A positive pole piece, its preparation method and electrochemical device

Abstract

The present application relates to the field of energy storage, in particular, to a positive pole piece, a preparation method thereof and an electrochemical device. The present application relates to a positive electrode sheet, including a positive electrode collector and a positive electrode membrane containing a positive electrode active material arranged on at least one surface of the positive electrode collector, and at least one positive electrode membrane is arranged on the surface of the side away from the positive electrode collector There is an inorganic layer with a thickness of 20nm-2000nm, the inorganic layer is a porous dielectric layer without binder, and the porosity of the inorganic layer is 10%-60%. In the present application, the positive electrode membrane significantly improves the cycle performance, high-temperature storage performance and safety of the electrochemical device.

Description

technical field [0001] The present application relates to the field of energy storage, in particular, to a positive pole piece, a preparation method thereof and an electrochemical device. Background technique [0002] Due to its high working voltage, high energy density, no memory effect, and environmental protection, lithium-ion batteries have become the main power source of various consumer electronics products, power products, and energy storage, and are used in all aspects of people's lives. In recent years, as the market, especially the power battery market, has higher and higher requirements for battery energy density and charging efficiency, this makes the demand for cathode materials with higher compaction density and higher capacity stronger. [0003] In the secondary battery, in order to meet the demand for large capacity of the battery, it is mainly achieved by increasing the charging cut-off voltage and increasing the gram capacity. However, for conventional pos...

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Problems solved by technology

However, for conventional positive electrode active materials, under high charge and discharge voltage, the positive electrode active material delithiates excessively, and its crystal structure is prone to structural changes or even collapse; under high voltage, organic solvents and additives in the electrolyte, due to Its chemical stability is poor and it is easy to decompose, especially when the lithium transition metal oxide contains strong oxidizing nickel ions, it is easy to have side reactions with the electrolyte, resulting in serious gas production problems, causing battery capacity attenuation and cycle performance. Poor, high-temperature storage performance is severely deteriorated, which not only brings irreversible damage to battery life, but also brings serious safety hazards

To increase the gram capacity is usually to use a lithium transition metal oxide with a higher theoretical capacity and increase its compaction density. However, as the compaction density of the pole piece increases, the porosity decreases, and the ability of the pole piece to absorb and store electrolyte It also weakens, the ion-conducting ability of the pole piece decreases, and the overall resistance of the battery cell increases, which leads to poor cycle performance of the battery

[0004] In order to solve the above problems, at present, the positive active material particles are mainly coated and modified to stabilize the crystal structure of the particles and avoid the side reaction of the electrolyte on the surface of the particles. Difficulties such as agglomeration and complex coating process, and because the outer surface of the particles is covered with chemically inert inorganic substances, the conductivity between the active material particles in the pole piece is poor, the DCR of the battery is high, and the protection of the electrolyte by the pole piece The problem of low liquid rate is not improved obviously

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