Positive electrode slurry, positive electrode plate, and secondary battery including such positive electrode plate

1. A positive electrode slurry, comprising a positive electrode active substance and polyether polyol, the polyether polyol having the following constitutional formula:

wherein

R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are each independently selected from H, a hydroxyl group, halogen, a C 2-10 alkyl group, a C 2-10 alkoxy group, and XM;

wherein

X is selected from —O—, —S—, and —NH—;

M has the following constitutional formula:

—(CH 2 —CHR—O) n D  formula 2

wherein

n is an integer ranging from 10 to 2000; and

D is H or a C 1-8 alkyl group;

each R is independently selected from H, halogen, a hydroxyl group, a halogenated C 1-8 alkyl group, R 7 , —OR 7 or R 7 OR 8 , wherein R 7 and R 8 are each independently selected from a straight-chain or branched-chain C 1-8 alkyl group, a phenyl group, a C 1-8 alkyl substituted phenyl group, a C 1-8 alkoxy substituted phenyl group, or a halogenated phenyl group; and

at least one of R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 is XM, and

wherein a weight ratio of the polyether polyol to the positive electrode active substance ranges from 0.0005 to 0.050.

2. The positive electrode slurry according to claim 1 , where the polyether polyol has a weight-average molecular weight ranging from 1,000 to 80,000.

3. The positive electrode slurry according to claim 1 , wherein

the positive electrode active substance is selected from at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium nickel oxide, or a mixture thereof.

4. The positive electrode slurry according to claim 1 , wherein

a gel state factor G of the positive electrode slurry ranges from 0 to 1;

wherein G=(m1−m2)/m1, the slurry is determined not to be gelled when G ranges from 0 to 0.3, and the slurry is determined to be gelled when G is greater than 0.3;

m1 is a mass of a positive electrode slurry obtained after 2 kg of an initial positive electrode slurry is filtered for 10 minutes using a 100-mesh filter; and

m2 is a mass of a positive electrode slurry obtained after 2 kg of a positive electrode slurry that has been left standing for 48 hours is filtered for 10 minutes using a 100-mesh filter; wherein

the positive electrode slurry used for determining m1 and the positive electrode slurry used for determining m2 are from the same batch of positive electrode slurry.

5. A positive electrode plate, comprising:

a positive electrode current collector; and

a positive electrode film layer on at least one surface of the positive electrode current collector, wherein the positive electrode film layer is prepared from the positive electrode slurry according to claim 1 , the positive electrode film layer has a mass per unit area on the electrode plate ranging from 13 mg/cm 2 to 35 mg/cm 2 , and the mass is a mass of a positive electrode film layer on a single surface of the electrode plate.

6. The positive electrode plate according to claim 5 ,

wherein the positive electrode plate is measured using a winding needle,

when a diameter R of the winding needle is greater than 0 and less than or equal to 3.0 mm, the positive electrode plate has no cracks; or

when a diameter R of the winding needle is equal to 3.0 mm, the positive electrode plate has cracks produced, but when the diameter R of the winding needle is equal to 4.0 mm, the positive electrode plate has no cracks produced.

7. The positive electrode plate according to claim 5 , wherein

the positive electrode plate has an infiltration increase rate I ranging from 2% to 20%;

wherein I=(I2−I1)/I1×100%;

I2 is an infiltration rate of the positive electrode plate in an electrolyte; and

I1 is an infiltration rate of a positive electrode plate containing no polyether polyol in an electrolyte;

wherein the positive electrode plate used for determining I1 is the same as the positive electrode plate used for determining I2, differing only in that the positive electrode plate used for determining I1 contains no polyether polyol, and the positive electrode plate used for determining I2 contains the polyether polyol.

8. A secondary battery, comprising the positive electrode plate according to claim 5 .

9. A secondary battery, comprising a positive electrode plate obtained from the positive electrode slurry according to claim 1 .