A new US patent (US 2024/0258501 A1) describes a systematic method to grow an artificial cathode-electrolyte interphase (CEI) directly on high-Ni positive active material surfaces – not by random electrolyte decomposition during electrolyte formation, but by controlled chemical engineering on the particle surface.
Why does this matter?
Because in modern Ni-rich systems (like NMC 811, NMC 90-series, NCA, and especially cobalt-lean high-Ni materials now in commercial qualification), surface instability is the single biggest failure mode. Ni-rich phases continuously react with carbonate electrolyte, generating HF, oxygen release, surface reconstruction, and impedance growth. The patent takes a fundamentally different track:
Instead of “try to suppress decomposition,” it “pre-installs” a rationally designed interphase with specific chemical motifs.
What is the invention about?
The patented method uses flux agents (including sulfate-based flux agents) and silica during high-temperature synthesis, forming surface compounds containing S, Si, and optionally P. These are not merely coatings: the document describes formation of defined S–Si or S–Si–P compounds directly bonded to the cathode surface. These compounds can include alkyl groups (C1 to C10 aliphatic hydrocarbon) to impart hydrophobicity and improve capacity retention.
Optionally, Co or Zr ultra-thin coatings (1–30 nm range) can be added afterward for further structural reinforcement. This is not just a simple “LZO” or “LPS” spray coating. It is a multi-element hetero-functional interphase which is bonded to the surface, formed during synthesis, not after.
Why is this disruptive?
Globally we see convergence: the frontier is chemical interface engineering.
This patent fits the same direction, but goes one step deeper: engineering the interphase ‘in-situ during synthesis’, not after-synthesis coating.
Commercial implications
If this approach moves into gigafactory lines, the impact is major:
- reduces electrolyte load (less parasitic CEI formation needed)
- improves high-temperature cycle stability
- reduces interfacial resistance
- improves gas suppression (since S–Si–P networks are extremely oxygen-stable)
- reduces exposure of Ni-rich surfaces to air/humidity during manufacturing
This is directly aligned with the future of cobalt-lean Ni-rich (Ni > 90%) which is highly sensitive to humidity.
Conclusion
This patent is a strong signal for where advanced cathode development is going: artificially-engineered CEI as a material-design layer, not an afterthought.
This is relevant not only to Li-ion gigafactory roadmap planning, but also to the emerging sodium-ion materials segment.
The 2020s was the decade of “bulk doping.”
The late-2020s and early-2030s may be the decade of “interphase engineering.”
