The significance of powder resistance

The rate performance of lithium-ion batteries is closely related to the battery resistance. The battery resistance includes ionic resistance and electronic resistance. The ionic resistance mainly refers to the resistance of lithium ions in the electrolyte in the electrode pores, the resistance of lithium ions through the SEI membrane, and the resistance of lithium ions and electrons. The charge transfer resistance of the active material/SEI film interface and the solid phase diffusion resistance of lithium ions inside the active material. The electronic resistance mainly refers to the resistance of the positive and negative active materials, the current collector resistance, the contact resistance between the active materials, and the contact resistance between the active material and the current collector. And the welding resistance of tabs. In the actual battery development and producti on process, the ionic resistance part needs to be evaluated at the finished battery end, and the electronic resistance part can be quickly evaluated at the material and pole piece end. Therefore, the accurate evaluation of the material and the electrode elect-ronic resistance is important for the battery. The resistance estimation is of great significance.

Measurement system analyze

Test condition: 5 samples, 3 operators, 3 times/pcs/operator

♦ Compact density : GRR-Excellent

♦ Powder Resistance : GRR-Excellent

Applications

Application cases

1.LCO material assessment (evaluation of electrical properties of modified powder(LCO))

Parameter: 10-200MPa, 5MPa steps, keep 15s

Results: When the Compact density of the modified powder is greater than 3.87g/cm3 (applied pressure > 75MPa), the conductivity of the modified powder is greatly improved.

The effectiveness of the modification can be evaluated.

2.NCM material assessment (relation of powder resistivity and electrode: NCM material)

Results Analyze

By adjusting the Ni content in the ternary material, the powder conductivity increases with the increase of Ni content.

Compared with three kinds of ternary electrodes with different Ni content, the conductivity of the electrode increases with the increasing of Ni content;

Powder resistivity and electrode have the same trend !

3.NCMA material assessment (relation of powder resistivity and electrode: NCMA material)

Results Analyze

The conductivity trend of the Quaternary powder and electrode under three different modification conditions is NCMAT > NCMA-2 > NCMA-3 ;

The conductivity of NCMA43 in powder state is much smaller than that of the former two samples, but there is a small difference in the electrode plate, which may be related to the addition of conductive in the electrode plate, which reduces the difference between the powder.

Powder resistivity and electrode have the same trend !

4.LFP material assessment (relation of powder resistivity and electrode: LFP material)

Results Analyze

Compared with the LFP powder and electrode sheet under four different modification conditions, the conductivity trend of LFP powder and electrode sheet is as follows

LFP-1>LFP-2>LFP-3>LFP-4

Powder resistivity and electrode have the same trend!

5.Graphite material assessment (compact density: parallel test 5 times)

Parameter: 20~200MPa, 20MPa steps, keep 30s, relief 3MPa steps, keep 10s

Results Analyze

The cov of five parallel samples is less than 0.1% in the whole pressure range, which indicates that the equipment has good repeatability.

With the increase of pressure, the Compact density of graphite material increases gradually and tends to be flat.

The rebound of powder thickness under pressure and pressure relief reaches the maximum value at 80MPa, which indicates that this condition is the maximum pressure that the powder can bear, and if it is too large, the material structure is likely to be damaged.

6.Carbon material assessment (compact density VS resistivity: parallel test 5 times)

Parameter: relief mode: 10~200MPa, 10MPa steps, keep 10s Results: The cov of five parallel samples is less than 0.3% in the whole pressure range, which indicates that the equipment has good repeatability.

With the increase of pressure, the Compact density of carbon material increases gradually, and the compaction range is 0.5-0.9 g / cm3 .

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