Toyota's name in battery research is attached to solid-state cells — the program it has talked up for years and that shows up repeatedly in its filings. So a week in which two of its newly published U.S. applications claim cathode materials from the lithium-iron-phosphate family is worth reading carefully, because a published application is a delayed signal: the work is roughly eighteen months old by the time it surfaces, and a body of filings is a lagging but real map of where the spending went. In the week of U.S. applications published March 19, 2026, Toyota published cathode-materials work pointed not at the solid-state frontier but at the low-cost chemistry that dominates affordable cells today.

The clearer of the two is US20260078014A1, a positive-electrode active material built as a hierarchy of particles — tertiary particles made of secondary particles made of primary particles — with the primary particles being lithium-manganese-iron-phosphate.

Each of the tertiary particles includes secondary particles. Each of the secondary particles includes primary particles. Each of the primary particles includes lithium manganese iron phosphate.— Positive electrode active material, electrode, battery, and method of producing positive electrode active material, US20260078014A1

Lithium-manganese-iron-phosphate, or LMFP, is the higher-voltage cousin of LFP — the cobalt- and nickel-free chemistry that has taken over the low-cost end of the cell market because its raw materials are cheap and abundant. LMFP adds manganese to lift the energy density of plain LFP while keeping the cost-and-safety profile. A particle-architecture application around LMFP is the language of a company trying to make that chemistry manufacturable and dense, the engineering work that sits between a known material and a sellable cell.

Doping the manganese-phosphate lattice

The second application, US20260078004A1, claims a lithium-manganese-phosphate active material with a crystal structure in the Pnma space group whose lithium site is doped with a dopant of ionic radius between 0.72 and 1.02 angstroms. Pure lithium-manganese-phosphate is attractive on paper for its voltage but notoriously poor at conducting; doping the lattice is one of the standard levers for improving it. A filing that pins down a dopant by ionic-radius range is the kind of incremental, materials-science work that signals a company is trying to make a difficult-but-cheap chemistry actually work rather than abandoning it — and it sits in the same manganese-phosphate family as the LMFP application, pointing the same direction.

The choice of chemistry carries its own economics. LFP-family cathodes are built from iron, manganese and phosphate rather than the nickel and cobalt of high-energy cells, which removes the two most volatile and supply-constrained inputs from the bill of materials and lowers exposure to the metals markets that have whipsawed cell costs. The tradeoff is energy density, and LMFP exists precisely to recover some of that density by adding manganese to LFP; the doped lithium-manganese-phosphate work attacks the same tradeoff from the conductivity side. Filings that engineer particle structure and lattice doping in this family are, in business terms, filings aimed at making a cheaper cell competitive enough to use — the work that decides whether the affordable tier is viable for a given maker.

The direction matters because of who is filing it. An LFP-family cathode program at Toyota reads as a signal that the affordable, manganese-phosphate end of the market is being treated as a research priority inside a company whose public battery story has emphasized the premium solid-state end. The two ambitions are not in tension — an automaker selling across price points needs chemistry across price points — but the filings indicate the cheaper chemistry is getting genuine R&D attention, not just procurement. The classifications bear this out, running through the C01B 25/45 phosphate class and the H01M 4/5825 phosphate-cathode and H01M 10/0525 lithium-ion classes rather than the solid-electrolyte classes.

The same week's other Toyota battery-adjacent applications reinforce that the company is filing across the whole pack, not only the cathode. US20260081314A1 describes a connection method for joining a bus bar and a voltage-detection line inside an assembled pack while reducing electric-shock risk during re-connection, and US20260081440A1 describes a power-supply system that switches a first and second battery between series and parallel connection to equalize their state of charge. Those are pack-integration and management applications — the everyday engineering of building and balancing a battery system — sitting alongside the cathode-materials work. The mix is itself informative: a company filing simultaneously on the cheapest cathode chemistry and on how to wire and balance the resulting packs is one treating the affordable tier as a complete system to be built, not a single material to be sourced.

It is also worth situating the LMFP work against the wider field. Lithium-manganese-iron-phosphate is the chemistry several large cell makers have moved toward to push LFP-family energy density upward without reintroducing nickel and cobalt, and the particle-engineering problem — getting dense, well-formed secondary and tertiary particles from a material that is intrinsically a poor conductor — is where much of the competitive effort sits. Toyota's tertiary-particle application (US20260078014A1) and its lithium-site doping application (US20260078004A1) are filings into exactly that problem space. They do not tell a reader how Toyota's approach compares to anyone else's; they tell a reader that Toyota is working the same problem, on its own filings, in the same window.

It is worth being precise about what these documents are and are not. They are applications, not grants — claims sought, not yet enforceable — and an application is not a product; nothing here says a Toyota cell with this cathode is shipping or will. What a pair of LMFP and doped-manganese-phosphate applications in one week does signal is where the research was pointed roughly eighteen months ago: into the lower-cost, manganese-rich corner of phosphate cathode chemistry. For a reader tracking the storage business, that is a useful tell. The cost floor of affordable cells is set by LFP-family chemistry, and the appearance of that chemistry in the filings of a company better known for solid-state suggests the affordable tier is being engineered, not ceded. The records show the direction of the work; the reader can judge what it implies for where Toyota's batteries are heading across the price ladder.