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CN-122025552-A - Positive plate, lithium ion battery and power utilization device

CN122025552ACN 122025552 ACN122025552 ACN 122025552ACN-122025552-A

Abstract

The invention belongs to the technical field of battery materials, and relates to a positive plate, a lithium ion battery and an electric device, wherein the positive plate comprises a lithium supplementing material, the lithium supplementing material comprises a lithium iron oxide inner core and a carbon layer coated on the surface of the lithium iron oxide inner core, the material of the lithium iron oxide inner core comprises LiFeO 2 , the carbon layer at least contains Fe x C, the peak area ratio corresponding to Fe x C in a Raman spectrum test is a, and the area ratio of a Fe 3+ characteristic peak to an O1 s characteristic peak of LiFeO 2 in an XPS spectrum test is b, so that the ratio of a multiplied by b to a multiplied by 2.2% is not more than 18.2%, and a is a percentage system. The lithium supplementing material in the positive plate provided by the invention can ensure the air stability, does not damage the lithium supplementing efficiency and the conductivity, remarkably prolongs the service life of the battery, and simultaneously gives consideration to the use safety.

Inventors

  • SHAN XUYI
  • QIAO ZHI
  • ZHU XIAOXUE
  • QIN KAIYAN
  • ZHANG ZIFANG

Assignees

  • 中创新航科技集团股份有限公司

Dates

Publication Date
20260512
Application Date
20260316

Claims (15)

  1. 1. The positive plate comprises a lithium supplementing material, and is characterized by comprising a lithium iron oxide core and a carbon layer coated on the surface of the lithium iron oxide core; wherein the material of the lithium iron oxide inner core comprises LiFeO 2 , and the carbon layer at least contains Fe x C; In a Raman spectrum test, the peak area ratio corresponding to Fe x C is a, in an XPS spectrum test, the area ratio of the Fe 3+ characteristic peak to the O1 s characteristic peak of LiFeO 2 is b, the ratio of a multiplied by b is more than or equal to 2.25% and less than or equal to 18.2%, a is a percentage system, and the range of x is 1-3.
  2. 2. The positive electrode sheet according to claim 1, wherein the peak area ratio a of Fe x C is 4% or more and 20% or less.
  3. 3. The positive electrode sheet according to claim 1, wherein the ratio b of the area of the characteristic peak of Fe 3+ to the characteristic peak of O1 s of LiFeO 2 is 0.5≤b≤1.15.
  4. 4. The positive electrode sheet according to any one of claims 1 to 3, wherein the average thickness of the carbon layer is 10 to 20nm.
  5. 5. The positive electrode sheet according to any one of claims 1 to 3, wherein the Fe x C comprises an orthorhombic Fe 3 C.
  6. 6. The positive electrode sheet according to claim 5, wherein the orthorhombic Fe 3 C has a peak area ratio a of 5% to 6%.
  7. 7. The positive electrode sheet according to any one of claims 1 to 3, wherein the positive electrode sheet has a surface resistance of 260 to 330mΩ.
  8. 8. A positive electrode sheet according to any one of claims 1 to 3, wherein the carbon material in the carbon layer comprises amorphous carbon and/or graphitized carbon.
  9. 9. The positive electrode sheet according to any one of claims 1 to 3, wherein the average particle diameter of the lithium iron oxide core is 6 to 11 μm.
  10. 10. The positive electrode sheet according to any one of claims 1 to 3, further comprising a positive electrode material having a particle diameter Dv50 of 0.2 to 2 μm.
  11. 11. The positive electrode sheet according to claim 10, wherein the positive electrode material includes a positive electrode active material selected from at least one of lithium iron phosphate, lithium manganese iron phosphate, or lithium transition metal oxide.
  12. 12. The positive electrode sheet according to claim 11, wherein the positive electrode active material is selected from lithium iron phosphate.
  13. 13. The positive electrode sheet according to claim 12, wherein the surface of the lithium iron phosphate is coated with a carbon layer, and/or the average thickness of the carbon layer is 10-100 nm.
  14. 14. A lithium ion battery, characterized in that the lithium ion battery at least comprises the positive electrode sheet according to any one of claims 1 to 13.
  15. 15. An electrical device comprising at least the lithium ion battery of claim 14.

Description

Positive plate, lithium ion battery and power utilization device Technical Field The invention belongs to the technical field of battery materials, and relates to a positive plate, in particular to a positive plate, a lithium ion battery and an electric device. Background The lithium ion battery has been widely used in the fields of new energy automobiles, energy storage systems, portable electronic devices and the like by virtue of the advantages of high energy density, long cycle life and the like. Along with the continuous upgrading of the application scene to battery performance requirement, the improvement of energy density and cycle stability becomes the key direction of industry research and development. In the first charge and discharge process of the lithium ion battery, irreversible capacity loss can be caused by the phenomena of negative electrode SEI film formation, positive electrode active substance lithium loss and the like, and the actual usable capacity of the battery is directly reduced, so that the introduction of a lithium supplementing material becomes an important means for compensating the loss and improving the battery performance. Currently, lithium supplementing materials developed in the industry include lithium transition metal oxides, lithium-based compounds and the like, wherein Li 5FeO4 is considered as one of lithium supplementing agents with great application potential due to high lithium content, abundant iron element resources, low cost and environmental friendliness. The lithium supplementing mechanism is that in the first charging process of the battery, li 5FeO4 can release a large amount of lithium ions, and the irreversible lithium loss in the electrode reaction is supplemented, so that the first coulomb efficiency and the energy density of the battery are obviously improved. However, li 5FeO4 has a fatal performance defect, i.e., poor air stability. From the crystal structure, a large number of active lithium ion and iron ion sites exist on the surface of Li 5FeO4, and the active sites are extremely easy to react with moisture and carbon dioxide in the air. Specifically, the moisture reacts with the active lithium ions to form lithium hydroxide (LiOH), and the carbon dioxide further reacts with the lithium hydroxide to form lithium carbonate (Li 2CO3), and these reaction products are inert substances, so that a dense coating layer is formed on the surface of Li 5FeO4. The inert coating layer can have a plurality of negative effects that on one hand, the inert coating layer can cover active sites of a lithium supplementing material to prevent deintercalation and transmission of lithium ions, so that lithium supplementing efficiency is greatly reduced and an expected lithium supplementing effect cannot be achieved, and on the other hand, the existence of the inert coating layer can increase internal resistance of a battery, reduce electron conduction efficiency, exacerbate polarization phenomenon in the charge and discharge processes of the battery, and lead to continuous attenuation of cycle performance. More serious, if the lithium supplementing material is oxidized and failed in the process of storage, transportation or battery preparation, the initial capacity of the battery is insufficient, the cycle life is shortened, and even the internal impedance of the battery is uneven, so that the use safety is affected. Therefore, how to provide a lithium supplementing material which can ensure the air stability and does not damage the lithium supplementing efficiency and the conductivity is a problem to be solved by the current technicians in the field. Disclosure of Invention Aiming at the defects in the prior art, the invention aims to provide a positive plate, a lithium ion battery and an electricity utilization device, which can ensure the air stability and do not damage the lithium supplementing efficiency and the electric conductivity. In order to achieve the aim of the invention, the invention adopts the following technical scheme: in a first aspect, the invention provides a positive electrode sheet, which comprises a lithium supplementing material, wherein the lithium supplementing material comprises a lithium iron oxide core and a carbon layer coated on the surface of the lithium iron oxide core. The lithium iron oxide inner core is made of LiFeO 2, and the carbon layer at least contains Fe x C. In a Raman spectrum test, the peak area ratio corresponding to Fe x C is a, in an XPS spectrum test, the area ratio of the Fe 3+ characteristic peak to the O1 s characteristic peak of LiFeO 2 is b, the ratio of a multiplied by b is more than or equal to 2.25% and less than or equal to 18.2%, a is a percentage system, and the range of x is 1-3. In a second aspect, the present invention provides a lithium ion battery, at least comprising the positive electrode sheet according to the first aspect. In a third aspect, the present invention provides an electrical device compris