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Li et al. J. Mater. Inf. 2025, 5, 21 https://dx.doi.org/10.20517/jmi.2024.87 Page 7 of 15

Table 1. 13 most promising K-/P-containing compounds after GT and BVSE analysis
2
Formula ICSD code Space group Migration map (GT/BVSE) E m σ (S·cm ) D (cm ·s ) C (mAh/g) E (eV)
-1
-1
g
g
K AuP 300201 Cmcm 3/3 0.45 7.01 × 10 -9 6.29 × 10 -14 175.12 0.95
2
-9 -14
K CuP 61082 Cmcm 3/3 0.68 1.38 × 10 1.18 × 10 310.41 1.14
2
-9 -14
K Cu P 12163 R3m 3/3 0.73 2.47 × 10 1.89 × 10 217.42 1.29
3 2
3
KMnP 89593 P4/nmm 2/2 0.45 2.34 × 10 -11 5.25 × 10 -16 214.43 0
-16 -21
K CdP 61084 C2/m 3/2 0.32 2.77 × 10 2.81 × 10 324.18 0.82
4 2
-3 -8 *
K InP 2 300141 Ibam 3/3 0.48 1.06 × 10 1.08 × 10 SE 0.79
3
K AlP 2 300130 P1 3/3 0.58 1.01 × 10 -5 6.61 × 10 -11 SE 0.70
3
-6 -11
K InP 300147 P1 3/3 0.40 4.50 × 10 3.41 × 10 SE 0.75
6 3
K P 25550 P6 /mmc 3/3 0.21 1.24 × 10 -6 9.67 × 10 -12 SE 0.21
3
3
-7 -12
K P 64625 Cmcm 3/3 0.77 7.33 × 10 6.18 × 10 SE 0
4 3
-8 -13
KP 14010 P2 2 2 3/3 0.39 3.01 × 10 2.72 × 10 SE 1.03
1 1 1
K BeP 2 300110 R3m 3/3 0.57 7.63 × 10 -8 6.04 × 10 -13 SE 1.14
4
-8 -13
K BP 300104 C2/c 3/3 0.87 3.89 × 10 3.67 × 10 SE 1.67
3 2
*
Potential base for solid electrolytes. GT: Geometrical-topological; BVSE: bond valence site energy.

Figure 3. Crystal structures of K CdP , illustrating the 3D potassium ionic migration map (left) from the GT approach and the 2D
4
2
migration map (right) derived from BVSE calculations. The relevant regions of the migration maps are highlighted in green. The
+
2+
elementary channels that are inaccessible to K migration due to surrounding Cd cations are highlighted in red. 3D: Three-dimensional;
GT: geometrical-topological; 2D: two-dimensional; BVSE: bond valence site energy.
typically lead to a wider band gap due to their smaller atomic radii and higher electronegativities, which
influence orbital overlap and the overall electronic structure. K InP belongs to the topological type 4 ,8T23,
3
3
2
3+
+
3-
where 4-coordinated cations (K and In ) are connected to 8-coordinated P anions. According to the
[78]
[79]
[78]
[77]
TopCryst system , five other compounds - Na AlP , Na AlAs , Ln NCl (Ln = La, Ce, Pr) - share the
2
2
3
3
3
2
same topological type and space group (Ibam). Notably, Na AlP demonstrates the potential for
3
2
3+
incorporating Al atoms into the phosphide framework of this structural motif. Na AlP shares the same
2
3
structural framework and symmetry as K InP ; it possesses a wider band gap (approximately 1.35 eV), which
2
3
is a key factor in its potential use for incorporating Al into the In sites of K InP , forming K In Al P with
1-x
x 2
3
3
2
an expanded band gap. This approach aligns with our goal of improving the material’s performance while
avoiding the redox issues observed in K InP .
3
2