Search

Silicon has become an integral negative electrode component for lithium-ion batteries in numerous applications including electric vehicles and renewable energy sources. However, its high capacity and low cycling stability represent a significant trade-off that limits its widespread implementation in high fractions in the negative electrode. Herein, we assembled high-capacity (1.8 Ah) cells using a nanoparticulate silicon–graphite (1:7.1) blend as the negative electrode material and a LiFePO4–LiNi0.5Mn0.3Co0.2O2 (1:1) blend as the positive electrode. Two types of cells were constructed: cylindrical 18650 and pouch cells. These cells were subjected both to calendar and cycling aging, the latter exploring different working voltage windows (2.5–3.6 V, 3.6–4.5 V, and 2.5–4.5 V). In addition, one cell was opened and characterised at its end of life by means of X-ray diffraction, scanning electron microscopy, and further electrochemical tests of the aged electrodes. Si degradation was identified as the primary cause of capacity fade of the cells. This work highlights the need to develop novel strategies to mitigate the issues associated with the excessive volumetric changes of Si. [ABSTRACT FROM AUTHOR]

Nickel-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) is one of the most promising Li-ion battery cathode materials and has attracted the interest of the automotive industry. Nevertheless, storage conditions can affect its properties and performance. In this work, both NMC811 powder and electrodes were storage-aged for one year under room conditions. The aged powder was used to prepare electrodes, and the performance of these two aged samples was compared with reference fresh NMC811 electrodes in full Li-ion coin cells using graphite as a negative electrode. The cells were subjected to electrochemical as well as ante- and postmortem characterization. The performance of the electrodes from aged NM811 was beyond expectations: the cycling performance was high, and the power capability was the highest among the samples analyzed. Materials characterization revealed modifications in the crystal structure and the surface layer of the NMC811 during the storage and electrode processing steps. Differences between aged and fresh electrodes were explained by the formation of a resistive layer at the surface of the former. However, the ageing of NMC811 powder was significantly mitigated during the electrode processing step. These novel results are of interest to cell manufacturers for the widespread implementation of NMC811 as a state-of-the-art cathode material in Li-ion batteries. [ABSTRACT FROM AUTHOR]

• Graphite was deposited in bi-layered configuration with different porosities. • Bi-layered electrodes were compared vs. regular coatings in half and full coin cells. • The layered structure affects the capacity retention and response to high currents. Lithium-ion batteries have been implemented worldwide in portable devices. Furthermore, they are strong candidates to facilitate the upcoming revolution associated with the electrification of vehicles. Nowadays, these cells are based on transition metal oxides in the positive electrode and graphite in the negative electrode. Despite focusing many efforts on developing novel materials for enhancing the performance of lithium-based batteries, there is still room for improvement by working on the electrode characteristics with widely industry-implemented and trustable state-of-the-art materials. In this work, we developed and characterized graphite electrodes with bi-layered structure consisting of two layers with different porosity. These electrodes were tested both in half and full coin cell configuration, the latter using LiNi 0.6 Mn 0.2 Co 0.2 O 2 as the positive electrode. Regular single-layer graphite electrodes with the same average porosity and loading were also elaborated and tested for comparison. Galvanostatic cycling, power tests and impedance spectroscopy were combined with post-mortem characterization to understand the influence of the multi-layer structure onto the electrochemical response. Results show that the bi-layered structure provides enhanced capacity retention during the beginning of life of cells. However, this advantage is lost when the repeated lithiation-delithiation cycles of graphite affect the pore size of the lower porosity layer. In any case, it is evidenced that by modulating the coating method and therefore the macroscopic properties of graphite, it is possible to have a significant impact on its electrochemical characteristics. This should be of high interest for battery manufacturers facing the uncertainties associated with the processing and implementation of novel materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Modified Box-Behnken L15 matrix used to define the experimental space. • Selected experimental outputs divided on two groups: feasibility and performance. • Mono- and multi-variant analysis of six experimental outputs performed. • Derringer-Suich's desirability functions applied to find the optimum. The battery R&D process should be accelerated towards a faster transition to a greener economy. However, typical battery electrode/electrolyte optimization process is still based on heuristic trial-and-error methodology, which is simple and robust but requires multiple attempts and, as a result, is high resource-time consuming. Therefore, a holistic algorithm for the optimization of a four-component (graphite, carbon black, thickener and binder) waterborne negative electrode formulation for lithium-ion batteries is proposed to improve efficiency, spend fewer resources, and speed-up the whole process. Briefly, the experimental space of possible electrode formulations is defined using a modified Box-Behnken cube matrix L15. Each inactive component's pre-selected range of content is divided into three symmetric levels. Fifteen slurries-electrodes are prepared and comprehensively studied by different experimental methods to obtain six preliminarily selected experimental outputs divided into two groups: feasibility (slurry rheology and electrode peel resistance) and electrochemical performance in half coin cells (initial coulombic efficiency and discharge capacity under 2D discharge C-rate) and full coin cells (inverse capacity degradation slope under 2C/2D cycling protocol and inverse internal cell resistance). Finally, a multi-variant analysis of the obtained experimental data array coupled with Derringer-Suich desirability functions specially defined for each experimental output are applied to find out an optimal negative electrode formulation with the best combination of the feasibility and electrochemical performance. [ABSTRACT FROM AUTHOR]