Battery Technology (ACE)

Primary Batteries

• Galvanic cells that produce electricity from sealed-in chemicals

• Cannot be recharged; once equilibrium is reached, they are discharged

• Example: dry cell, lithium copper sulfide cell

Requirements:

• Economically and environmentally benign

• Provide a constant voltage and a long discharge duration

• High energy density and longer shelf life

• Compact, lightweight and made from easily available materials

Secondary Batteries

• Rechargeable cells that can be used through multiple charging and discharging cycles

• External electricity reverses the spontaneous cell reaction during charging.

• Ex: Nickel cadmium cell, lead acid battery, lithium ion battery

Requirements:

• High power-to-weight ratio

• Provide high voltage

• Long cycle life and shelf life

• Short recharge time

Galvanic Cells

• Convert chemical to electrical energy

• Produces electricity as a result of the spontaneous redox reaction occurring inside it

Anode (-):

• Oxidation occurs

• Electrons are produced

• Desired characteristics: Low reduction/redox potential, high specific capacity, reversibility, and good conductivity.

Cathode (+):

• Reduction occurs

• Electrons are consumed

• Desired characteristics: High reduction potential, high specific capacity, reversibility, and stability.

Galvanic vs Electrolytic Cells

Daniel Cell

The cell consists of a zinc electrode in a zinc sulfate solution and a copper electrode in a copper sulfate solution

Anode: Zn → Zn²⁺ +2e^-

Cathode: Cu²⁺ + 2e^- → Cu

Cell reaction: Zn + Cu²⁺ → Zn²⁺ + Cu

Key Battery Performance Metrics

• Current

• Capacity

  • C = (m x n x F)/M

  • m → mass of active material

  • M → molar mass

  • n → number of electrons transferred

• Energy efficiency

  • % Energy efficiency = (Energy released on discharge / Energy required for charging) × 100

• Cycle life

  • Number of charge-discharge cycles that can be achieved before failure occurs

• Shelf life

• Energy Density

• Power density

Traditional Liquid Electrolyte

• Low vicosity, high energy density

• High discharge, charge rate

• Operational temperature: -40 to 60

• Low flammability

Polymetric Electrolytes

• Solid or gel form

• Solid: High flexibility, energy density, safety and stability

• Gel: High ionic conductivity, multifunctional, chemically stable

  Advantages of Solid Polymeric Electrolytes:

• No leakage.

• Non-flammable.

• Non-volatile.

• Thermal and mechanical stability.

• Easy fabrication.

• High achievable power density and cyclability.

Lead Acid Battery/Storage Battery

• Anode: spongy lead (Pb)

• Cathode: lead dioxide (PbO₂)

• Electrolyte: sulfuric acid solution (H₂SO₄)

• Anode reaction:

  • Pb → Pb²⁺ + 2e^-

  • Pb²⁺ + SO₄^2- → PbSO₄

  • Overall: Pb + SO₄^2- → PbSO₄ + 2e^-

• Cathode reaction:

  • PbO₂ + 4H⁺ + 2e^- → Pb²⁺ + 2H₂O

  • Pb²⁺ + SO₄^2- → PbSO₄

  • Overall: PbO₂ + 4H⁺ + 2e^- + SO₄^2- → PbSO₄ + 2H₂O

• Overall reaction: Pb + PbO₂ + 4H⁺ + 2SO₄^2- → 2PbSO₄ + 2H₂O

Overcharging of Lead Acid Batteries

• If charging is pushed beyond full capacity, electrolysis of water occurs.

  • Anode: 2H₂O → O₂ + 4H⁺ + 4e^-

  • Cathode: 2H⁺ + 2e^- → H₂

  • Overall: 2H₂O → O₂ + 2H₂

• Consequences:

  • Lowers acid level → damages electrode grids.

  • Gas pressure may build up → risk of explosion.

  • Older batteries require topping up with water.

• Solution:

  • Maintenance-free batteries

  • Pb-Ca alloy anode reduces water electrolysis

  • Catalysts (ceria + platinum) recombine gases into water; no maintenance is needed

  • Sealed design prevents leakage

Applications of Lead Acid

1. Automotive Batteries: Starting, Lighting, Ignition (SLI) for cars and trucks

2. Industrial Batteries: Motive and standby power for heavy-duty applications

3. Consumer Batteries: Emergency lighting, security systems, power tools, UPS

Advantages of Lead Acid

1. High Efficiency: Voltage efficiency ~80%

1. Reversibility: Fast chemical reactions, high negative free energy change

2. Longevity: 300–1500 recharge cycles (up to 2000 for sealed batteries)

3. Quick Recharging: Approximately 2–8 hours

4. Low Self-Discharge: Maintains charge when not in use

5. High Current Capability: 12 V car batteries can deliver over 10 A

Disadvantages of Lead Acid

1. Sulfation: Formation of large PbSO₄ crystals if left partially charged

2. Weight: Low energy-to-weight ratio (~35 Wh/kg)

3. Concentration Dependent: Cell potential drops as sulfuric acid is consumed

4. Temperature Sensitivity: Reduced efficiency at lower temperatures

5. Overcharging Risks: Potential electrode damage and explosion

6. Toxicity: Environmental and health concerns with lead

7. Corrosion: Lead grid corrosion at the lead dioxide electrode

Nickel-Metal Hydride (NiMH) battery

• Anode: Hydrogen-absorbed alloys

• Cathode: Nickel hydroxide

• Electrolyte: Alkaline, mainly potassium hydroxide

• Anode reaction:

  • MH + OH^- → M + H₂O + e^-

• Cathode reaction:

  • NiOOH + H₂O + e^- → Ni(OH)₂

• Overall Reaction:"

  • MH + NiOOH → M + Ni(OH)₂

• They have about twice the energy density of Ni-Cd batteries but a similar operating voltage

Advantages of NiMH battery

1. High Energy Density: Surpasses Ni-Cd batteries, with capacities ranging from 1000mAh to 3000mAh or higher

2. Long Cycle Life: Hundreds to thousands of recharge cycles

3. Environmentally Friendly: Fewer harmful materials, no toxic cadmium

4. Safety: Stable, lower risk of thermal runaway or fire hazards

5. Cost-Effective: Long-term economic power solution with fewer replacements needed

Disadvantages of NiMH battery

1. Self-Discharge: Loses 1–5% charge per day when idle

2. Memory Effect: Potential issues if not fully discharged before recharging

3. Temperature Sensitivity: Performance affected by extreme temperatures

4. Charging: Slower charging rates, limited fast charging capability

5. Voltage Output: Lower compared to newer battery chemistries

Applications of NiMH battery

1. Consumer electronics

2. Power tools

3. Hybrid Vehicles

4. Emergency lighting and backup power

5. Flashlights and portable devices

6. Electric bicycles and scooters

7. Renewable energy storage
   
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Lithium Ion Batteries

• Anode: Lithium-carbide type intercalate (Li_xC₆)

  • Li (C) → Li⁺ + C + e^-

• Cathode: Transition metal oxide MO₂ of variable oxidation state

  • Li⁺ + CoO₂ + e^- → LiCoO₂

• Overall Cell Reaction: Li (C) + CoO₂ → LiCoO₂ + C

• The electrolyte is usually inert (polar) dry ether or carbonates(diethyl carbonate or propylene carbonate)

Applications of Lithium Ion Batteries

1. Used in applications where one or more of the advantages(size, weight or energy) outweigh the additional cost, such as mobile telephones and mobile computing devices.

2. Used when the battery design matters in a particular application, as different designs are possible (Cylindrical,jelly-roll design, flat rectangular).

3. Used in current-generation laptops, cellular phones, videorecorders, portable CD players, televisions and implantable medical devices.

Mobile telephones/cellular phones → (has a screen) → laptop, televisions → (video related) → videorecorders, portable CD players

Advantages of Lithium Ion Batteries

1. Designed to overcome the safety problems associated with the highly reactive properties of Lithium metal.

2. Long cycle life (400-1200 cycles).

3. Smaller, lighter and provide greater energy density than either nickel-cadmium or nickel-metal-hydride batteries

4. Can be operated in a wide temperature range and can be recharged before they are fully charged.

5. Typically designed to be recharged in the device rather than in an external charger.

6. The average voltage of a Li-ion battery is equivalent to three Ni-Cd cells.

7. A typical Li-ion battery can store 150 watt-hours of electricity in 1kilogram of battery, as compared to lead acid batteries, which can store only 25 watt-hours of electricity in one kilogram.

Disadvantages of Lithium Ion Batteries

1. Poor charge retention

2. Self-discharge rate is about 10% per month

3. High cost

4. Traditional Li-ion batteries rely on liquid electrolytes, which are flammable and can pose a fire risk if the battery ruptures or overheats

Safety Concerns with Lithium-Ion Batteries

• Damage, puncture or malfunction can lead to dangerous heating, pressure buildup and thermal runaway

• Over time, batteries degrade, becoming more prone to overheating and thermal runaway

Safety Measures and Environmental Impact of Battery Production

• Battery Management System: Monitors and controls charging/discharging to prevent hazards.

• Thermal Management Systems: Utilize heat sinks and fans to prevent thermal runaway.

• Quality Control and Testing: Ensures detection and correction of cell flaws before market entry

• Safety Standards and Regulations: Established by authorities to ensure safe battery use.

Sodium-Ion Batteries

• Lithium (Li): Limited supply, energy-intensive extraction, costly and geographically restricted.

• Sodium (Na): Abundant (6th most in Earth’s crust, seawater, salt), simpler extraction, cheaper and more stable supply → promising for large-scale storage.

Similarities

• Both are alkali metals (Group 1), lose one valence electron to form Li⁺ / Na⁺, making them good for batteries.

• Both work by ion flow between electrodes during charge/discharge.

Differences

• Ionic size: Li⁺ (0.76 Å) < Na⁺ (1.00 Å).

• Larger Na⁺ ions struggle to fit into electrode materials designed for Li⁺ → lower efficiency.

Challenges & Advances in Na-ion

• Electrode design: Need new materials (e.g., Prussian blue analogues, layered sodium vanadates) to handle bigger Na⁺ ions.

• Performance: Current Na-ion batteries have lower energy & power density than Li-ion.

• Research: Focused on optimising electrodes & electrolytes to improve efficiency.

Emerging Battery Technologies

1. Solid State Batteries

   • Solid electrolyte

   • High energy density and enhanced safety

   • Ability to revolutionize EV sector

2. Lithium-Sulfur Batteries

   • Higher energy density than lithium ion

   • Sulfur is more abundant and affordable

   • Challenges: low electric conductivity of sulfur and polysulfide dissolution

3. Lithium-Air Batteries

   • Extremely high theoretical energy density

   • Lithium metal anode, oxygen from air cathode

   • Challenges: cycle life and lithium stability

4. Flow Batteries

   • Liquid electrolytes in external tanks

   • Electrolytes contain active materials that undergo oxidation and reduction reactions during charge and discharge cycles.

   • Scalable, flexible capacity

   • Research on better energy density and cost

5. Metal Air Batteries

   • Metal (Zn or Al) anode, atmospheric oxygen cathode

   • High theoretical energy densities, potentially low cost

   • Challenges: Reversibility, efficiency, and cycle life

Fuel Cells

• A fuel cell is a galvanic cell of a special type in which chemical energy contained in a fuel–oxidant system is converted directly into electrical energy

• The reactants (i.e. fuel + oxidant) are constantly supplied from outside and the products are removed at the same rate as they are formed.

Advantages of Fuel Cells

• High efficiency: 70–75% vs. only 35–40% for coal-based thermal plants.

• Eco-friendly: No noise, chemical, or thermal pollution.

• Decentralized use: Can be installed near point of use , reducing ~30% transmission losses.

• Continuous power: Provides steady electricity as long as fresh reactants is supplied.

Methanol Fuel Cell

• Electrolyte: Sulphuric acid

• Electrodes: Typical gas diffusion electrodes, made up of porous C coated with Pt catalyst

• Fuel: Methanol Oxidant

• Air Catalyst: Platinum

• Anode reaction:

  • CH₃OH + H₂O → CO₂ + 6H⁺ + 6e^-

• Cathode reaction:

  • 3/2 O₂ + 6H⁺ + 6e^- → 3H₂O

• Net reaction:

  • CH₃OH + 3/2 O₂ → CO₂ + 2H₂O

Proton Exchange Membrane Fuel Cell

• Electrolyte: Ion exchange polymeric membranes.

• Electrodes: Typical gas diffusion electrodes, made up of porous C coated with Pt catalyst.

• Fuel: Hydrogen

• Oxidant: Air

• Catalyst: Platinum

• Operate at relatively low temperatures, around 80 ^°C → Quick start-up, less wear, better durability.

• Efficiency of 60 % → Power output of 50-250kW

• Anode Reaction:

  • H₂ → 2H⁺ + 2e^-

• Cathode Reaction:

  • ½ O₂ + 2H⁺ + 2e^- → H2O(l)

• Overall Reaction:

  • H₂ + ½ O₂ → H₂O

• Challenges:

  • Require expensive platinum catalyst.

  • Platinum is highly sensitive to CO poisoning, so extra processing is needed to clean fuel → higher cost.

Role of Proton conducting membranes:

• Functions: Acts as electrolyte (ionic conduction) and separator (keeps reactant gases apart).

• Proper proton & water transport is critical.

  • Too dry → low proton conductivity.

  • Too wet → electrolyte flooding.

• Advantages:

  • No liquid electrolyte → simpler flow control than alkaline/phosphoric acid cells.

  • CO₂ tolerant.

• Breakthrough: DuPont’s Nafion (perfluorinated ionomer) membranes (since 1966).

  • Durable (>60,000 hours at 353 K).

Advantages and Disadvantages of PEMFC

Used in transportation: passenger vehicles such as cars and buses

Advantages:

• Solid electrolyte provides excellent resistance to gas crossover.

• Low operating temperature allows rapid start-up

• Capable of high current densities

Disadvantages:

• Dehydration of the membrane reduces proton conductivity, and excess water can lead to flooding of the electrolyte. Both the conditions leading to poor performance

• High cost

• Sensitive to poisoning by trace levels of contaminants, including CO, sulfur species and ammonia.

Environmental Impact of Battery Production

• Resource Extraction: Mining for battery materials can lead to ecological damage.

• Energy Intensity: High energy consumption in production; renewable energy can reduce impact.

• Chemical Pollution: Handling and disposal of hazardous chemicals must be managed safely.

• Water Usage: Significant water use in production; conservation and recycling are key

End-of-Life Management

• Crucial Disposal Management: Essential to minimize environmental harm.

• Recycling Infrastructure: Development needed to prevent pollution.

• Material Reuse: Advocacy for reusing battery materials to reduce impact.
  
  Remember as RRR

• Reduce Environment Harm

• Recycling Infrastructure

• Reuse Material

Environmental Considerations

• Vital Role of Batteries: Key in renewable energy and electrification transition.

• Mitigation of Environmental Impact: Necessary at all life stages of batteries.

• Sustainable Practices: Implementation critical for environmental protection.

• Technical Advancements: Adoption can address manufacturing concerns.

• Regulatory Frameworks: Establishment helps ensure environmental safety.