[material] lithium battery material: high stability aluminum nickel oxide layered material

In the past 20 years, lithium-ion batteries (LIBS) have been widely used because of their excellent battery performance (high energy density, high output voltage, long cycle life and low environmental pollution ）It has achieved great success in the field of portable electronic equipment With the development of science and technology and the increasing demand for lithium batteries in electric vehicles, aerospace and other fields, people need lithium-ion batteries with higher energy density and power density to meet the needs of all aspects However, as an important part of lithium-ion battery, the cathode material seriously restricts the improvement of the overall performance of the battery At present, the cathode materials mainly include lithium cobaltic acid system, lithium manganate system, lithium nickel acid system, ferrophosphate system, ternary system, etc among them, the ternary system materials composed of manganese, cobalt and nickel not only have low manufacturing cost, but also relatively high energy density, so they have become the cathode materials of lithium batteries which are only inferior to lithium cobaltic acid in industrialization The key factor for ternary materials with such high capacity is that they contain nickel However, although the introduction of nickel can greatly improve the performance of the battery, when the nickel content is more than 70%, the high nickel layered oxide is easy to react with water and carbon dioxide in the air to generate Li 2CO 3, Lihco3 and LiOH (residual lithium on the surface), lithium hydroxide is easy to react with LiPF6 in the electrolyte to generate HF, lithium carbonate and lithium bicarbonate will swell seriously at high temperature, so the residual lithium on the surface will greatly affect the performance of lithium-ion batteries Recently, Professor arumugam manthiram of the University of Texas at Austin has developed an aluminum doped nickel oxide, which has excellent stability and can effectively prevent the reaction of nickel oxide with humid carbon dioxide in the air This achievement was published in German Applied Chemistry (DOI: 10.1002 / anie 201801533) under the title of "modified high nickel methods with stable surface chemistry against ambient air for lithium ion batteries" Figure 1 Residual lithium increment on the surface of different nickel oxide layered materials (picture source: angel Chem Int ed., 2018, early view) after preparing materials with different components and contents (lini 0.7 co 0.15 Mn 0.15 O2, 71515; lini 0.8 co 0.1 Mn 0.1 O2, 811; lini 0.9 co 0.05 Mn 0.05 O2, 90505; lini 0.94 co 0.06 O2, 9406; lini 0.92 al 0.02 co 0.06 O2 By means of chemical titration, time-of-flight secondary ion mass spectrometry, inductively coupled plasma atomic emission spectrometry and X-ray photoelectron spectroscopy, the material was characterized to determine its exact structure After that, the author studied the reaction activity of different materials to carbon dioxide and water in the air (Fig 1) The results showed that the residual lithium content on the surface of composite materials with the same composition, whether they were newly prepared or exposed to air for 30 days, would increase with the increase of nickel content (7158119055 ）However, the al-9406 shows the highest surface residual lithium content and chemical activity, while the al-9406 shows the lowest surface residual lithium content and the highest stability Figure 2 The morphology and composition of the layered nickel oxide materials before and after doping aluminum (picture source: angel Chem Int ed., 2018, early view) Then, through comparative analysis of the composition and theoretical calculation of the surface nickel oxide of the composite before and after doping aluminum (Figure 2), the author found that the improvement of the stability of nickel oxide is due to the Al-O bond in the material Because the modification of aluminum will improve the binding energy of oxygen, which will prevent oxygen from separating from the compound to some extent, and thus hinder the reaction of nickel in the layered material of nickel oxide with water and carbon dioxide in the air Finally, the nickel oxide layered materials were made into the cathode of lithium battery, and the effect of aluminum on the electrochemical properties of the electrode materials was studied The results show that the introduction of aluminum also retains its ability to increase the chemical stability of nickel oxide when the electrode material is prepared By comparing the capacity of the two electrodes after 30 days, it is found that the capacity retention rate of the aluminum doped electrode after 30 days of recycling is 88%, while the electrode without aluminum doping loses about 79% of the initial capacity after 30 days of recycling Figure 3 Effect of aluminum doping on electrode performance of nickel oxide layered materials (picture source: angel Chem Int ed., 2018, early view) Full text author: ya you, Hugo celio, Jianyu Li, Andrei dolocan, and arumugammanthiram, corresponding author: arumugam manthiram