Lithium-ion battery, lithium-rich anode sheet and preparation method thereof

Abstract

The invention provides a lithium ion battery as well as a lithium-rich positive piece and a preparation method thereof. The lithium-rich positive piece comprises a current collector and a diaphragm, wherein the diaphragm contains a positive active substance and is formed on the current collector. The diaphragm and the current collector form an initial positive piece, one side, away from the current collector, of the diaphragm is a surface layer, and one side, close to the current collector, of the diaphragm is a bottom layer; after the diaphragm of the initial positive piece is infiltrated in electrolyte and charged to be enriched with lithium, a lithium-rich layer and a non-lithium-rich layer are formed on the diaphragm, and the thickness of the lithium-rich layer is smaller than that of the diaphragm; a metal lithium layer is also distributed on the surface layer of the diaphragm, and the lithium sum of the lithium-rich layer and the metal lithium layer is matched with the lithium-rich capacity needed by the initial positive piece. The lithium ion battery comprises the lithium-rich positive piece. An SEI (solid electrolyte interphase) membrane is produced only in the area which is infiltrated by the electrolyte, the environmental requirement of a winding procedure is low, the lithium can be uniformly enriched, and the hardness of the lithium-rich pole piece also can meet the winding requirement.

Description

technical field [0001] The invention relates to a lithium ion battery, in particular to a lithium ion battery, a lithium-rich anode sheet and a preparation method thereof. Background technique [0002] The first coulombic efficiency of traditional anode materials is low. Taking silicon anode materials as an example, the first coulombic efficiency is between 65% and 85%. In order to greatly increase the energy density of the cell, it is necessary to increase the first Coulombic efficiency of the cell. Therefore, experts at home and abroad have carried out extensive research and achieved some results: the Chinese patent application publication number CN102315422A proposes a lithium-enriching method for the lithium-supplementing cathode, that is, the cathode, the separator and the anode are assembled into an electric battery by stacking sheets. Then put the lithium-supplementing cathode side on the side of the battery cell, apply a voltage charge between the lithium-supplement...

AI Technical Summary

Problems solved by technology

Both of these two patents compensate for the first irreversible capacity by forming an SEI film on the surface of the anode before assembling the battery cell; however, when this method is used to replenish lithium, the SEI film formed on the surface of the active material has a certain thickness, and some lithium ions will Embedded in the active material makes the volume of the active material expand, resulting in the reduction of the gap between the active material particles, the diaphragm becomes hard and brittle, the diaphragm will fall off during the winding process, and the self-discharge of the prepared battery is serious, and the formation of The anode behind the SEI film needs to strictly control the humidity and atmosphere of the environment when assembling the battery, and the production cost is high

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