Lithium-Air Cathode Pore Clogging

Discharge Conditions

Discharge current 0.40 mA/cm²

O₂ partial pressure 1.00 atm

Cathode pore size Mesoporous

Discharging…

Cell State

Cell voltage

2.96 V

Capacity

0 mAh/g

Pore-mouth blockage

Sim time

0.0 h

How it works

On discharge, a Li-O₂ cell reduces oxygen inside its porous carbon cathode and precipitates solid lithium peroxide as characteristic toroidal particles:

2Li⁺ + O2 + 2e⁻ → Li2O2 (solid, E° ≈ 2.96 V vs Li/Li+)

O₂ must diffuse from the air/O₂ side into the pore network (Fick's law), while its effective diffusivity falls as pores fill with discharge product (Bruggeman relation):

∂C/∂t = ∂/∂x( D_eff ∂C/∂x ) − R(x,t)
D_eff = D0 · ε^1.5   (ε = remaining open pore fraction)
C_gas ∝ p(O2)          (Henry's law)

Because the pore mouths closest to the O₂ source react fastest, they clog first and choke off transport to the still-open interior — cell voltage collapses well before the cathode's full capacity is used. This "sudden death" via pore-mouth clogging (not cathode saturation) is a well-documented failure mode of aprotic Li-O₂ batteries.

Discharge current — higher current consumes O₂ faster than it can diffuse in, triggering clogging and sudden death sooner.
O₂ partial pressure — sets the boundary concentration via Henry's law; pure O₂ sustains higher current than air before mass-transport limits kick in.
Pore size — macroporous cathodes diffuse O₂ faster and hold more Li2O2 before clogging; mesoporous cathodes clog earlier but pack reaction sites more densely.

Porous carbon cathode Diffusing O₂ Li2O2 toroids (discharge product)

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