rundown of key battery chemistry knowledge

Battery Validation Engineer: ensuring the safe and reliable performance of batteries in a wide range of applications.

1. Battery Types and Chemistries:

• Lithium-ion (Li-ion): most common type and there are variations.
  • Lithium Cobalt Oxide (LiCoO2): High energy density, but prone to overheating.
  • Lithium Manganese Oxide (LiMn2O4): Good safety profile, but lower energy density.
  • Lithium Nickel Manganese Cobalt Oxide (NMC): Widely used in EVs, offering good balance of performance and safety.
  • Lithium Iron Phosphate (LiFePO4): Excellent safety, long cycle life, but lower energy density.
• Lead-Acid: Widely used in cars, cheap, but heavy and low energy density.
• Nickel-Cadmium (NiCd): High cycle life, but toxic and poor energy density.
• Nickel-Metal Hydride (NiMH): Higher energy density than NiCd, but lower cycle life.
• Flow Batteries: For large-scale energy storage, using liquid electrolytes.

2. Battery Components and Their Roles:

• Anode: The negative electrode, where lithium ions are stored during charging. Common materials include graphite, silicon, and lithium metal.
• Cathode: The positive electrode, where lithium ions are stored during discharging. Common materials include various lithium metal oxides.
• Electrolyte: A liquid or solid material that conducts ions between the electrodes. Separator: A thin membrane that physically separates the electrodes, preventing short circuits.
• Current Collector: A conductive material (often copper or aluminum) that collects current from the electrodes.

3. Battery Performance Metrics:

• Capacity (Ah): The amount of electrical charge a battery can store.
• Voltage (V): The electrical potential difference between the electrodes.
• Energy Density (Wh/kg or Wh/L): The amount of energy stored per unit mass or volume.
• Power Density (kW/kg or kW/L): The rate at which the battery can deliver power.
• Cycle Life: The number of charge-discharge cycles a battery can endure before significant degradation.
• Internal Resistance: The resistance within the battery that affects charge/discharge rates and efficiency.

4. Battery Degradation and Failure Mechanisms:

• Electrolyte Decomposition: Chemical reactions that degrade the electrolyte, reducing capacity and increasing internal resistance.
• Solid Electrolyte Interphase (SEI) Formation: A protective layer on the anode that can grow and hinder lithium ion movement.
• Dendrite Formation: Metallic “trees” that can grow from the anode and cause short circuits.
• Thermal Runaway: An uncontrolled heat generation that can lead to explosions or fires.
• Mechanical Stress: Cracks or deformations in the electrodes or separator that can compromise battery performance.

5. Safety Considerations:

• Thermal Management: Controlling battery temperature to prevent overheating and safety hazards.
• Overcharge Protection: Preventing overcharging that can damage the battery and cause hazards.
• Overdischarge Protection: Preventing deep discharge that can damage the battery’s structure.
• Short Circuit Protection: Protecting against short circuits that can cause fires or explosions.

6. Battery Testing and Characterization:

• Standard Test Methods to reveal specific performance characteristics.
  • constant current,
  • constant voltage,
  • pulse testing
• Interpretation of Data: Analyzing test results to assess battery performance, degradation, and potential failure mechanisms.
• Correlation of Testing to Real-World Applications: Knowing how test results translate to real-world conditions => driving range for electric vehicles.