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US-12626919-B2 - Positive active material and electrochemical device containing same

US12626919B2US 12626919 B2US12626919 B2US 12626919B2US-12626919-B2

Abstract

A positive active material, containing a compound with a P6 3 mc space group. In an XRD pattern of the positive active material, a (002) crystal plane of the compound with the P6 3 mc space group is located between 17.5° and 19°, and a full width at half maximum of the (002) crystal plane falls between 0.05 and 0.1. The positive active material at a high voltage of 4.8 V exhibits a considerable discharge capacity and desirable structural reversibility and cycle stability.

Inventors

  • Xia Wu

Assignees

  • NINGDE AMPEREX TECHNOLOGY LIMITED

Dates

Publication Date
20260512
Application Date
20221207
Priority Date
20200608

Claims (14)

  1. 1 . A positive active material, comprising: a first positive active material containing a compound with a P6 3 mc space group, wherein, in an XRD pattern of the positive active material, a (002) crystal plane of the compound with the P6 3 mc space group is located between 17.5° and 19°, and a full width at half maximum of the (002) crystal plane falls between 0.05 and 0.1; and a second positive active material, the second positive active material is selected from Li 1±b Co 1-a R a O 2 with an R-3m space group, a nickel cobalt manganese ternary material, a lithium-rich manganese-based material, and lithium manganese oxide, wherein 0≤b<0.1, 0≤a<0.1, and R comprises at least one selected from the group consisting of Al, Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr, and Zr; a first layer and a second layer, wherein the second layer is located between a current collector and the first layer, wherein the first layer comprises the first positive active material and the second layer comprises the second positive active material, a thickness ratio between the first layer and the second layer being 0.1 to 2.
  2. 2 . The positive active material according to claim 1 , wherein, in a DSC pattern of the first positive active material, an exothermic peak of the compound with the P6 3 mc space group exists between 250° C. and 400° C., and a full width at half maximum of the exothermic peak falls between 15° C. and 40° C.
  3. 3 . The positive active material according to claim 1 , wherein the compound with the P6 3 mc space group satisfies at least one of conditions (a) to (e): (a) an average particle diameter of the compound with the P6 3 mc space group is 8 μm to 30 μm; (b) a tap density of the compound with the P6 3 mc space group is 2.2 g/cm 3 to 3 g/cm 3 ; (c) pores exist on a particle of the compound with the P6 3 mc space group; (d) cracks exist inside the particle of the compound with the P6 3 mc space group; and (e) the compound with the P6 3 mc space group comprises Li x Na z Co 1-y M y O 2 , wherein 0.6<x <0.85, 0≤y<0.15, 0≤z<0.03, and M comprises at least one selected from the group consisting of Al, Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr, and Zr.
  4. 4 . An electrochemical device, comprising a positive electrode plate, the positive electrode plate comprises a positive current collector and a positive active layer disposed on at least one surface of the positive current collector, and the positive active layer comprises: a first positive active material containing a compound with a P6 3 mc space group, wherein, in an XRD pattern of the positive active material, a (002) crystal plane of the compound with the P6 3 mc space group is located between 17.5° and 19°, and a full width at half maximum of the (002) crystal plane falls between 0.05 and 0.1; and a second positive active material, the second positive active material is selected from Li 1±b Co 1-a R a O 2 with an R-3m space group, a nickel cobalt manganese ternary material, a lithium-rich manganese-based material, and lithium manganese oxide, wherein 0≤b<0.1, 0≤a<0.1, and R comprises at least one selected from the group consisting of Al, Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr, and Zr; the positive active layer comprising a first layer and a second layer, wherein the second layer is located between the positive current collector and the first layer, wherein the first layer comprises the first positive active material and the second layer comprises the second positive active material, a thickness ratio between the first layer and the second layer being 0.1 to 2.
  5. 5 . The electrochemical device according to claim 4 , wherein, in a DSC pattern of the first positive active material, an exothermic peak of the compound with the P6 3 mc space group exists between 250° C. and 400° C., and a full width at half maximum of the exothermic peak falls between 15° C. and 40° C.
  6. 6 . The electrochemical device according to claim 4 , wherein the compound with the P6 3 mc space group satisfies at least one of conditions (a) to (e): (a) an average particle diameter of the compound with the P6 3 mc space group is 8 μm to 30 μm; (b) a tap density of the compound with the P6 3 mc space group is 2.2 g/cm 3 to 3 g/cm 3 ; (c) pores exist on a particle of the compound with the P6 3 mc space group; (d) cracks exist inside the particle of the compound with the P6 3 mc space group; and (e) the compound with the P6 3 mc space group comprises Li x Na z Co 1-y M y O 2 , wherein 0.6<x<0.85, 0≤y<0.15, 0≤z<0.03, and M comprises at least one selected from the group consisting of Al, Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr, and Zr.
  7. 7 . The electrochemical device according to claim 4 , wherein a compacted density of the second layer is 4.1 g/cm 3 to 4.35 g/cm 3 .
  8. 8 . The electrochemical device according to claim 4 , wherein a compacted density of the positive active layer is 4.0 g/cm 3 to 4.5 g/cm 3 .
  9. 9 . The electrochemical device according to claim 4 , wherein the electrochemical device is configured to satisfy at least one of conditions (f) to (h): (f) a growth rate of cracked particles of the first positive active material is not higher than 5% as measured by cycling the electrochemical device for 20 cycles at a voltage of 4.8 V and a current rate of 0.5 C when a discharge capacity per gram is not less than 180 mAh/g; (g) a growth rate of a direct current resistance DCR of the first positive active material per cycle on average is lower than 2% as measured by cycling the electrochemical device for 20 cycles at a voltage of 4.8 V and a current rate of 0.5 C when the discharge capacity per gram is not less than 180 mAh/g; and (h) the electrochemical device further comprises a negative electrode plate, the negative electrode plate comprises a negative current collector and a negative active layer disposed on at least one surface of the negative current collector, and an increment of a packing concentration of cobalt packed on a surface of the negative active layer per cycle on average is denoted by R; as measured by cycling the electrochemical device for 20 cycles at a voltage of 4.8 V and a current rate of 0.5 C when the discharge capacity per gram is not less than 180 mAh/g, wherein R≤5 ppm.
  10. 10 . The electrochemical device according to claim 4 , wherein, the electrochemical device is configured such that when a discharge capacity per gram of the electrochemical device is 180 mAh/g to 200 mAh/g, a thickness of a by-product of the positive electrode of the electrochemical device is denoted by η, wherein η≤0.5 μm.
  11. 11 . An electronic device, comprising an electrochemical device, the electrochemical device comprises a positive electrode plate, the positive electrode plate comprises a positive current collector and a positive active layer disposed on at least one surface of the positive current collector, and the positive active layer comprises; a first positive active material containing a compound with a P6 3 mc space group, wherein, in an XRD pattern of the positive active material, a (002) crystal plane of the compound with the P6: mc space group is located between 17.5° and 19°, and a full width at half maximum of the (002) crystal plane falls between 0.05 and 0.1; and a second positive active material, the second positive active material is selected from Li 1±b Co 1-a R a O 2 with an R-3m space group, a nickel cobalt manganese ternary material, a lithium-rich manganese-based material, and lithium manganese oxide, wherein 0≤b<0.1, 0≤a<0.1, and R comprises at least one selected from the group consisting of Al, Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr, and Zr; the positive active layer comprising a first layer and a second layer, wherein the second layer is located between the current collector and the first layer, wherein the first layer comprises the first positive active material and the second layer comprises the second positive active material, a thickness ratio between the first layer and the second layer being 0.1 to 2.
  12. 12 . The electronic device according to claim 11 , wherein, in a DSC pattern of the first positive active material, an exothermic peak of the compound with the P6 3 mc space group exists between 250° C. and 400° C., and a full width at half maximum of the exothermic peak falls between 15° C. and 40° C.
  13. 13 . The electronic device according to claim 11 , wherein the compound with the P6 3 mc space group satisfies at least one of conditions (a) to (e): (a) an average particle diameter of the compound with the P6 3 mc space group is 8 μm to 30 μm; (b) a tap density of the compound with the P6 3 mc space group is 2.2 g/cm 3 to 3 g/cm 3 ; (c) pores exist on a particle of the compound with the P6 3 mc space group; (d) cracks exist inside the particle of the compound with the P6 3 mc space group; and (e) the compound with the P6 3 mc space group comprises Li x Na z Co 1-y M y O 2 , wherein 0.6<x<0.85, 0≤y<0.15, 0≤z<0.03, and M comprises at least one selected from the group consisting of Al, Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr, and Zr.
  14. 14 . The electronic device according to claim 11 , wherein a compacted density of the second layer is 4.1 g/cm 3 to 4.35 g/cm 3 .

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This present application is a continuation application of PCT application PCT/CN2021/098940, filed on Jun. 8, 2021, which claims priority to Chinese Patent Application No. 202010511491.1 filed on Jun. 8, 2020, the disclosure of which is hereby incorporated by reference in its entirety. TECHNICAL FIELD This application relates to the field of energy storage, and in particular, to a positive active material and an electrochemical device containing the positive active material, and especially a lithium-ion battery. BACKGROUND With popularization of electronic products such as a notebook computer, a mobile phone, a handheld game console, and a tablet computer, people are posing higher requirements on the battery of the products. Among multitudinous batteries, lithium-ion batteries are widely used in fields such as portable electronic products, electric transportation, national defense, aviation, and energy reserve by virtue of advantages such as a high energy storage density, a high power density, high safety, environmental friendliness, a long service life, a low self-discharge rate, and adaptability to a wide range of temperatures. As an important component of a lithium-ion battery, a positive electrode material exerts a significant impact on the performance of the battery. Therefore, it is essential to optimize and improve the positive electrode material continuously. With the upgrade of electronic products, the pursuit of a high energy density and a high power density has become a development trend of the positive electrode material of the lithium-ion battery: As the earliest commercialized lithium-ion positive electrode material, lithium cobalt oxide has been researched in depth extensively. The lithium cobalt oxide has exhibited the best overall performance in terms of reversibility, discharge capacity, charging efficiency, voltage stability, and the like, and has become a positive electrode material most massively used in the lithium-ion batteries currently. After decades of development, structural characteristics and electrochemical properties of the lithium cobalt oxide have been researched thoroughly, and a synthesis process and industrial production of the lithium cobalt oxide have become quite mature. By virtue of a relatively high discharge voltage plateau and a relatively high energy density, the lithium cobalt oxide has been in a dominant position in the positive electrode materials of the consumer lithium-ion batteries all along. At present, the most prevalently commercially used LiCoO2 positive electrode material in the 3C fieldis an O3-phase structure, this material is characterized by a theoretical capacity of 273.8 mAh/g, high cycle performance and safety performance, a high compacted density, and simplicity of manufacture. Since being put into commercial use by Sony Corporation in 1991, the LiCoO2 positive electrode material has been in a dominant position in the market of lithium-ion battery materials all along. To achieve a higher specific capacity, LiCoO2 shows a tendency toward cycling at a higher voltage (>4.6V vs. Li/Li+). When LiCoO2 is charged until a voltage of 4.5 V, the capacity is no more than 190 mAh/g. People attempt to achieve a higher specific capacity by deintercalating more Lit from its crystal structure. However, when the voltage increases to a higher level, a large number of Lit ions are deintercalated, and the crystal structure undergoes a series of irreversible phase transitions (from an O3 phase to an H1-3 phase, and from an H1-3 phase to an O1 phase), thereby deteriorating the cycle performance and safety performance of the material drastically. In addition, when the voltage is high, side reactions intensify at an interface, and cobalt metal is dissolved out severely. However, the electrolytic solution technology is hardly adaptable to the high voltage, and a conventional electrolytic solution decomposes and fails more quickly at the high voltage, thereby leading to drastic fading of capacity. Therefore, it is urgent to seek a positive electrode material characterized by a high specific capacity, a high voltage plateau, desirable structural reversibility, and a steady interface at a high voltage for lithium-ion batteries. SUMMARY This application provides a positive active material. The positive active material at a high voltage of 4.8 V exhibits a considerable discharge capacity and desirable structural reversibility and cycle stability. In an embodiment, this application provides a positive active material. The positive active material contains a compound with a P63mc space group. In an XRD pattern of the positive active material, a (002) crystal plane of the compound with the P63mc space group is located between 17.5° and 19°, and a full width at half maximum of the (002) crystal plane falls between 0.05 and 0.1. In some embodiments, in a DSC pattern of the positive active material, an exothermic peak of the compound with th