Gregory Lazaris

Disordered rock-salt (DRX) cathodes have emerged as promising Ni- and Co-free alternatives for lithium-ion batteries, combining the cost advantages of LiFePO₄ with the high energy density of layered oxides. Composed of earth-abundant elements such as Mn and Ti, they deliver specific energies above 900 Wh kg^-1 and capacities over 250 mAh g^-1, rivaling or surpassing conventional layered oxides. A critical challenge, however, is their intrinsically low electronic conductivity (10^-10-10^-8 S cm^-1), which makes electrochemical performance highly dependent on the type of conductive additives and how they are processed. This need is typically met through mechanical mixing of carbon via ball milling, but the consequences of this process on material stability and electrode performance remain insufficiently understood. Using Li_1.2Mn_0.6Nb_0.2O₂ as a model DRX system, we reveal that excessive mechanical carbon mixing induces carbothermal reduction (CTR), producing the more soluble Mn²⁺ from Mn³⁺ and converting conductive carbon into insulating lithium carbonate surface species, both of which severely degrade electrochemical performance. These reactions prevent the intended benefits of carbon mixing, leading to increased overpotential, reduced discharge voltage, and accelerated capacity fade. To overcome this challenge, we introduce a direct electrode-slurry mixing method using acid-treated multi-walled carbon nanotubes, which avoids high-energy milling, ensures uniform dispersion, and mitigates CTR-related degradation. This approach enhances cycling stability and voltage retention while remaining compatible with industry-standard slurry processing. Our findings provide mechanistic insights into processing-induced degradation in DRX cathodes and establish a practical pathway toward their scalable, high-performance application in next-generation lithium-ion batteries.

Disordered rock-salt oxides and oxyfluorides are promising positive electrode materials for high-performance lithium-ion batteries free of nickel and cobalt. However, conventional synthesis methods rely on post-synthesis pulverization to achieve cycling-appropriate particle sizes, offering limited control over particle microstructure and crystallinity. This accelerates degradation and complicates secondary particle processing. Here we present a synthesis strategy that enhances nucleation while suppressing particle growth and agglomeration across various disordered rock-salt compositions, including lithium–manganese–titanium oxide, lithium–manganese–niobium oxide, and lithium–nickel–titanium oxide systems. Applied to Li_1.2Mn_0.4Ti_0.4O₂, this method yields highly crystalline, well-dispersed sub-200 nm particles that form homogeneous electrode films with stable cycling behavior. Tested in cells with lithium metal as the counter electrode, these electrodes deliver ~200 mAh/g with 85% capacity retention relative to the first cycle after 100 cycles (20 mA/g, 1.5–4.8 V), and an average discharge voltage loss of 4.8 mV per cycle, compared to 38.6% retention and 7.5 mV loss per cycle for electrodes derived from pulverized solid-state particles. This approach suggests a route to enhance the performance and durability of disordered rock-salt electrodes for sustainable lithium-ion batteries.

The global transition to electric vehicles and large-scale energy storage systems requires cost-effective and abundant alternatives to commercial Co/Ni-based cathodes (e.g., LiNi0.6Mn0.2Co0.2O2) for Li-ion batteries (LIBs). Manganese-based disordered rock-salts (Mn-DRXs) can outperform conventional cathodes at lower cost, achieving >900 Wh/kg-AM (per active material, AM), but such performance has been demonstrated exclusively in cell constructions far removed from commercial viability, namely with diluted electrode films (~70 wt%-AM) containing excessive carbon and binder. Herein, our work involves a comprehensive study to attain AM-concentrated Mn-DRX cathodes (>95 wt%-AM), covering from inherent material properties to the microstructure of electrodes, to address the formidable challenges in Mn-DRX research. We reveal that Mn-DRXs’ failures in AM-concentrated electrodes originate from their extremely low electrical conductivity (10^-10-10^-8 S/cm) and the collapse of the electrical network with volume change over cycling. These failure modes are resolved through electrical percolation engineering and enhancement of electrode mechanical properties, allowing our demonstration of nearly all-AM Mn-DRX cathodes (~96 wt%-AM) and the highest application-level energy density (~1050 Wh/kg-cathode) reported to date. This work further unveils the trade-off role of Mn-content on Mn-DRXs’ electrical conductivity and volume change, providing guidelines for material design to 33 advance Co/Ni-free LIB's technology readiness.