Rice research suggests stress amongst misaligned particles in LiFePO4 cathodes limits stream


The Rice lab of supplies scientist Ming Tang has analyzed nano- and micro-scale interactions inside lithium iron phosphate cathodes by modeling and imaging supplied by the transmission X-ray microscopy capabilities at Brookhaven Nationwide Laboratory and Argonne Nationwide Laboratory. Their paper, printed within the journal ACS Vitality Letters, helps theories Tang and his colleagues fashioned a number of years in the past that foresaw how lithium travels within the dynamic atmosphere inside a typical industrial cathode.

As an necessary battery cathode materials, response distribution in lithium iron phosphate (LiFePO4) has been extensively studied in dispersed particle techniques, however stays poorly understood for mesoscopic agglomerates (or secondary particles) which might be utilized in most industrial batteries. Herein, we apply three-dimensional X-ray spectroscopic imaging to characterize the two-phase construction in LiFePO4 secondary particles throughout electrochemical biking.

(De)lithiated domains are discovered to not type the generally assumed core–shell construction however develop extremely anisotropic filamentary morphology that’s charge impartial and symmetric between charging and discharging. Section-field simulations elucidate that the noticed 1D part progress conduct will not be brought on by the 1D lithium diffusivity of LiFePO4 however the elastic interplay between main particles, which provides rise to stronger response heterogeneity than dispersed nanoparticles. Consequently, uniform lithium (de)intercalation doesn’t happen on the secondary particle floor even at excessive biking charges.

—Wang et al.


A part map of an agglomerated particle in a standard lithium iron phosphate (LFP) battery electrode exhibits the cost distribution because it goes from 4% to 86%. FP refers to iron phosphate. Rice College scientists discovered that the FP part spreads nonuniformly on an combination floor upon charging, relatively than the anticipated even unfold of lithium over the floor. The size bar is 10 microns. (Credit score: Mesoscale Supplies Science Group/Rice College)

Batteries have loads of particle aggregates that take in and quit lithium, and we wished to know what occurs on their surfaces, how uniform the response is. Usually, we at all times need a extra uniform response so we are able to cost the battery quicker.

—Ming Tang

In pictures taken at Brookhaven’s highly effective X-ray synchrotron, the researchers noticed some areas contained in the cathode had been higher at absorption than others. The flexibility to take a look at single or aggregated particles in 3D confirmed that relatively than reacting over their complete surfaces, lithium favored explicit areas over others.

That is very totally different from standard knowledge.
Probably the most fascinating statement is that these response areas are formed like one-dimensional filaments mendacity throughout the floor of those aggregated particles. It was sort of bizarre, however it matched what we noticed in our fashions.

—Ming Tang


A research by Rice College supplies scientists means that lithium batteries would profit from extra porous secondary (agglomerated) particles with better-aligned crystallites that don’t restrict lithium distribution. The scientists studied 3D transmission X-ray pictures of cycled battery electrodes to investigate the part change between lithium iron phosphate (blue) and iron phosphate (crimson) on the floor of particle agglomerates that make up the electrodes. (Credit score: Mesoscale Supplies Science Group/Rice College)

Tang mentioned the lithium filaments appeared one thing like thick nanotubes and had been a number of hundred nanometers vast and several other microns lengthy. He mentioned stress between misaligned crystallites within the particle agglomerates prevents lithium from being uniformly inserted into or extracted from the mixture floor as a result of that can generate too giant an vitality penalty. As an alternative, lithium is compelled to stream into or out of the aggregates at “sizzling spots” that develop the filament form.

As a result of the lithium can’t go into the cathode uniformly, it slows down the intercalation mechanics, Tang defined.

What our research affords is a few potential methods to assist make lithium insertion or extraction extra uniform on these aggregates or particular person particles. Introducing some porosity within the particle agglomerates may sacrifice some vitality density, however on the similar time would enable lithium to go in additional uniformly. That would help you get extra vitality at a given cost/discharge charge.

One other thought is that if we are able to one way or the other align the orientation of those small particles so their most growth is perpendicular to one another, they’ll higher accommodate lithium intercalation.

We don’t have sufficient expertise in synthesis to know make that occur. What we’re offering is bait. Let’s see if someone bites.

—Ming Tang

The Division of Vitality, Primary Vitality Sciences (DE-SC0019111) and the Nationwide Science Basis (CMMI-1929949) supported the analysis.


  • Fan Wang, Kaiqi Yang, Mingyuan Ge, Jiajun Wang, Jun Wang, Xianghui Xiao, Wah-Keat Lee, Linsen Li, and Ming Tang (2022) “Response Heterogeneity in LiFePO4 Agglomerates and the Position of Intercalation-Induced Stress”
    ACS Vitality Letters 0, 7
    doi: 10.1021/acsenergylett.2c00226


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