What is a power lithium battery? Detailed solution of the next generation of power lithium battery

2022/04/08

  Author :Iflowpower – Portable Power Station Supplier

At present, vigorously developing new energy vehicles have become a consensus to achieve energy conservation and emission reduction, to meet climate change, and many countries will rise to the national strategic height of new energy vehicles to national strategies. The major automobile groups in the United States, Europe, Japan, have launched their respective development programs. If the public puts forward the "2025 Strategy", it is expected that more than 30 electric vehicles have been launched by 2025, and sales will compete to reach 3 million units.

Especially since 2016, important auto power has increased the support of the new energy automotive industry: German government and industry supply a total of 1.2 billion euros subsidized funds, and implement special purchase subsidies; US government supplies 45 billion Dollar loan guarantee, vigorously promote electric vehicle infrastructure construction, and invest in developed high-energy density batteries. However, the scale application of electric vehicles is still subject to multiple constraints such as renewal mileage, safety, cost, etc.

There is a significant new increase in kilometers, and the carbon emissions in the full life cycle are improved. The price of the whole vehicle will also increase the boat, so the fundamental solution strategy still needs to significantly improve the performance of the battery. Take the Modra Electric Motor in the United States as an example, in order to solve the "mileage anxiety" problem, nearly 7,000 3.

1ah 18650 lithium-ion batteries are used, so that the battery has reached more than 400km, but its battery weight reaches 500kg. The price of the car is as high as 79,000 US dollars, to a certain extent, and its promotion is promoted in the market. my country's power supply as a technical route, the battery used by the vehicle is higher, and the energy density and safety of the battery makes a more demanding requirement, so it is urgent to develop a high-specific, high-security power lithium battery.

Also taking into account power characteristics, cycle life and cost, etc. The significant improvement of each battery performance is essentially a major change in battery material system. From the first generation of nickel-hydride batteries and lithium-manganese acid, the second generation of lithium iron ion batteries, to the third generation of third-generation ternary batteries, which are currently widely used and expected to last until 2020, their energy density and cost Exhibit a significant trend of step-oriented rising and decline, respectively.

Therefore, what kind of battery system is selected from the next generation of cars, regarding the implementation of battery goals in 2020 to 2025. In the current various new battery systems, solid-state batteries use new solid electrolytes to replace current organic electrolyte and diaphragm, high safety, high volume energy density, and simultaneously with different high-grade energy electrode systems (such as lithium sulfur systems, metal - Air system, etc.) has broad adhesive, further enhances its mass energy density, which is expected to become the final solution of the next generation of power lithium batteries, causing many research institutions such as Japan, the United States, Germany, startups and some car companies.

1 Solid State Battery Overview Traditional Lithium Ion Battery Adopt Organic Liquid Electrolyne Electrolyne Fluids, the battery is easy to heat up, resulting in electrolysis, spontaneous combustion, or even explosion, and severe safety hazards. Solid-state-based lithium-ion batteries based on solid electrolytes developed in the 1950s, due to the use of solid electrolytes, excluding flammable, volatile components, completely eliminating battery smoke caused by the battery due to leakage liquid, fire, etc. Space battery system.

Regarding the energy density, China, the United States, the Japanese government hopes to develop 400 ~ 500Wh / kg prototype devices in 2020, and realize mass production 2025 ~ 2030. To achieve this goal, the most likely the most likely used is the use of metal lithium negative electrodes, metal lithium exists in conventional liquid lithium ion batteries, deceased, powder, SEI (solid electrolyte membrane) unstable, surface side reactance Many more technical challenges, while the compatibility of solid electrolytes and metallic lithium makes it possible to use lithium as a negative electrode, thereby significantly enhanced energy density. Table 1 Compares traditional lithium-ion batteries and full solid lithium ion batteries, which can be understood from the basic characteristics of solid lithium ion batteries.

Further, as shown in Table 2, the desired requirements of the vehicle battery application, based on their own characteristics, the solid state battery system gives possible solutions one by one. Table 2 Battery Application Requirements and Solid State Battery System Solution 2 Solid State Battery Core Componizers Solid Electrolyte About Solid State Battery It is normal temperature) to maintain high lithium ion conductivity; negligible or absence of grain boundary impedance; match the thermal expansion coefficient of the electrode material; during battery charge and discharge, the positive and negative electrode material maintains good chemical stability, especially Metal lithium or lithium alloy negative electrode; electrochemical width, high decomposition voltage (> 5.5vvs.

li/li +); not easy to absorb, low price, simple preparation; environmentally friendly. The following will be specifically discussed from the composition, basic characteristics, technical status, problems and modification strategies of different types of solid electrolytes from current focus. 2.

1 Polymer solid electrolyte polymer solid state electrolyte is a kind of lithium-ion conductor composed of an organic polymer and a lithium salt, with a quality of light, easy film, viscoelasticity. Applying in a lithium-ion battery, high-proportioned energy, high-power, long cycling battery can be obtained in a wide working temperature range, and the battery can be prepared into various shapes, and the effective space of electrochemical devices can be utilized. Polymer lithium ion batteries can withstand the temperature and shape changes of extrusion, collision, and battery interior during assembly, use and transportation.

Further, the polymer electrolyte can also serve as the diaphragm, isolation of the positive and negative electrode, and the volume change of the electrode material, the tight contact of the electrode and electrolyte is maintained in the battery charge and discharge process. The polymer electrolyte can also inhibit the growth of lithium dendrites, reduce the reaction activity between electrolyte and electrode materials, and improve the safety of the battery. The polymer electrolyte is also advantageous for the battery to make a large scale production, which is expected to reduce production costs.

At present, commercialized polymer lithium-ion batteries have been gradually applied to mobile phones, laptops, mobile charging power and other electronic equipment fields. The solid polymer battery can be approximated as a solid solution system that is directly dissolved in the polymer in the polymer, and its important performance is determined by the polymer, lithium salt, and various additives. Regarding the choice of lithium salt is actually the choice of anion, in the polymer solvent of the nonpropracy, the polymer solvent of the low dielectric constant plays an important use of the polymer electrolyte.

The formation capacity of the polymer electrolyte depends on the relative size of the solvate use of the cation and the salt crystal energy, the greater the crystal energy, the weaker the ability to form the polymer electrolyte with the polymer. The upper limit of the lithium salt crystal can generally consider 850J / mol, different lithium salts, crystal energy sizes, common lithium salt crystal soft sort: f-> cl-> br-> i-> SCN-> CLO4- ~ Cf3so3-> bf4- ~ 6ASF6-. In addition to the crystal and anionic charge density distribution, the dissociation constant of the lithium salt also has a certain effect.

PEO is a typical polymer electrolyte comprising the -CH2CH2O- and -CH2CH2CH2O- unit, the optimum distribution of the ether oxygen atom in PEO, so that it can form a complex with a plurality of lithium salts, and the PEO-based polymer electrolyte is therefore Get extensive research and application [3]. Regarding the inorganic additive, the inorganic filler having chemical inert, high-proportional surface can improve the thermal stability of the polymer electrolyte, inhibit the formation of the passivation layer on the electrode interface, supply electrolyte electrical conductivity and cationic migration, etc., commonly used inorganic Additives include SiO2, Al2O3, MgO, ZrO2, TiO2, LitaO3, Li3n, Lialo2, etc.

At present, the polymer electrolyte is significantly improved in the safety of the liquid electrolyte, but there is still a need to further improve the lithium ion conductivity of the electrolyte, maintain the mechanical stability of the polymer and chemical stability. 2.2 Inorganic Solid Electrolyte Inorganic Solid Electrolyte Plays the advantages of single ion conduction and high stability, used in full solid-state lithium ion batteries, high thermal stability, not easy to combustion, environmentally friendly, high cycle stability, strong impact resistance The advantages have been widely concerned, and it is expected to be used on new lithium-ion batteries such as lithium sulfur batteries and lithium air batteries.

It is an important direction for future electrolyte development. According to the material structure, the inorganic solid electrolyte can be divided into two major categories of crystalline and amorphous (glass), each of which can be divided into oxide and sulfide according to different elements. 2.

2.1 Amorphous (glass) inorganic electrolyte glass inorganic solid electrolyte has a width of components, ion conduction isogebraic, relatively low interface impedance, easy to process film formation, has a good application in full solid state cells prospect. According to the composition, it can be divided into an oxide system glass electrolyte and a sulfide system glass electrolyte, in which the electrochemical stability and thermal stability of the oxide glass electrolyte, but the ionic conductivity is relatively low, although the sulfide glass electrolyte has a high ion conductance.

Rate, but poor electrochemical stability, difficult to prepare. The oxide glass system electrolyte is composed of a network to form an oxide (e.g.

, SiO2, B2O3, P2O5, etc.) and a network modifier (e.g.

, Li2O), and the network forms an oxide to form a glass network, a network modified oxide Break the oxygen bridge in the network, allowing lithium ions to migrate between its networks. Improve the oxide glass system electrolyte conductivity can be achieved by a variety of ways: First, the content of the network modifier can be added. Regarding the increase in the amount of LI2O, the content of the oxide glass is increased, while the content of Li2O has increased to a certain extent, the number of non-oxide ads can be added, and the non-oxygen bridge atom can capture lithium ions.

Thereby reducing the oxide glass conductivity, and the mixed network can be used to form oxides. The use of an oxide using a network of two or more binary or more, there is a hybrid network effect, the defective structure in the new network, improve the transmission bottleneck in the lithium ion conduction channel, and improve lithium ion conduction. Such as Li2O-P2O5-B2O3 ternary system glass, when the lithium ion concentration is 5 mol%, the conductivity is 9×10 ^ (- 5) s / cm.

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