UC San Diego Turns Old EV Batteries Into Higher-Energy Cathodes

Battery recycling usually means grinding old cells down to raw chemicals and rebuilding from scratch. Engineers at the University of California San Diego have proposed a much shorter path: keep most of the old material intact and upgrade it in place. Their new method, described this week in the journal Joule, takes the cathodes from used lithium iron phosphate (LFP) batteries and converts them into higher-capacity lithium manganese iron phosphate (LMFP) — a cathode chemistry that stores meaningfully more energy per kilogram.

LFP batteries have quietly taken over huge parts of the electric-vehicle and grid-storage markets. They are safer than traditional nickel-based lithium-ion cells, last longer, and now account for roughly half of the global lithium-ion battery market. But their energy density is modest, and when they finally wear out, existing recycling pipelines rely on high heat or aggressive acids that consume a lot of energy and produce a lot of waste. UC San Diego's approach avoids most of that.

From jelly roll to LMFP

The process starts by unspooling the "jelly roll" — the tightly wound layers of coated foil inside a used cell — and soaking the sheets in plain water. That separates the cathode coating from the aluminum current collector without solvents. After drying and grinding, what remains is a black powder of spent LFP.

Here is where the upcycling begins. The researchers mix the powder with lithium, manganese and phosphate salts. But LFP and the raw salts don't share a compatible crystal structure, so the team first creates an intermediate material — lithium manganese phosphate, or LMP — that does. With careful mechanical grinding and heating, LMP blends uniformly with the leftover LFP. As the mixture heats further, manganese atoms slip into the crystal lattice and partially replace iron, producing a single, well-mixed LMFP structure. A thin carbon coating forms on the outside, which helps electrons move through the material.

The result is a cathode that stores more energy than the original LFP while keeping the qualities that made LFP popular in the first place: durability, thermal safety, and long cycle life.

Why LMFP matters

LMFP is one of the most talked-about next-generation cathode chemistries because it sits in a rare sweet spot. Compared with LFP, it delivers noticeably higher voltage and energy density — enough to close much of the gap with more exotic nickel-manganese-cobalt (NMC) chemistries — but it retains LFP's cheap, abundant iron backbone. Several major Chinese automakers have already announced LMFP-based EV packs, and the material is expected to see rapid adoption in mid-range electric vehicles and stationary storage over the next few years.

The UC San Diego process is significant because it means those higher-performance packs might not have to be built entirely from freshly mined material. Instead, they could partly come from the mountain of aging LFP batteries starting to reach end-of-life.

Scale and next steps

The team showed the method works on spent LFP batteries from different manufacturers — an important point, since real-world recycling streams are messy — and can be scaled up to kilogram batches. The upcycled cathode performed reliably in both small coin-cell test batteries and larger pouch cells.

Next steps focus on improving efficiency, controlling the microstructure of the resulting particles, and hitting the yields needed to make the process industrially viable. Global battery demand is expected to roughly quadruple by 2030, and every avoided ton of new mining and every avoided megawatt-hour of processing energy adds up quickly.

The broader idea is a shift in how the industry thinks about "recycling." Instead of tearing batteries down to elemental building blocks and rebuilding, the UC San Diego team is asking whether spent materials can simply be upgraded to something better. If more chemistries can be upcycled this way, the batteries powering yesterday's cars could turn out to be the raw material for tomorrow's longer-range EVs — with far less mine, mill and furnace in between.