Polymer protecting layer, lithium metal negative electrode, lithium secondary battery

Abstract

The present disclosure provides a polymer protecting layer, a lithium metal negative electrode, a lithium secondary battery. In the lithium secondary battery of the present disclosure, a polymer protecting layer comprising a polymer ionic liquid is coated on a surface of a lithium metal sheet, which can effectively slow down or even inhibit the growth of the lithium dendrite, improve the first charge-discharge cycle coulombic efficiency of the lithium secondary battery, and significantly improve the cycle performance and the safety performance of the lithium secondary battery.

What is claimed is: 
     
         1 . A polymer protecting layer, comprising a polymer ionic liquid with a formula I; 
       
         
           
           
               
               
           
         
         in formula I, 
         X being one selected from the group consisting of —COO − , —SO 3   − , —SO 2 N − SO 2 F, —RCOO − , —RSO 3   −  and —RSO 2 N − SO 2 R f , R representing C1 to C10 hydrocarbylene group, or R representing C1 to C10 hydrocarbylene group with one or more hydrogen atoms being substituted by one or more elements selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus, R f  being one selected from the group consisting of fluorine, chlorine, cyanide, C1 to C10 hydrocarbyl group, or R f  representing C1 to C10 hydrocarbyl group with one or more hydrogen atoms being substituted by one or more elements selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus; 
         Y being one selected from the group consisting of nitrogen, sulfur and phosphorus; 
         R 1 , R 2  each being independently one selected from the group consisting of C1 to C10 hydrocarbylene group, or R 1 , R 2  each being independently one selected from the group consisting of C1 to C10 hydrocarbylene group with one or more hydrogen atoms being substituted by one or more elements selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus; 
         R 3  being one selected from the group consisting of C1 to C10 hydrocarbyl group, or R 3  being one selected from the group consisting of C1 to C10 hydrocarbyl group with one or more hydrogen atoms being substituted by one or more elements selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus; 
         50≦l≦2500; 
         50≦n≦2500; 
         0≦m≦3000; 
         p being 2 or 3, and the value of p being related with the valence state of Y. 
       
     
     
         2 . The polymer protecting layer according to  claim 1 , wherein
 R is one selected from the group consisting of C1 to C8 hydrocarbylene group, C1 to C8 fluorohydrocarbylene group and C1 to C8 hydrocarbylene group with two or more hydrogen atoms being substituted by fluorine atoms and oxygen atoms at the same time;   R f  is one selected from the group consisting of fluorine, C1 to C8 fluorohydrocarbyl group and C1 to C8 hydrocarbyl group with two or more hydrogen atoms being substituted by fluorine atoms and oxygen atoms at the same time;   Y is one selected from the group consisting of nitrogen and phosphorus;   R 1  is one selected from the group consisting of C1 to C4 hydrocarbylene group, or R 1  is one selected from the group consisting of C1 to C4 hydrocarbylene group with one or more hydrogen atoms being substituted by one or more elements selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus;   R 2  is selected from C1 to C8 hydrocarbylene group or C1 to C8 hydrocarbylene group with one or more hydrogen atoms being substituted by one or more oxygen atoms;   R 3  is one selected from the group consisting of C1 to C8 hydrocarbyl group, C1 to C8 fluoroalkyl group and C1 to C8 fluoroalkoxy.   
     
     
         3 . The polymer protecting layer according to  claim 1 , wherein the polymer protecting layer further comprises a macromolecular compound, the macromolecular compound is one or more selected from the group consisting of polymethylmethacrylate, polyethylene oxide, polyvinylidene fluoride, copolymer of vinylidene fluoride and hexafluoropropylene, and polyacrylonitrile. 
     
     
         4 . The polymer protecting layer according to  claim 1 , wherein the polymer protecting layer further comprises inorganic nanoparticles, the material of the inorganic nanoparticles is one or more selected from the group consisting of silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide, zirconium dioxide, zinc oxide, ferroferric oxide, barium titanate, lead titanate, lithium nitride, aluminum lithium oxide, sodium montmorillonite clay and molecular sieves. 
     
     
         5 . A lithium metal negative electrode, comprising:
 a lithium metal sheet; and   a polymer protecting layer provided at the lithium metal sheet;   the polymer protecting layer comprising a polymer ionic liquid with a formula I;   
       
         
           
           
               
               
           
         
         in formula I, 
         X being one selected from the group consisting of —COO − , —SO 3   − , —SO 2 N − SO 2 F, —RCOO − , —RSO 3   −  and —RSO 2 N − SO 2 R f , R representing C1 to C10 hydrocarbylene group, or R representing C1 to C10 hydrocarbylene group with one or more hydrogen atoms being substituted by one or more elements selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus, R f  being one selected from the group consisting of fluorine, chlorine, cyanide, C1 to C10 hydrocarbyl group, or R f  representing C1 to C10 hydrocarbyl group with one or more hydrogen atoms being substituted by one or more elements selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus; 
         Y being one selected from the group consisting of nitrogen, sulfur and phosphorus; 
         R 1 , R 2  each being independently one selected from the group consisting of C1 to C10 hydrocarbylene group, or R 1 , R 2  each being independently one selected from the group consisting of C1 to C10 hydrocarbylene group with one or more hydrogen atoms being substituted by one or more elements selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus; 
         R 3  being one selected from the group consisting of C1 to C10 hydrocarbyl group, or R 3  being one selected from the group consisting of C1 to C10 hydrocarbyl group with one or more hydrogen atoms being substituted by one or more elements selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus; 
         50≦l≦2500; 
         50≦n≦2500; 
         0≦m≦3000; 
         p being 2 or 3, and the value of p being related with the valence state of Y. 
       
     
     
         6 . The lithium metal negative electrode according to  claim 5 , wherein
 R is one selected from the group consisting of C1 to C8 hydrocarbylene group, C1 to C8 fluorohydrocarbylene group and C1 to C8 hydrocarbylene group with two or more hydrogen atoms being substituted by fluorine atoms and oxygen atoms at the same time;   R f  is one selected from the group consisting of fluorine, C1 to C8 fluorohydrocarbyl group and C1 to C8 hydrocarbyl group with two or more hydrogen atoms being substituted by fluorine atoms and oxygen atoms at the same time;   Y is one selected from the group consisting of nitrogen and phosphorus;   R 1  is one selected from the group consisting of C1 to C4 hydrocarbylene group, or R 1  is one selected from the group consisting of C1 to C4 hydrocarbylene group with one or more hydrogen atoms being substituted by one or more elements selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus;   R 2  is selected from C1 to C8 hydrocarbylene group or C1 to C8 hydrocarbylene group with one or more hydrogen atoms being substituted by one or more oxygen atoms;   R 3  is one selected from the group consisting of C1 to C8 hydrocarbyl group, C1 to C8 fluoroalkyl group and C1 to C8 fluoroalkoxy.   
     
     
         7 . The lithium metal negative electrode according to  claim 6 , wherein
 R is one selected from the group consisting of C1 to C8 alkylene group, C1 to C8 fluoroalkylene group and C1 to C8 fluoroalkoxy;   R f  is one selected from the group consisting of fluorine, C1 to C8 fluoroalkyl group and C1 to C8 fluoroalkoxy;   R 1  is one selected from the group consisting of C1 to C4 alkylene group, or R 1  is one selected from the group consisting of C1 to C4 alkylene group with one or more hydrogen atoms being substituted by one or more elements selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus;   R 2  is selected from C1 to C8 alkylene group or C1 to C8 alkoxy;   R 3  is one selected from the group consisting of —CH 3 , —C 2 H 5 , —C 3 H 7 , —C 4 H 9  and —(CH 2 CH 2 O) s CH 3 , s is an integer of 1˜8.   
     
     
         8 . The lithium metal negative electrode according to  claim 5 , wherein the polymer protecting layer further comprises a macromolecular compound, the macromolecular compound is one or more selected from the group consisting of polymethylmethacrylate, polyethylene oxide, polyvinylidene fluoride, copolymer of vinylidene fluoride and hexafluoropropylene, and polyacrylonitrile. 
     
     
         9 . The lithium metal negative electrode according to  claim 5 , wherein the polymer protecting layer further comprises inorganic nanoparticles, the material of the inorganic nanoparticles is one or more selected from the group consisting of silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide, zirconium dioxide, zinc oxide, ferroferric oxide, barium titanate, lead titanate, lithium nitride, aluminum lithium oxide, sodium montmorillonite clay and molecular sieves. 
     
     
         10 . The lithium metal negative electrode according to  claim 9 , wherein a mass percentage of the inorganic nanoparticles in the polymer protecting layer is more than 0 and less than or equal to 50%. 
     
     
         11 . A lithium secondary battery, comprising a lithium metal negative electrode,
 the lithium metal negative electrode comprising:   a lithium metal sheet; and   a polymer protecting layer provided at the lithium metal sheet;   the polymer protecting layer comprising a polymer ionic liquid with a formula I;   
       
         
           
           
               
               
           
         
         in formula I, 
         X being one selected from the group consisting of —COO − , —SO 3   − , —SO 2 N − SO 2 F, —RCOO − , —RSO 3   −  and —RSO 2 N − SO 2 R f , R representing C1 to C10 hydrocarbylene group, or R representing C1 to C10 hydrocarbylene group with one or more hydrogen atoms being substituted by one or more elements selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus, R f  being one selected from the group consisting of fluorine, chlorine, cyanide, C1 to C10 hydrocarbyl group, or R f  representing C1 to C10 hydrocarbyl group with one or more hydrogen atoms being substituted by one or more elements selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus; 
         Y being one selected from the group consisting of nitrogen, sulfur and phosphorus; 
         R 1 , R 2  each being independently one selected from the group consisting of C1 to C10 hydrocarbylene group, or R 1 , R 2  each being independently one selected from the group consisting of C1 to C10 hydrocarbylene group with one or more hydrogen atoms being substituted by one or more elements selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus; 
         R 3  being one selected from the group consisting of C1 to C10 hydrocarbyl group, or R 3  being one selected from the group consisting of C1 to C10 hydrocarbyl group with one or more hydrogen atoms being substituted by one or more elements selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus; 
         50≦l≦2500; 
         50≦n≦2500; 
         0≦m≦3000; 
         p being 2 or 3, and the value of p being related with the valence state of Y. 
       
     
     
         12 . The lithium secondary battery according to  claim 11 , wherein the number-average molecular weight of the polymer ionic liquid with the formula I ranges from 40,000 to 1,000,000. 
     
     
         13 . The lithium secondary battery according to  claim 11 , wherein l:m:n=1:(0.5˜1.5):(0.5˜1.5). 
     
     
         14 . The lithium secondary battery according to  claim 11 , wherein
 R is one selected from the group consisting of C1 to C8 hydrocarbylene group, C1 to C8 fluorohydrocarbylene group and C1 to C8 hydrocarbylene group with two or more hydrogen atoms being substituted by fluorine atoms and oxygen atoms at the same time;   R f  is one selected from the group consisting of fluorine, C1 to C8 fluorohydrocarbyl group and C1 to C8 hydrocarbyl group with two or more hydrogen atoms being substituted by fluorine atoms and oxygen atoms at the same time;   Y is one selected from the group consisting of nitrogen and phosphorus;   R 1  is one selected from the group consisting of C1 to C4 hydrocarbylene group, or R 1  is one selected from the group consisting of C1 to C4 hydrocarbylene group with one or more hydrogen atoms being substituted by one or more elements selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus;   R 2  is selected from C1 to C8 hydrocarbylene group or C1 to C8 hydrocarbylene group with one or more hydrogen atoms being substituted by one or more oxygen atoms;   R 3  is one selected from the group consisting of C1 to C8 hydrocarbyl group, C1 to C8 fluoroalkyl group and C1 to C8 fluoroalkoxy.   
     
     
         15 . The lithium secondary battery according to  claim 14 , wherein
 R is one selected from the group consisting of C1 to C8 alkylene group, C1 to C8 fluoroalkylene group and C1 to C8 fluoroalkoxy;   R f  is one selected from the group consisting of fluorine, C1 to C8 fluoroalkyl group and C1 to C8 fluoroalkoxy;   R 1  is one selected from the group consisting of C1 to C4 alkylene group, or R 1  is one selected from the group consisting of C1 to C4 alkylene group with one or more hydrogen atoms being substituted by one or more elements selected from the group consisting of fluorine, chlorine, bromine, iodine, nitrogen, oxygen, sulfur, silicon, boron and phosphorus;   R 2  is selected from C1 to C8 alkylene group or C1 to C8 alkoxy;   R 3  is one selected from the group consisting of —CH 3 , —C 2 H 5 , —C 3 H 7 , —C 4 H 9  and —(CH 2 CH 2 O) s CH 3 , s is an integer of 1˜8.   
     
     
         16 . The lithium secondary battery according to  claim 11 , wherein a mass percentage of the polymer ionic liquid with a formula I in the polymer protecting layer ranges from 5% to 100%. 
     
     
         17 . The lithium secondary battery according to  claim 11 , wherein the polymer protecting layer further comprises a macromolecular compound, the macromolecular compound is one or more selected from the group consisting of polymethylmethacrylate, polyethylene oxide, polyvinylidene fluoride, copolymer of vinylidene fluoride and hexafluoropropylene, and polyacrylonitrile. 
     
     
         18 . The lithium secondary battery according to  claim 17 , wherein a mass percentage of the macromolecular compound in the polymer protecting layer is more than 0 and less than or equal to 20%. 
     
     
         19 . The lithium secondary battery according to  claim 11 , wherein the polymer protecting layer further comprises inorganic nanoparticles, the material of the inorganic nanoparticles is one or more selected from the group consisting of silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide, zirconium dioxide, zinc oxide, ferroferric oxide, barium titanate, lead titanate, lithium nitride, aluminum lithium oxide, sodium montmorillonite clay and molecular sieves. 
     
     
         20 . The lithium secondary battery according to  claim 19 , wherein a mass percentage of the inorganic nanoparticles in the polymer protecting layer is more than 0 and less than or equal to 50%.