Search

CN-122025625-A - Positive electrode material and lithium ion secondary battery

CN122025625ACN 122025625 ACN122025625 ACN 122025625ACN-122025625-A

Abstract

The invention relates to the technical field of batteries, in particular to an O2-phase lithium cobalt oxide positive electrode material and a lithium ion secondary battery comprising the O2-phase lithium cobalt oxide positive electrode material. The O2 phase lithium cobalt oxide positive electrode material contains Na, and the mass content of Na in the O2 phase lithium cobalt oxide positive electrode material is a > b. The method comprises the steps of a, mixing deionized water and aqua regia according to a volume ratio of 1:1 to obtain diluted aqua regia, taking 10mL of diluted aqua regia, soaking 100mg of O2-phase lithium cobalt oxide anode material for 1 hour at 80 ℃, filtering, taking the mass content of Na obtained by inductively coupled plasma testing filtrate, b, taking the filter residue obtained by soaking diluted aqua regia, soaking 10mL of aqua regia for 10min at 350 ℃, filtering, and taking the mass content of Na obtained by inductively coupled plasma testing filtrate. The lithium ion secondary battery has excellent cycle performance and rate performance.

Inventors

  • TIAN LINYUAN
  • SHEN BENCHAO

Assignees

  • 珠海冠宇电池股份有限公司

Dates

Publication Date
20260512
Application Date
20260312

Claims (10)

  1. 1. The O2-phase lithium cobalt oxide positive electrode material is characterized by comprising Na element, wherein the mass content of the Na element in the O2-phase lithium cobalt oxide positive electrode material is 250ppm-1000ppm, and the mass content of the Na element in the O2-phase lithium cobalt oxide positive electrode material is a > b; wherein a is diluted aqua regia prepared by mixing deionized water and aqua regia according to the volume ratio of 1:1, 10mL of diluted aqua regia is taken to soak 100mg of O2-phase lithium cobalt oxide anode material for 1 hour at 80 ℃, and then the solution is filtered, and the mass content of Na element obtained by inductively coupled plasma test of the filtrate is taken; and b, soaking the filter residue soaked in the dilute aqua regia for 10min at 350 ℃ by adopting 10mL of aqua regia, filtering, and taking the mass content of Na element obtained by inductively coupled plasma testing of the filtrate.
  2. 2. The O2-phase lithium cobalt oxide cathode material according to claim 1, wherein the mass content of Na element in the O2-phase lithium cobalt oxide cathode material is 400ppm to 800ppm; and/or, a is 250ppm to 1200ppm, preferably 400ppm to 850ppm; and/or b is 100ppm to 1000ppm, preferably 250ppm to 700ppm.
  3. 3. The O2-phase lithium cobalt oxide cathode material according to claim 1 or 2, wherein the O2-phase lithium cobalt oxide cathode material further contains Ni element and Mn element; Preferably, the mass content of Ni element in the O2-phase lithium cobalt oxide positive electrode material meets the requirement that d is more than C, wherein C is diluted aqua regia prepared by mixing deionized water and aqua regia according to the volume ratio of 1:1, 10mL of diluted aqua regia is taken to soak 100mg of the O2-phase lithium cobalt oxide positive electrode material for 1 hour at 80 ℃, the diluted aqua regia is filtered, the mass content of Ni element obtained by an inductive coupling plasma test of filtrate is taken, d is filter residue obtained by taking the diluted aqua regia to soak for 10 minutes at 350 ℃, and the mass content of Ni element obtained by an inductive coupling plasma test of filtrate is taken to filter; Preferably, the mass content of Mn element in the O2-phase lithium cobalt oxide positive electrode material meets f > e, wherein e is diluted aqua regia prepared by mixing deionized water and aqua regia according to a volume ratio of 1:1, 10mL of diluted aqua regia is taken to soak 100mg of the O2-phase lithium cobalt oxide positive electrode material for 1 hour at 80 ℃, filtration is carried out, the mass content of Mn element obtained by inductively coupled plasma testing filtrate is taken, f is filter residue obtained by taking the diluted aqua regia to soak, 10mL of aqua regia is adopted to soak for 10min at 350 ℃, and filtration is carried out, and the mass content of Mn element obtained by inductively coupled plasma testing filtrate is taken.
  4. 4. The O2 phase lithium cobalt oxide positive electrode material according to claim 3, wherein c is 0.3ppm to 850ppm, preferably 0.3ppm to 250ppm; and/or d is 1.5ppm to 1400ppm, preferably 1.5ppm to 400ppm; and/or e is 1ppm to 1400ppm, preferably 1ppm to 400ppm; And/or f is 2ppm to 1500ppm, preferably 2ppm to 500ppm; And/or the molar ratio of Li element to Co element in the O2 phase lithium cobalt oxide positive electrode material is 0.8-1.05, preferably 0.85-1.05, and the molar ratio of Na element to Co element is 0.002-0.003; And/or the valence state of Ni element comprises +2 valence and +3 valence, the valence state of Mn element comprises +3 valence and +4 valence, and the atomic percentage of ions in different valence states in the O2 phase lithium cobalt oxide positive electrode material meets the following conditions ：Mn 4+ /Co 3+ >Ni 2+ /Co 3+ >Ni 3+ /Co 3+ >Mn 3+ /Co 3+ ; And/or, let w1=b+d+f, w2=a+c+e, wherein, w1/w2 is more than or equal to 0.2 and less than or equal to 1.5; preferably, the method comprises the steps of, w1 is more than or equal to 0.5 w2 is less than or equal to 1.2.
  5. 5. The O2-phase lithium cobalt oxide positive electrode material according to claim 4, wherein the O2-phase lithium cobalt oxide positive electrode material further contains Al elements, 10 sites are sequentially selected along the radial direction from the center to the surface of the O2-phase lithium cobalt oxide positive electrode material, the mass content of the Al elements in each site is C 1 by using an energy spectrometer, and the average value of the maximum value and the minimum value of the mass content of the Al elements in the 10 sites is C 2 ,C 1 and C 2 , wherein I (C 1 -C 2 ）|×100%/C 2 is less than or equal to 10 percent; And/or the mass content of Co element in the O2-phase lithium cobalt oxide positive electrode material is 1.1-8, preferably 2-6, wherein g is diluted aqua regia prepared by mixing deionized water and aqua regia according to the volume ratio of 1:1, 10mL of diluted aqua regia is taken to soak 100mg of the O2-phase lithium cobalt oxide positive electrode material for 1 hour at 80 ℃, the solution is filtered, the mass content of Co element obtained by inductively coupled plasma test of filtrate is taken, h is the mass content of Co element obtained by inductively coupled plasma test of filtrate, the filter residue obtained by soaking diluted aqua regia is taken, 10mL of aqua regia is taken to soak for 10min at 350 ℃, and the solution is filtered, and the mass content of Co element obtained by inductively coupled plasma test of filtrate is taken; And/or the mass content of Al element in the O2-phase lithium cobalt oxide positive electrode material is more than or equal to 0.6 and less than or equal to 2, preferably, 0.85 and less than or equal to 1.5, wherein j is the mass content of Al element obtained by soaking 100mg of the O2-phase lithium cobalt oxide positive electrode material for 1 hour at 80 ℃ by adopting deionized water and aqua regia according to the volume ratio of 1:1, filtering, taking the filtrate to obtain the mass content of Al element by inductive coupling plasma test, k is the filter residue obtained by taking the diluted aqua regia to soak, and filtering after soaking 10mL of aqua regia for 10 minutes at 350 ℃, and taking the mass content of Al element obtained by the filtrate by inductive coupling plasma test; preferably j is 1500ppm to 7000ppm; preferably, k is 1500ppm to 7000ppm; more preferably, let w3=b/(k+d+f), w4=a/(j+c+e), where, w4/w3 is more than or equal to 0.5 and less than or equal to 5; preferably, the method comprises the steps of, w4 is more than or equal to 0.8% w3 is less than or equal to 3.
  6. 6. The O2-phase lithium cobalt oxide positive electrode material according to claim 5, wherein the O2-phase lithium cobalt oxide positive electrode material exhibits an I-th characteristic peak at 18.6 ° ± 0.2 ° of 2Θ in an X-ray diffraction pattern; In the buckling process of taking lithium metal as a counter electrode, charging to 4.55V, wherein the O2-phase lithium cobalt oxide positive electrode material contains a characteristic peak II at a position of 17.8+/-0.15 DEG of 2 theta, a characteristic peak III at a position of 18.2+/-0.15 DEG of 2 theta and a characteristic peak IV at a position of 19.2+/-0.15 DEG of 2 theta in an X-ray diffraction spectrogram; preferably, the diffraction angle corresponding to the II characteristic peak and the IV characteristic peak is different by 1.4 ° ± 0.15 °.
  7. 7. The O2-phase lithium cobalt oxide positive electrode material according to claim 1 or 2, wherein the O2-phase lithium cobalt oxide positive electrode material further contains a P2 phase; and/or the morphology of the O2-phase lithium cobalt oxide positive electrode material comprises a sheet shape, wherein the sheet diameter d1 of the O2-phase lithium cobalt oxide positive electrode material along the long axis direction is 1-20 mu m, the sheet diameter d2 along the short axis direction is 0.2-10 mu m, and the thickness d3 of the sheet is 0.2-10 mu m.
  8. 8. A lithium ion secondary battery comprises a positive plate, and is characterized in that the positive plate comprises a positive current collector and a positive active layer positioned on at least one side surface of the positive current collector, wherein the positive active layer comprises a positive material, and the positive material comprises the O2 phase lithium cobalt oxide positive electrode material according to any one of claims 1-7; Preferably, the O3 phase lithium cobaltate cathode material includes at least one of Al, mg and Y elements; more preferably, the mass content of Al element in the positive electrode active layer is 4500ppm-15000ppm; more preferably, the mass content of Mg element in the positive electrode active layer is 100ppm-1500ppm; More preferably, the mass content of the Y element in the positive electrode active layer is 100ppm to 1500ppm.
  9. 9. The lithium ion secondary battery of claim 8, wherein the lithium ion secondary battery further comprises a negative electrode sheet comprising a negative electrode current collector and a negative electrode active layer on at least one side surface of the negative electrode current collector, the negative electrode active layer comprising a silicon-carbon material comprising a porous carbon matrix and silicon particles in the internal pores of the porous carbon matrix; preferably, the mass content of silicon element in the negative electrode active layer is 3% -70%, more preferably 3% -20%; Preferably, the anode active layer further comprises single-walled carbon nanotubes; More preferably, the diameter of the single-walled carbon nanotubes is 1nm to 10nm; and/or the charge cut-off voltage of the lithium ion secondary battery is more than or equal to 4.5V.
  10. 10. The lithium ion secondary battery of claim 8, wherein the lithium ion secondary battery further comprises an electrolyte comprising fluoroethylene carbonate; preferably, the mass content of fluoroethylene carbonate in the electrolyte is 5% -20%.

Description

Positive electrode material and lithium ion secondary battery Technical Field The invention relates to the technical field of batteries, in particular to a positive electrode material and a lithium ion secondary battery comprising the positive electrode material. Background The O2-phase lithium cobaltate is used as an important lithium battery anode material, and the crystal structure of the O2-phase lithium cobaltate presents a unique ABAC oxygen atom stacking mode and has excellent structural stability and lithium ion diffusivity. As the demand for lithium ion batteries for energy density continues to rise in recent years for portable electronic devices, electric vehicles, and other consumer electronic devices, the development of high-capacity cathode materials has become an urgent need for current lithium ion batteries. In the prior art, the gram capacity of the O2-phase lithium cobaltate can be effectively improved by increasing the charge cut-off voltage to 4.5V or above. However, under the condition of high voltage or high-rate charge and discharge, the lithium cobalt oxide has a deeper lithium removal degree, particularly the lithium removal degree of the surface layer is obviously higher than that of the bulk phase, the non-uniform lithium removal causes larger change of the unit cell volume, irreversible phase change occurs, local distortion and local stress concentration of the crystal lattice are caused, and finally the lithium cobalt oxide particles are broken, so that the problems of rapid capacity attenuation, poor cycle stability and the like are caused. Therefore, it is required to improve the cycle stability of the lithium cobaltate cathode material under high voltage conditions. Disclosure of Invention The present invention has been made to overcome the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide an O2-phase lithium cobalt oxide positive electrode material and a lithium ion secondary battery including the same. According to the lithium ion secondary battery (hereinafter simply referred to as a battery), the lithium cobalt oxide positive electrode material is modified, so that gram capacity exertion and high-voltage resistance of the positive electrode material are effectively improved, irreversible phase transformation of the lithium cobalt oxide positive electrode material caused by uneven surface layer and bulk lithium removal under high voltage can be effectively inhibited, and the cycle stability and dynamic performance of the battery under high voltage are remarkably improved. Based on the above problems, the inventors have conducted a great deal of targeted studies and found that: The O2 phase lithium cobalt oxide positive electrode material can optimize the whole crystal phase structure of the positive electrode material by utilizing the unique stacking sequence of an oxygen atom layer and a cobalt lithium layer (ABAC), so that the severe expansion and shrinkage of a unit cell in the high-voltage lithium removal process are effectively inhibited, the distortion degree and stress accumulation of a crystal lattice under high-voltage circulation are reduced, the structural stability of lithium cobalt oxide is remarkably improved, meanwhile, adjacent oxygen layers in the crystal structure of the O2 phase are directly opposite, the interlayer distance of lithium ions is larger, diffusion channels are more smooth, and therefore, the lithium ions migrate faster, and the lithium removal and intercalation dynamics performance of the positive electrode material is effectively improved. Furthermore, the O2 phase lithium cobaltate anode material contains Na element, and the mass content of the Na element is regulated to be a > b. The method comprises the steps of a, mixing deionized water and aqua regia according to a volume ratio of 1:1 to obtain diluted aqua regia, taking 10mL of diluted aqua regia, soaking 100mg of O2-phase lithium cobalt oxide anode material for 1 hour at 80 ℃, filtering, taking the mass content of Na element obtained by inductively coupled plasma test of filtrate, and b, taking the filter residue obtained by soaking diluted aqua regia, soaking 10mL of aqua regia for 10min at 350 ℃, filtering, and taking the mass content of Na element obtained by inductively coupled plasma test of filtrate. According to the invention, the concentration gradient distribution of Na element from the surface layer to the bulk phase is constructed by regulating and controlling the mass content a of Na element in the surface layer of the O2-phase lithium cobalt oxide positive electrode material to be larger than the mass content b of Na element in the bulk phase. Na element occupies lithium position after entering O2 phase lithium cobalt oxide positive electrode material, effective filling and charge compensation are formed, and the problem of crystal stress concentration caused by deep lithium removal of the lithium cobalt oxide posit