Search

US-12620576-B2 - Secondary battery and electric device

US12620576B2US 12620576 B2US12620576 B2US 12620576B2US-12620576-B2

Abstract

A secondary battery and an electric device are disclosed. The secondary battery includes a positive electrode sheet and a negative electrode sheet. The positive electrode sheet has a film layer comprising a positive electrode active material that contains transition metal elements, where nickel accounts for at least 85% of the total molar content of the transition metals. The energy per unit area of the positive electrode film layer on one side of the sheet ranges from 15 to 35 mWh/cm 2 . The negative electrode sheet includes a film layer with a carbon-silicon composite active material, in which silicon nanoparticles are attached to a carbon matrix having a carbon skeleton. The combination of a high-nickel positive electrode and a carbon-silicon composite negative electrode enhances the energy density of the secondary battery.

Inventors

  • MiaoMiao DONG
  • Lili Wu
  • Xuan Li
  • Xingbu CHEN
  • Liang Yun
  • Xin Sun

Assignees

  • CONTEMPORARY AMPEREX TECHNOLOGY CO., LIMITED

Dates

Publication Date
20260505
Application Date
20250807
Priority Date
20230410

Claims (20)

  1. 1 . A secondary battery, comprising: a positive electrode plate, wherein the positive electrode plate comprises a positive electrode film layer, the positive electrode film layer comprises a positive electrode active material containing transition metal elements, based on a total molar number of the transition metal elements in the positive electrode active material, a molar content of a nickel element is not lower than 85%, and an energy per unit area of the positive electrode film layer on a single side of the positive electrode plate is 15-35 mWh/cm 2 ; a density per unit area of the positive electrode film layer on a single side of the positive electrode plate is 18 mg/cm 2 to 45 mg/cm 2 ; and a negative electrode plate, wherein the negative electrode plate comprises a negative electrode film layer, the negative electrode film layer comprises a negative electrode active material containing a carbon-silicon composite material, and the carbon-silicon composite material comprises carbon matrix particles having a carbon skeleton and silicon nanoparticles attached to the carbon skeleton, a mass percentage content A of a carbon element of the carbon-silicon composite material relative to a total mass of the carbon-silicon composite material has a decreasing trend in a direction from a geometric center of the carbon-silicon composite material to an outer surface of the carbon-silicon composite material, the battery is a pouch cell, a housing weight z of the secondary battery and a bare cell weight JR of the secondary battery satisfy the following relationship: 0.01≤z/JR≤0.1.
  2. 2 . The secondary battery according to claim 1 , wherein a housing weight z of the secondary battery and a bare cell weight JR of the secondary battery satisfy the following relationship: 0.02≤z/JR≤0.07.
  3. 3 . The secondary battery according to claim 1 , the carbon matrix particles comprise a three-dimensional network cross-linked pore structure, and at least a part of the silicon nanoparticles are disposed in the three-dimensional network cross-linked pore structure.
  4. 4 . The secondary battery according to claim 1 , wherein in an outer peripheral area of the carbon-silicon composite material, the mass percentage content A1 of the carbon element of the carbon-silicon composite material relative to the total mass of the carbon-silicon composite material and a mass percentage content B1 of a silicon element of the carbon-silicon composite material relative to the total mass of the carbon-silicon composite material satisfy 0.8≤B1/A1≤2.5, wherein the outer peripheral area of the carbon-silicon composite material is an area extending from an outer surface of the carbon-silicon composite material to an interior of the carbon-silicon composite material by a distance of r/2 or less, wherein r represents a short diameter of the carbon-silicon composite material.
  5. 5 . The secondary battery according to claim 1 , wherein in a central area of the carbon-silicon composite material, a mass percentage content A2 of carbon element of the carbon-silicon composite material relative to the total mass of the carbon-silicon composite material and a mass percentage content B2 of a silicon element of the carbon-silicon composite material relative to the total mass of the carbon-silicon composite material satisfy 1.05≤A2/B2≤50, wherein the central area of the carbon-silicon composite material is an area with a distance from a geometric center of the carbon-silicon composite material within r/2, wherein r represents a short diameter of the carbon-silicon composite material.
  6. 6 . The secondary battery according to claim 1 , wherein a mass percentage content B of a silicon element of the carbon-silicon composite material relative to the total mass of the carbon-silicon composite material has an increasing trend in the direction from the geometric center of the carbon-silicon composite material to the outer surface of the carbon-silicon composite material.
  7. 7 . The secondary battery according to claim 1 , wherein a mass percentage content of the silicon nanoparticles in the carbon-silicon composite material is greater than or equal to 40%.
  8. 8 . The secondary battery according to claim 1 , wherein the negative electrode active material further comprises a carbon-based active material.
  9. 9 . The secondary battery according to claim 8 , wherein the carbon-based active material comprises one or more of graphite, hard carbon, soft carbon, and porous carbon.
  10. 10 . The secondary battery according to claim 1 , wherein a mass percentage content α of the carbon-silicon composite material is 10% to 100%, based on a total mass of the negative electrode active material.
  11. 11 . The secondary battery according to claim 1 , wherein the negative electrode film layer comprises a conductive agent, the conductive agent comprises carbon nanotubes, and an aspect ratio of the carbon nanotubes is >2500, and/or, a mass percentage content of the carbon nanotubes is 0.1% to 0.5%.
  12. 12 . The secondary battery according to claim 1 , wherein the negative electrode plate satisfies that: a density per unit area of the negative electrode film layer on a single side of the negative electrode plate is 4 mg/cm 2 to 15 mg/cm 2 , and/or, a compaction density of the negative electrode film layer on a single side of the negative electrode plate is 1.6 g/cm 3 to 1.8 g/cm 3 .
  13. 13 . The secondary battery according to claim 1 , wherein the positive electrode active material comprises Li a Ni x Co y M 1-x-y O 2-b , wherein M comprises at least one of Mn, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg, and Nb, and optionally, the M comprises at least one of Mn, Al, B, Zr, Sr, W, Mg, and Nb; 0.2≤a≤1.2, and 0.2≤b≤0.2; 0.85≤x≤1, and 0≤y≤0.15.
  14. 14 . The secondary battery according to claim 1 , wherein a compaction density of the positive electrode film layer on a single side of the positive electrode plate is 3.3 g/cm 3 to 3.6 g/cm 3 .
  15. 15 . The secondary battery according to claim 1 , wherein a mass energy density of the secondary battery is 280 Wh/kg to 500 Wh/kg; and/or, a capacity C0 of the secondary battery is 35 Ah to 200 Ah, and optionally, 45 Ah to 190 Ah.
  16. 16 . An electric device, comprising the secondary battery according to claim 1 .
  17. 17 . The secondary battery according to claim 3 , wherein the carbon matrix particles are porous with inter-connected pores having diameters of 2 nm-50 nm, forming the three-dimensional network cross-linked structure.
  18. 18 . The secondary battery according to claim 4 , wherein in the outer peripheral area of the carbon-silicon composite material, A1 and B1 satisfy 1≤B1/A1≤1.5.
  19. 19 . The secondary battery according to claim 5 , wherein in the central area of the carbon-silicon composite material, A2 and B2 satisfy 1.05≤A2/B2≤3.
  20. 20 . The secondary battery according to claim 13 , wherein in Li a Ni x Co y M 1-x-y O 2-b , 0.92≤x≤0.98, and 0<y≤0.08.

Description

CROSS-REFERENCE TO RELATED APPLICATION The present application is a continuation of International Application No. PCT/CN2024/097989, filed on Jun. 7, 2025, which claims priority to Application No. PCT/CN2023/087384, entitled “SECONDARY BATTERY AND ELECTRIC DEVICE” and filed on Apr. 10, 2023, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD The present application relates to the technical field of lithium batteries, and in particular, to a secondary battery with a high energy density and an electric device. BACKGROUND In recent years, as secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power stations, as well as in various fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace, there are growing demands for the performance of the secondary batteries in the market. Lithium-ion batteries are small secondary batteries with a high mass energy density that are widely applied at present, but with the rapid development of the application field thereof, the energy density thereof is urgently needed to be further improved. SUMMARY The present application is made in view of the above problems, and an objective thereof is to provide a secondary battery having a high energy density. In a first aspect of the present application, provided is a secondary battery, which includes: a positive electrode plate, where the positive electrode plate includes a positive electrode film layer, the positive electrode film layer includes a positive electrode active material containing transition metal elements, based on a total molar number of the transition metal elements in the positive electrode active material, a molar content of a nickel element is not lower than 85%, and an energy per unit area of the positive electrode film layer on a single side of the positive electrode plate is 15-35 mWh/cm2, and optionally 20-35 mWh/cm2; and a negative electrode plate, where the negative electrode plate includes a negative electrode film layer, the negative electrode film layer includes a negative electrode active material containing a carbon-silicon composite material, and the carbon-silicon composite material includes carbon matrix particles having a carbon skeleton and silicon nanoparticles attached to the carbon skeleton. The present application breaks through the limit of the theoretical capacity of the positive electrode material and the negative electrode material in the prior art by matching the positive electrode active material with a high nickel content and the carbon-silicon composite material, and achieves the preparation of the secondary battery with a high energy density. In any embodiment, a housing weight z of the secondary battery and a bare cell weight JR of the secondary battery satisfy the following relationship: 0.01≤z/JR≤0.42; optionally, 0.01≤z/JR≤0.1 or 0.02≤z/JR≤0.07. With the above structural design, the mass of the secondary battery is further reduced, and the energy density of the battery is significantly improved. In any embodiment, the carbon matrix particles include a three-dimensional network cross-linked pore structure, and at least a part of the silicon nanoparticles are disposed in the three-dimensional network cross-linked pore structure. Although the theoretical specific capacity of the silicon nanoparticles is large, the expansion rate is large and the structural stability is poor during the charging and discharging process, which deteriorates the cycle performance of the battery. The carbon matrix particles of the present application have a stable three-dimensional network cross-linked porous skeleton structure, and can provide a large amount of space for the silicon nanoparticles, such that the silicon nanoparticles are not easy to agglomerate, and meanwhile, the adverse effect of volume expansion on the negative electrode plate is relieved, thereby effectively improving the cycle performance of the secondary battery. The high nickel content can increase the specific capacity of the positive electrode plate, thereby improving the energy density of the secondary battery. However, too high nickel content may cause the increase in the mixed discharge of lithium and nickel, thereby causing the transition metal to be easily dissolved out and deposited on the negative electrode plate, and affecting the cycle performance of the battery. The three-dimensional cross-linked carbon skeleton of the carbon-silicon material of the present application can be matched with the positive electrode active material, such that the deposition of the transition metal on the silicon nanoparticles is reduced, the negative influence of the deposition of the transition metal on the negative electrode plate on the performance of the silicon-based material is reduced, and thus the cycle performance of the secondary battery is further improved