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Battery solid state – the ultimate overview and guide
With the rapid development of new energy technologies, battery solid state, as a new type of energy storage device with great potential, are gradually moving from the laboratory to industrialization. It has attracted worldwide attention for its high energy density, superior safety performance and long cycle life.
The article will provide a comprehensive guide to the overview, principles, advantages and disadvantages of battery solid state.
What is a battery solid state?
A battery solid state is a type of battery that uses a solid electrode and a solid electrolyte. The negative electrode material of the solid-state battery may be a composite negative electrode of nano silicon and graphite, and the cathode materials may be lithium manganate, lithium-rich manganate-based materials or non-lithium cathode materials. The electrolyte is a solid electrolyte with an energy density of 300 to 450 watt-hours/kg.
Battery solid state uses solid electrolytes to replace the electrolyte and lithium battery separator, which is safer, have higher energy density and stronger cycling performance, and has become the main research and development direction of next-generation power batteries.
Based on electrolyte materials, battery solid state can be divided into polymer, oxide, sulfide three electrolytes. According to the different types of negative electrodes, solid-state lithium batteries can be divided into all-solid-state lithium ion batteries and all-solid-state lithium metal batteries.
Ion conduction mechanism of battery solid state
Solid electrolyte is generally divided into inorganic solid electrolyte and polymer-based solid electrolyte. Ion migration in crystalline materials of inorganic solid electrolytes usually follows the Arrhenius formula, which depends on the concentration and distribution of defects in the crystal structure. The ion diffusion mechanism based on Schottky and Frenkel point defects includes simple vacancy diffusion and relatively complex bivacancy mechanism, gap mechanism and gap-displacement exchange mechanism.
Solid polymer electrolyte is generally a solid solution formed by a uniform mixture of the polymer matrix and lithium salt. Compared with inorganic solid electrolyte, polymer solid electrolyte has the advantages of good softness, high viscosity, low cost and easy processing.
The polar groups in the polymer electrolyte, such as C = O, C = N, -O -, one S -, etc., can coordinate with lithium ions to promote the dissolution of lithium salts and produce freely moving ions. At present, most studies believe that ion transport in polymer electrolytes mainly occurs in the amorphous region above Tg, so the motion ability of its chain segments is also the key to efficient ion transport.
Advantages of solid-state lithium batteries
Good safety
Flammable organic electrolyte is completely abandoned in the solid-state lithium battery, so it can eliminate electrolyte leakage and overcharge or overdischarge of electrolyte decomposition, gasification, combustion and other safety hazards. The high thermal decomposition temperature of the solid electrolyte can eliminate the risk of deformation or decomposition of the polymer membrane in the event of thermal abuse.
In addition, the solid electrolyte has a high Young’s modulus, especially the inorganic solid electrolyte, which can reduce the risk of internal short circuit caused by the growth of lithium dendrites, while the solid electrolyte has good thermal stability and low reactivity to the positive and negative electrodes, and is not easy to produce chain reactions, which can reduce the risk of thermal runaway. Therefore, all-solid-state lithium batteries have high safety characteristics.
High energy density
The high safety of solid electrolytes makes the application of high specific energy lithium metal anode in battery solid state possible. The battery solid state can realize bipolar stacking due to the non-fluidity of the solid-state electrolyte, which simplifies the battery production process and reduces the proportion of non-electrochemically active components such as outer packaging.
In addition, solid-state batteries can operate in a wide temperature range, thus simplifying the temperature control system. The high-capacity lithium metal cathode and the compact battery structure together give solid-state lithium batteries potential advantages in terms of energy density.
High power density
The lithium ion concentration (1-2 mol dm-3) and ion migration number in liquid organic electrolyte are low (about 0.4-0.5), and the insufficient migration rate of anions and cations leads to the ion concentration gradient when charging and discharging under high current density conditions, so it is unable to provide continuous and rapid ion transport.
In contrast, inorganic solid electrolytes generally have a high concentration of lithium ions (about 35 mol dm-3 in the Li10GeP2S12 electrolyte) and a high ion migration number (close to 1), and can still provide continuous and rapid ion conduction when operating at a high current density. Therefore, solid-state lithium batteries have potential advantages in terms of output power.
Long working life
Wide operating temperature range
The disadvantages of solid-state lithium batteries
The ionic conductivity of material end is low
High cost
The cost of solid-state batteries is higher than that of liquid batteries, mainly reflected in solid-state electrolytes and positive and negative electrodes.
The solid electrolyte is currently difficult to thin. Some of the rare metal raw materials used are relatively high in price. For example, the oxide electrolyte contains zirconium, the sulfide electrolyte contains germanium, and the highly active positive and negative electrode materials used in the superposition of high energy density are not mature.
The copper lithium composite belt price is 10,000 yuan /kg, so the solid state also puts forward more stringent requirements on the production process, cost and quality control.
Conclusion
In summary, solid-state batteries, with their significant performance advantages, have become the development direction of high battery performance technology in the future. Despite the technical challenges and economic issues, with the acceleration of global research and development and the continuous optimization of new material systems, solid-state batteries are expected to achieve commercial applications in the near future, bringing revolutionary changes to many fields.