Integrating a Ferroelectric Interface with a Well-Tuned Electronic Structure in Lithium-Rich Layered Oxide Cathodes for Enhanced Lithium Storage.

Li-rich layered oxides (LLOs) are considered promising candidates for new high-energy-density cathode materials for next-generation power batteries. However, their large-scale applications are largely hindered by irreversible Li/O loss, structural degradation, and interfacial side reactions during cycling. Herein, we demonstrate an integration strategy that tunes the electronic structure by La/Al codoping and constructs a ferroelectric interface on the LLOs surface through Bi0.5Na0.5TiO3 (BNT) coating. Experimental characterization reveals that the synergistic effect of the ferroelectric interface and the well-tuned electronic structure can not only promote the diffusion of Li+ and hinder the migration of On- but also suppress the lattice volume changes and reduce interfacial side reactions at high voltages up to 4.9 V vs Li+/Li. As a result, the modified material shows enhanced initial capacities and retention rates of 224.4 mAh g-1 and 78.57% after 500 cycles at 2.0-4.65 V and 231.7 mAh g-1 and 85.76% after 200 cycles at 2.0-4.9 V at 1C, respectively.

Controllable Edge Epitaxy of Helical GeSe/GeS Heterostructures.

Emerging twistronics based on van der Waals (vdWs) materials has attracted great interest in condensed matter physics. Recently, more neoteric three-dimensional (3D) architectures with interlayer twist are realized in germanium sulfide (GeS) crystals. Here, we further demonstrate a convenient way for tailoring the twist rate of helical GeS crystals via tuning of the growth temperature. Under higher growth temperatures, the twist angles between successive nanoplates of the GeS mesowires (MWs) are statistically smaller, which can be understood by the dynamics of the catalyst during the growth. Moreover, we fabricate self-assembled helical heterostructures by introducing germanium selenide (GeSe) onto helical GeS crystals via edge epitaxy. Besides the helical architecture, the moiré superlattices at the twisted interfaces are also inherited. Compared with GeS MWs, helical GeSe/GeS heterostructures exhibit improved electrical conductivity and photoresponse. These results manifest new opportunities in future electronics and optoelectronics by harnessing 3D twistronics based on vdWs materials.

Construction of Co3 O4 /ZnO Heterojunctions in Hollow N-Doped Carbon Nanocages as Microreactors for Lithium-Sulfur Full Batteries.

Lithium-sulfur (Li-S) batteries are promising alternatives of conventional Li-ion batteries attributed to their remarkable energy densities and high sustainability. However, the practical applications of Li-S batteries are hindered by the shuttling effect of lithium polysulfides (LiPSs) on cathode and the Li dendrite formation on anode, which together leads to inferior rate capability and cycling stability. Here, an advanced N-doped carbon microreactors embedded with abundant Co3 O4 /ZnO heterojunctions (CZO/HNC) are designed as dual-functional hosts for synergistic optimization of both S cathode and Li metal anode. Electrochemical characterization and theoretical calculations confirm that CZO/HNC exhibits an optimized band structure that effectively facilitates ion diffusion and promotes bidirectional LiPSs conversion. In addition, the lithiophilic nitrogen dopants and Co3O4/ZnO sites together regulate dendrite-free Li deposition. The S@CZO/HNC cathode exhibits excellent cycling stability at 2 C with only 0.039% capacity fading per cycle over 1400 cycles, and the symmetrical Li@CZO/HNC cell enables stable Li plating/striping behavior for 400 h. Remarkably, Li-S full cell using CZO/HNC as both cathode and anode hosts shows an impressive cycle life of over 1000 cycles. This work provides an exemplification of designing high-performance heterojunctions for simultaneous protection of two electrodes, and will inspire the applications of practical Li-S batteries.

Achieving Ultralow Lattice Thermal Conductivity and High Thermoelectric Performance in GeTe Alloys via Introducing Cu2Te Nanocrystals and Resonant Level Doping.

The binary compound of GeTe emerging as a potential medium-temperature thermoelectric material has drawn a great deal of attention. Here, we achieve ultralow lattice thermal conductivity and high thermoelectric performance in In and a heavy content of Cu codoped GeTe thermoelectrics. In dopants improve the density of state near the surface of Femi of GeTe by introducing resonant levels, producing a sharp increase of the Seebeck coefficient. In and Cu codoping not only optimizes carrier concentration but also substantially increases carrier mobility to a high value of 87 cm2 V-1 s-1 due to the diminution of Ge vacancies. The enhanced Seebeck coefficient coupled with dramatically enhanced carrier mobility results in significant enhancement of PF in Ge1.04-x-yInxCuyTe series. Moreover, we introduce Cu2Te nanocrystals' secondary phase into GeTe by alloying a heavy content of Cu. Cu2Te nanocrystals and a high density of dislocations cause strong phonon scattering, significantly diminishing lattice thermal conductivity. The lattice thermal conductivity reduced as low as 0.31 W m-1 K-1 at 823 K, which is not only lower than the amorphous limit of GeTe but also competitive with those of thermoelectric materials with strong lattice anharmonicity or complex crystal structures. Consequently, a high ZT of 2.0 was achieved for Ge0.9In0.015Cu0.125Te by decoupling electron and phonon transport of GeTe. This work highlights the importance of phonon engineering in advancing high-performance GeTe thermoelectrics.