Lithium-ion secondary battery, battery module, battery pack, and powered device

A lithium-ion secondary battery, comprising:

• a positive electrode sheet,
• a negative electrode sheet,
• a separator, and
• an electrolyte solution,
• wherein the positive electrode sheet comprises a positive electrode current collector, and a positive electrode material layer arranged on at least one surface of the positive electrode current collector, the positive electrode material layer comprising a positive electrode active material and carbon,
• wherein
• the electrolyte solution comprises a heat-stable salt and a low-impedance additive;
• and
• a chemical formula of the heat-stable salt is (My+)x/yR1(SO2N−)xSO2R2, wherein the My+ is a metal ion, R1 and R2 are each independently a fluorine atom, an alkyl with 1-20 carbon atoms, a fluoroalkyl with 1-20 carbon atoms, or a fluoroalkoxy with 1-20 carton atoms, the x is 1, 2, or 3, the y is 1, 2, or 3;
• and a mass percent of the heat-stable salt in the electrolyte solution is set as k2%;
• wherein a temperature rise coefficient of the positive electrode sheet k1=Cw/Mc, Cw is a positive electrode material load per unit area (mg/cm2) on the surface of any side of the positive electrode current collector on which the positive electrode material layer is loaded, and Mc is a carbon content (wt %) of the positive electrode material layer, 18≤Cw≤30, 1≤Mc≤7;
• wherein the lithium-ion secondary battery satisfies 0.34≤k2/k1≤8;
• and
• wherein the low-impedance additive is
• a fluorosulfonate NSO3F,
• wherein N is a metal ion of a salt.