Abstract
AbstractThis work reveals the impact of particle size distribution of spherical graphite active material on negative electrodes in lithium‐ion batteries. Basically all important performance parameters, i. e. charge/discharge characteristics, capacity, coulombic and energy efficiencies, cycling stability and C‐rate capability are shown to be affected by distribution shapes. A narrow distribution with smaller particles results in better cell performance than broader and coarser distributions. However, particle size reduction has a limitation as extremely small particles show negative effect in performance. More critically, independent of the particle size distribution, the existence of coarse particles are found to promote lithium plating, which lowers cell performance and threatens the safety of battery operation. Furthermore, impedance analysis and cycling stability show huge differences for different electrodes. Our study shows that a better understanding of the influence of particle size distribution is an important base to engineer electrodes with higher C‐rate capability, higher performance, and lower safety risk due to lithium plating.
Highlights
Introduction active materialFor silicon as anode material, ball milling delivers one of the most promising outcomes in terms of economic aspect as well as performance.[4,5,6,7,8] It is shown that through ball milling structures with micrometric silicon agglomerates can be attained
The performance differences between particle size and particle size distribution (PSD) are evaluated in terms of their coulombic and energy efficiencies
This behavior is expected as higher currents reveal kinetic losses such as concentration overpotentials which are strongly dependent on surface areas and diffusion lengths: The narrow medium PSD (F2) showed the highest capacity during the C-rate and cycling test with a very low standard deviation
Summary
We will first analyse the impact of particle sizes and PSD on discharge capacity. The kinetic contributions in F3 as well as in source material suggest an improvement in kinetics A broader PSD is experienced to lead to faster degradation of cycling behavior, and significantly reduces the performance of cells, because it contains the aging effects from both small and coarse particles: The small particle size causes strong SEI growth during formation and the coarse particle size results in high kinetic and capacity loss as well as lithium plating. We recommend that the particle size and the PSD must be considered for experimental or model-based optimization
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