Every advancement in the positive electrode of a ternary lithium-ion battery (also known as a cathode material) will greatly improve the performance of the ternary lithium-ion battery, and of course it will bring some difficulties to material processing. The cathode material can be from lithium iron phosphate, lithium manganate, lithium cobalt, nickel cobalt manganese ternary materials, from low nickel ternary materials to high nickel ternary materials, from NCM to NCA, from traditional materials T to lithium ion donors. . A high-voltage material consisting of binary particles formed by agglomeration. Sub-particles are large single-crystal particles, materials with uniform element distribution to the core-shell structure, gradient coatings and doped materials... Every advancement of the cathode material will greatly improve the performance of lithium-ion batteries. Of course, it will also bring some difficulties to material processing. This series will start with the relevant detection methods of cathode materials, and the theory will be related to the actual situation. It will give you a preliminary understanding of the detection methods of related materials.
1. Through the EDS analysis of the ternary material, the mass ratio of the ternary material can be obtained, and the type of the material can be judged. In addition, EDS technology can also be used to analyze the surface distribution of elements. The electron beam scans the sample in two dimensions by a scanning observation device. The intensity of the characteristic X-rays is measured. On the cathode ray tube of the cathode ray tube cathode ray tube, in synchronization with the scanning signal, a two-dimensional fractal of the characteristic X-ray intensity is obtained. The image of the fabric has a wide range of applications in the study of doping and homogeneity of materials.
By analyzing the surface distribution of different elements, the distribution of elements can be seen, which has a strong guiding significance for the preparation of materials. In addition, there are XRF (X-ray fluorescence spectrometer), EDX (referred to as energy scattering X-ray fluorescence spectrometer, also known as EDXRF), and the analysis results are very similar, and will not be repeated here.
2. Moisture test: The moisture content in the material is also an important indicator for battery manufacturers. Lithium iron phosphate lithium ion battery is related to the length of drying time and the setting of related parameters. The Karl Fischer method is generally used for testing. The principle is that when the Kjeldahl reagent in the electrolysis cell of the instrument reaches equilibrium, water is injected into the aqueous sample, and water participates in the oxidation-reduction reaction of iodine and sulfur dioxide. In the presence of pyridine and methanol, pyridine hydroiodide and pyridine methylsulfate are formed, and iodine consumed is generated by anodic electrolysis to continuously carry out an oxidation-reduction reaction. Ok, until the water is completely depleted, according to Faraday's law of electrolysis, the production of iodine is proportional to the amount of electricity consumed during electrolysis. After the reaction, the excess free iodine was brownish red and was determined to be the end point.
3. Residual alkali content detection: If the alkalinity of lithium manganese oxide lithium ion battery is too high, it will bring some difficulties in the reprocessing process. Therefore, it is necessary to control the residual alkali content of the material. Generally, the titration method is used for detection, and the detection materials are generally For lithium. Lithium hydroxide and lithium carbonate, a small amount of powder and deionized water are mixed for a period of time, filtered, and then titrated, the method is simple and feasible. Atomic Absorption Spectrophotometer (AAS): Based on the influence of ground state atomic vapor on characteristic radiation absorption, metal elements can be analyzed. It can be used sensitively and reliably for the determination of trace or trace elements. By analyzing the lithium ion battery cathode material before and after use, the content of each element can be determined, and the content of each element and the solubility of the metal can be analyzed. It can also be detected by the ICP-AES method, which has been described in the introduction of the negative electrode and is not described in detail here.
4. Material electrical performance test:
This is no longer familiar to the vast number of colleagues in lithium-ion power supply, capacity, power, high and low temperature, cycle, power, safety, etc., major companies also have their own test standards and test methods, not to introduce more here.
In recent years, the use of rotary kiln to sinter lithium battery powder has developed rapidly. Among them, the cathode material rotary kiln independently developed by Jiangsu Fenggu Energy Saving Technology Co., Ltd. Due to the high production efficiency of the rotary kiln, the powder in the form of dynamic tumbling is more uniform in heating, so that various lithium electric powder materials can be uniformly and stably sintered, and the chemical properties of the materials such as the positive electrode and the negative electrode are greatly improved.
to sum up:
This paper mainly introduces some characterization methods of cathode materials. It should be noted that the performance of the material is derived from the comprehensive analysis of the test indicators and cannot be judged by a single indicator. It is believed that with the development of science and technology, more and more advanced characterization methods will go out of scientific research institutions. As we enter the lithium battery business, we will gradually deepen our understanding of the material itself.