GB/T 20251-2006Nickel foam for battery (English PDF)

4.1 Product classification

According to the method of production, nickel foam is divided into two kinds: coiled strip and sheet-form block.

4.2 Chemical composition

The chemical composition of the nickel foam shall comply with Table 1, in per cent.

Nickel plus cobalt not less than 99.7. Impurity content by mass fraction, not greater than: carbon 0.030; sulfur 0.008; iron 0.020; copper 0.010; silicon 0.005; phosphorus 0.20.

4.3 Dimensions and permissible deviations

The dimensions and the permissible deviations of the nickel foam shall comply with Table 2.

Length less than 400 m with a permissible deviation of plus or minus 50 mm; width up to 0.5 m with a permissible deviation of plus or minus 0.5 mm and width above 0.5 m with a permissible deviation of plus or minus 1 mm; thickness up to 2.5 mm with a permissible deviation of plus or minus 0.05 mm; and not more than four joints within every 200 m of length, with the shortest distance between two joints not less than 20 m.

Note: where the purchaser has special requirements for the dimensions and their permissible deviations, these may be agreed between supplier and purchaser and noted in the contract. The length and joint number indicators apply to coiled strip nickel foam. Nickel foam thicker than 2.5 mm should not use the thickness indicator given, and its specific requirements shall be agreed separately between supplier and purchaser.

4.4 Mechanical properties

The room temperature mechanical properties of the nickel foam shall comply with Table 3.

Tensile strength Rm not less than 1.25 N/mm2 in the longitudinal direction and not less than 0.90 N/mm2 in the transverse direction. Elongation after fracture A not less than 5.0 % longitudinally and not less than 10.0 % transversely. Flexibility, expressed as the number of bends without fracture in the longitudinal direction: not less than 7 for thickness up to 1.6 mm; not less than 6 for thickness above 1.6 mm and up to 1.8 mm; not less than 5 for thickness above 1.8 mm and up to 2.0 mm; and not less than 4 for thickness above 2.0 mm and up to 2.5 mm. In the transverse direction not less than 15.

Note 1: the tensile strength values in the table apply to nickel foam of 500 g/m2 areal density and 1.6 mm thickness. At the same thickness, for every 1 g/m2 reduction in areal density the tensile strength value shall be reduced correspondingly by 0.003 N/mm2; at the same areal density, the tensile strength value is inversely proportional to the thickness.

Note 2: nickel foam of more than 2.5 mm thickness or more than 600 g/m2 areal density shall not use the indicators in the table, and its specific requirements shall be agreed separately between supplier and purchaser.

Note 3: nickel foam with a pore number above 110 PPI, or an areal density of 550 g/m2 or more, or an areal density of 300 g/m2 or less, should not use the flexibility values in the table, and the specific values shall be agreed separately.

The indicator values in the table are the average results of the samples, and the number of samples below the standard value shall not exceed two.

4.5 Physical properties

The physical properties of the nickel foam shall comply with Table 4.

Areal density 300 to 600 g/m2, with a permissible deviation of plus or minus 8 % below 400 g/m2 and plus or minus 7 % at 400 g/m2 and above. Pore number 60 to 140 PPI, with a permissible deviation of plus or minus 10 PPI. Porosity not less than 95.0 %.

4.6 Appearance quality

4.6.1 The surface of the nickel foam shall have a silver-grey metallic lustre and shall be clean.

4.6.2 Slight water marks and micro spots are permitted on the nickel foam.

4.6.3 The nickel foam shall be free from cracks and from visible carbon black and missing plating.

4.6.4 The nickel foam shall have no through-holes larger than 2 mm in diameter, no nickel skin longer than 2 mm and no scratches longer than 3 mm. Within each square metre, the total number of defects consisting of through-holes 1 mm to 2 mm in diameter, nickel skin 1 mm to 2 mm long and scratches 2 mm to 3 mm long shall not exceed ten.

4.6.5 After the edges of coiled strip nickel foam have been trimmed, the strip shall be wound evenly.

4.7 Other requirements

Where the purchaser has other special requirements for the nickel foam, such as the thickness deposit ratio (TDR) or the resistivity, these shall be agreed between supplier and purchaser and noted in the contract.

5.1 Method of analysis of the chemical composition

The analysis of the chemical composition of the nickel foam shall be carried out in accordance with GB/T 8647.

5.2 Inspection of dimensions and permissible deviations

5.2.1 Length: sheet-form block nickel foam is measured with a straight rule; coiled strip nickel foam is measured with a length meter.

5.2.2 Width: where the width of the nickel foam is not greater than 0.5 m, a vernier caliper with an accuracy of 0.02 mm is used; where the width is greater than 0.5 m, a straight rule with an accuracy of 1 mm is used.

5.2.3 Thickness: measured with a micrometer of 0.01 mm accuracy.

5.2.4 Number of joints: the joints of the coiled nickel foam are counted by sampling.

5.3 Inspection of mechanical properties

5.3.1 The tensile strength and the elongation after fracture are determined in accordance with GB/T 228.

5.3.2 The flexibility is determined in accordance with Annex A.

5.4 Inspection of physical properties

5.4.1 Areal density: inspected with an electronic balance of 0.01 g accuracy and a vernier caliper of 0.02 mm accuracy.

5.4.2 Pore number: inspected with an optical microscope at 100 times magnification.

5.4.3 Porosity: determined in accordance with GB/T 5164.

5.5 Inspection of appearance quality

Visual inspection shall be made in a well-lit environment, and surface defects shall be measured with a vernier caliper of 0.02 mm accuracy.

5.6 Inspection of other special requirements

5.6.1 Thickness deposit ratio (TDR): the inspection method is given in Annex B.

5.6.2 Resistivity: the inspection method is given in Annex C.