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Ultrahigh Molecular Weight polyethylene oxide (UHMW PEO) and NaPF₆ diglyme produce solid electrolytes with chemical and electrochemical stability in Prussian White (PW)//Hard Carbon (HC) and Na//Al cells. Both the NaPF₆ concentration and the polymer content rule the rheology, and the mechanical and electrochemical properties of the electrolytes. The use of UHMW PEO allows to incorporate minimum concentrations with maximum rheological impact. The solid character is achieved by the formation of rigid scaffold consisting of PEO/Na⁺ crystalline complexes, which stops flow and provides a mechanical barrier between electrodes. To maximize the benefits of polymer addition, it is worthwhile to test formulations in which the concentration of Na⁺ and PEO are varied. This is because the PEO/Na⁺ crystalline complexes reduce the amount of mobile Na⁺ cations. Na⁺ complexation and crystalline phase distribution is studied by FTIR, XRD and DSC in NaPF₆ in diglyme solutions of concentration 0.9 to 1.5 m, and their solid electrolytes where PEO varies from 5 to 10 wt%. Ion mobility (conductivity and diffusivity) is studied in relation to their chemical composition and phase distribution, and their electrochemical behaviour is investigated in PW//HC and Na//Al cells. Cells with solid polymer electrolytes show remarkable performance even at room temperature and high current rate (1C).

Sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) are potential alternatives to lithium-ion batteries. However, knowledge about the solid electrolyte interphase (SEI) in SIBs and PIBs is still limited. Here, the formation and stability of SEI in SIBs and PIBs are compared to understand ageing related to SEI characteristics in electrolyte solutions based on 1 M KPF₆ or 1 M NaPF₆ in ethylene carbonate:diethyl carbonate (EC:DEC). Galvanostatic cycling coupled with pause testing was used to quantify the amount of charge consumed for electrolyte reduction for initial SEI formation and for SEI reformation required due to the dissolution of SEI. Proton nuclear magnetic resonance (1H-NMR) spectroscopy was used to reveal changes in the composition of electrolyte solutions due to SEI formation and dissolution. ¹H-NMR findings were supported by X-ray photoelectron spectroscopy (XPS) analysis showing the evolution of SEI composition during a 50 h pause.

Hard carbon (HC) is currently the predominant anode material for sodium-ion batteries; however, its practical application is still limited by insufficient initial Coulombic efficiency (ICE) and plateau capacity. Meanwhile, conventional HC production relies on energy-intensive carbonization processes with considerable carbon emissions. Here, an induction heating carbonization strategy is developed for extruded biocarbon columns derived from biomass-based biochar and bio-oil, enabling simultaneous enhancement of electrochemical performance and production sustainability. Bio-oil combined with high-pressure extrusion suppresses open pores, whereas induction heating generates localized eddy currents and concentrated Joule heating that accelerate carbon rearrangement and promote closed pore formation. As a result, the closed-to-open pore volume ratio increases from 0.32 to 85.18, leading to improved ICE (95.0% vs. 84.4%) and plateau capacity ratio (77.6% vs. 64.7%) relative to conventional carbonized HC. Life-cycle assessment further indicates an approximately 35% reduction in global warming potential. Overall, this work presents an energy-efficient, low-emission route for producing high-performance HC anodes.

The development of high-performance, sustainable sodium-ion batteries requires a mechanistic understanding of cathode redox processes and structural stability. Na₄Fe₃(PO₄)₂(P₂O₇) (NFPP) is a promising cathode material due to its non-toxicity, high average working voltage, and excellent structural and thermal stability. However, its practical application is hindered by impurity phase formation and low intrinsic electronic conductivity. To address these challenges, Na₄Fe_3-xM_x(PO₄)₂(P₂O₇) (M: Mn, Ni) composites are synthesized via a sol-gel method. A comprehensive characterization approach combining X-ray diffraction (XRD), X-ray absorption spectroscopy (XANES/EXAFS, soft XAS), and resonant inelastic X-ray scattering (RIXS) revealed that low-level substitution of Mn²⁺ and Ni²⁺ into Fe sites suppresses the formation of electrochemically inactive maricite NaFePO₄ and modifies the Fe-O coordination environment. These effects may result in lower ion migration energy barriers and better electrochemical reversibility. Among the doped samples, Mn-NFPP exhibited the best electrochemical performance, delivering a discharge capacity of ∼92 mAh g⁻¹ at 0.1 C and ∼80 mAh g⁻¹ at 2 C, with 99.5 % capacity retention after 100 cycles at 0.1 C. This work provides fundamental insights into the redox mechanism and atomic-scale structure–property relationship of NFPP, guiding the design of high-performance polyanionic cathodes for sodium-ion batteries.

The incorporation of small amounts of polymers into liquid electrolytes to produce gel electrolytes has many benefits. Decreasing, or even avoiding flow reduces accidents caused by leaks, allows for simpler and more flexible geometries and configurations, stabilizes electrochemical cycling, and may even permit the separate recycling of each cell component. Direct mixing of polymers with liquid electrolytes is very frequently possible, and it is a sustainable and scalable procedure that avoids evaporation stages and produces thermoreversible materials. In this work, some of the polymers most commonly used for gel electrolyte formation-polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), polyvinyl chloride (PVC), poly(methyl methacrylate) (PMMA), and poly(ethylene oxide) (PEO)-are employed to produce gels with the electrolyte NaPF6 1.1 m in diglyme, and their behavior and performance are described. All these polymers are soluble in the electrolyte, and the ultrahigh molecular weight (UHMW) PEO and the halogenated polymers are able to form self-standing gels at concentrations ranging from 5 to 10 wt %. The fluorinated polymer gels left standing in an Ar glovebox progressively become colored, turning almost black after one month, showing a lack of long-term chemical stability. PVC 10 wt % and UHMW PEO 5 wt % gels, however, become hard gels with no macroscopic phase separation and remain stable for periods of months. Their electrochemical stability against Na electrodes was tested, showing that the PVC gel is not stable, and only the UHMW PEO 5 wt % gels were further tested with Prussian white (PW) cathodes. The PEO gel electrolyte, without any physical separator, showed equivalent performance in PW||Na half-cells as the baseline electrolyte with a glass fiber separator, while also being self-standing and solid-like in consistency. The PEO gel electrolytes also showed applicability to PW||HC full cells. Moreover, after electrochemical testing, the coin cells with PEO gels were easily disassembled, and their components were recovered.

Sodium-ion batteries (SIBs) are emerging as a promising alternative to lithium-ion batteries due to their potential for efficient and sustainable energy storage. Thus, the demand for high-performance battery materials with a sustainable supply chain, particularly hard carbon (HC) as the primary anode material for SIBs, is rapidly increasing. This study focuses on enhancing the production and electrochemical performance of HC products by leveraging Sweden's abundant forestry resources and advanced biomass refining processes. Specifically, we propose a novel HC production process that compresses sawdust-derived biocarbon with bio-oil derived from the same pyrolysis process to produce HC with improved properties, where the bio-oil serves as both a binder and a surface engineering agent for the biocarbon. This approach effectively modifies surface defects, leading to increased initial Coulombic efficiency (ICE), reaching values of 90 % in half-cell tests. Moreover, laboratory measurements and Life Cycle Assessment (LCA) results quantified that this production method achieves nearly 50 % higher HC yields and reduces greenhouse gas (GHG) emissions by approximately 20 % compared to the conventional production method. As a result, this offers a potentially more sustainable and economically viable solution for advancing the SIB anode material production.

The demand for lithium-ion batteries in applications for transportation and energy storage is leading to significant pressure on critical metal reserves, whereas end-of-life batteries create an increasing waste management issue. This work offers a scalable, low-cost recycling method through a cooperative strategy involving ammonium chloride-assisted processing, battery sorting, statistical optimization, and recovery of secondary materials, reducing metal separation costs and increasing metal recovery efficiency. Microwave-assisted roasting was explored as an energy-efficient alternative to conventional heating, resulting in reduced processing times and associated costs. The produced liquid waste and the consumption of reagents were minimized using statistical optimization via design of experiments for enhanced recovery rates of metals beyond 90 %. The recovered materials were pristine battery-grade materials. The developed Mn_xNi_yCo_zCO₃-based asymmetric supercapacitors exhibited outstanding electrochemical performance, compared to those synthesized from commercial precursors, with a specific capacitance, energy density, and power density of 97 F/g, 34.5 Wh/kg, and 598.5 W/ kg, respectively. Environmental investigations revealed reduced emissions, while the feasible regeneration of reagents and the valorization of valuable byproducts improved the process sustainability, ensuring industrial scalability while adhering to the principles of the circular economy.

Sodium-ion batteries are a promising alternative to lithium-ion batteries due to their potential for lower cost and greater sustainability. However, achieving stable cycling performance, particularly at high mass-loadings and elevated temperatures, remains a challenge. The stable cycling of high mass-loading sodium-ion battery cells is here made possible by addition of prop-1-ene-1,3-sultone (PES) to a non-flammable and fluorine-free electrolyte solution of sodium bis(oxalato)borate (NaBOB) salt in triethyl phosphate (TEP). This study investigates the thermal stability and electrochemical performance of such electrolyte at 40 degrees C and 55 degrees C, contrasting their performance with base NaBOB in TEP with and without ethylene sulfate (DTD) additive and with a reference carbonate electrolyte of NaPF6 in ethylene carbonate:diethylene carbonate (EC:DEC). Nuclear Magnetic Resonance spectroscopy was used to reveal degradation products formed in the electrolyte following a 4-weeks storage at 55 degrees C. Results from galvanostatic cycling at 55 degrees C demonstrated comparable performance of NaBOB-TEP + PES electrolyte and the reference carbonate electrolyte. The internal cell resistance was initially lower when cells were cycled at 55 degrees C than at 40 degrees C for all studied electrolytes.

This study aims to demonstrate the feasibility of the atmospheric plasma spraying (APS) technique to fabricate individual constituents of solid-state batteries (SSBs) such as anode, solid electrolyte (SE) and cathode as well as further produce their half-cell (anode|SE) and full-cell (anode|SE|cathode) configurations. The materials targeted in this work were Li4Ti5O12 (LTO) as an anode, Li7La3Zr2O12 (LLZO) as a SE and LiNi1/3Mn1/3Co1/3O2 (NMC111) as a cathode, with aluminium substrates being used as current collectors. The microstructure of the LTO and LLZO layers exhibited a characteristic lamellar structure along with the presence of a secondary phase attributed to delithiation at high temperatures, whereas the NMC111 layer was found to undergo substantial structural change. X-ray diffraction (XRD) analysis suggested that both LTO and LLZO layers retain most of the characteristic peaks along with the presence of secondary phases while NMC111 layers undergone significant change in the crystal structure. The XPS analysis confirms the presence of expected elements and oxidation states for the LTO layer. In the case of the LLZO layer, a metal carbonate surface reaction layer was observed, while the NMC111 layer reveals the presence of Li, Ni, Mn, Co, and O along with feeble metal carbonate. Fabrication of half-cell and full-cell configurations shows encouraging results by revealing a well-intact interface demonstrating the feasibility of the APS technique to accomplish such layered structures. This proof-of-concept effort provides valuable insights into the efficacy of APS for fabricating SSB components for further development, benefiting both the battery and thermal spray communities.

Spinel Li₄Ti₅O₁₂ (LTO) is a promising anode material for solid state thin film batteries (SSTB) due to its almost-zero volume change and promising Li-ion mobility. However, preparing LTO anodes for SSTB demands tedious vacuum-based processing steps that are not cost effective. In this context, the present study embarks on evaluating the versatile suspension plasma spraying (SPS) approach to fabricate LTO coatings without using any binder. The microstructure and stoichiometry of the fabricated LTO coatings developed through the SPS route reveals retention of ∼76 wt.% of the spinel LTO from the starting feedstock, with minor amounts of rutile and anatase TiO₂. The SPS experiments yielded varying thickness build up rates of the LTO coatings depending on the processing parameters adopted. The electrochemical data of the produced LTO based electrode tested in a half-cell through galvanostatic cycling show reversible lithiation and delithiation at expected potential, thereby validating the promise of the SPS technique for potential fabrication of SSTB components once fully optimized.