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Time: 2021-04-15 16:04:29 Views: 217 Author: Hi-Chipcom
1. Electrode material
(1) On the basis of traditional cathode materials (LiCoO2, LiMn2O4, LiFePO4, etc.), develop various related derivative materials, through doping, coating, adjusting microstructure, controlling material morphology, size distribution, specific surface area, impurity content And other technical means to comprehensively improve its specific capacity, rate, cyclability, compaction density, electrochemistry, chemical and thermal stability.
(2) The ternary materials (LiNixCoyMn1-x-y) and lithium-rich materials (Mn-based and V-based) have a large development and technical research space and broad application prospects. Therefore, nickel-cobalt-manganese ternary materials, lithium-rich manganese-based vanadium-based materials, composite cathode materials with excellent performance, and high-efficiency and energy-saving polyanion group cathode materials are the mainstream of lithium-ion battery cathode materials in the future; to develop more efficient and energy-saving new cathodes Materials to overcome and replace the existing defective cathode materials are also research hotspots.
(3) A series of transition metal fluorides, oxides, sulfides, and nitrides have been proven to achieve multi-electron transfer and high capacity. The electrode material based on the conversion reaction mechanism to achieve the function of lithium storage has a specific capacity that is more than 2 to 4 times higher than that of the traditional lithium ion battery electrode material based on the lithium ion insertion and extraction mechanism. However, there are still many problems to be solved. There are relatively few studies on this type of material, and there are still many unclear points in the mechanism.
(4) Looking at the literature, there are people who have made organic cathode materials, which are mainly divided into conductive polymers, sulfur compounds, nitroxide radical compounds and carbonyl compounds, etc. (I don’t know much about it. Hope to be able to add).
Among them, P1 and P2 are organic electrode materials (small molecules or polymers), M+, A+ are doped positive and negative ions, usually Li+, Na+, (C4H9)4N+, Cl\CICV, PF6-, etc. P1-M+, P2+A-, PI+A-, P2-M+ are doped organic electrode materials.
(1) Carbon-based materials
Including important future development will focus on high-power graphite anodes and non-graphite high-capacity carbon anodes (soft carbon, hard carbon, etc.) to meet the needs of future power and high-energy batteries. New types of carbon materials: such as carbon nanotubes (CNT) and graphene. Due to their special one-dimensional and two-dimensional flexible structure, excellent thermal conductivity and electrical conductivity, their cost is reduced towards high energy density, high cycle characteristics and low cost. Direction development.
(2) Non-carbon materials
LTO can be compared to carbon-based materials. Metals or semiconductor materials such as Fe, Ge, Sn, Si, etc. are the hotspots of current research. It is formed around the directions of coating, surface modification, nanometerization, and composite in order to reduce its volume expansion. Stable SEI film. The specific capacity of this type of metal material, especially Si, is very high. It should be an ideal cathode material for the next generation of lithium-ion batteries. However, the problems of volume expansion and SEI instability have not been well resolved yet. To a certain extent, its development is restricted, especially the advantages of volumetric energy density related to graphite anode are far inferior to theoretical calculations. Therefore, it is not an absolute advantage in application. In the end, the anode material of lithium-ion batteries is likely to return to Li The single substance itself, metal lithium rechargeable lithium-ion batteries, all-solid-state lithium-ion batteries, lithium-sulfur batteries, and lithium-air batteries are being extensively studied.
2. Electrolyte material
It is important to increase the voltage window of the electrolyte, reduce the cost, the temperature range of the electrolyte, increase the ionic conductivity of the solid electrolyte, and control the formation of a stable SEI film.
At this stage, LiPF6 is generally used, EC plus one or several linear carbonates as solvents, and various types and occasions are tested by adding different additives, using different solvents and replacing different lithium salts, because LIPF6/ EC: The working temperature range of DMC electrolyte system is -20～50℃. At this stage, there are many attempts to use ionic liquids, which have a wider temperature range and lower vapor pressure, good electrochemical performance and electrochemical stability, but they are very expensive (Professor Dai Hongjie’s aluminum ion battery Nature is an ionic liquid used) Then there is the development of gel/solid electrolyte; the second is high-voltage electrolyte to solve by purifying solvent, using ionic liquid, fluorocarbonate, adding positive electrode surface film additives, etc. The same development of solid electrolyte can also significantly increase the voltage range.
Commonly used gel-type polymer electrolyte matrixes are: polyacrylonitrile (PAN), polyethylene oxide (PEO), polymethacrylic acid, methyl ester (PMMA), polyvinylidene fluoride (PVDF) and so on. Gel-type polymer electrolytes have little pollution to the environment and better safety performance in use, and are very popular in the battery market. In recent years, the trend of development is to modify, copolymerize or blend with nanoparticles (commonly used inorganic fillers are SiO2, Al2O3) to obtain higher porosity, lower electrical resistance, higher tear strength, and better acid and alkali resistance. Capable and flexible electrolyte membrane.
Solid electrolytes are generally called fast ion conductors, which require high ionic conductivity, low electronic conductivity and low activation energy. To be honest, I think solid electrolyte should be the final BOSS of lithium ion electrolyte. The proposal is to solve all the problems of lithium ion electrolyte at this stage, so the development goal is to fundamentally solve the safety problems of lithium ion batteries currently used and improve Energy density, cycleability, service life, lower battery cost, etc.
3. Development and Prospects
When the metal lithium dendrites and safety issues are solved, lithium metal is likely to become the final negative electrode material for lithium-ion batteries. The figure below is a literature on the development plan of lithium-ion batteries from the perspective of theoretical calculations, from lithium-ion batteries to lithium metal batteries, and then to lithium fuel power batteries.
Therefore, based on this point: For lithium-ion batteries, from the perspective of increasing energy density year by year, the future development trend of rechargeable lithium-ion batteries may be:
A new generation of lithium-ion batteries using high-capacity anodes, high-voltage anodes, and high-capacity anodes, such as LiNi1/2Mn3/2O4, xLi2MnO3(1–x)LiNi1/3Co1/3Mn1/3O2 as the anode, and high-capacity Si-based materials as the anode Lithium-ion battery.
A rechargeable lithium ion battery with metallic lithium as the negative electrode. The working voltage of fluorinated graphite (CF)n is 2.9V, and the lithium storage capacity is 800mAh/g. Li/(CF)n batteries have high mass energy density, but they cannot be recycled at present. Other lithium-ion batteries, such as Li/FeF3, Li/MnO2, Li/FeS2 battery cycle, safety and other comprehensive performance can not fully meet the requirements of the application.
It is expected that the first realization may be a rechargeable lithium-ion battery using metal lithium as the negative electrode and using the existing lithium-ion battery positive electrode material.
The final high-energy density battery should be a rechargeable lithium-ion battery with metal lithium as the negative electrode and O2, H2O, CO2, and S as the positive electrode.
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