The reference page on LFP’s cathode-electrolyte interface covers coatings and doping as the two established levers. There is a third, newer one that deserves its own look: treating the CEI itself, or the process that forms it, as the thing being engineered. Three recent papers take genuinely different routes to that same goal, and reading them side by side says more about where this field actually is than any one of them does alone.
Route one: shape the CEI through the coating chemistry
The most direct approach is to design the surface coating so that the CEI which forms on top of it comes out a particular way. A 2025 study out of Rice University used flash Joule heating, a process that deposits a carbon coating in about ten seconds, and built fluorine heteroatoms into that coating deliberately [1]. The point of the fluorine was not the carbon layer itself but what it did to the CEI that grew on top of it afterwards: pushing its composition toward an inorganic-rich, more conductive film rather than the organic-heavy layer that forms on uncoated LFP. The coated cathodes reached 96 mAh/g at 10C against 58 mAh/g for a commercial LFP reference at the same rate [1]. That is a real result, but it is worth being precise about what was actually engineered: the carbon coating’s chemistry, with the CEI composition as a downstream consequence rather than something built directly.
Route two: build the interphase directly with plasma treatment
A separate 2025 paper in the Journal of Colloid and Interface Science takes a more literal reading of “engineered CEI”: using plasma treatment to construct a hybrid LiF/Al2O3 interphase on LFP particles directly, rather than relying on a bulk oxide coating that reacts with ambient HF over time to build a fluoride layer indirectly [2]. That is a meaningful difference in approach from the oxide-scavenger coatings covered on the interface page: instead of applying an oxide and waiting for it to be consumed doing its job, the LiF component is placed there from the start. We have not been able to verify the specific capacity and cycling figures from this one independently, so treat those as a claim to check against the paper directly rather than as a number we are repeating here, but the design logic (build the fluoride-rich layer rather than let it form and deplete) is a distinct and interesting third answer to the same underlying problem.
Route three: engineer the formation protocol instead of the material
The most surprising of the three does not touch the particle, the coating, or the electrolyte at all. A study published in Nano-Micro Letters in early 2026 looked at LiFePO4/graphite pouch cells and compared a standard constant-current formation charge against a four-step “indirect activation” protocol (0.4C to 3.32V, 0.3C to 3.38V, 0.2C to 3.43V, then 0.1C to 3.65V, followed by 0.1C discharge) [3]. Nothing about the cell’s materials changed between the two groups: only the charge profile used to form the cell in the first place did.
The difference in the resulting interphases was substantial. The multi-step protocol produced what the authors describe as “a thin and uniform CEI layer” with reduced carbonate content and suppressed LiF formation, against a thicker, more heterogeneous film from continuous constant-current activation. The same pattern showed up at the graphite anode’s SEI. X-ray diffraction showed the multi-step group completing a cleaner LiFePO4-to-FePO4 phase transition during cycling, and laser ablation ICP-MS found markedly less iron migrating from cathode to anode. After 650 accelerated ageing cycles at 45°C with a 2.0V over-discharge step, the multi-step group retained 87.45% capacity against 82.01% for the constant-current group [3]. That gap opened up from a charging protocol change alone, with everything else about the cell held constant.
What reading these together actually tells you
Put the three next to each other and “engineered CEI” turns out to mean at least three different things depending on which lever a given research group is pulling: the coating chemistry (Rice), the interphase material itself, built directly rather than left to form (the plasma LiF/Al2O3 work), and the electrochemical conditions the cell sees before it ever leaves the factory (the Nano-Micro Letters formation study).
*capacity retention after 650 accelerated ageing cycles at 45°C
None of these three papers cite each other or appear to be responding to one another, which suggests the field has not yet settled on a single meaning for “engineering the CEI,” let alone which of these three routes produces the more durable result over the timescales that actually matter for an EV or stationary storage pack. The formation-protocol result is the one worth watching most closely from a manufacturing standpoint, precisely because it is the only route of the three that would not need a change to cell materials or the supply chain behind them, only to how existing production lines run the first charge.
References
- J. Chen, O. E. Onah, Y. Cheng, K. J. Silva, C. H. W. Choi, W. Chen, S. Xu, L. Eddy, Y. Han, B. I. Yakobson, Y. Zhao and J. M. Tour, Cathode-Electrolyte Interphase Engineering toward Fast-Charging LiFePO4 Cathodes by Flash Carbon Coating, 2025 Small Methods 9(1), e2400680
- Plasma-engineered LiF/Al2O3 hybrid CEI for high-rate and stable LiFePO4 cathodes, 2025 Journal of Colloid and Interface Science
- Y. Liu, J. Dong, J. Zhou, Y. Guan, Y. Wei, J. Zhao, J. Liang, X. Shi, K. Yan, Y. Lu, N. Li, Y. Su, F. Wu, L. Chen et al., Interfacial Evolution and Accelerated Aging Mechanism for LiFePO4/Graphite Pouch Batteries Under Multi-Step Indirect Activation, 2026 Nano-Micro Letters 18, 136