Lithium iron phosphate (LiFePO₄ or LFP) is a promising cathode material for lithium-ion batteries (LIBs), but side reactions between the electrolyte and the LFP electrode can degrade battery performance. This study introduces an innovative coating strategy, using atomic layer deposition (ALD) to apply a thin (5 nm and 10 nm) Al₂O₃ layer onto high-mass loading LFP electrodes. Galvanostatic charge–discharge cycling and electrochemical impedance spectroscopy (EIS) were used to assess the electrochemical performance of coated and uncoated LFP electrodes. The results show that Al₂O₃ coatings enhance the cycling performance at room temperature (RT) and 40 °C by suppressing side reactions and stabilizing the cathode–electrolyte interface (CEI). The coated LFP retained 67% of its capacity after 100 cycles at 1C and RT, compared to 57% for the uncoated sample. Post-mortem analyses, including scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), were conducted to investigate the mechanisms behind the improved performance. These analyses reveal that Al₂O₃ coatings are highly effective in reducing LFP electrode degradation during cycling, demonstrating the potential of ALD Al₂O₃ coatings to enhance the durability and performance of LFP electrodes in LIBs.

Sustainable wastewater treatment: acid–base machines perform work from entropic energy for operations between acid and base reservoirs.

Sodium vanadium fluorophosphate (NVPF) has shown promising properties as a positive electrode in sodium-ion batteries mainly due to its high operating voltage; however, it has significant electronic and kinetic limitations that must be addressed. In this study, we investigated how a simple and straightforward mechanochemical treatment can be a valuable alternative to overcome these limitations. NVPF electrodes before and after (NVPF-bm) mechanochemical treatment were compared. For NVPF-bm, the contribution from the sodiation/desodiation of Na₁ ⁺ increased from 23 to 40% as Na₂ ⁺ decreased from 38 to 48% of the total produced capacity at ∼0.5 C (70 mA g⁻¹); additionally, the discharge capacities were 30% greater than those of NVPF at 0.8 C (100 mA g⁻¹); nevertheless, after 150 cycles, NVPF-bm presented a coulombic efficiency of 96.2% and a capacity retention of 82.6%. The calculated diffusion coefficients for NVPF-bm were 22 × 10⁻¹⁰ and 1.0 × 10⁻¹⁰ cm² s⁻¹, compared to 6.5 × 10⁻¹¹ and 2.5 × 10⁻¹¹ cm² s⁻¹ for NVPF for the sodiation and desodiation processes, respectively. Furthermore, for the charge and discharge processes, NVPF-bm presented a charge transfer resistance three times smaller and diffusion lengths of 2.1 and 0.3 μm, respectively, compared to 8.0 and 13 μm, respectively, for NVPF. These results demonstrate the kinetic enhancements of the electrode as a direct consequence of the mechanochemical treatment. Therefore, this approach impacts not only the synthesis and morphology but also the inherent electrochemical storage capacity of the NVPF.

The Nobel Prize in Chemistry 2019 recognized the importance of Li-ion batteries and the revolution they allowed to happen during the past three decades. They are part of a broader class of electrochemical energy storage devices, which are employed where electrical energy is needed on demand and so, the electrochemical energy is converted into electrical energy as required by the application. This opens a variety of possibilities on the utilization of energy storage devices, beyond the well-known mobile applications, assisting on the decarbonization of energy production and distribution. In this series of reviews in two parts, two main types of energy storage devices will be explored: electrochemical capacitors (part I) and rechargeable batteries (part II). More specifically, we will discuss about the materials used in each type of device, their main role in the energy storage process, their advantages and drawbacks and, especially, strategies to improve their performance. In the present part, electrochemical capacitors will be addressed. Their fundamental difference to batteries is explained considering the process at the electrode/electrolyte surface and the impact in performance. Materials used in electrochemical capacitors, including double layer capacitors and pseudocapacitive materials will be reviewed, highlighting the importance of electrolytes. As an important part of these strategies, synthetic routes for the production of nanoparticles will also be approached (part I).