Technical guide
What Is Prelithiation?
Prelithiation is a way to manage the lithium inventory before a cell begins normal cycling. Its value is easiest to understand by looking at what the first charge consumes, and what that leaves available for the rest of the cell’s life.
In short
Prelithiation adds lithium to the anode before cell assembly, so the lithium consumed by SEI formation during the first charge is supplied by an additional source rather than taken from the cathode. The aim is to retain more of the cathode’s lithium for reversible cycling.
Why first-cycle lithium loss matters
The solid electrolyte interphase (SEI) protects the anode from continued electrolyte decomposition, but building it consumes lithium irreversibly. Trapping and other irreversible reactions can consume more lithium, particularly in high-capacity anodes.
Without an additional lithium source, first-cycle loss must be supplied by extra cathode material. The share of cathode capacity used to compensate that loss never contributes to reversible cycling, even though its mass and volume remain in the cell. Practical cell energy density therefore falls below what the active materials could otherwise deliver.
| Anode material | First-cycle lithium loss |
|---|---|
| Graphite | 6–10 % |
| Silicon-carbon (Si/C) | 12–25 % |
| Silicon | 15–30 % |
| Silicon oxide (SiO) | 25–45 % |
| Tin oxide (SnO₂) | 30–50 % |
These broad literature ranges are planning context, not measured 70.energy results or dosing inputs. Particle size, formulation, electrolyte and test protocol can move the actual result outside these ranges. Measure the real electrode batch before choosing a dose.
What prelithiation changes
By supplying the lithium needed for first-cycle loss separately, prelithiation can preserve the cathode’s full intended lithium inventory for cycling. The amount has to be matched to the real electrode: too little leaves a loss, while too much can create an over-lithiated or unsafe surface.
A small lithium reserve can delay capacity fade. It cannot stop slow SEI growth over hundreds of cycles; electrode architecture, binder and electrolyte design still govern long-term stability.
- More cathode lithium retained for cycling
- Higher effective first-cycle efficiency
- Higher usable cell energy density when cell balance is validated
- A route towards practical silicon and SiO high-capacity anodes
Seven routes at a glance
Not every route treats the anode before assembly. SLMP and cathode additives deliver their lithium inside the filled cell, and therefore differ from routes that pre-form the SEI outside it.
Electromechanical prelithiation (HypSi™)
HypSi™ is 70.energy’s industrialisation solution for electromechanical prelithiation. It adds lithium and pre-forms the SEI before cell assembly in one continuous roll-to-roll step — from 70 seconds per process step.
Electrochemical prelithiation
An electrode is lithiated against a lithium source in a cell-like arrangement. Measuring the charge passed provides a direct basis for dose control, but treatment adds assembly and recovery steps.
Chemical prelithiation
A reagent solution transfers lithium to the electrode by chemical reaction. Reagent chemistry and compatibility with the binder, solvent and electrode structure determine how the treatment must be calibrated.
Direct-contact prelithiation
Contact between an electrode and a lithium source enables lithium transfer in the presence of electrolyte. The setup is simple, but contact uniformity and the ability to stop at the intended dose need careful validation.
Stabilised lithium metal powder (SLMP)
Protected lithium micro-particles are applied to the anode. After electrolyte filling, the protective shell dissolves and lithium transfers within the cell; powder safety and uniform distribution remain important constraints.
Vapour-phase deposition (PVD)
Physical vapour deposition places a thin lithium film on the anode in vacuum. It can produce uniform, precisely dosed films, but requires vacuum equipment and immediate inert handling after deposition.
Cathode additives
Lithium-donating additives in the cathode release additional lithium during formation. Their straightforward integration has to be weighed against gas generation, occupied cathode volume and the behaviour of residual products.
Key points
- Prelithiation supplies a separate source of lithium for first-cycle losses.
- Literature loss ranges help with planning; measured batch data determine the dose.
- Electrode balance and the N/P ratio must be checked after adding lithium.
- First-cycle compensation is not a cure for continued SEI growth.
- Choose a route against dose control, handling and production-chain requirements.