Electrochemical device and electronic device comprising the same
An electrochemical device includes a positive electrode, a negative electrode, a separator, and an electrolyte, where the electrolyte contains a nitrile compound and transition metal ions, and satisfies 5≤A/B≤30000, where based on a molar mass of the electrolyte, a molar percentage of a cyano group in the electrolyte is A %, and based on a weight of the electrolyte, a weight percentage of the transition metal ions in the electrolyte is B %. The electrochemical device ensures that the cyano group and the transition metal ions in the electrolyte satisfy a specified relationship, to reduce leaching of the transition metal ions from a positive electrode active material and stabilize structural distortion of the positive electrode active material in a charge and discharge process, thereby improving high-temperature cycle performance and floating charge performance of the electrochemical device.
1 . An electrochemical device, comprising:
a positive electrode, wherein the positive electrode contains a positive electrode active material that contains aluminum; and based on a total weight of the positive electrode active material, a weight percentage of the aluminum is C %, and 0.001<C<1; a negative electrode; a separator; and an electrolyte,
wherein, the electrolyte contains a nitrile compound and transition metal ions, the transition metal ions comprise cobalt ions and copper ions; based on a total weight of the electrolyte, a weight percentage of the cobalt ions in the electrolyte is less than 0.1%, and a weight percentage of the copper ions in the electrolyte is less than 0.1%;
the nitrile compound comprises a compound of formula II:
R 21 , R 22 , and R 23 are each independently selected from a single bond, substituted or unsubstituted C 1 to C 5 alkylidene groups, and substituted or unsubstituted C 1 to C 10 alkyleneoxy groups, when substitution is performed, a substituent group is selected from at least one of halogen, a cyano group, or a carboxyl group;
based on a total molar mass of the electrolyte, a molar percentage of a cyano group in the electrolyte is A %, based on the total weight of the electrolyte, a weight percentage of the transition metal ions in the electrolyte is B %, 5≤A/B≤30000, and 0.01≤A/C≤170.
2 . The electrochemical device according to claim 1 , wherein a curve of the positive electrode active material obtained through a differential scanning calorimetry test comprises a first exothermic peak and a second exothermic peak, a temperature corresponding to the first exothermic peak is X, 240° C.≤X≤280° C., a temperature corresponding to the second exothermic peak is Y, and 280° C.<Y≤340° C.
3 . The electrochemical device according to claim 2 , wherein a peak area of the first exothermic peak is ≤50 J/g, and a peak area of the second exothermic peak is ≤800 J/g.
4 . The electrochemical device according to claim 1 , wherein the electrolyte further comprises a compound of formula IV:
R 41 is selected from substituted or unsubstituted C 1 to C 12 alkyl groups, substituted or unsubstituted C 3 to C 12 cycloalkyl groups, substituted or unsubstituted C 2 to C 12 alkenyl groups, substituted or unsubstituted C 2 to C 12 alkynyl groups, substituted or unsubstituted C 6 to C 22 aryl groups, and substituted or unsubstituted C 5 to C 22 heteroaryl groups,
when substitution is performed, a substituent group is selected from at least one of halogen, a cyano group, or a carboxyl group; and
based on the total weight of the electrolyte, a weight percentage of the compound of formula IV is 0.001% to 5%.
5 . The electrochemical device according to claim 1 , wherein the electrolyte further comprises a first additive; the first additive comprises at least one of vinyl ethylene carbonate, fluorobenzene, lithium difluorophosphate, lithium tetrafluoroborate, 1,3,2-dioxathiolane,2,2-dioxide, fluoroethylene carbonate, vinylene carbonate, or 1,3-propane sultone; and based on the total weight of the electrolyte, a weight percentage of the additive is 0.001% to 13%.
6 . An electronic device, comprising: the electrochemical device according to claim 1 .
7 . The electronic device according to claim 6 , wherein a curve of the positive electrode active material obtained through a differential scanning calorimetry test comprises a first exothermic peak and a second exothermic peak, a temperature corresponding to the first exothermic peak is X, 240° C.≤X≤280° C., a temperature corresponding to the second exothermic peak is Y, and 280° C.<Y≤340° C.
8 . The electronic device according to claim 2 , wherein a peak area of the first exothermic peak is ≤50 J/g, and a peak area of the second exothermic peak is ≤800 J/g.
9 . The electronic device according to claim 6 , wherein the electrolyte further comprises a compound of formula IV:
R 41 is selected from substituted or unsubstituted C 1 to C 12 alkyl groups, substituted or unsubstituted C 3 to C 12 cycloalkyl groups, substituted or unsubstituted C 2 to C 12 alkenyl groups, substituted or unsubstituted C 2 to C 12 alkynyl groups, substituted or unsubstituted C 6 to C 22 aryl groups, and substituted or unsubstituted C 5 to C 22 heteroaryl groups,
when substitution is performed, a substituent group is selected from at least one of halogen, a cyano group, or a carboxyl group; and
based on the total weight of the electrolyte, a weight percentage of the compound of formula IV is 0.001% to 5%.
10 . The electronic device according to claim 6 , wherein the electrolyte further comprises a first additive, the first additive comprises at least one of vinyl ethylene carbonate, fluorobenzene, lithium difluorophosphate, lithium tetrafluoroborate, 1,3,2-dioxathiolane,2,2-dioxide, fluoroethylene carbonate, vinylene carbonate, or 1,3-propane sultone, and based on the total weight of the electrolyte, a weight percentage of the additive is 0.001% to 13%.
11 . The electrochemical device according to claim 1 , wherein 2≤A≤10.
12 . The electronic device according to claim 6 , wherein 2≤A≤10.
13 . The electrochemical device according to claim 1 , wherein 0.002≤B≤0.2.
14 . The electronic device according to claim 6 , wherein 0.002≤B≤0.2.