Extended Data Fig. 2: Galvanostatic cycling at 2C of LCO in an optical cell and in a coin cell.

a, Specific capacity plots for 5 cycles of LCO electrodes in the optical cell (blue trace, as shown in Fig. 1b, c) and in a coin cell (grey trace), each cycled at a rate of 2C from 3.0 V to 4.2 V. b, Corresponding differential capacity plots. The positive absolute value of dQ/dV is displayed for delithiation, and the negative absolute value is displayed for lithiation. Peaks attributed to the biphasic transitions (I and IV) and lithium ordering (II and III) are indicated. Both cells were cycled about 20 times at 2C before obtaining the displayed data. The sets of results are in good agreement with each other and with previous reports¹⁶ for LCO. The slightly higher overpotentials and lower capacity seen in the optical cell compared to the coin cell were probably caused by a higher internal resistance in the optical cell, perhaps due to the lower stack pressure.