Formation and Inhibition of Metallic Lithium Microstructures in Lithium Batteries Driven by Chemical Crossover

Transcription

1 Supplementary Information Formation and Inhibition of Metallic Lithium Microstructures in Lithium Batteries Driven by Chemical Crossover Wangda Li, a Un-Hyuck Kim, b Andrei Dolocan, a Yang-Kook Sun, b,* and Arumugam Manthiram a,* Materials Science and Engineering Program and Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, USA. manth@austin.utexas.edu Department of Energy Engineering, Hanyang University, Seoul , Republic of Korea. yksun@hanyang.ac.kr 1

2 (b) (a) Fig. S1 Calibration of the Cs + sputtering rate on graphite electrodes (500 ev ion energy, ~ 40 na measured sample current): (a) Optical profilometry mapping of a Cs + -sputtered area ( µm 2 ) for 45 h on a pristine graphite composite electrode. (b) Vertical profiles of the optical map along the planes indicated in (a). The sputtering rate of the graphite electrode is estimated to be around 0.04 nm s -1. 2

3 Fig. S2 EPMA line scan of the integrated atomic ratio of transition metals acquired on the FCG LiNi 0.61 Co 0.12 Mn 0.27 O 2 (NCM) cathode as a function of distance from the particle center to the surface. 3

4 Fig. S3 TOF-SIMS depth profiles of (a) 58 NiF 3 - and (b) CoF 3 - collected on extensively cycled FCG-NCM cathodes in coin/pouch cells. 4

5 Fig. S4 TOF-SIMS spectra in positive polarity on pristine and extensively cycled graphite (undoped FCG-NCM) integrated over 200 s of O - 2 sputtering (5 s sampling step), showing the accumulating of transition-metal species (Mn, Ni, and Co) after cell operation. The two spectra are drawn to the same scale. 5

6 Fig. S5 TOF-SIMS depth profiles (normalized to maximum) of several secondary ions of interest collected on extensively cycled graphite electrodes after 3,000 cycles in pouch cells, paired with FCG-NCM: (a) positive and (b) negative modes. 6

7 Fig. S6 TOF-SIMS depth profiles (normalized to maximum) of several secondary ions of interest acquired on (a) Li metal in coin cells after 100 cycles and (b) graphite anodes in pouch cells after 3,000 cycles, paired with FCG-NCM. 7

8 Fig. S7 EPMA line scan of the integrated atomic ratio of transition metals acquired on the Al-doped FCG-NCM (LiNi 0.60 Co 0.12 Mn 0.27 Al 0.01 O 2 ) cathode from the particle center to the surface. 8

9 FCG 3,000 Cycles FCG-Al 3,000 Cycles 10 µm 10 µm Fig. S8 SEM images of extensively cycled (3,000 cycles in pouch cells) (a) undoped and (b) Al-doped (1 mol %) FCG-NCM electrodes. 9

10 Fig. S9 TOF-SIMS depth profiles of active mass dissolution products (MnF 3 -, 58 NiF 3 - and CoF 3 - ) collected on (a) undoped and (b) Al-doped FCG-NCM cathodes in pouch cells after 3,000 cycles. 10

11 Fig. S10 Electrochemical performance of undoped and Al-doped FCG-NCM cathode samples in coin-type half cells ( V, 30 o C): (a) initial charge-discharge profiles at a C/10 rate, and 30 o C, and (b) short-term cycling performance under C/2. 11

12 Fig. S11 Impacts of crossover transition-metal cations on Li deposition: TOF-SIMS depth profiles of a handful of secondary ions of interest acquired on 3,000-cycle graphite anodes paired with undoped FCG-NCM (left) and Al-doped FCG-NCM (right), representing deposited transition metal species from the cathodes (upper row), and plated lithium (lower row). Insets in the upper row are corresponding magnified regions at the initial stage of ion sputtering. 12

13 Fig. S12 Calculation of the thickness of plated Li on graphite during cycling (undoped FCG-NCM): (a) 200 cycles and (b) 3,000 cycles. The dashed line indicates the normalized intensity of 0.5. Based on Fig. 4, the separation between depth profiles of 7 LiO - and 7 Li - can be used to yield a rough estimate of the thickness of metallic Li deposits. Since Li metal readily reacts with the electrolyte, it is believed that a portion of the Li oxides/carbonates ( 7 LiO - ) originates from metallic Li ( reacted Li, estimated by the separation between C 2 HO - and 7 Li - depth profiles). In Table S3 and Fig. 6b, all values are based the separation between 7 LiO - and 7 Li - ( metallic Li only). 13

14 Fig. S13 Calculation of the thickness of plated Li on graphite during cycling (Al-doped FCG-NCM): (a) 200 cycles and (b) 3,000 cycles, using the similar method described in Fig. S7. 14

15 Table S1: The amount of crossed over transition-metal cations is estimated from combining the integrated yield of three representative fragments of interest (MnF - 3, 58 NiF - 3, and CoF - 3 ; sputtering time: 500 s; 5 s sampling time). Data were collected on multiple locations on two graphite anodes and this table summarizes those paired with undoped FCG-NCM. The unit is total counts. Cycle number ,000 # MnF 3-58 NiF 3 - CoF 3-1 4,750 3,828 1, ,040 4,658 2, ,634 4,828 2,139 Mean 12,160 σ 1, ,192 16,887 6, ,453 13,241 4, ,543 14,925 5,684 Mean 42,262 σ 4, ,358 24,276 10, ,491 24,153 9, ,074 23,242 10, ,428 19,714 9,782 Mean 85,670 σ 8,930 15

16 Table S2: (Continuing from Table S1) data for the graphite paired with Al-doped FCG- NCM are shown in this table. Cycle number ,000 # MnF 3-58 NiF 3 - CoF 3-1 3,021 3,201 1, ,764 3,348 1, ,365 3,205 1,526 Mean 8,096 σ ,397 3,694 1, ,398 4,998 2, ,895 3,258 1,473 Mean 11,614 σ 2, ,684 5,754 3, ,010 5,584 3, ,526 5,624 3,690 Mean 18,036 σ

17 Table S3: Estimated thickness (nm) for deposited metallic Li structures using the method depicted in Fig. S11 and S12 ( metallic lithium only). The sputtering rate is around 0.04 nm s -1 on the basis of standard sample calibration in Fig. S1. Data were collected on multiple locations on two graphite anodes and this table summarizes those paired with undoped FCG-NCM. Note that the unit is seconds for the raw data ( 7 Li - and 7 LiO - ) and nm for the calculated thickness ( Diff. ). Cycle number ,000 # 7 Li - 7 LiO - Diff Mean 24.1 σ , , , Mean 38.7 σ , , , , Mean 80.3 σ

18 Table S4: (Continuing from Table S3) data for the graphite paired with Al-doped FCG- NCM are shown in this table. Cycle number ,000 # 7 Li - 7 LiO - Diff Mean 3.69 σ Mean 7.71 σ , , Mean 17.9 σ