Negative electrode plate, lithium metal battery, and apparatus including the lithium metal battery
This application provides a negative electrode plate, a lithium metal battery, and an apparatus including the lithium metal battery. The negative electrode plate includes a negative electrode current collector and a lithium-metal negative electrode disposed on at least one surface of the negative electrode current collector, where a polymer protective film is disposed on a surface of the lithium-metal negative electrode away from the negative electrode current collector, the polymer protective film includes a citric acid copolymer, and a number-average molecular weight Mn of the citric acid copolymer is 10,000 to 1,000,000. In this application, a polymer protective film with high tensile strength, high puncture strength, high elongation, and high electrolyte holding capacity may be formed on the surface of the lithium-metal negative electrode in the negative electrode plate.
1. A negative electrode plate, comprising a negative electrode current collector and a lithium-metal negative electrode disposed on at least one surface of the negative electrode current collector, wherein
a polymer protective film is disposed on a surface of the lithium-metal negative electrode away from the negative electrode current collector, the polymer protective film comprises a citric acid copolymer, and a number-average molecular weight Mn of the citric acid copolymer is 10,000 to 1,000,000.
2. The negative electrode plate according to claim 1 , wherein the citric acid copolymer comprises a reactive block polymer represented by formula (I) and/or formula (II):
wherein m is an integer selected from 10 to 5000, and n is an integer selected from 10 to 5000.
3. The negative electrode plate according to claim 2 , wherein the reactive block polymer meets the following conditions: m is an integer selected from 400 to 600, n is an integer selected from 1000 to 2000, and the number-average molecular weight Mn is 80,000 to 350,000.
4. The negative electrode plate according to claim 2 , wherein the citric acid copolymer comprises a mixture of reactive block polymers represented by formula (I) and formula (II), wherein a mass ratio of the reactive block polymers represented by formula (I) and formula (II) is 1:1 to 1:2, and n/m is 2.5 to 3.5.
5. The negative electrode plate according to claim 1 , wherein the polymer protective film further comprises a fluorine-containing lithium salt, a fluorine-containing film former, and an inorganic filler, wherein the fluorine-containing lithium salt is selected from one or more of lithium bistrifluoromethanesulfonimide, lithium bisfluoromethanesulfonimide, and lithium difluoro (oxalate) borate;
the fluorine-containing film former is selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropene, and polytetrafluoroethylene; and
the inorganic filler is selected from one or more of Al 2 O 3 , TiO 2 , and SiO 2 .
6. The negative electrode plate according to claim 5 , wherein a particle size of the inorganic filler is 10 nm to 1000 nm.
7. The negative electrode plate according to claim 1 , wherein the polymer protective film further comprises lithium bis(oxalate)borate, a fluorine-containing film former, and an inorganic filler;
the fluorine-containing film former is selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropene, and polytetrafluoroethylene; and
the inorganic filler is selected from one or more of Al 2 O 3 , TiO 2 , and SiO 2 .
8. The negative electrode plate according to claim 1 , wherein
the citric acid copolymer comprises a reactive block polymer;
the polymer protective film further comprises a fluorine-containing lithium salt, a fluorine-containing film former, and an inorganic filler; and
parts by mass of the reactive block polymer, the fluorine-containing film former, the inorganic filler, and the fluorine-containing lithium salt in the polymer protective film are respectively 25 parts to 60 parts, 30 parts to 80 parts, 1 part to 10 parts, and 1 part to 10 parts.
9. The negative electrode plate according to claim 1 , wherein thickness of the polymer protective film is 5 μm to 30 μm.
10. The negative electrode plate according to claim 1 , wherein tensile strength of the polymer protective film is 0.5 MPa to 3.0 MPa;
puncture strength of the polymer protective film is 0.5 MPa to 2.0 MPa; and
elongation of the polymer protective film is 100% to 500%.
11. The negative electrode plate according to claim 1 , wherein electrolyte holding capacity of the polymer protective film is 50% to 200%.
12. A lithium metal battery, comprising a positive electrode plate, a negative electrode plate, a separator sandwiched between the positive electrode plate and the negative electrode plate, and an electrolyte, wherein the negative electrode plate is the negative electrode plate according to claim 1 .
13. The lithium metal battery according to claim 12 , wherein the electrolyte comprises fluoroethylene carbonate, linear carbonate, and fluorine-containing lithium salt,
a mass percentage of the fluoroethylene carbonate is 20% to 50%; and
the fluorine-containing lithium salt is selected from one or more of lithium bistrifluoromethanesulfonimide, lithium bisfluoromethanesulfonimide, and lithium difluoro (oxalate) borate.
14. An apparatus, comprising the lithium metal battery according to claim 12 .