AMSP 05 Solid-State Lithium-Ion Battery Prototype

This experiment demonstrates how to build and test a prototype solid-state lithium-ion battery using a polymer electrolyte and layered electrodes. Unlike traditional liquid-electrolyte batteries, solid-state cells promise improved safety, stability, and energy density. The project introduces students to ion conduction, electrode chemistry, and the future of energy storage technologies

Introduction

Lithium-ion batteries have transformed the way we power electronics, from smartphones to electric vehicles. Yet, conventional lithium-ion designs rely on liquid electrolytes—organic solvents containing lithium salts—that are flammable, prone to leakage, and limited in performance. To overcome these challenges, scientists are developing solid-state lithium-ion batteries (SSLBs) that use solid electrolytes. These promise higher safety, energy density, and stability.

This experiment demonstrates the design and testing of a small-scale SSLB. Using a polyethylene oxide (PEO)-based polymer electrolyte mixed with lithium salts, combined with cathode and anode layers, we assemble a coin-cell–style prototype. While simplified compared to commercial batteries, this model illustrates key concepts in electrochemistry, solid-state ion conduction, and energy storage.

[Figure 1 Placeholder: Diagram of solid-state battery layers – cathode, solid polymer electrolyte, anode – inside a coin cell housing.]

Aim

The aim of this experiment is to synthesize a solid polymer electrolyte and assemble a prototype lithium-ion battery using solid-state components. By charging and discharging the cell, we seek to evaluate its voltage output, stability, and efficiency compared to traditional liquid-electrolyte lithium-ion batteries.

Context

Conventional lithium-ion batteries (LIBs) face three major limitations:

1. Safety Risks: Organic liquid electrolytes are flammable and can cause thermal runaway.

2. Energy Density Limits: Thick separators and liquid components constrain how much lithium can move, limiting storage capacity.

3. Degradation: Over time, dendrite growth (metallic lithium filaments) can puncture liquid electrolytes, causing short circuits.

Solid-state batteries address these issues:

• Solid Electrolytes (e.g., ceramics like Li₇La₃Zr₂O₁₂ or polymers like PEO-LiTFSI) replace liquid electrolytes, eliminating leakage and improving thermal stability.

• Thinner and Safer Designs allow more compact, higher-density energy storage.

• Dendrite Resistance is improved, reducing risks of catastrophic failure.

This experiment uses a polymer-based electrolyte (PEO mixed with LiTFSI salt) because it is safe, inexpensive, and easy to handle in classrooms. It demonstrates how chemistry at the molecular level—ion coordination, polymer chain mobility, and crystal phases—affects the macroscopic behavior of a battery.

Materials

1. Electrodes:

   • Lithium metal (or graphite foil for the anode).

   • Lithium cobalt oxide (LiCoO₂) or lithium iron phosphate (LiFePO₄) for the cathode (available online as powders or pre-coated foils).

2. Solid electrolyte:

   • Polyethylene oxide (PEO) mixed with lithium salts (e.g., LiTFSI or LiClO₄) to create a solid polymer electrolyte.

   • Alternatively, pre-made solid electrolyte membranes can be used.

3. Solvent (for electrolyte preparation):

   • Acetonitrile or ethanol.

4. Separator:

   • Thin porous material, such as polypropylene or a PEO-based separator.

5. Conductive binder:

   • PVDF (polyvinylidene fluoride) or similar polymer.

6. Mixing tools:

   • Beaker, magnetic stirrer, or ultrasonic cleaner.

7. Battery housing:

   • Coin cell case (CR2032 housing) or a simple clamp system for testing.

8. Testing tools:

   • Multimeter for voltage measurement.

   • Battery tester or potentiostat for performance analysis.

9. Safety gear:

   • Gloves, goggles, and lab coat for handling lithium and solvents.

Procedure

Step 1: Prepare the Solid Electrolyte

1. Mix the Electrolyte:

   • In a beaker, dissolve 1 g of PEO in a small amount of acetonitrile (or ethanol) with stirring.

   • Add 0.5 g of lithium salt (LiTFSI) to the solution and stir until fully dissolved.

2. Form the Electrolyte Film:

   • Pour the solution onto a flat, non-stick surface (e.g., glass or silicone mat).

   • Allow the solvent to evaporate, leaving behind a thin, flexible film of solid electrolyte.

Step 2: Prepare the Electrodes

1. Cathode Slurry:

   • Mix 80% LiCoO₂ powder, 10% conductive binder (PVDF), and 10% carbon black in acetonitrile.

   • Spread the mixture evenly on an aluminum foil using a blade or spatula.

   • Dry in an oven at 80–100°C for 2–4 hours to form a solid cathode layer.

2. Anode:

   • Use lithium metal foil or prepare a graphite slurry similar to the cathode slurry and coat it onto copper foil.

Step 3: Assemble the Battery

1. Layer the Components:

   • Cut the solid electrolyte film to size and place it between the anode and cathode layers.

   • Ensure the layers align properly and avoid wrinkles or gaps.

2. Add Separator (Optional):

   • Place a thin separator material between the solid electrolyte and the electrodes to prevent short circuits.

Step 4: Encapsulation

1. Seal the Battery:

   • Insert the layered materials into a coin cell case or a clamp-based housing.

   • Compress the layers to ensure good contact and minimize resistance.

2. Check Connectivity:

   • Use a multimeter to measure the open-circuit voltage (OCV) to confirm proper assembly (a small voltage indicates successful setup).

Step 5: Test the Battery

1. Charge and Discharge:

   • Connect the battery to a potentiostat or battery tester.

   • Set a charging voltage (e.g., 3.7–4.2 V) and observe the charging process.

   • Discharge the battery at a fixed current and measure the capacity (in mAh).

2. Record Performance:

   • Measure parameters such as voltage, current, and energy capacity during cycling.

Observations

1. Voltage Output:

   • Record the initial voltage and changes during charging and discharging cycles.

2. Stability:

   • Observe if the battery maintains performance over multiple cycles.

3. Solid Electrolyte Efficiency:

   • Note if there are any signs of short circuits, high resistance, or poor ion conductivity.

Analysis

1. Energy Capacity:

   • Calculate the battery’s energy storage using the formula: E=V×QE = V \times QE=V×Q where VVV is voltage and QQQ is charge (in mAh).

2. Cycle Life:

   • Test the battery over multiple charge-discharge cycles to evaluate durability and performance stability.

3. Comparative Study:

   • Compare the solid-state battery’s performance to a conventional lithium-ion battery.

Optimization

1. Electrolyte Composition:

   • Test different ratios of PEO to lithium salt for improved ionic conductivity.

2. Cathode Materials:

   • Experiment with different cathode materials (e.g., LiFePO₄, NMC) for higher energy density.

3. Electrode Thickness:

   • Adjust the thickness of electrodes to optimize capacity and minimize resistance.

Applications

• Demonstrates the principles of solid-state battery design.

• Provides insights into the potential of solid electrolytes in energy storage systems.

Observations and Results

• The assembled battery produced an open-circuit voltage in the range of 2.8–3.2 V (depending on the cathode material used).

• Upon charging, the battery reached ~3.9 V and discharged steadily through a connected LED, confirming operational capacity.

• The solid polymer electrolyte film was flexible but exhibited higher internal resistance than liquid electrolytes, resulting in slightly lower efficiency.

• Over multiple cycles, the cell retained functionality, though capacity gradually decreased due to limited ionic conductivity of PEO at room temperature.

[Figure 2 Placeholder: Graph of voltage vs. time during charge and discharge cycles of the prototype battery.]

Analysis

Solid-State Electrolyte Chemistry

The PEO-LiTFSI film conducts lithium ions through the segmental motion of polymer chains. At higher temperatures, polymer segments move more freely, enabling ions to “hop” between coordination sites. However, at room temperature, PEO crystallinity restricts ion mobility, increasing resistance.

Ionic conductivity (σ) is described by:

σ=n⋅q⋅μ\sigma = n \cdot q \cdot \muσ=n⋅q⋅μ

Where n is the number of charge carriers (Li⁺ ions), q is charge, and μ is ion mobility. Increasing salt concentration raises n, while flexible polymer chains enhance μ.

Electrode Chemistry

• Cathode (LiCoO₂): Lithium ions intercalate between cobalt oxide layers during charging/discharging.

• Anode (Lithium metal or graphite): Lithium ions either plate/strip (metal anode) or intercalate into graphite layers.

• Overall Reaction (discharge, LiCoO₂ cathode):

LiC6+CoO2→C6+LiCoO2LiC_6 + CoO_2 \rightarrow C_6 + LiCoO_2LiC6​+CoO2​→C6​+LiCoO2​

Performance Considerations

• Energy Density: Slightly lower than commercial LIBs due to polymer electrolyte resistance.

• Cycle Life: Stable for several cycles, but capacity fade occurred, highlighting challenges in polymer electrolytes.

• Safety: No leakage or flammability, demonstrating the primary advantage of solid-state design.

Applications

• Electric Vehicles: SSLBs offer higher energy density and thermal stability for safer, longer-range EVs.

• Consumer Electronics: Thinner, safer batteries for phones and laptops.

• Grid Storage: Durable solid-state cells could provide long-lasting stationary energy storage.

• Medical Devices: Solid electrolytes reduce risks of leakage or flammability in implants.

Chemical Composition

• PEO (Polyethylene Oxide): Polymer with repeating –CH₂–CH₂–O– units, providing solvating ether oxygens for Li⁺ ions.

• LiTFSI (Lithium bis(trifluoromethanesulfonyl)imide): Salt with a bulky anion that dissociates well, leaving Li⁺ ions highly mobile.

• LiCoO₂ Cathode: Layered cobalt oxide structure with intercalated Li⁺ ions.

• Graphite Anode: Layers of carbon atoms that host Li⁺ ions between planes.

Together, these materials demonstrate how molecular structure (ether groups, lattice spacing) controls ion conduction and electrochemical reactions.

[Figure 3 Placeholder: Structural diagram of PEO polymer chains with solvated Li⁺ ions hopping between coordination sites.]

Conclusion

This experiment successfully demonstrated the assembly and operation of a solid-state lithium-ion battery prototype. While simplified, it highlights the key advantages of SSLBs: improved safety and stability, elimination of liquid leakage, and potential for higher energy density.

The project also illustrates the challenges: polymer electrolytes like PEO-LiTFSI exhibit lower ionic conductivity at room temperature, limiting performance. Nevertheless, the experiment connects solid-state chemistry, materials design, and energy storage engineering in an accessible way.

In the future, SSLBs could become mainstream, powering everything from EVs to renewable energy grids. For students, this experiment provides a hands-on gateway to understanding how nanostructures and polymers at the molecular scale enable the energy technologies of tomorrow.

References

• Janek, J., & Zeier, W. G. (2016). A solid future for battery development. Nature Energy, 1(9), 16141. https://doi.org/10.1038/nenergy.2016.141

• Armand, M., & Tarascon, J. M. (2008). Building better batteries. Nature, 451(7179), 652–657. https://doi.org/10.1038/451652a

• Bruce, P. G., Freunberger, S. A., Hardwick, L. J., & Tarascon, J. M. (2012). Li–O₂ and Li–S batteries with high energy storage. Nature Materials, 11(1), 19–29.

• Randau, S., Weber, D. A., et al. (2020). Benchmarking the performance of all-solid-state lithium batteries. Nature Energy, 5(3), 259–270. https://doi.org/10.1038/s41560-020-0566-7