Negative electrode slurry and application thereof

Abstract

The invention discloses a negative electrode slurry and an application thereof. The negative electrode slurry comprises a first negative electrode active substance, a second negative electrode active substance, a solid electrolyte, conductive carbon and a binder, the lithium intercalation platform potential of the first negative electrode active substance is 0.1 V-0.2V, and the lithium intercalation plateau potential of the second negative electrode active material is at least 0.4 V higher than the lithium intercalation plateau potential of the first negative electrode active material. By adopting the negative electrode slurry, the diffusion impedance of lithium ions in the negative electrode plate can be reduced on the premise of not increasing the proportion of the conductive agent and the solid electrolyte, and the transmission capability of the lithium ions in the negative electrode plate is improved, so that the rate capability and the quick charging capability of the battery are improved; and compared with methods for increasing the content of a conductive agent or a solid electrolyte, the invention has the advantages of lower cost and higher battery energy density.

Description

technical field [0001] The invention belongs to the technical field of solid-state batteries, and in particular relates to a negative electrode slurry and an application thereof. Background technique [0002] The solid-state battery replaces the flammable organic liquid electrolyte with a non-flammable solid-state battery electrolyte, which greatly improves the safety of the battery system. At the same time, it can better adapt to high-energy positive and negative electrodes and reduce the weight of the system to achieve a simultaneous increase in energy density. Among all kinds of new battery systems, solid-state batteries are the next-generation technology closest to industrialization, which has become the consensus of the industry and the scientific community. [0003] However, the rate performance of solid-state batteries is generally poorer than that of liquid batteries. This is because there is no liquid infiltration in solid-state batteries, which makes the solid part...

AI Technical Summary

Problems solved by technology

[0003] However, the rate performance of solid-state batteries is generally poorer than that of liquid batteries. This is because there is no liquid infiltration in solid-state batteries, which makes the solid particles only rely on solid-solid contacts to connect together, thereby reducing the lithium ion. Transmission channels, and because non-lithium ion conductors such as binders need to be added to the solid-state battery pole piece, further restricting the transmission of lithium ions in the pole piece

[0004] When the solid-state battery is in the charging state, the side of the negative electrode sheet close to the electrolyte layer will first receive the lithium ions transported by the positive electrode side, but the conduction of lithium ions in the negative electrode sheet is not smooth, resulting in polarization. Appears, which in turn affects the charging performance of the battery; especially under high current, this phenomenon is more obvious, which in turn affects the fast charging performance of the battery

[0005] In order to solve the problem of poor rate performance and large ion transport impedance in solid-state batteries, one of the methods currently used is to increase the proportion of conductive carbon in the positive and negative electrodes to solve this problem.

However, this method has obvious defects: (1) The conductive carbon is all nano-powder particles, which are difficult to disperse evenly in the slurry, especially when the content increases, it is easier to form agglomerates, resulting in poor construction of the conductive network , but makes the electronic conductivity decrease

(2) The solid-state electrolytes used in solid-state batteries, such as sulfide electrolytes, are unstable under high pressure, especially when they are in contact with conductive carbon, they are more likely to decompose under high pressure, resulting in a decrease in the ionic conductivity of the sulfide electrolyte, so When more conductive carbon is added to the positive and negative pole pieces, it will cause rapid deterioration of the contact section between the solid electrolyte and the conductive carbon, which will cause a significant decline in battery performance.

(3) The increase in the conductive carbon content will inevitably occupy the proportion of other substances in the pole piece, and the reduction in the proportion of active materials in the positive and negative pole pieces will reduce the energy that can be released, which in turn will cause the overall energy density of the battery to decline; At the same time, the content of solid electrolyte decreases, which will make the ion conductive network in the negative electrode coating not well constructed, resulting in the limited energy of ion conduction not being able to play normally.

(4) Although conductive carbon is a good conductor of electrons, its transmission effect on lithium ions is poor, and it cannot solve the problem of limited lithium ion conduction in the positive and negative electrodes, so it cannot fundamentally alleviate the rate performance of solid-state batteries poor underlying problem

[0006] In order to solve the problems of poor rate performance and large ion transport impedance in solid-state batteries, the second method currently used is to increase the proportion of solid electrolyte in the positive and negative electrodes to solve this problem.

However, the disadvantages of this method are as follows: (1) The increase in the proportion of solid electrolyte will inevitably occupy the proportion of other substances in the pole piece: the reduction in the proportion of active materials in the positive and negative electrodes will cause a decrease in the capacity of the pole piece, thereby causing the overall battery drop in energy density

(2) The cost of solid-state electrolytes, especially sulfide solid-state electrolytes and halogen solid-state electrolytes is very high. At present, the price of solid-state electrolytes is about 2,500 times that of positive active materials of the same mass, and about 2,000 times that of negative active materials of the same mass. An increase in the proportion of solid electrolyte in the battery pole piece will significantly increase the manufacturing cost of the battery

[0007] Therefore, the existing technologies to solve the problems of poor rate performance and large ion transport impedance in solid-state batteries need to be further explored.

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