Views: 0 Author: Site Editor Publish Time: 2025-04-15 Origin: Site
Solid state battery refers to the use of solid electrolyte instead of traditional electrolyte lithium battery, according to the amount of solid electrolyte can be divided into semi-solid state battery and all-solid state battery. Usually we use 10% of the liquid content in the battery as the dividing line between semi-solid batteries and liquid batteries, while all-solid batteries will use solid electrolytes entirely and the liquid content will be reduced to 0%.
Solid state lithium battery is mainly composed of positive electrode, negative electrode and solid electrolyte, the most essential difference is to replace the liquid battery electrolyte and diaphragm with solid electrolyte, to achieve no or less use of diaphragm and electrolyte.
1. The positive electrode is usually lithium metal or similar materials. When lithium ions move from the solid electrolyte to the positive electrode, the positive material undergoes an oxidation reaction, releasing electrons.
2. The negative electrode is generally made of lithium alloy or similar materials. When lithium ions move from the solid electrolyte to the negative electrode, the negative material will undergo a reduction reaction and receive electrons.
3. Solid electrolyte is composed of solid materials that can conduct electricity, such as inorganic salts containing lithium, polymers or ceramic materials. This electrolyte has high ion mobility and low resistance, and is chemically stable.
According to the electrolyte classification, the battery can be subdivided into liquid (25wt%), semi-solid (5-10wt%), quasi-solid (0-5wt%) and all-solid (0wt%) four categories, of which semi-solid, quasi-solid and all-solid three are collectively referred to as solid-state batteries. Car companies use solid-state batteries, with safety as a short-term driver and energy density as a long-term driver.
Compared with the liquid battery, the semi-solid battery reduces the amount of liquid electrolyte, and increases the composite electrolyte of oxides and polymers, wherein the oxides are mainly added in the form of diaphragm coating and positive and negative electrode coating, and the polymer is filled in the form of frame network, in addition, the negative electrode is upgraded from the graphite system to the pre-lithium silicon based negative electrode and lithium metal negative electrode. The positive electrode is upgraded from high nickel to high nickel + high voltage, lithium rich manganese base and other positive electrodes, the membrane is still retained and coated with solid electrolyte coating, the lithium salt is upgraded from LiPF6 to LiTFSI, and the energy density can reach more than 350 Wh/ kg. Although semi-solid batteries reduce the amount of liquid electrolyte, there is still a risk of flammability.
Compared with the liquid battery, the all-solid-state battery cancels the original liquid electrolyte, chooses oxides, sulfides, polymers, etc., as solid electrolytes, and divides the positive and negative electrodes in the form of a thin film, thus replacing the role of the diaphragm, of which the oxides are progressing faster, the future potential of sulfides is the largest, and the upper limit of polymer performance is lower. The negative electrode has been upgraded from the graphite system to the pre-lithium silicon based negative electrode and lithium metal negative electrode, and the positive electrode has been upgraded from high nickel to ultra-high nickel, lithium nickel manganate, lithium rich mangan-based positive electrode, and the energy density can reach 500 Wh/ kg.
Depending on the material and characteristics of the solid electrolyte, solid state batteries can be divided into several main categories, including sulfide, oxide and polymer solid state batteries.
Sulfide solid state batteries use inorganic sulfide materials as electrolytes, which typically have high lithium-ion conductivity that approaches or exceeds the levels of traditional liquid electrolytes.
Sulfide solid electrolytes have attracted much attention due to their high ionic conductivity, for example, the conductivity of the Li10GeP2S12 (LGPS) electrolyte can reach 1.2×10^-2 S/cm. However, the sulfide electrolyte is sensitive to water vapor, easily reacts with water to produce toxic H2S gas, and has irreversible chemical reactions with oxygen and water vapor in the air, resulting in the reduction of ionic conductivity and structural damage.
Therefore, the development of sulfide solid electrolyte is difficult and the production environment is strict.
Oxide solid state batteries use oxide materials as electrolytes, which generally have low ionic conductivity, but have good mechanical properties and chemical stability.
The representative oxide electrolyte is the garnet type structure of Li7La3Zr2O12 (LLZO), its ionic conductivity is high, at room temperature up to 10^-4 S/cm. The compact morphology of the oxide electrolyte makes it have higher mechanical strength, good stability in air and high voltage resistance. However, due to its high mechanical strength, poor deformability and softness of oxide electrolyte, the electrolyte sheet is easy to crack, and the solid-solid interface contact loss is large, which limits its application.
Polymer solid state battery is composed of polymer matrix and lithium salt, the ionic conductivity is low at room temperature, but when heated to more than 60℃, the ionic conductivity is significantly improved.
The polymer electrolyte has the characteristics of light weight, good elasticity and excellent machining performance, and its process is close to the existing lithium battery, which is easy to large-scale production. However, the thermal stability of polymer electrolytes is limited due to their low ionic conductivity at room temperature and the risk of short circuit caused by lithium dendrite penetration.
In addition to the three main types of solid-state batteries mentioned above, there are also Combined solid-state battery, such as composite solid-state electrolytes, which are electrolytes obtained from the combination of sulfide/oxide and polymer electrolytes. This composite electrolyte combines the advantages of inorganic and organic solid electrolytes with high lithium-ion conductivity and electrochemical stability.
In addition, there are chloride solid electrolytes, which have the high ionic conductivity of sulfide, deformability, and oxide stability for high-voltage cathode materials, but it is not feasible in terms of large-scale commercialization.
Solid electrolytes are less fluid than electrolytes, so the direct contact between solids and solid particles is poor, coupled with electrochemical instability, leading to many interface problems. However, the potential advantages of solid-state batteries compared to liquid batteries are:
High safety: non-volatile and non-flammable solid electrolytes have higher safety than organic electrolytes.
Good temperature adaptability: All-solid-state batteries can operate over a wider temperature range, especially at higher temperatures.
High energy density: All-solid-state batteries are expected to solve the safety problem of lithium metal negative electrode (lithium dendrites). Furthermore, the energy density of lithium-ion batteries is improved on the basis of the graphite and silicon-carbon negative electrodes of commercial lithium-ion batteries.
Simplified cell, module, system design: Since solid electrolytes do not have fluidity, internal strings can be used.
As an important direction of energy technology in the future, solid-state battery has a broad development prospect. With the advancement of technology, the promotion of policies and the expansion of the market, solid-state batteries are expected to achieve large-scale commercial applications.
Technological progress: With the continuous development of materials science, electrochemistry and other fields, the technical problems of solid-state batteries will be gradually solved. For example, the ionic conductivity and fast charge performance of solid-state batteries can be improved by means of material composite and interface optimization.
Policy promotion: The Chinese government attaches great importance to the development of the solid-state battery industry and has introduced a series of supporting policies. The release of these policies provides a clear, broad market prospect and a good production and operation environment for the development of the solid-state battery industry.
Market demand: The rapid growth of the new energy vehicle market and the increase in energy storage demand provide a broad market space for solid-state batteries. In the future, with the popularization of new energy vehicles and the wide application of energy storage systems, the demand for solid-state batteries will increase significantly.
