What are the core components of a fully solid lithium secondary battery?

Solid electrolyte is the core component of all-solid lithium secondary battery, and its progress directly affects the industrialization process of all-solid lithium secondary battery. At present, the research of solid electrolytes mainly focuses on three types of materials: polymers, oxides and sulfides.

Polymer solid electrolyte (SPE), consisting of polymer Matrix (such as polyester, polyether, polyamine, etc.) and lithium salts (such as LiClO4, LiAsF6, LiPF6, etc.), since 1973 P.V. Wright found ion conductivity in alkali metal salt complexes, Polymer materials are widely concerned because of their light quality, good elasticity and good mechanical properties of solid electrochemistry. SPE is also the earliest solid electrolyte to be used in practice. As early as 2011, the French company Boluolei began to deliver Autoolib electric vehicles to Paris. The car uses a full-solid lithium battery system based on SPE.

Oxide solid electrolytes can be classified into crystalline and amorphous states according to their structure. Among them, crystalline electrolytes include perovskite, anti-perovskite, garnet, NASICON, LISICON, etc., amorphous oxidation. The research hotspots are LiPON type electrolytes and partially crystallized amorphous materials used in thin film batteries.

The sulfide solid electrolyte is derived from an oxide solid electrolyte in which an oxygen element in the oxide body is replaced by a sulfur element. Since the electronegativity of sulfur is smaller than that of oxygen, the binding of lithium ions is small, which is beneficial to obtain more free-moving lithium ions. At the same time, the radius of the sulfur element is larger than that of the oxygen element. When the sulfur element replaces the oxygen element, the lattice structure is expanded to form a larger lithium ion channel and the conductivity is improved, and the room temperature can reach 10-4-10-2 S/cm.

(2). Positive materials

The positive electrode of the all-solid lithium secondary battery generally adopts a composite electrode, and includes a solid electrolyte and a conductive agent in addition to the electrode active material, and functions to simultaneously transport ions and electrons in the electrode. LiCoO2, LiFePO4 and LiMn2O4 are more common. Later, it is possible to develop high-nickel layered oxides, lithium-rich manganese-based and high-voltage nickel-manganese spinel-type positive electrodes. At the same time, attention should be paid to the research and development of new cathode materials without lithium.

(3). Negative material

The negative electrode materials of all-solid lithium secondary batteries are currently mainly concentrated in three categories: metal lithium negative electrode materials, carbon negative electrode materials, and oxide negative electrode materials. Each of the three major materials has its own advantages and disadvantages. Among them, the metal lithium negative electrode material has become one of the most important negative electrode materials for all-solid lithium batteries due to its high capacity and low potential.

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