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The growing demand for lithium-ion batteries (LIBs) and the reliance on scarce metals in cathode active materials (CAMs) have prompted a search for sustainable alternatives. However, the performance of Mn-rich CAMs formulated with less Co suffer from transition metal dissolution (TMD). TMD can be suppressed by applying a thin film of carbon or oxide to the CAM but the assumed need for a continuous film necessitates bottom-up coating methods. This has been a challenge for LIB production as well as limiting material choices. Here we show that particulate coatings can also suppress TMD, allowing for scalable, material-independent, dry coating methods. Dry coating the Mn-rich CAM surfaces with graphene encapsulated nanoparticles (GEN) (1 wt%) suppresses TMD while nearly doubling the cycle life and improving rate capacities up to 42% under stressful conditions. The ability to suppress TMD is attributed to the unique chemical and electronic properties of the GEN produced by plasma enhanced chemical vapor deposition. The method is general and could provide a scalable path to CAM with less Co. 

Li-ion batteries are crucial for the global energy transition to renewables; however, their scalability is limited by the supply of key elements used in commercial cathodes (e.g., Ni, Mn, Co, P). Therefore, there is an urgent need for next-generation cathodes composed of widely available and industrially scalable elements. Here, we introduce a Li-rich cathode based on the known material Li2FeS2, composed of low-cost elements (Al, Fe, S) that are globally mined and refined at an industrial scale. The substitution of redox-inactive Al3+ for Fe2+ achieves remarkably high degrees of anion redox, which, in turn, yields high gravimetric capacity (≈450 mAh·g−1) and energy density (≳1000 Wh·kg−1). We show that Al3+ enables high degrees of delithiation by stabilizing the delithiated state, suppressing phase transformations that would otherwise prevent deep delithiation and extensive anion redox. This mechanistic insight offers new possibilities for developing scalable, next-generation Li-ion battery cathodes to meet pressing societal needs. 

The heat capacities of nanocrystalline Ni3Fe and control materials with larger crystallites were measured from 0.4300 K. The heat capacities were integrated to obtain the enthalpy, entropy, and Gibbs free energy and to quantify how these thermodynamic functions are altered by nanocrystallinity. From the phonon density of states (DOS) measured by inelastic neutron scattering, we find that the Gibbs free energy is dominated by phonons and that the larger heat capacity of the nanomaterial below 100 K is attributable to its enhanced phonon DOS at low energies. Besides electronic and magnetic contributions, the nanocrystalline material has an additional contribution at higher temperatures, consistent with phonon anharmonicity. The nanocrystalline material shows a stronger increase with temperature of both the enthalpy and entropy compared to the bulk sample. Its entropy exceeds that of the bulk material by 0.4 kB/atom at 300 K. This is insufficient to overcome the enthalpy of grain boundaries and defects in the nanocrystalline material, making it thermodynamically unstable with respect to the bulk control material.