Energy Materials

The formation of a stable cathode-electrolyte interphase (CEI) is critical for the performance of lithium–sulfur (Li–S) batteries with carbonate-based electrolytes, as it suppresses parasitic polysulfide reactions and enables solid-state sulfur conversion. In nanoporous carbon hosts, the CEI together with nanopore confinement plays a key role in capacity retention and long-term cycling. Yet, its spatial formation, stability, and contribution to electrochemical performance remain poorly understood, partly due to challenges in characterization caused by beam and air sensitivity. Here, we employ cryogenic transmission electron microscopy (cryo-TEM) with electron energy loss spectroscopy and energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and electrochemical testing together with galvanostatic intermittent titration technique measurements to elucidate how carbon particle size affects CEI formation and electrochemical performance. We find that the CEI is not a uniform surface film but extends heterogeneously into the particle bulk. Mass transport during the first discharge dictates CEI development, and larger particles suffer from inactive regions due to the preferential CEI formation only in the outer regions of the particles. During extended cycling, charge transfer resistance at confined CEI/active material/carbon interfaces emerges as the dominant performance-limiting factor. These findings show that particle size controls CEI formation during initial discharge, offering guidance for designing carbon hosts from nano- to micrometer length scales in Li–S battery cathodes.

In this work, hierarchically porous materials have been prepared by the self-assembly and pore formation of different amphiphilic block copolymers (BCPs) in the vicinity of cellulose paper sheets. For this, polystyrene-block-polysolketal methacrylate (PS-b-SMA) as a linear BCP and polymethyl methacrylate-block-polysolketal methacrylate (PMMA-b-SMA)n as a star-shaped BCP were prepared using living anionic polymerization. Under mild acidic conditions, the amphiphilic properties were revealed by converting the PSMA block segment to poly(dihydroxypropyl methacrylate) (PDHPMA). The BCPs were incorporated onto cellulose linters fiber-based sheets by a self-assembly and nonsolvent-induced phase separation (SNIPS) process. The resulting porous materials have been further modified with 3-aminopropyltriethoxysilane (APTES) and 3,3,3-trifluoropropyl dimethyl chlorosilane (TFPCS) using a vapor-phase modification approach. This strategy enabled further tuning of the surface properties of the resulting porous structures to adjust surface polarity. The characteristics of the modified porous materials were confirmed at the microscopic scale by solid-state nuclear magnetic resonance (NMR) combined with selectively enhanced dynamic nuclear polarization (DNP) and Fourier transform infrared (FTIR) spectroscopy. The influence of APTES and TFPCS was further analyzed at the macroscopic level using water contact angle (WCA) measurements and water permeance testing, where changes were observed for both modifiers. Using this convenient strategy, the fabrication of functional porous cellulose composite materials is demonstrated, paving the way for a new family of cellulose-based porous materials.

The development of efficient carbon-based materials is crucial for overcoming the performance limitations of traditional electrodes in capacitive deionization (CDI). However, the practical performance of heteroatom-doped carbon electrodes for desalination in complex multi-ion water matrices remains largely unexplored. In this work, we studied the ion selectivity toward Li+ and the removal efficiency of nitrogen‑sulfur co-doped and boron-doped carbon electrodes in brackish water, using multi-salt cation solutions containing monovalent (Li+, Na+, K+) and divalent (Ca2+, Mg2+) ions. These modifications enhanced charge distribution, wettability, and ion diffusion within the electrodes. As a result, the N,S-AC electrode exhibited pronounced lithium selectivity in brackish water, while the B-AC electrode delivered higher adsorption capacity. The B-AC electrode achieved both high capacity and enhanced lithium selectivity even under strong competition from Na+, Mg2+, and Ca2+. These findings demonstrate the distinct and complementary roles of N,S-co-doping and B-doping, offering valuable insights into how heteroatom engineering can advance CDI performance.

Transition metal oxalates have been proven to be a promising electrode material for lithium-ion batteries. Here, we have designed a series of multi-phase transition metal oxalates with different structures and compositions by simply adjusting the proportions of five transition metal elements. Among them, the multi-phase mixture (MC2O4·2H2O – CuC2O4 – MC2O4·2H2O, M = Mn, Fe, Co, Ni, Cu) provides a more stable framework for the material during lithiation and delithiation, effectively alleviating the structural collapse during the cycling process. In addition, the electron transport and fast charge compensation processes of multiple electrochemically active metal pairs also contribute to the improvement of performance. Therefore, the multi-phase transition metal oxalate TMOx-2 electrode with an additional CuC2O4 phase exhibits high reversible capacity and long-term cycling stability. After 400 cycles at 100 and 500 mA/g, the specific discharge capacities are 827 mAh/g and 498 mAh/g, respectively. Constructing multi-metal, multi-phase systems by combining different transition metals enables control over potential, reaction pathways, and stability of high-performance electrodes.

Electrochemical nitrate reduction (eNO3RR) mitigates environmental nitrate pollution while offering a sustainable approach for green NH3 synthesis, but is plagued by limited electrocatalytic activity and unsatisfactory stability. Accordingly, we adopted an exfoliation-induced in situ electrochemical deep reconstruction strategy to construct an amorphous/crystalline heterostructure using a multilayer CuCoAl layered double hydroxide (LDH) as a precursor. The characterization results illustrate that the few-layer CuCoAl LDH underwent a deep reconstruction process to transform into a structure with co-existing metallic Cu, crystalline Co(OH)2, and amorphous CoOOH. Among these, CoOOH can firmly anchor the Cu cluster to promote the transformation of NO3 – to NO2 -, while Co(OH)2 mainly facilitates the subsequent hydrogenation steps. These three species act cooperatively to endow the reconstructed few-layer LDH with extraordinary eNO3RR activity (99.5% Faradaic efficiency, 95.7% NH3 selectivity, and 1.92 mol h-1 g-1 yield rate at -0.57 V vs. RHE in 0.1 m nitrate) and stability. The Zn-NO3 – battery assembled with FA2-CuCoAl LDH simultaneously achieved environmental remediation, energy storage, and sustainable ammonia synthesis. Thus, this study reveals the reconstruction behavior of CuCoAl LDH, demonstrates the positive effect of the exfoliation step, and provides a novel strategy for designing efficient and stable eNO3RR catalysts based on amorphous/crystalline heterostructure engineering.

Silicon is a promising anode material for lithium-ion batteries due to its high capacity and potential for fast charging. However, its electrochemical behavior is dominated by pronounced voltage hysteresis, particle-size-dependent voltage plateaus, and relaxation processes induced by hysteresis. Conventional Doyle–Fuller–Newman models cannot capture these phenomena. Here, we present a multi-species, multi-reaction framework that explicitly considers the multiphase lithium–silicon system by assigning an independent equilibrium potential to each phase, derived from modified Nernst equations and parameterized with experimental and atomistic data. The model captures both asymmetric lithiation and delithiation pathways as well as phase-fraction evolution in silicon half-cells. Quantitative comparison yields root-mean-square errors of 5.4–36.9 mV during constant-current and pulse protocols, corresponding to a relative root mean square error of 0.6–4.1% of the overall voltage window. Simulations further reveal that phase fractions continue to evolve during relaxation through thermodynamic redistribution of lithium between phases, governed by phase-specific equilibrium potentials and kinetics. This cross-dimensional approach enables a mechanistic representation of voltage hysteresis, providing a pathway toward improved state estimation, cell design, and battery management.

Commercialization of lithium–sulfur batteries (Li–S) remains complex due to limited cycling stability related to the solubility of polysulfide intermediates, specifically higher-order polysulfides (Li2S4 to Li2S8). Some studies have utilized microporous carbons with pore sizes ≤0.7 nm, which can accommodate only short-chain polysulfides (Li2S2–4) to resolve the challenge of polysulfide shuttling. However, the discharge products of long-chain polysulfides, Li2S8 and Li2S6 molecules with diameters of 0.84 nm and 0.76 nm, are not entirely confined in the micropores due to the poor affinity of the carbon host and polysulfides. In this study, we created microporous carbon (AC900) with a pore size of 1.2 nm that can accommodate both long and short-chain polysulfides and infiltrated it with sulfur (AC900S). To mitigate capacity fading, we further modified the carbon using urea (AC900NS) and nickel sulfate (AC900S-Ni) treatments. The latter did not result in detectable Ni incorporation but induced partial changes in carbon hybridization and surface structure. The synthesis-driven structural adjustment in AC900S-Ni influenced solid-state conversion and improved electrochemical stability compared to AC900S and AC900NS. The AC900S-Ni cathode demonstrated a capacity retention of 72% with a capacity of 773 mAh gS−1 after 100 cycles and 1000 mAh gS−1 in the first cycle at C/20, higher than those of AC900S and AC900NS. An improvement in capacity retention to 96% was noted at C/10, with a discharge capacity of 722 mAh gS−1 after 100 cycles, compared to 805 mAh gS−1 in the first cycle. The results identify the factor contributing to capacity fading in unmodified AC900S and demonstrate that chemical/structural modification of microporous carbon combined with a carbonate electrolyte provides a promising pathway for Li–S systems. This study offers a facile approach to tune carbon hosts and expand their applicability in Li–S batteries.

Porous and functional cellulose-based materials play a key role in the field of novel sensors and membrane technologies, yet their full potential remains unexplored. This article elaborates on a procedure for creating porous coatings with reactive chemical groups on their surfaces by covering a cellulose membrane with hybrid core–shell particles. The silica cores of these particles, synthesized via the Stöber procedure, could easily be etched with hydrofluoric acid. The cross-linked polymer shell of the particles was synthesized via emulsion polymerization. These particles were analyzed via dynamic light scattering and transmission electron microscopy. After coating the cellulose and an etching process, the former core particles formed pores within the matrix of the shell polymer, as observed via scanning electron microscopy and atomic force microscopy. The coated area also featured chemical functionalities via appropriate polymers used in the shell of the particles, enabling further cellulose modification. In particular, hydroxy groups were incorporated into a copolymer containing 2-hydroxyethyl methacrylate, and epoxy groups were incorporated using glycidyl methacrylate. These functionalities can be combined to yield a wide range of specific properties. For this reason, this work paves the way for advanced smart and stimuli-responsive porous filtration systems, paper-based sensors, and adsorbers.

Lithium is a critical resource for high-energy batteries and emerging energy storage technologies. Conventional extraction methods, such as solar evaporation of brines, are energy-intensive and environmentally harmful, highlighting the need for sustainable alternatives. Here, we present an electrochemical strategy for selective lithium recovery using a hybrid intercalation-based electrochemical cell that exploits the unique properties of lithium manganese oxide (LMO). Unlike traditional carbon-based electrodes, LMO features a spinel crystal structure that enables reversible Li+ intercalation under controlled potentials, providing intrinsic ion selectivity. To improve durability and performance, the LMO electrode was functionalized with the anionic polyelectrolyte poly(sodium 4-styrenesulfonate) (PSS). At the same time, the activated carbon counter-electrode was coated with the cationic polyelectrolyte poly(diallyldimethylammonium chloride) (PDADMAC). Experiments in single-salt (LiCl) and mixed-salt (LiCl + NaCl) systems, including highly asymmetric brines, reveal that Li+ uptake strongly depends on the applied cell voltage, reaching values above 40 mg g−1 at 1.2 V. The PSS coating is expected to mitigate Mn dissolution and alters desorption dynamics, favoring Na+ release while maintaining Li+ selectivity. These results demonstrate the potential of LMO-based hybrid electrodes for energy-efficient lithium recovery from complex saline environments.

Electro-enhanced adsorption and desorption (electrosorption) is emerging as a versatile route to remove and concentrate trace organic contaminants, including PFAS and pharmaceuticals, by coupling conductive adsorbents with electrical control. Many systems borrow process concepts from capacitive deionization (CDI), yet at environmentally relevant influent levels, they operate in a low-loading regime where affinity, competition, and transport dominate rather than charge-storage-limited salt/ion uptake. The electrical step also enables controlled release (electrodesorption) for regeneration, recovery, and enrichment, supporting capture-concentrate operation. This Making Waves article proposes a mechanism-consistent vocabulary and a compact reporting framework that links treatment goals to key metrics: affinity- and process-relevant descriptors (adsorption coefficient, selectivity, breakthrough/retardation, recovery, and enrichment) when electrosorption of trace organic compounds is the goal. Clear terminology and reporting will improve comparability across studies and accelerate rational design of electrosorption technologies tailored to trace organic pollutants.