## 2 Materials and Methods
### High-Resolution Neutron Diffraction and In-Situ XRD of the Electrode Powders  
Ex-situ high-resolution neutron powder diffraction experiments were performed at the Frank Laboratory of Neutron Physics of the Joint Institute for Nuclear Research (Dubna, Russia) using a high-resolution Fourier diffractometer (HRFD) realized at the IBR-2 pulsed reactor, as described in [57; 58]. HRDF is a time-of-flight (TOF) diffractometer with a fast Fourier chopper, which allows one to measure diffraction patterns with d-spacing resolution \(\Delta\)d/d \(\approx\) 0.0015 at d = 2 A. The NPD TOF patterns for the NCNCO01, NCNCO03, and NCNCO04 samples were collected for 2 h at 50 \({}^{\circ}\)C under the following conditions:  
1. as-synthesized samples, in static air;
2. samples after heating in static air to 500 \({}^{\circ}\)C, annealing at this temperature for 2 h and cooling down to 50 \({}^{\circ}\)C with a heating/cooling rate of 300 \({}^{\circ}\)C h\({}^{-1}\), in static air;
3. samples after (2), in a vacuum (10\({}^{-6}\) bar);
4. samples after heating in a vacuum to 500 \({}^{\circ}\)C, annealing at this temperature for 2 h, heating to 800 \({}^{\circ}\)C annealing for 2 h, and cooling down to 50 \({}^{\circ}\)C, with a heating/cooling rate of 300 \({}^{\circ}\)C h\({}^{-1}\).  
The NCNCO00-NCNCO02 samples were studied by an in-situ synchrotron XRD (SXRD) at a High Precision Diffractometry II station at the synchrotron radiation facility of the VEPP-3 storage ring (Siberian Synchrotron and Terahertz Radiation Centre, Novosibirsk, Russia) [59]. The station diffractometer was equipped with a position-sensitive parallax-free linear OD-3M detector [60] with a working range of approximately 30\({}^{\circ}\) and a 20 resolution of approximately 0.01\({}^{\circ}\). The exposure time was 60 s per frame. The radiation wavelength of 0.10102 nm was established using a flat Si (220) crystal. The radiation wavelength of 0.16405 nm was set by a single reflection of the incoming white synchrotron radiation beam from a Ge (111) crystal. Samples were heated/cooled at a rate of 600 \({}^{\circ}\)C h\({}^{-1}\) first in a synthetic air flow (20 vol.% O\({}_{2}\)/80 vol.% He) and then in the He flow in the temperature range of 30-700 \({}^{\circ}\)C using an XRK 900 reactor chamber (Anton Paar, Graz, Austria). The rate of the gas flow was 100 SCCM.  
The NCNCO03 and NCNCO04 samples were studied by an insitu XRD using a Bruker D8 Advance diffractometer (Karlsruhe, Germany) equipped with a Lynneye linear detector. The diffraction patterns were obtained in a 0/20 configuration using Ni-filtered CuK\(\alpha\) radiation (\(\lambda\) = 0.15418 nm). Diffraction patterns during stepwise heating/cooling in the temperature range of 30-700 \({}^{\circ}\)C (every 100 \({}^{\circ}\)C after temperature 100 \({}^{\circ}\)C, a heating/cooling rate of 600 \({}^{\circ}\)C h\({}^{-1}\)) were collected in a 26 range of 53-60\({}^{\circ}\) with a step of 0.02\({}^{\circ}\) and a counting time of 3 s at each point using an XRK 900 reactor chamber, first, in static air, and then, in a 100 SCCM He flow. The phases were identified using a powder diffraction database, PDF-4+. The unit cell parameters were determined using a GSAS-II software package [61].