Lithium-ion safety has always been an issue of concern to the industry. Because of the increasing requirement of energy density in application and policy level, the trend of ternary battery becoming the mainstream technology is irreversible.
But today, the security of the three-dimensional battery is still not well resolved, even the so-called BMS to do the world's best Tesla, is also a safety accident, 2017 alone in the domestic two models serious fire occurred, the security of ternary batteries is still being questioned. With the development of new energy vehicles, high energy density, high security batteries become the market's inevitable goal.
Some experts believe that the use of solid-state electrolytes to replace traditional electrolytes is essentially the only way to improve the safety of lithium batteries. All solid-state lithium-ion batteries, using solid-state electrolytes instead of traditional organic liquid electrolyte, are expected to solve the problem of battery safety from the root, which is the ideal chemical power supply for electric vehicles and large-scale storage.
The structure of all solid-state lithium-ion batteries comprises a cathode, an electrolyte and a negative electrode, all of which are composed of solid materials.
Advantages compared with the traditional electrolyte lithium ion battery Completely eliminates the electrolyte corrosion and the leakage safety hidden danger, the heat stability is higher. Because of the flammable organic solution contained in the liquid electrolyte, it is easy to burn and explode when the short circuit temperature rises, and the safety device structure of resisting temperature rise and short circuit need to be installed.
The solid-state electrolyte is nonflammable, non-corrosive, non-volatile, does not exist the leakage problem, also overcomes the lithium dendrite phenomenon, thus the whole solid-state battery has the extremely high security. No need to encapsulate liquid, support serial stacking arrangement and bipolar structure, improve production efficiency;
Because of the solid-state properties of solid electrolytes, multiple electrodes can be superimposed; The Electrochemical stable window width (up to 5V or above) can be matched with high voltage electrode material. The solid electrolyte is a single ionic conductor with little side effects and longer service life.
Relatively light, compared to liquid batteries, the same capacity of batteries, solid-state electrolyte batteries are relatively light, such as Tesla-Panasonic production of ternary lithium battery quality of 900kg, while the solid-state battery start-up company Seeoinc production of the same capacity of the battery is only 323kg, close to the former One-third. However, solid-state batteries also have drawbacks. The overall low conductivity of solid electrolyte leads to the overall low magnification performance, large internal resistance, slow charging speed, and high cost, now solid-state battery if and ordinary lithium-ion batteries in the traditional market competition, and not much advantage.
Therefore, to play the solid-state battery itself high security, high temperature stability, possible flexibility and other multi-functional features, and traditional lithium-ion batteries in the differentiated market competition, may be a solid state battery in the near future a more promising market breakthrough direction.
Polymer solid-state electrolytes (SPE) 4Composed of: polymer substrates (such as polyester, polymerase and polyamine) and lithium salts (e.g. Liclo 4, liasf 6, LIPF 4, LIBF
, etc.) constitute.
Features: Light quality, good viscoelasticity, excellent machining performance, etc.
Main categories: poly (ethylene oxide), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), poly (PMMA), poly (propylene oxide) (PEO), polyvinylidene chloride (PVDC) and single ion polymer electrolyte. Mechanism: the ion transmission in solid polymer electrolyte mainly occurs in amorphous region, but the crystallinity of PEO at room temperature is high, which leads to low ionic conductivity, which seriously affects the charging and discharging ability of large current. In order to improve the conductivity of the PEO chain by reducing the crystallinity, the most simple and effective method is to treat the polymer matrix with inorganic particle hybridization. 2O3At present, more research on inorganic fillers including MgO, Al 2, SiO and other metal oxides nanoparticles and zeolite, montmorillonite and so on, the addition of these inorganic particles disrupts the order of the polymer chain in the matrix, reduces its crystallinity, the interaction between the polymer, the lithium salt and the inorganic particles, increases the lithium-ion transmission channel, improves the conductivity and the ion migration number.
Inorganic fillers can also play the role of absorbing trace impurities (such as moisture) in the composite electrolyte and improving the mechanical properties. As a whole, solid state battery preparation technology has yet to be strengthened, to form capacity of enterprises limited, large-scale expansion of technology needs to overcome many difficulties, still in the promotion of development period.
