Method for measuring particle size of primary particles of positive electrode material

Abstract

The invention relates to a method for measuring the primary particle size of a positive electrode material, which comprises the following steps of: performing SEM (scanning electron microscope) test on a calibrated positive electrode material to obtain an average primary particle size L; performing XRD (X-Ray Diffraction) test on the calibrated positive electrode material to obtain a sub-grain size l; establishing a relational expression L = a * l between the average primary particle size L and the subgrain size l for calibrating the positive electrode material to obtain a value of a coefficient a; the to-be-tested positive electrode material is subjected to XRD testing to obtain the corresponding sub-grain size l, the sub-grain size l is substituted into the relational expression corresponding to the same type of positive electrode material to obtain the primary particle size of the to-be-tested positive electrode material, and the calibration positive electrode material and the to-be-tested positive electrode material are the same in type. The test method provided by the invention overcomes the problems that a laser particle analyzer cannot reflect the primary particle size of the material and the error of the primary particle size of the SEM test material is large, and can efficiently and quickly test the primary particle size of the positive electrode material.

Description

technical field [0001] The invention relates to the field of lithium ion batteries, in particular to a method for measuring the primary particle size of positive electrode materials. Background technique [0002] The positive electrode material is one of the key materials that determine the electrical performance of lithium-ion batteries, and has a greater impact on lithium-ion batteries. The mainstream cathode materials currently used in lithium-ion batteries include lithium cobalt oxide (LCO), lithium iron phosphate (LFP), lithium manganese oxide (LMO), ternary materials nickel cobalt lithium manganate (NCM) and nickel cobalt lithium aluminate ( NCA) etc. [0003] Lithium iron phosphate (LFP) material is orthorhombic olivine structure, 1 PO 4 tetrahedron with 1 FeO 6 Octahedral, 2 LiO 6 Octahedrons share edges, thus forming a three-dimensional space network structure. Among them, the conductive unit FeO 6 Due to the arrangement of common vertices of octahedrons, elec...

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Problems solved by technology

[0006] 2. Although the primary particles of the material can be observed and the single particle size can be measured by SEM, since SEM can only observe the sample part within the field of view, the observed primary particle size is not representative

In particular, for secondary sphere type cathode materials (such as polycrystalline NCM / NCA ternary cathode), since the primary particles inside the secondary sphere cannot be observed by SEM, the internal primary particles can only be estimated from the primary particles on the surface. At the same time, the primary particles in the outer layer of the secondary ball are densely arranged, and the particles cover each other. The whole picture of the primary particles cannot be truly observed through SEM, so the observation error of the primary particle size is relatively large

[0007] 3. A more feasible solution is to conduct SEM observations in multiple fields of view, and then take the average of several obtained primary particle sizes, but this solution will cause complex testing procedures, low testing efficiency, and high testing costs The problem

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