Although Li-ion batteries have emerged as the battery of choice for electric vehicles and large-scale smart grids, significant research efforts are devoted to identifying materials that offer higher energy density, longer cycle life, lower cost, and/or improved safety compared to those of conventional Li-ion batteries based on intercalation electrodes. By moving beyond intercalation chemistry, gravimetric capacities that are 2–5 times higher than that of conventional intercalation materials (e.g., LiCoO2 and graphite) can be achieved. The transition to higher-capacity electrode materials in commercial applications is complicated by several factors. This Review highlights the developments of electrode materials and characterization tools for rechargeable lithium-ion batteries, with a focus on the structural and electrochemical degradation mechanisms that plague these systems.

Controlling the surface composition of shaped bimetallic nanoparticles could offer precise tunability of geometric and electronic surface structure for new nanocatalysts. To achieve this goal, a platform for studying the intermixing process in a shaped nanoparticle was designed, using multilayered Pd‐Ni‐Pt core–shell nanocubes as precursors. Under mild conditions, the intermixing between Ni and Pt could be tuned by changing layer thickness and number, triggering intermixing while preserving nanoparticle shape. Intermixing of the two metals is monitored using transmission electron microscopy. The surface structure evolution is characterized using electrochemical methanol oxidation. DFT calculations suggest that the low‐temperature mixing is enhanced by shorter diffusion lengths and strain introduced by the layered structure. The platform and insights presented are an advance toward the realization of shape‐controlled multimetallic nanoparticles tailored to each potential application.

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Nb 2 O 5 is a Li + intercalation transition metal oxide that is of current interest for lithium ion battery and capacitor electrodes. For orthorhombic (T) Nb 2 O 5 films prepared by electrophoretic deposition (EPD) and subjected to lithiation/ delithiation cycling, a remarkably reproducible degradation process is observed. It is characterized by the onset of irreversible capacity loss from a baseline specific capacity, C sp , of 400 (±50) F/g at 1000 (± 500) cycles. A gradual reduction of C sp occurs during the ensuing 9000 cycles after which the C sp stabilizes at 200 (±25) F/ g. We investigate this degradation using six ex situ instrumental methods and more than 100 individual Nb 2 O 5 films to characterize and understand the composition, atomic scale structure, chemical bonding, electrochemical, and electrical properties of these films during these 10,000 cycles. What emerges is a multidimensional picture of the degradation process in which the decline in C sp occurs concurrently with an increase in the charge transfer resistance, a loss of crystalline order, and the dissolution of niobium from the film.

Abbreviations: LOD = limit of detection, BP = black phosphorus, NRs = nanoribbons, CNT = carbon nanotubes, AAO = anodic aluminum oxide, HT = hydrothermal synthesis, CVD = chemical vapor deposition, OTS = octadecyltrichlorosilane, DEP = dielectrophoresis, CR = chemiresistive, AM = amperometric, FET = field-effect transistor, AQP4 = aquaporin-4, HER2 = human epidermal growth factor receptor 2, PSA = prostatespecific antigen, NPY = neuropeptide Y, DHEAS = dehydroepiandrosterone sulfate, HCHO = formaldehyde, THC = tetrahydrocannabinol, N/A = information not available, and τ res / τ rec = reported or estimated response time/recovery time.