Search for: All records

Abstract Motivated by the high-performance solid-state lithium batteries enabled by lithium superionic conductors, sodium superionic conductor materials have great potential to empower sodium batteries with high energy, low cost, and sustainability. A critical challenge lies in designing and discovering sodium superionic conductors with high ionic conductivities to enable the development of solid-state sodium batteries. Here, by studying the structures and diffusion mechanisms of Li-ion versus Na-ion conducting solids, we reveal the structural feature of face-sharing high-coordination sites for fast sodium-ion conductors. By applying this feature as a design principle, we discover a number of Na-ion conductors in oxides, sulfides, and halides. Notably, we discover a chloride-based family of Na-ion conductors Na_xM_yCl₆(M = La–Sm) with UCl₃-type structure and experimentally validate with the highest reported ionic conductivity. Our findings not only pave the way for the future development of sodium-ion conductors for sodium batteries, but also consolidate design principles of fast ion-conducting materials for a variety of energy applications. 

We propose a three-track detection system for two dimensional magnetic recording (TDMR) in which a local area influence probabilistic (LAIP) detector works with a trellis-based Bahl-Cocke-Jelinek-Raviv (BCJR) detector to remove intersymbol interference (ISI) and intertrack interference (ITI) among coded data bits as well as media noise due to magnetic grain-bit interactions. Two minimum mean-squared error (MMSE) linear equalizers with different response targets are employed before the LAIP and BCJR detectors. The LAIP detector considers local grain-bit interactions and passes coded bit log-likelihood ratios (LLRs) to the channel decoder, whose output LLRs serve as a priori information to the BCJR detector, which is followed by a second channel decoding pass. Simulation results under 1-shot decoding on a grain-flipping-probability (GFP) media model show that the proposed LAIP/BCJR detection system achieves density gains of 10.16% for center-track detection and 3.13% for three-track detection compared to a standard BCJR/1D-PDNP. The proposed system's BCJR detector bit error rates (BERs) are lower than those of a recently proposed two-track BCJR/2D-PDNP system by factors of (0.55, 0.08) for tracks 1 and 2 respectively. 

Abstract The development of solid‐state sodium‐ion batteries (SSSBs) heavily hinges on the development of an superionic Na⁺conductor (SSC) that features high conductivity, (electro)chemical stability, and deformability. The construction of heterogeneous structures offers a promising approach to comprehensively enhancing these properties in a way that differs from traditional structural optimization. Here, this work exploits the structural variance between high‐ and low‐coordination halide frameworks to develop a new class of halide heterogeneous structure electrolytes (HSEs). The halide HSEs incorporating a UCl₃‐type high‐coordination framework and amorphous low‐coordination phase achieves the highest Na⁺conductivity (2.7 mS cm⁻¹at room temperature, RT) among halide SSCs so far. By discerning the individual contribution of the crystalline bulk, amorphous region, and interface, this work unravels the synergistic ion conduction within halide HSEs and provides a comprehensive explanation of the amorphization effect. More importantly, the excellent deformability, high‐voltage stability, and expandability of HSEs enable effective SSSB integration. Using a cold‐pressed cathode electrode composite of uncoated Na_0.85Mn_0.5Ni_0.4Fe_0.1O₂and HSEs, the SSSBs present stable cycle performance with a capacity retention of 91.0% after 100 cycles at 0.2 C.