Lithium batteries may be replaced by solid-state batteries in the future

by:CTECHi     2021-07-12

Lithium battery safety has always been a concern of the industry. Due to the ever-increasing requirements for energy density at the application and policy levels, the trend of ternary batteries becoming the mainstream technology route has been irreversible. But to this day, the safety of the ternary battery has not been solved well. Even Tesla, which claims to be the best BMS in the world, has continued to have safety accidents. In 2017, there were two serious domestic ModelS models. In the fire incident, the safety of the ternary battery is still being questioned by everyone.

With the development of new energy vehicles, high-energy-density and high-safety batteries have become the indispensable targets of the market. Some experts believe that the use of solid electrolytes to replace traditional electrolytes is essentially the only way to improve the safety of lithium batteries.

All solid-state lithium-ion batteries use solid electrolytes to replace traditional organic liquid electrolytes, which are expected to fundamentally solve battery safety issues. They are ideal chemistry for electric vehicles and large-scale energy storage. power supply. The structure of an all-solid-state lithium-ion battery includes a positive electrode, an electrolyte, and a negative electrode, all of which are composed of solid materials.

Compared with traditional electrolyte lithium-ion batteries, it has advantages

Completely eliminates the safety of electrolyte corrosion and leakage Hidden danger, higher thermal stability. Since the liquid electrolyte contains flammable organic solutions, it is easy to burn and explode when the short-circuit temperature rises sharply. It is necessary to install a safety device structure that resists temperature rise and short-circuits. The solid electrolyte is non-flammable, non-corrosive, non-volatile, and does not have the problem of liquid leakage. It also overcomes the phenomenon of lithium dendrites, so the all-solid-state battery has extremely high safety.

No need to encapsulate liquid, support serial superposition arrangement and bipolar structure, improve production efficiency; due to the solid-state characteristics of solid electrolyte, multiple electrodes can be superimposed;

The electrochemical stability window is wide (up to 5V or more), which can match high-voltage electrode materials; solid electrolytes are generally single-ion conductors with almost no side reactions, and have a longer service life; relatively light Compared with liquid batteries, solid electrolyte batteries with the same capacity are relatively lighter. For example, the mass of the ternary lithium battery pack produced by Tesla-Panasonic reaches 900kg, while the mass of the same capacity battery pack produced by the solid-state battery startup company SeeoInc But only 323kg, close to one-third of the former.

However, solid-state batteries also have disadvantages. The overall low conductivity of solid electrolyte leads to overall low rate performance, large internal resistance, slow charging speed, and overall high cost. If solid-state batteries are to compete with ordinary lithium-ion batteries in the traditional market, they will not Too much advantage. Therefore, using solid-state batteries with their own high safety, high-temperature stability, and possible flexibility and other multi-functional characteristics to compete with traditional lithium-ion batteries in a differentiated market may be a promising market breakthrough for solid-state batteries in the near future. direction.

Solid polymer electrolyte (SPE)

Composed of: a polymer matrix (such as polyester, polymerase and polymer Amine, etc.) and lithium salt (such as LiClO4, LiAsF4, LiPF6, LiBF4, etc.).

Features: lighter weight, good viscoelasticity, excellent machining performance, etc.

Main categories: polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA) , Polypropylene oxide (PPO), polyvinylidene chloride (PVDC) and single ion polymer electrolyte.

Mechanism: The ion transport in the solid polymer electrolyte mainly occurs in the amorphous region, and the unmodified PEO has high crystallinity at room temperature, resulting in higher ionic conductivity. Low, which seriously affects the high-current charging and discharging capabilities. Researchers improved the mobility of the PEO segment by reducing the crystallinity, thereby increasing the electrical conductivity of the system. The simplest and most effective method is to hybridize the polymer matrix with inorganic particles. At present, the most researched inorganic fillers include metal oxide nanoparticles such as MgO, Al2O3, SiO2, and zeolite, montmorillonite, etc. The addition of these inorganic particles disturbs the order of polymer segments in the matrix and reduces its crystallinity , The interaction between polymer, lithium salt and inorganic particles increases the lithium ion transport channel and improves the conductivity and ion mobility. Inorganic fillers can also play a role in adsorbing trace impurities (such as moisture) in the composite electrolyte and improving mechanical properties.

From an overall point of view, the current maturity of the preparation technology of solid-state batteries needs to be strengthened. There are only a limited number of companies that can form large-scale production capacity. Many are still in the stage of promotion and development. However, it can be expected that with the continuous development of Ru0026D and industrial technology, the scientific and technological problems in all solid-state batteries will gradually be alleviated. In the next few years, the market for solid-state battery products will usher in opportunities for vigorous development.

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