Surface-modified high-nickel ternary positive material, preparation thereof, and battery prepared from surface-modified high-nickel ternary positive material

Abstract

The invention provides a surface-modified high-nickel ternary positive material. A surface modification layer is covered on an inner core of a high-nickel ternary positive material; the inner core ofthe high-nickel ternary positive material is Li1 plus kNixCoyMzO2, wherein k is larger than or equal to -0.1 and smaller than or equal to 0.1, x is larger than 0 and smaller than 1, y is larger than 0and smaller than 1, and z is larger than 0 and smaller than 1. The surface modification layer is formed by two surface modification matters, wherein one is yttria-stabilized zirconia, and the other one is selected from one or more of metal oxide MeOx, metal fluoride MeFx, metal phosphate Me(PO4)x or C. The invention also provides a preparation method of the surface-modified high-nickel ternary positive material, and a battery prepared from the surface-modified high-nickel ternary positive material. According to the surface-modified high-nickel ternary positive material provided by the invention, the surface modification matters are covered on the surface of the body material, so that the side reaction of the high-nickel ternary positive material and an electrolyte is reduced, the irreversible capacity loss of the material is inhibited, and the cycle performance is improved.

Description

technical field [0001] The invention belongs to the field of battery materials, and in particular relates to a ternary positive electrode material of a lithium ion battery, a preparation method thereof, and a battery made of the positive electrode material. Background technique [0002] Since the first generation of lithium-ion batteries designed and produced by Sony Corporation in 1991, the layered transition metal oxide lithium cobaltate (LiCoO 2 ) as the cathode material, lithium-ion batteries have been widely used from the initial small portable electronic devices to later electric vehicles and energy storage grids. [0003] At a cut-off voltage of 4.2V relative to the metal lithium anode, lithium cobalt oxide (LiCoO 2 ) The actual specific capacity of the positive electrode is 140mAh g -1 , to meet the general needs of portable electronic devices. Further, in response to the ever-increasing demand for high energy density, low cost, and environmental adaptability, Li[...

AI Technical Summary

Problems solved by technology

However, there are still some problems with this system material as a candidate material for high-energy lithium-ion batteries: first, during the high-temperature synthesis process due to the Ni 3+ unstable and easily reduced to Ni 2+ and due to and The similar ionic radius of the resulting Li + / Ni 2+ Mixed arrangement makes the solid-phase diffusion of lithium ions more difficult and increases the polarization of the material; secondly, due to the easily reduced Ni 4+ Especially in the highly delithiated state, the surface of the positive electrode material is prone to side reactions with the electrolyte to form an electrochemically inert layer, accompanied by the generation of impurity phases such as spinel phase and rock salt, which inhibits the The diffusion of lithium ions, accompanied by the loss of oxygen in the bulk material at the same time, reduces the safety performance; in addition, during the lithium intercalation process, the generation of microcracks inside the secondary particles caused by the multiphase transformation causes the electrolyte to The corrosion of the material is further intensified, and the surface resistance is further increased

Patent CN 107331852A proposes a kind of oxide (Nb 2 o 5 , ZrO 2 and Y 2 o 3 ) method of coating the surface of the ternary positive electrode material. The coating reduces the side reaction between the electrolyte and the positive electrode material to a certain extent, improves the cycle performance and thermal stability of the material, but the effect is limited, and it will bring negative effects at the same time. Effect, because the coated metal oxide is an inert material, which inhibits the transport of lithium ions and electrons

Shao-Kang Hu et al. (Journal of Power Sources, 188, (2009) 564-569) pass Zr(OC 3 h 7 ) 4 and LiNi 1 / 3 co 1 / 3 mn 1 / 3 o 2 Perform wet mixing and stirring in propanol, evaporate to dryness at 80-90°C, and then roast at 450°C for 5 hours to obtain ZrO 2 Surface-coated LiNi 1 / 3 co 1 / 3 mn 1 / 3 o 2 Cathode material, ZrO 2 The surface coating layer reduces the side reaction between the bulk material and the electrolyte to a certain extent, inhibits the capacity fading, and improves the cycle performance, but it also inevitably leads to the decline of the first discharge specific capacity and rate performance.

Patent CN 107240690 A adopts wet mixing method to coat nano silicon dioxide or zirconium dioxide on the surface of the ternary material. Although the cycle performance has been improved, the first discharge specific capacity is also reduced to a certain extent. In addition, its The wet process used cannot fully avoid the influence of the processing process on the structure of the bulk material, and the process is complicated and difficult to achieve industrialization

Patent CN 104995769 A dry-coats layered materials by doping oxides, and the cycle performance is improved, but the contribution function of the coating layer to the material performance is single, and the methods are all coated on the finished product, using high-temperature post-processing Heat treatment, it is difficult to form a layered material doped on the surface, only a certain thickness of the coating layer is formed, which hinders the diffusion of lithium ions

Patent CN 105938901 A coats layered materials by oxide dry method, which improves the cycle performance, but the coating amount is small, and there is no suitable post-heat treatment, which makes it difficult for the coating layer to evenly coat the material. The solid interface between the cladding and the bulk material is not connected, which hinders the diffusion of lithium ions and hinders the diffusion of electrolyte

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