Supporting Data: Structure–Electrochemistry Correlation in LiMO 2 Cathode Materials (M = Co, Ni)
Description
This dataset collects the numerical data underlying the manuscript for three layered oxide cathodes, LiCoO 2 (LCO), LiNiO 2 (LNO) and LiNi0.5Co0.5(LNCO), prepared by an aqueous sol-gel route with citric acid. It covers synthesis conditions, instrument settings, Rietveld structural parameters, BET surface areas and particle sizes, half-cell electrochemistry (rate and 100-cycle tests), in situ XRD lattice-parameter evolution during first charge, and on-line electrochemical mass spectrometry (OEMS) gas-evolution events. All values are as reported in the manuscript; section 8 lists the raw-data files that correspond to each figure.
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Steps to reproduce
1. Sol-gel precursor preparation Dissolve Li(CH₃COO) and the metal acetate (Co(CH₃COO)₂·4H₂O for LiCoO₂, Ni(CH₃COO)₂·4H₂O for LiNiO₂, or a 1:1 Ni:Co mixture for LiNi₀.₅Co₀.₅O₂) in deionized water at 0.25 mol L⁻¹. Use Li:M = 1.2:1 (Li:Ni:Co = 1.2:0.5:0.5 for the mixed compound). Add citric acid in a 1:1 molar ratio to the transition metal as chelating agent. Adjust the pH to 6 with NH₄OH (1 M). Stir at 80 °C until a gel forms, then dry the gel. 2. Calcination - LiCoO₂: static synthetic air, 1 K min⁻¹ to 400 °C (1 h), then 5 K min⁻¹ to 700 °C (6 h). - LiNiO₂: pre-calcine in synthetic air at 600 °C for 6 h, grind, then calcine in pure O₂ at 800 °C for 13 h. - LiNi₀.₅Co₀.₅O₂: same heat treatment as LiNiO₂ (O₂, 800 °C). 3. Characterization - SEM: JEOL JCM-6000, 10–15 kV. - BET: N₂ adsorption at 77 K (Quantachrome Autosorb iQ). - TGA/MS: Mettler Toledo TGA/DSC1 STARe with Pfeiffer Vacuum MS, 10 K min⁻¹, synthetic air. - XRD: STOE STADI P, Mo Kα₁ (λ = 0.70932 Å), Debye-Scherrer geometry. Refine with FullProf in space group R-3m, including Li/Ni site exchange for LiNiO₂. 4. Electrode and cell preparation Coat electrodes on Al foil (active material : PVdF : Super C65 = 92:4:4 or 80:10:10 wt%). Dry at 120 °C overnight under vacuum and punch 10 mm discs. Assemble Swagelok T-cells in an Ar glovebox with LP57 electrolyte and a Li metal counter electrode. 5. Electrochemical testing Cycle at 25 °C between 2.5 and 4.2 V. Run C-rate tests from C/10 to 2C and a 100-cycle lifetime test at C/2. Report the mean and standard deviation of 3 cells. 6. In situ XRD Use pouch cells in transmission mode on the STOE STADI P. Charge at C/20 or C/10 and collect one pattern every 42 min (to 4.8 V for LiCoO₂, 5.2 V for LiNiO₂, 5.0 V for LiNi₀.₅Co₀.₅O₂). Refine lattice parameters (a, c, c/a) from each pattern. 7. OEMS Use a custom two-compartment cell with a Pfeiffer Vacuum QMA 410 mass spectrometer, sampling the headspace at 1 µL min⁻¹. Charge at C/10 to 4.8 V. Monitor m/z 2 (H₂), 18 (H₂O), 28 (CO), 32 (O₂) and 44 (CO₂), and normalize all signals to m/z 36 (Ar).
Institutions
- Indian Institute of Science Education and Research KolkataWest Bengal, Kolkata