*2.2. Mixing Ratio Variation*

Beside the variation of the BP itself (with fixed mixing ratios of AM/CB/BP 70/20/ 10 wt%), the influence of different mixing ratios was systematically investigated. The goal of the variation was to improve the energy density of the positive electrode. Therefore, this variation aimed at finding an advantageous mixing ratio with maximized active material share while still maintaining the electrochemical performance (i.e., the electrical conductivity driven by the CB content). The investigated mixing rations are graphically summarized using a ternary plot visualization in Figure 6.

The following criteria were considered for the positive electrode coatings:


tally determined capacity of ~160 mAh·g−<sup>1</sup> of MnO2) and high-energy (<1C, here: <160 mA·g<sup>−</sup>1) applications.



**Figure 6.** Graphical scheme with the mixing ratios being tested using the ternary plot visualization. The black squares represent the seven different mixing ratios of Table 3.

In Figure 7, the results of the RCT are shown by plotting the specific capacities and energies for different current rates over the cycle number. Here, the specific values were calculated by dividing the absolute capacity values by the total mass loading of the electrode (AM, CB, and BP, instead of only considering the AM mass loading as for the binder polymer variation in Section 2.1). This calculation method was chosen to be able to identify the influences of the different mixing ratios of the electrode coatings on the resulting capacity and energy values, respectively.

The results of the RCT with the specific discharge capacities (see Figure 7a) show that a low polymer binder percentage of 3 wt% is possible in the electrode coating, still enabling a cycling with a discharge capacity of ~140 mAh·g−<sup>1</sup> @ 40 mA·g<sup>−</sup>1. Nevertheless, the CB share, especially, and its ratio to the BP share has a high influence on the current rate stability:


Therefore, a higher ratio of CB to BP improves the performance, as for the 75/20/05 mixture with a CB/BP ratio of 4 (20 wt% divided by 5 wt%) the performance for all current rates is significantly better compared to the 80/10/10 mixture with a CB/BP ratio of 1 (10 wt% divided by 10 wt%). For the other mixtures with ratio values between 1.5 to 3, the performances are located between the above-mentioned mixtures. The interpretation of the results by analysing the CB/BP ratio can be explained as the lower the CB/BP ratio, the lower the electrical conductivity of the electrode coating—resulting in a higher share of electrically isolating BP.

**Figure 7.** Specific discharge (DCH) capacity (**a**) and energy (**b**) with the efficiency values, respectively, for the investigated mixing ratios (the mixing ratios are given in the order AM/CB/BP and in wt%). The markers 1 and 2 show the efficiency values of the first cycle and after a change of the current rate, respectively, whereas they do not represent a typical efficiency value for the chosen current rate (see Supplementary Figure S9).

(**a**)

(**b**)

This observation leads to the differentiation of the interpretation of different CB shares depending on the application, i.e., high-power (HP) and high-energy (HE) applications.


The RCT showing the specific discharge energies (see Figure 7b) also considers the potential, in addition to the capacity value, which provides a better insight into the inner resistance of the battery cell during cycling (see the previous section and Supplementary Figure S11). Although basically showing the same characteristics of the results of the different mixing ratios as the capacity representation (regarding the order of the different electrode material compositions, see marker 1), slight differences of the capacity vs. energy level order of the different mixture ratios can be observed, especially for the last RCT step with 80 mA·g<sup>−</sup>1, herein for the PAN (aq) binder as an example. The differences of the order of capacity/energy plots can refer to the different potential plateau levels during cycling, which is only considered by the energy representation (see the equation in Supplementary Figure S5).

Basically, this type of energy representation is introduced as a useful and more application-oriented alternative to the established capacity representation. This applies, in particular, to the aqueous battery chemistries such as the ARZIB technology with significant distinctions in the potential plateaus as a consequence of various cell constructions, as the literature shows.

Finally, it must be noted that the results were generated with the aqueous PAN-based *LA133* binder. For other binder polymers, the results could differ. Still, the characteristics of the variation of the mixing ratio of the electrode components should stay comparable.
