Adding 10 mM KPF6 to the 1 M LiPF6 in ethylene carbonate/dimethyl carbonate electrolyte of symmetrical Li | Li cells eliminated the growth of dendrites at 0.5 mA cm–2 current density and massively reduced, but did not eliminate, the growth of dendrites at 2.5 mA cm–2. The added KPF6 increased the fraction of inorganic salts in the solid electrolyte interface, making it thinner and more Li+ conductive. It overcame the growth of dendrites resulting from inadequate nucleation density but not dendrite growth into the depletion layer, which scales with the layer’s thickness, i.e., the current density.

Lead has been studied as a potential anode material in lithium-ion batteries. [1][2][3][4][5][6][7][8][9][10][11][12][13] Wang et al. chemically synthesized a series of Li-Pb alloys and measured the equilibrium electrochemical potentials of electrodes made thereof, proposing the intermediates shown in Eqs. 1-4 with a corresponding fully-lithiated phase of Li 4.5 Pb.14 However, Goward et al. reported In the present study, the various Li-Pb phases were synthesized by dynamic electrochemical lithiation of pure Pb in 1M LiPF 6 in 1:1 fluoroethylene carbonate (FEC)/diethyl carbonate (DEC, 1:1 w/w) at room temperature. The compositions of the Li-Pb phases were determined by ex situ XRD measurement and compared to the coulometric data. Notably, the most lithium-rich compound of the phase diagram, Li 17 Pb 4 , was not reached during dynamic electrochemical lithiation. A similar discovery was made about the lithiation of silicon, which had historically been thought to have a final lithiation phase of Li 22 Si 5 but was later found to only have an electrochemically-reachable phase of Li 15 Si 4 . 19 ExperimentalLead electrodes were prepared by mixing 83% of -100 mesh Pb powder (Alfa Aesar), 7% of polyacrylonitrile (Sigma Aldrich, 150 kDa) binder, and 10% of Super P Li conductive carbon (Timcal) with enough dimethylformamide to form a viscous slurry, which was coated onto copper foil and dried in a vacuum oven at 120• C for at least 6 h. The resulting composite film was punched into disks that formed the working electrodes of CR 2032 coin-type cells. Each electrode had an average Pb mass loading of 2.4-2.6 mg cm −2 . Prior to assembly into coin cells, each electrode was soaked in a 1 wt% aqueous solution of disodium ethylenediaminetetraacetic acid (EDTA) for approximately * Electrochemical Society Fellow. * * Electrochemical Society Member. z E-mail: mullins@che.utexas.edu five minutes to remove any surface oxide. The electrodes were then rinsed with deionized water and ethanol and immediately transferred into an argon-filled glove box to prevent re-oxidation. Cells were assembled with Li foil as the counter/reference electrode and Celgard 2400 polypropylene membrane as the separator. A solution of 1M LiPF 6 in fluoroethylene carbonate (Solvay Fluor)/diethyl carbonate (1:1 w/w) was used as the electrolyte. Electrochemical measurements were performed on an Arbin BT 2143 multichannel battery testing system. For the ex situ XRD, electrodes were discharged or charged to a particular potential vs. Li/Li + in a series of coin cells. Open circuit potentials were measured after allowing cells to relax for 48 h. Each coin cell was opened in the glove box, and the electrode was extracted and rinsed lightly with DEC to remove any residual LiPF 6 salt. The electrode was taped to a glass slide using air-and humidity-impermeable Kapton tape, and its XRD spectrum was measured using a Rigaku MiniFlex 600 diffractometer with a Cu Kα radiation source at 40 kV and 15 mA. To correct for height errors introduced by securing the electrode to ...

Because lead telluride (PbTe) was found to rapidly and reversibly lithiate to form Li + -conductive Li 2 Te and a series of Li-Pb alloys, we explored the reversibility and rate of lithiation of PbSe. As expected, PbSe was also reversibly lithiated to Li 2 Se and Li-Pb alloys, but the electrode was less stable and could not be cycled as rapidly. When the electrode was cycled at a slow rate, an electroactive polymer gel film derived of the 1 M LiPF 6 in 1:1 fluoroethylene carbonate/diethyl carbonate (w/w) electrolyte built up in the initial 25 cycles. Electroreduction and electrooxidation of this film added to the capacity by as much as 300 mAh g −1 above its theoretical value.