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In situ synchrotron powder X-ray diffraction (PXRD) is used to study the formation of LiFePO4 nanoparticles during hydrothermal synthesis from LiOH, H3PO4, and two different iron precursors, FeSO4 and (NH4)2Fe(SO4)2. Furthermore, the synthesis of Li(Fe1-xMnx)PO4 (x = 0.25, 0.50 and 0.75) from LiOH, H3PO4 and FeSO4/MnSO4 is studied. The reactions involve an unknown intermediate phase, which is not the previously observed intermediate NH4FePO4·H2O. The intermediate phase quickly transforms into LiFePO4 and Li(Fe1-xMnx)PO4 even at rather low temperatures. The presence of ammonium enhances the formation of LiFePO4, and it also leads to a significant reduction in the concentration of Li-Fe antisite defects. The in situ PXRD technique allows one to follow the influence of time, temperature and manganese doping on the antisite defect concentration, and it is shown that even under supercritical conditions a reaction time of several minutes is required to suppress the defects. This makes flow synthesis of defect-free LiFePO4 and Li(Fe1-xMnx)PO4 nanoparticles challenging.
Supporting information
For all compounds, program(s) used to refine structure: FULLPROF.
Crystal data top
? | c = 4.7325 (2) Å |
Mr = ? | V = 297.91 (2) Å3 |
Orthorhombic, Pnma | Z = ? |
Hall symbol: -P 2ac 2n | ? radiation, λ = 0.998140 Å |
a = 10.4008 (4) Å | ?, ? × ? × ? mm |
b = 6.0523 (2) Å | |
Data collection top
Radiation source: Synchrotron | 2θmin = 3.204°, 2θmax = 41.754°, 2θstep = 0.035° |
Refinement top
Rp = 0.384 | 1096 data points |
Rwp = 0.620 | 41 parameters |
Rexp = 0.179 | 0 restraints |
RBragg = 4.198 | |
χ2 = NOT FOUND | |
Crystal data top
? | c = 4.7325 (2) Å |
Mr = ? | V = 297.91 (2) Å3 |
Orthorhombic, Pnma | Z = ? |
a = 10.4008 (4) Å | ? radiation, λ = 0.998140 Å |
b = 6.0523 (2) Å | ?, ? × ? × ? mm |
Data collection top
2θmin = 3.204°, 2θmax = 41.754°, 2θstep = 0.035° | |
Refinement top
Rp = 0.384 | χ2 = NOT FOUND |
Rwp = 0.620 | 1096 data points |
Rexp = 0.179 | 41 parameters |
RBragg = 4.198 | 0 restraints |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
Li1 | 0.00000 | 0.00000 | 0.00000 | 0.00000* | 0.996 (4) |
Fe1 | 0.2822 (3) | 0.25000 | 0.9769 (11) | 0.00000* | 0.996 (4) |
P1 | 0.0991 (8) | 0.25000 | 0.416 (2) | 0.00000* | |
O1 | 0.094 (2) | 0.25000 | 0.726 (4) | 0.00000* | |
O2 | 0.458 (2) | 0.25000 | 0.207 (2) | 0.00000* | |
O3 | 0.1638 (13) | 0.046 (2) | 0.2807 (17) | 0.00000* | |
Fe2 | 0.00000 | 0.00000 | 0.00000 | 0.00000* | 0.010 (4) |
Li2 | 0.2822 (3) | 0.25000 | 0.9769 (11) | 0.00000* | 0.010 (4) |
Crystal data top
? | c = 4.72107 (7) Å |
Mr = ? | V = 295.93 (1) Å3 |
Orthorhombic, Pnma | Z = ? |
Hall symbol: -P 2ac 2n | ? radiation, λ = 0.944490 Å |
a = 10.37894 (15) Å | ?, ? × ? × ? mm |
b = 6.03945 (9) Å | |
Data collection top
Radiation source: Synchrotron | 2θmin = 3.628°, 2θmax = 43.965°, 2θstep = 0.037° |
Refinement top
Rp = 0.312 | 1081 data points |
Rwp = 0.373 | 44 parameters |
Rexp = 0.004 | 0 restraints |
RBragg = 1.441 | |
χ2 = NOT FOUND | |
Crystal data top
? | c = 4.72107 (7) Å |
Mr = ? | V = 295.93 (1) Å3 |
Orthorhombic, Pnma | Z = ? |
a = 10.37894 (15) Å | ? radiation, λ = 0.944490 Å |
b = 6.03945 (9) Å | ?, ? × ? × ? mm |
Data collection top
2θmin = 3.628°, 2θmax = 43.965°, 2θstep = 0.037° | |
Refinement top
Rp = 0.312 | χ2 = NOT FOUND |
Rwp = 0.373 | 1081 data points |
Rexp = 0.004 | 44 parameters |
RBragg = 1.441 | 0 restraints |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
Li1 | 0.00000 | 0.00000 | 0.00000 | 0.00000* | 1.0000 (17) |
Fe1 | 0.28314 (11) | 0.25000 | 0.9735 (4) | 0.00000* | 0.4981 (17) |
Li2 | 0.28314 (11) | 0.25000 | 0.9735 (4) | 0.00000* | 0.0038 (17) |
0.0000 | 0.0968 (3) | 0.25000 | 0.4151 (5) | 0.00000* | |
O1 | 0.0947 (6) | 0.25000 | 0.7343 (10) | 0.00000* | |
O2 | 0.4551 (7) | 0.25000 | 0.2079 (9) | 0.00000* | |
O3 | 0.1660 (5) | 0.0496 (8) | 0.2829 (6) | 0.00000* | |
Fe | 0.00000 | 0.00000 | 0.00000 | 0.00000* | 0.0038 (17) |
Mn | 0.28314 (11) | 0.25000 | 0.9735 (4) | 0.00000* | 0.50193 |
Crystal data top
? | c = 4.73357 (13) Å |
Mr = ? | V = 298.63 (1) Å3 |
Orthorhombic, Pnma | Z = ? |
Hall symbol: -P 2ac 2n | ? radiation, λ = 0.944490 Å |
a = 10.4072 (3) Å | ?, ? × ? × ? mm |
b = 6.06188 (14) Å | |
Data collection top
Radiation source: Synchrotron | 2θmin = 3.442°, 2θmax = 43.966°, 2θstep = 0.037° |
Refinement top
Rp = 0.414 | 1086 data points |
Rwp = 0.610 | 48 parameters |
Rexp = 0.333 | 0 restraints |
RBragg = 3.948 | |
χ2 = NOT FOUND | |
Crystal data top
? | c = 4.73357 (13) Å |
Mr = ? | V = 298.63 (1) Å3 |
Orthorhombic, Pnma | Z = ? |
a = 10.4072 (3) Å | ? radiation, λ = 0.944490 Å |
b = 6.06188 (14) Å | ?, ? × ? × ? mm |
Data collection top
2θmin = 3.442°, 2θmax = 43.966°, 2θstep = 0.037° | |
Refinement top
Rp = 0.414 | χ2 = NOT FOUND |
Rwp = 0.610 | 1086 data points |
Rexp = 0.333 | 48 parameters |
RBragg = 3.948 | 0 restraints |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
Li1 | 0.00000 | 0.00000 | 0.00000 | 0.00000* | 0.999 (3) |
Fe1 | 0.2828 (2) | 0.25000 | 0.9705 (7) | 0.00000* | 0.497 (3) |
Mn1 | 0.2828 (2) | 0.25000 | 0.9705 (7) | 0.00000* | 0.50175 |
P1 | 0.0952 (6) | 0.25000 | 0.4169 (11) | 0.00000* | |
O1 | 0.0939 (13) | 0.25000 | 0.731 (2) | 0.00000* | |
O2 | 0.4495 (15) | 0.25000 | 0.2062 (14) | 0.00000* | |
O3 | 0.1604 (8) | 0.0537 (14) | 0.2778 (12) | 0.00000* | |
Fe2 | 0.00000 | 0.00000 | 0.00000 | 0.00000* | 0.004 (3) |
Li2 | 0.2828 (2) | 0.25000 | 0.9705 (7) | 0.00000* | 0.004 (3) |
Crystal data top
? | c = 4.74531 (18) Å |
Mr = ? | V = 300.97 (2) Å3 |
Orthorhombic, Pnma | Z = ? |
Hall symbol: -P 2ac 2n | ? radiation, λ = 0.944490 Å |
a = 10.4303 (3) Å | ?, ? × ? × ? mm |
b = 6.08084 (19) Å | |
Data collection top
Radiation source: Synchrotron | 2θmin = 3.444°, 2θmax = 43.968°, 2θstep = 0.037° |
Refinement top
Rp = 0.363 | 1086 data points |
Rwp = 0.489 | 46 parameters |
Rexp = 0.353 | 0 restraints |
RBragg = 3.567 | |
χ2 = NOT FOUND | |
Crystal data top
? | c = 4.74531 (18) Å |
Mr = ? | V = 300.97 (2) Å3 |
Orthorhombic, Pnma | Z = ? |
a = 10.4303 (3) Å | ? radiation, λ = 0.944490 Å |
b = 6.08084 (19) Å | ?, ? × ? × ? mm |
Data collection top
2θmin = 3.444°, 2θmax = 43.968°, 2θstep = 0.037° | |
Refinement top
Rp = 0.363 | χ2 = NOT FOUND |
Rwp = 0.489 | 1086 data points |
Rexp = 0.353 | 46 parameters |
RBragg = 3.567 | 0 restraints |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
Li1 | 0.00000 | 0.00000 | 0.00000 | 0.00000* | 1.000 (2) |
Fe1 | 0.28274 (17) | 0.25000 | 0.9712 (6) | 0.00000* | 0.244 (2) |
Mn1 | 0.28274 (17) | 0.25000 | 0.9712 (6) | 0.00000* | 0.75623 |
P1 | 0.0944 (5) | 0.25000 | 0.4155 (10) | 0.00000* | |
O1 | 0.0988 (11) | 0.25000 | 0.7297 (18) | 0.00000* | |
O2 | 0.4542 (12) | 0.25000 | 0.2048 (12) | 0.00000* | |
O3 | 0.1600 (7) | 0.0515 (12) | 0.2797 (10) | 0.00000* | |
Fe2 | 0.00000 | 0.00000 | 0.00000 | 0.00000* | 0.008 (2) |
Li2 | 0.28274 (17) | 0.25000 | 0.9712 (6) | 0.00000* | 0.008 (2) |
Experimental details
| (LiFePO4345) | (LiFe075Mn025PO4345) | (LiFe050Mn050PO4345) | (LiFe025Mn075PO4345) |
Crystal data |
Chemical formula | ? | ? | ? | ? |
Mr | ? | ? | ? | ? |
Crystal system, space group | Orthorhombic, Pnma | Orthorhombic, Pnma | Orthorhombic, Pnma | Orthorhombic, Pnma |
Temperature (K) | ? | ? | ? | ? |
a, b, c (Å) | 10.4008 (4), 6.0523 (2), 4.7325 (2) | 10.37894 (15), 6.03945 (9), 4.72107 (7) | 10.4072 (3), 6.06188 (14), 4.73357 (13) | 10.4303 (3), 6.08084 (19), 4.74531 (18) |
V (Å3) | 297.91 (2) | 295.93 (1) | 298.63 (1) | 300.97 (2) |
Z | ? | ? | ? | ? |
Radiation type | ?, λ = 0.998140 Å | ?, λ = 0.944490 Å | ?, λ = 0.944490 Å | ?, λ = 0.944490 Å |
Specimen shape, size (mm) | ?, ? × ? × ? | ?, ? × ? × ? | ?, ? × ? × ? | ?, ? × ? × ? |
|
Data collection |
Diffractometer | ? | ? | ? | ? |
Specimen mounting | ? | ? | ? | ? |
Data collection mode | ? | ? | ? | ? |
Scan method | ? | ? | ? | ? |
2θ values (°) | 2θmin = 3.204 2θmax = 41.754 2θstep = 0.035 | 2θmin = 3.628 2θmax = 43.965 2θstep = 0.037 | 2θmin = 3.442 2θmax = 43.966 2θstep = 0.037 | 2θmin = 3.444 2θmax = 43.968 2θstep = 0.037 |
|
Refinement |
R factors and goodness of fit | Rp = 0.384, Rwp = 0.620, Rexp = 0.179, RBragg = 4.198, χ2 = NOT FOUND | Rp = 0.312, Rwp = 0.373, Rexp = 0.004, RBragg = 1.441, χ2 = NOT FOUND | Rp = 0.414, Rwp = 0.610, Rexp = 0.333, RBragg = 3.948, χ2 = NOT FOUND | Rp = 0.363, Rwp = 0.489, Rexp = 0.353, RBragg = 3.567, χ2 = NOT FOUND |
No. of data points | 1096 | 1081 | 1086 | 1086 |
No. of parameters | 41 | 44 | 48 | 46 |
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