Volume variation and the associated mechanical fracture of electrode materials upon Li extraction/insertion are a main cause limiting lifetime performance of lithium-ion batteries. For LiNi1–x–y Co x Mn y O2 (NCM) cathodes, abrupt anisotropic collapse of the layered lattice structure at deep charge is generally considered characteristic to high Ni content and can be effectively suppressed by elemental substitution. Herein, we demonstrate the lattice collapse is a universal phenomenon almost entirely dependent on Li utilization, and not Ni content, of NCM cathodes upon delithiation. With Li removal nearing 80 mol %, very similar c-axis lattice shrinkage of around 5% occurs concurrently for NCMs synthesized in-house regardless of nickel content (90, 70, 50, or 33 mol %); meanwhile, the a-axis lattice contracts for high-Ni NCM, but it expands for low-Ni NCM. We further reveal Co–Mn cosubstitution in NCM barely, if at all, affects several key structural aspects governing the lattice distortion upon delithiation. Our results highlight the importance of evaluating true implications of compositional tuning on high-Ni layered oxide cathode materials to maximize their charge-storage capacities for next-generation high-energy Li-ion batteries.

The pursuit for high-energy-density batteries has inspired the resurgence of metallic lithium (Li) as a promising anode, yet its practical viability is restricted by the uncontrollable Li dendrite growth and huge volume changes during repeated cycling. Herein, a new 3dimensional (3D) framework configured with Mo 2 N-mofidied carbon nanofiber (CNF) architecture is established as a Li host via a facile fabrication method. The lithiophilic Mo 2 N acts as a homogeneously pre-planted seed with ultralow Li nucleation overpotential, thus spatially guiding a uniform Li nucleation and deposition in the matrix. The conductive CNF skeleton effectively homogenizes the current distribution and Li-ion flux, further suppressing the Li-dendrite formation. As a result, the 3D hybrid Mo 2 N@CNF structure facilitates dendrite-free morphology with greatly alleviated volume expansion, delivering a significantly improved Coulombic efficiency of ~ 99.2% over 150 cycles at 4 mA cm-2. Symmetric cells with Mo 2 N@CNF substrates stably operate over 1,500 h at 6 mA cm-2 for 6 mA h cm-2. Furthermore, full cells paired with LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NMC811) cathodes in conventional carbonate electrolytes achieve a remarkable capacity retention of 90% over 150 cycles. This

Approaches are needed for stabilizing transition metals in lithium-ion battery cathodes

By virtue of their prominent advantages in terms of capacity and voltage output and cost, O3-type layered transition-metal oxides are considered promising cathode materials for sodium-ion batteries (SIBs). However, their unstable electrochemistry at high voltages due to complex multiphase evolution in the bulk structure and continuous degradation of the electrolyte-cathode interphase hampers their practical viability. Here, we reveal a dual-stabilization effect of the cation dopants on the evolution of the bulk structure and electrode-electrolyte interphase of a Li-substituted O3-type cathode upon Na (de)intercalation. The incorporation of Li into the transition-metal layer could mitigate the Jahn-Teller distortion of the Ni 3+ ion and prevent the loss of active transition-metal ions so that the unfavorable high-voltage phase transition and the degradation of the electrolyte-cathode interphase are suppressed. As a result, the Li-incorporated cathode material displays a high reversible capacity with good highvoltage durability to facilitate its service in high-energy-density SIBs.

The practical viability of Li–S cells depends on achieving high electrochemical utilization of sulfur under realistic conditions, such as high sulfur loading and low electrolyte/sulfur (E/S) ratio. Here, metallic 2D 1T′‐ReS2 nanosheets in situ grown on 1D carbon nanotubes (ReS2@CNT) via a facile hydrothermal reaction are presented to efficiently suppress the “polysulfide shuttle” and promote lithium polysulfide (LiPS) redox reactions. The designed ReS2@CNT nanoarchitecture with high conductivity and rich nanoporosity not only facilitates electron transfer and ion diffusion, but also possesses abundant active sites providing high catalytic activity for efficient LiPS conversion. Li–S cells fabricated with ReS2@CNT exhibit high capacity with superior long‐term cyclability with a capacity retention of 71.7% over 1000 cycles even at a high current density of 1C (1675 mA g−1). Also, pouch cells fabricated with the ReS2@CNT/S cathode maintain a low capacity fade rate of 0.22% per cycle. Furthermore, the electrocatalysis mechanism is revealed based on electrochemical studies, theoretical calculations, and in situ Raman spectroscopy.