FeS2 composite positive electrode and all-solid-state battery device

Abstract

The invention provides a FeS2 composite positive electrode and an all-solid-state battery device, a sulfide solid electrolyte with lithium supplement and moisture absorption effects is adopted, FeS2 is used as a positive electrode active material, the sulfide solid electrolyte has the following chemical composition: Li < 7 + y-z > MyAs < 1-y > S < 6-z > X < z >, M is at least one of Si, Ge, Sn, Ti and Zr, X is a halogen element, y is more than or equal to 0 and less than or equal to 1, and z is more than or equal to 0 and less than or equal to 2. The positive electrode and the all-solid-state battery which are low in cost, high in loading capacity and long in cycle life and can be charged and discharged under high magnification and large current density are obtained, meanwhile, the consumption of conductive carbon can be reduced, and the problem of huge volume change of FeS2 is solved.

Description

technical field [0001] The invention relates to the technical field of battery materials, in particular to a sulfide solid electrolyte with lithium supplementation and moisture absorption, and its combination with FeS 2 Composite cathodes and all-solid-state battery devices made. Background technique [0002] Lithium-ion batteries, as high-efficiency energy storage devices, have achieved commercial applications in the fields of consumer electronics and electric vehicles. However, lithium-ion batteries have reached a bottleneck in the improvement of energy density, and their safety issues are also worrying. The all-solid-state battery using solid-state electrolyte and metal lithium anode is a key technology to realize high-safety and high-energy-density batteries, which has attracted widespread attention from academia and industry. All-solid-state batteries use solid-state electrolytes with high thermal stability, density, and mechanical strength as ionic conductors to repl...

AI Technical Summary

Problems solved by technology

According to the theory of soft and hard acids and bases, the sulfide electrolyte containing P element has poor air stability, and it is easy to react with moisture and oxygen in the air, accompanied by the generation of toxic hydrogen sulfide gas, which destroys the structure of the electrolyte itself, and the chemical composition Changes occur, accompanied by irreversible changes in structure and performance, which lead to a sharp deterioration in its ionic conductivity and other properties

The extremely poor air stability of sulfide solid-state electrolytes affects the production, storage, and transportation of sulfide solid-state electrolyte materials, and the production, manufacture, and use of sulfide all-solid-state batteries, severely restricting its output and increasing the production and production costs. The difficulty of processing limits its large-scale application in all-solid-state lithium batteries and increases the cost of production and processing

The idea of ​​the existing technical solution is to dope and modify the material to improve the ion conductivity or the stability of the wet air or the stability to metal lithium, such as Li 6 P.S. 5 The ionic conductivity of I is only 10 -6 On the order of S / cm, materials doped with a series of elements such as In, Si, Ge, Sn, F, etc., the ionic conductivity is generally 10 -5 -10 -4 S / cm level, up to 1.1×10 -3 S / cm, it is difficult to reach 10 -2 S / cm

[0004] Sulfide solid electrolytes without P element, such as Li 4 GeS 4 , Li 4 SnS 4 , Li 3 Sb 4 etc., although they have high air stability, they have the following problems: (1) the ionic conductivity is generally very low, far below 1mS / cm; (2) due to the high-valent metal ions, the electrochemical reduction is stable (3) Due to the generation of electronic and ion-conducting alloy by-products, it is impossible to form a kinetically stable interface passivation layer with metallic lithium, resulting in a continuous increase in interface impedance and deterioration of battery performance (rapid capacity decay)

[0005] At the level of solid-state battery devices, it is limited by the low room temperature ionic conductivity of the electrolyte material (<10mS / cm), the low electronic conductivity of the positive electrode active material (<1mS / cm), and the chemical relationship between the sulfide electrolyte and the positive electrode active material. And electrochemical stability problems, including the space charge layer effect between the sulfide electrolyte and the oxide positive electrode, interdiffusion of elements, electrochemical interaction, etc., have led to the current sulfide all-solid-state battery devices in terms of multiple performance indicators. , especially the active material loading, current density, and rate performance at room temperature (generally need to work at a low rate of 0.1C), etc. cannot reach the level of liquid lithium-ion batteries.

[0006] The ionic conductivity of sulfide solid electrolytes currently reported is generally lower than 10mS / cm at room temperature. In addition, because solid electrolytes do not have the fluidity and wettability of liquid electrolytes, they cannot penetrate into the pores of the primary particles and / or secondary particles of positive active materials. , can only rely on a limited contact area for lithium ion conduction, so it is difficult to achieve high active material loading, high surface capacity, high current density or high rate charge and discharge

[0007] The first-week Coulombic efficiency of the currently reported sulfide all-solid-state batteries is generally lower than 90%, which is mainly due to the formation of an interface layer by side reactions that consume lithium ions.

In addition, the currently reported all-solid-state batteries have serious interface problems, resulting in generally low cycle life (the number of cycles when the specific capacity is reduced to 80% of the initial or reversible specific capacity) even at low rates.

[0008] Starting from the level of (sulfide) solid-state electrolyte materials, indirectly introducing lithium supplements to the positive electrode to improve battery performance, including technical solutions for first-week Coulomb efficiency, rate performance, and long-term cycle stability, have not yet been reported.

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