries (NiCd) (Power tools)
- Nickel - Metal Hydride batteries (NiMH) (Consumer Electronics)
- Lithium - Ion Batteries (Li-ion) (Portable Electronics)
How does a battery work?
Batteries convert chemical energy into electrical energy through electrochemical reactions. Each battery consist of one or more electrochemical cells, each containing two electrodes (ANODE and CATHODE) separated by an electrolyte.
What is the working principle of a LiB?
The lithium ions move between the cathode and anode during charge and discharge cycles.
Charging - External power source applies a voltage greater than the battery’s current voltage, forcing lithium ions to move from the cathode to anode.
Discharging- The stored lithium ions at the anode are released back into the electrolyte and move towards the cathode.
What are the key materials used to store lithium in LiBs?
Cathode materials:
Lithium Cobalt Oxide
Lithium Iron Phosphate
Lithium Manganese Oxide
Lithium Nickel Manganese Cobalt Oxide
Lithium Nickel Cobalt Aluminium Oxide
Anode materials:
Graphite
Lithium Titanate
Silicon
Electrolyte - Typical Lithium salt dissolved in organic solvent
Separator - A porous membrane
What materials are used as current collectors? Why?
For the Cathode
Aluminium (AI)
For the Anode
Copper (Cu)
Why?
High electrical conductivity
Chemical stability
Mechanical Properties
Cost and Availability
What materials are used as electrolyte components? Why?
Lithium salts
Lithium Hexafluorophosphate
Organic solvents
Ethylene Carbonate
Why?
High ionic Conductivity
Electrochemical Stability
Compatibility with Electrode Materials
Low flammability
What is the role of the remaining component separator?
Electrical Insulation
Ionic Conductivity
Mechanical Stability
Thermal Stability
Chemical Compatibility
Contributing to Battery safety
What are the main degradation mechanisms on the anode side?
Solid Electrolyte Interphase (SEI) Formation and Growth
Mechanical Stress and Volume Changes
Lithium plating
Electrolyte Decomposition
High temperature Effects
Electrical stress
What are the main degradation mechanisms on the cathode side?
Structural and Phase Changes
Transition Metal Dissolution
Surface Film Formation
Electrolyte Oxidation
Mechanical Stress
Microstrutural Degradation
How do the degradation mechanisms depend on the choice of active materials?
Energy Density vs. Stability: Higher energy density materials often operate at higher voltages, which can stress the electrolyte and active materials, accelerating degradation.
Termal stability: Materials with higher termal stability are less prone to degradation mechanisms triggered by elevated temperatures, such as electrolyte decomposition and active material dissolution.
Mechanical Stability: Active materials that undergo minimal volume changes during cycling exhibit lionger lifespans due to reduces mechanical stress and particle fracturing.
How do the operation conditions influence the degradation of LiBs?
Temperature
High - Faster SEI layer growth
Low - Lithium plating on the anode
State of charge
High - Cathode crystal structure can change
Deep discharge - Irreversible capacity loss.
Charging Rate
Fast - Uneven lithium ion distribution
Slow - Less efficient an contribute to SEI growth
Discharging rate
High - Increase temperature and mechanical stress in electrodes
External Mechanical stress - Vibration - Increase risk of internal short circuits
Cycling Frequency
Environmental conditions
What are the preparation steps of a lithium ion battery? (Cylindrical cell)
Materials
Mixing
Coating
Drying
Calandering
Slitting
Tab welding
Winding
Canning
Electrolyte filling
Formation
What is the anode and Cathode material?
Anode - Copper
Cathode - Aluminium
What is BMS?
Battery management system.
System that protects against over voltage, over current and discharging the battery too much.
Keeps track of what goes in and what goes out and reversed
What is electrochemical potential?
It’s the tendency to lose electrones
How do you calculate battery capacity?
C = I * t
I is the current (A), t is the time (h)
Calculates how much charge a battery can store and deliver over time
How do you calculate the energy Capacity?
E = V *C
V is the nominal voltage and C is the capacity.
Calculates the total energy a battery can store.
How do you calculate C-rate?
C-rate = I/C
I is the current, and C is the capacity.
Calculate the charge and discharge rates of a battery relative to its capacity.
How do you calculate the Efficiency of a battery?
Efficiency = Energy Output / Energy Input *100%
Calculates the efficiency of a battery.
What is the benefits and limitations with cylindrical cells?
Benefits:
Robust design
Good thermal management, but central parts of the cell might be more prone to heat buildup
Manufacturing and consistency
Limitations:
Space Efficiency- Potential inefficiencies in packaging.
Weight - Slightly heavier due to more robust casing.
What is the benefits and limitations with Prismatic cells?
Benefits:
Space Utilization - Can be packed closely together.
Scalability - Available in various sizes
Limitations:
Cost - More complex manufacturing processes, leading to higher costs
Thermal Management - Challenges due to their larger flat surfaces
What is the benefits and limitations with pouch cells?
Benefits:
Lightweight and flexible design - Soft and flexible packaging
High Energy Density - The absence of heavy casing allows for a higher ratio of active material, enhancing energy density.
Limitations:
Swelling - Can swell due to gas buildup over time.
Durability - Less durable and more susceptible to punctures and swelling.
