Lithium Replenishment Technology: Enhancing Energy Density and Cycle Life in Lithium-Ion Batteries

In recent years, the rapid growth of new energy vehicles has raised the bar for lithium-ion battery performance. Among all requirements, improving energy density has become the most urgent.

Currently, there are two main approaches to boost energy density:

1. Structural optimization – through technologies like CTP (cell-to-pack), CTC (cell-to-chassis), and CTB (cell-to-body).
2. Material iteration – using advanced electrode materials, such as high-nickel ternary cathodes, high-voltage nickel-manganese materials, and high-capacity silicon or tin-based alloy anodes.

Another important method is lithium replenishment technology, also known as pre-lithiation, which directly addresses lithium loss during initial cycling.

Why Lithium Replenishment Matters

When a lithium-ion battery is first charged, the electrolyte decomposes on the anode surface (e.g., graphite), forming a Solid Electrolyte Interface (SEI). While necessary, this consumes a significant amount of lithium, lowering the initial cycle efficiency (ICE) and reducing overall capacity and energy density.

Further lithium loss occurs due to inactive anode particles and irreversible lithium deposition. Over time, these factors degrade performance.

Lithium replenishment technology solves this by pre-loading lithium into the battery before operation. By compensating for lithium losses, it improves ICE, extends cycle life, and enhances energy density.

For graphite anodes, irreversible capacity loss exceeds 6%. For high-capacity silicon and tin-alloy anodes, it can reach 10–30%. Pre-lithiation offsets these losses, unlocking their full potential.

Two Approaches to Lithium Replenishment

Lithium replenishment falls into two categories:

• Negative electrode replenishment
• Positive electrode replenishment

I. Negative Electrode Replenishment

This method introduces active lithium into the anode. Common approaches include:

1. Physical Mixing

Researchers have directly pressed lithium foil onto graphite or silicon anodes to restore lithium. For example, in 2019, Tongji University developed a roll-to-roll pre-lithiation process using Sn and lithium foils. The resulting LixSn material proved stable in air and retained 90% capacity after humidity exposure, making it suitable for LFP|Sn cells.

2. Vacuum Winding Plating

By using vacuum coating in roll-to-roll operations, large-scale uniform lithiation can be achieved. However, commercialization is still limited by cost and safety.

3. Chemical Lithiation

This involves reactions between lithium-rich agents (e.g., lithium powder, LiOH, molten lithium, or Li-organic composites) and the anode. FMC’s Stabilized Lithium Metal Powder (SLMP) is a leading example, applied through spraying or slurry coating.

4. Self-Discharge Mechanism

Here, lithium foil contacts the anode in an electrolyte environment, triggering spontaneous lithium insertion. This method is useful for studying morphology-performance relationships.

5. Electrochemical Lithiation

Widely used in research, this method introduces metallic lithium with the anode and controls lithiation through electrochemical cycling. Huawei and Tesla hold patents in this area, while Xiaomi has already commercialized high-silicon pre-lithiation in mobile phone batteries.

II. Positive Electrode Replenishment

Compared to the anode approach, cathode pre-lithiation is simpler, safer, and cheaper. Lithium-rich additives can be blended into the cathode slurry without altering existing manufacturing processes.

Requirements for Effective Cathode Replenishment:

1. The additive’s delithiation potential must fit within the cathode’s operating voltage range.
2. It should have high specific and volumetric capacity (>350 mAh/g).
3. It must be chemically stable with current binders, solvents, and electrolytes.
4. It should remain stable in air or dry environments.

Key Materials

• Binary lithium compounds: Li2O, Li2O2, Li3N, Li2S
  • Example: Guoxuan High-Tech’s rGO@Li2O/Co nanocomposites improved conductivity and stability.
  • Tesla’s patents include Li2O, Li2O2, and Li3N as sacrificial additives.
• Lithium-rich compounds: Li5FeO4, Li2NiO2
  • Li5FeO4 offers high capacity but requires better air stability.
  • Li2NiO2 can improve ICE but struggles with stability and impedance.
• Lithium composites: Li2S/Co, LiF/Co, Li2O/Co
  • These materials combine high capacity with improved conductivity and stability, though residues can remain after cycling.

Industrialization Challenges and Outlook

Negative electrode pre-lithiation, despite being well-studied, faces safety risks with metallic lithium and remains difficult to commercialize at scale. Positive electrode pre-lithiation offers better safety and process compatibility, but material challenges remain.

Future research must focus on:

• Stable, safe pre-lithiation agents with low decomposition potential
• Materials that don’t generate gas or harmful byproducts
• Compatibility with mainstream battery manufacturing

Conclusion

Lithium replenishment technology is emerging as a key enabler for next-generation lithium-ion batteries, improving both energy density and cycle life. While challenges remain—particularly in material stability and manufacturing—ongoing research and patents from major players like Tesla, Huawei, CATL, and Xiaomi indicate strong momentum toward commercialization.

As the energy transition accelerates, lithium replenishment could become a cornerstone technology for advancing electric vehicles, consumer electronics, and energy storage systems.