Improved Mechanistic Degradation Modes Modeling of Lithium and Sodium Plating

Lithium and Sodium plating are inevitable when using negative electrodes with an electrochemical potential close to the one of the charge carrier. Typical testing and modeling usually assumed that plating occurs at 0V when measured against the charge carrier. While this might be true under thermodynamic equilibrium, this is not true outside of steady state. This has significant implications as, by taking this into account, the testing voltage window of negative electrodes could be extended to allow gathering data for more complete discharges at higher rates. Moreover, from a modeling standpoint, it could also allow to more accurately predict plating initiation potentials dynamically. This work presents preliminary results on the investigation of what parameters are influencing the plating potential and how to take them into account in testing and modeling

Aqueous solution discharge of cylindrical lithium-ion cells

The development of mass-market electric vehicles (EVs) using lithium-ion batteries (LIBs) is helping to propel growth in LIB usage, but end-of-life strategies for LIBs are not well developed. An important aspect of waste LIB processing is the stabilisation of such high energy-density devices, and energy discharge is an obvious way to achieve this. Salt-water electrochemical discharge is often mentioned as the initial step in many LIB recycling studies, but the details of the process itself have not often been mentioned. This study presents systematic discharge characteristics of different saline and basic solutions using identical, fully charged LIB cells. A total of 26 different ionic solutes with sodium (Na+), potassium (K+), and ammonium (NH4+) cations have been tested here using a fixed weight percentage concentration. An evaluation of possible reactions has also been carried out here. The results show good discharge for many of the salts, without significant damaging visual corrosion. The halide salts (Cl−, Br−, and I−) show rapid corrosion of the positive terminal, as does sodium thiosulphate (Na2S2O3), and the solution penetrates the cell can. Mildly acidic solutions do not appear to cause significant damage to the cell can. The most alkaline solutions (NaOH and K3PO4) appear to penetrate the cell without any clear visual damage at the terminals. Depending on what is desired by the discharge (i.e. complete cell destruction and stabilisation or potential re-use or materials recovery), discharge of individual Li-ion cells using aqueous solutions holds clear promise for scaled-up and safe industrial processes

The effect of copper doping in α-MnO2 as cathode material for aqueous Zinc-ion batteries

Copper-doped Manganese Dioxide has been synthesised through a simple hydrothermal method at different doping levels. The synthesised materials have been characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM) to determine the composition, structure, and morphology. All the Cu doped MnO2 are found to be single phased. Their electrochemical properties as cathode for Zinc-ion batteries are studied by cyclic voltammetry (CV), galvano-static charge / discharge (GCD) and electrochemical impedance spectroscopy (EIS), using 3 M ZnSO4 + 0.3 MnSO4 solution as the electrolyte. 3.8% Cu doped MnO2 has shown the highest initial capacity of 379.5 mAh g−1 at 0.02 A·g−1, and 304.4 mA h g−1 at 0.5 A g−1, but experienced fast fading with a poor capacity retention of 56.8% after 100 cycles. 7.4% Cu doping gives lower capacity, while 5.9% doping shows a higher discharging capacity (320.0 mAh·g−1 at 0.02 A·g−1 and 269.3 mAh·g−1 at 0.5 A·g−1) and improved stability (85.8% capacity retention after 100 cycles), better than non-doped MnO2 electrode (284.4 mAh g−1 at 0.02 A g−1 and 252.1 mAh·g−1 at 0.5 A g−1, capacity retention 76.7%). The samples show satisfactory capacity and rate capability while the cycling stability is not ideal, which may relate to the needle like morphology and nanoscale particle size. CV tests revealed that the electrochemical process is mainly diffusion controlled. The zinc ion diffusion coefficient is tested to be in the range of 10−12 cm2·s−1 from both CV and EIS tests and showed the same trend in their electrochemical capacity. Doping of Copper in MnO2 reduced the polarization on electrode, improved the electrochemical reversibility, as evidenced by the reduction of the redox peak potential difference from 0.31 to 0.24 V at 1.1 mV·s−1, and from 0.45 V to 0.31 V at 5 mV·s−1. Whilst the cell resistance of non-doped MnO2 increased from 1.78 Ω to 7.39 Ω after cycling, the cell resistances of all Cu-doped cathodes reduced, indicating improved electronic conductivities after cycling. These results indicate that Cu-doping is effective to increase the conductivity of the materials, reduce the polarization during charge and discharge, and improve the cycling stability of MnO2 cathode