▎ 摘　　要

NOVELTY - Method for evaluating structural stability of positive electrode material, involves preparing to-be-evaluated positive electrode materials into positive electrode sheets, assembling each positive electrode sheet into a button cell using an in-situ X-ray diffraction (XRD) test mold, charging, performing in-situ XRD scanning on the positive electrode sheet to obtain peak position of (003) peak in each in-situ XRD scanning process and corresponding state of charge of the button cell, and determining positive electrode maximum deformation amount (B1), positive electrode maximum deformation percentage (C1%), positive electrode charging end deformation amount (B2), positive electrode charging end deformation percentage (C2%), positive electrode deformation rate (D1) and positive electrode charging end deformation rate (D2). When B1, C1% and D1 are minimum, the structural stability of the positive electrode material corresponding to the button cell is high. USE - Method for evaluating structural stability of positive electrode material. ADVANTAGE - The method enables quickly evaluating the structure positive electrode of the material, and characterizing the change of the cell positive electrode in the charging and discharging process through the method of in-situ XRD test, so as to reach the purpose of evaluating a structure of the positive electrode. The method allows the material structure of positive electrode to be evaluated in a short period of time, thus reducing the test resource and time consumption. DETAILED DESCRIPTION - Method for evaluating structural stability of positive electrode material, involves preparing to-be-evaluated positive electrode materials into positive electrode sheets under same conditions, assembling each positive electrode sheet into a button cell using an in-situ X-ray diffraction (XRD) test mold, charging button cell, simultaneously performing in-situ XRD scanning on the positive electrode sheet to obtain peak position of (003) peak in each in-situ XRD scanning process and corresponding state of charge of the button cell, and determining positive electrode maximum deformation amount (B1), positive electrode maximum deformation percentage (C1%), positive electrode charging end deformation amount (B2), positive electrode charging end deformation percentage (C2%), positive electrode deformation rate (D1) and positive electrode charging end deformation rate (D2). The deformation amount (B1) is determined by the formula: A1-A2, where A1 is A1 is the peak position angle of the (003) peak of the positive electrode material when the state of charge of the button cell is 0%, and A2 is the minimum angle of the peak position of the (003) peak of the positive electrode material during the charging process. The maximum deformation percentage (C1%) is determined by the formula: (A1-A2)/A1. The positive electrode charging end deformation amount (B2) is determined by the formula: A3-A2, where A3 is the peak position angle of the (003) peak of the positive electrode material when the state of charge of the coin cell is 100%. The positive electrode charging end deformation percentage (C2%) is determined by the formula: (A3-A2)/A1. The positive electrode deformation rate (D1) is determined by the formula: (A1-A2)/SOC1, where SOC1 is the state of charge of the button cell when the peak position of the (003) peak of the positive electrode material during the charging process is minimum. The positive electrode charging end deformation rate (D2) is determined by the formula: (A3-A2)/(1-SOC1). The deformation amount (B1), maximum deformation percentage (C1%) and positive electrode deformation rate (D1) are compared, and the positive electrode charging end deformation amount (B2), positive electrode charging end deformation percentage (C2%) and positive electrode charging end deformation rate (D2) are compared. When B1, C1% and D1 are minimum, the structural stability of the positive electrode material corresponding to the button cell is high. When B2, C2% and D2 are minimum, the structural stability of the positive electrode material corresponding to the button cell is high and high-voltage performance is improved. DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the in-situ X-ray diffraction test mold. 1Positive electrode base 2in-situ X-ray diffraction test window 3Positive electrode 4Conductive foil 5Positive electrode sheet 6Separator 7Negative electrode sheet 8Insulating sealing rubber ring 9Conductive support bracket 10Negative electrode top cover 11Negative electrode 12Insulating fixing nut 13Insulation separating rubber ring 14Screw 15Through-hole