A low-temperature high-performance cathode material, its preparation method and application

Abstract

This invention discloses a low-temperature high-performance cathode material, its preparation method, and its application, relating to the field of lithium-ion battery cathode material technology. The cathode material is a layered LiNi alloy. 0.6 Co 0.2 Mn 0.2 Using O2 as a matrix, a composite interface layer is constructed in situ on the particle surface. This composite interface layer comprises an outer continuous coating layer and an inner near-surface control layer. Surface reactions and heat treatment using a Li2O, B2O3, and Li3PO4 precursor system are employed to suppress interfacial side reactions, stabilize the near-surface structure, and achieve low-temperature Li... + Improved transport capacity. At -20°C, the preferred sample achieved a discharge specific capacity of 154.21 mAh g⁻¹ in the 10th cycle. ‑1 The rate performance, cycle stability and polarization index are all superior to the original sample and the key control group.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery cathode materials technology, specifically to a ternary layered oxide cathode material, its preparation method, and its applications, particularly to a material in LiNi... 0.6 Co 0.2 Mn 0.2 A cathode material with improved low-temperature electrochemical performance is developed by constructing a crystalline Li3PO4 / boron-containing amorphous dual-phase outer layer on the surface of O2 particles and forming a B / P near-surface gradient control layer. The material's preparation method and its application in lithium-ion batteries are also discussed. Background Technology

[0002] LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622) combines high specific capacity, good structural stability, and cost advantages, making it one of the promising ternary layered cathode materials for high-energy-density lithium-ion batteries. However, at low temperatures, this material is prone to interfacial charge transfer hysteresis and Li... + Problems such as hindered diffusion, increased electrode polarization, accelerated capacity decay, and enhanced interfacial side reactions lead to a significant decrease in rate performance and cycle stability. For nickel-containing layered cathodes, these degradations typically occur first on the particle surface and near-surface regions, further inducing surface residual alkali, increased secondary phases, decreased oxygen stability, and local structural instability. Existing technologies typically employ single phosphate coating, single boron-containing layer coating, heterometallic doping, combined doping and coating, or general interfacial modulation techniques to improve the performance of ternary cathodes, but these still have the following shortcomings: First, a single physical isolation layer often cannot simultaneously satisfy the rapid ion transport at low temperatures; second, a single shallow layer modulation cannot simultaneously address the suppression of interfacial side reactions and near-surface lattice stability. Therefore, developing a composite modification strategy that can simultaneously construct a recognizable dual-phase outer layer and a near-surface gradient layer without destroying the NCM622 layered main phase structure, and exhibit a nonlinear synergistic effect under low-temperature conditions, is of great significance. Summary of the Invention

[0003] This solution addresses the problems and needs raised above by proposing a low-temperature high-performance cathode material, its preparation method, and its applications. The above-mentioned technical objectives are achieved by adopting the following technical features, and it also brings about several other technical benefits.

[0004] One object of this invention is to provide a low-temperature high-performance cathode material, comprising: layered LiNi 0.6 Co 0.2 Mn 0.2 O2 matrix particles and formed in the layered LiNi 0.6 Co 0.2 Mn 0.2A composite interface layer on the surface of O2 matrix particles; the composite interface layer is formed in situ by surface reaction and heat treatment of lithium-containing, boron-containing and phosphorus-containing components, and includes an outer continuous coating layer and a near-surface regulation layer located between the outer continuous coating layer and the matrix particles; wherein, the outer continuous coating layer contains both crystalline Li3PO4 phase and boron-containing amorphous phase, and the near-surface regulation layer is a shallow region enriched with B and P elements and distributed in a gradient decreasing towards the interior of the matrix.

[0005] In addition, the low-temperature high-performance cathode material, its preparation method, and its application according to the present invention may also have the following technical features: In one example of the present invention, the average thickness of the outer continuous coating layer is 5 to 12 nm, wherein the crystalline Li3PO4 phase exhibits lattice fringes of 0.30 to 0.35 nm under a high-resolution transmission electron microscope.

[0006] In one example of the present invention, the cathode material maintains an α-NaFeO2 type layered structure with space group R-3m, and the main phase structure of the matrix is ​​not destroyed after modification.

[0007] In one example of the present invention, the lithium-containing component, the boron-containing component, and the phosphorus-containing component are Li2O, B2O3, and Li3PO4, respectively, and the molar ratio of the feed is (2-4):(5-7):(0.3-2).

[0008] Another object of the present invention is to provide a method for preparing the cathode material as described above, comprising the following steps: S10: Provides layered LiNi 0.6 Co 0.2 Mn 0.2 O2 matrix materials; S20: Weigh Li2O, B2O3 and Li3PO4 according to a predetermined ratio and disperse them in a solvent to form a modified precursor system; S30: Combine the modified precursor system with layered LiNi 0.6 Co 0.2 Mn 0.2 O2 matrix material is mixed and evenly distributed; S40: After solvent removal and heat treatment, the layered LiNi... 0.6 Co 0.2 Mn 0.2 The composite interface layer is formed in situ on the surface of the O2 matrix material.

[0009] In one example of the present invention, in step S20, the solvent is anhydrous ethanol; the stirring time is 0.5~2h; and the mixing time of the matrix particles and the precursor system is 0.5~2h.

[0010] In one example of the present invention, in step S40, the drying temperature is 80–120°C; the drying time is 8–16 h; and the heating rate is 3–10°C / min. -1 .

[0011] In one example of the present invention, the heat treatment temperature is 450–550°C; the holding time is 8–12 h; the heat treatment atmosphere is oxygen or an oxygen-enriched atmosphere, and the gas flow rate is 20–100 mL / min. -1 .

[0012] Another objective of this invention is to provide a positive electrode sheet prepared from the aforementioned low-temperature high-performance positive electrode material.

[0013] Another object of the present invention is to provide a lithium-ion battery comprising the positive electrode sheet described above.

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) By constructing a dual-level composite interface structure of “crystalline Li3PO4 / boron-containing amorphous dual-phase outer layer + B / P near-surface gradient control layer”, a multi-functional synergy that is difficult to achieve with simple Li3PO4 coating, simple boron-containing layer or general doping + coating is realized. (2) The outer continuous coating layer can serve as a stable physical / chemical dual interface, reducing the direct contact between the electrolyte and the positive electrode active material, and inhibiting interfacial side reactions and the dissolution of transition metals; (3) The B and P elements enriched near the surface and shallowly penetrated can pin and regulate the surface lattice, reduce the mixing of Li / Ni cations, and maintain the stability of the layered structure. (4) The composite interface layer formed by the present invention can also reduce surface residual alkali, improve surface chemical state and low temperature Li + Transport kinetics were optimized to improve the material's capacity, rate performance, and cycle stability at low temperatures; the preferred sample achieved a discharge specific capacity of 154.21 mAh g⁻¹ in the 10th cycle at -20°C and 0.2C. -1 It was significantly better than the original sample and the key control group; (5) By setting up control samples with only Li3PO4 coating, only boron layer and B / P physical mixture, it can be further proved that the present invention is not a simple splicing of the prior art, but has unexpected advantages under low temperature conditions.

[0015] The preferred embodiments of the invention will be described in more detail below with reference to the accompanying drawings, so as to facilitate an understanding of the features and advantages of the invention. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. The drawings are merely illustrative of some embodiments of the present invention and are not intended to limit the scope of the present invention to all embodiments.

[0017] Figure 1 The XRD patterns of different samples and the Rietveld refinement results are schematic diagrams according to embodiments of the present invention. Figure 2 The above images show the surface distribution of the samples according to embodiments of the present invention, including SEM, TEM, HR-TEM, and EDS images. Figure 3 The above figures show the XPS and depth profile results of the sample according to an embodiment of the present invention. Figure 4 GITT, CV, and Li of the samples according to embodiments of the present invention + Diffusion coefficient analysis diagram; Figure 5 The constant current charge-discharge curves, average discharge voltage, rate performance, and long cycle performance of the samples according to embodiments of the present invention at -20°C are shown in the figure. Figure 6 This is a TOF-SIMS depth distribution map of a sample according to an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, “an” or “a” and similar terms do not necessarily indicate a quantity limitation. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described object changes.

[0020] According to a first aspect of the present invention, a low-temperature high-performance cathode material comprises: layered LiNi 0.6 Co 0.2 Mn 0.2 O2 matrix particles and formed in the layered LiNi 0.6 Co 0.2 Mn 0.2 A composite interface layer on the surface of O2 matrix particles; the composite interface layer is formed in situ by surface reaction and heat treatment of lithium-containing, boron-containing and phosphorus-containing components, and includes an outer continuous coating layer and a near-surface regulation layer located between the outer continuous coating layer and the matrix particles; wherein, the outer continuous coating layer contains both crystalline Li3PO4 phase and boron-containing amorphous phase, and the near-surface regulation layer is a shallow region enriched with B and P elements and distributed in a gradient decreasing towards the interior of the matrix.

[0021] This cathode material achieves multifunctional synergy that is difficult to achieve with simple Li3PO4 coating, simple boron-containing layer or general doping + coating by constructing a two-level composite interface structure of "crystalline Li3PO4 / boron-containing amorphous dual-phase outer layer + B / P near-surface gradient control layer". The continuous outer coating layer of the cathode material can serve as a stable physical / chemical dual interface, reducing direct contact between the electrolyte and the cathode active material, and suppressing interfacial side reactions and the dissolution of transition metals. The B and P elements enriched and shallowly permeated near the surface of the cathode material can pin and regulate the surface lattice, reduce Li / Ni cation mixing, and maintain the stability of the layered structure. The composite interface layer formed by this cathode material can also reduce surface residual alkali, improve surface chemical state, and reduce low-temperature Li +Transport kinetics were optimized to improve the material's capacity, rate performance, and cycle stability at low temperatures; the preferred sample achieved a discharge specific capacity of 154.21 mAh g⁻¹ in the 10th cycle at -20°C and 0.2C. -1 It was significantly better than the original sample and the key control group; By setting up control samples with only Li3PO4 coating, only boron layer, and B / P physical mixture, this positive electrode material can further prove that the present invention is not a simple splicing of existing technologies, but has unexpected advantages under low temperature conditions.

[0022] In one example of the present invention, the average thickness of the outer continuous coating layer is 5–12 nm, preferably 8–12 nm; in a preferred embodiment, the average thickness is approximately 9.82 ± 1.25 nm. The crystalline Li3PO4 phase exhibits lattice fringes of 0.30–0.35 nm, preferably approximately 0.324 nm, under a high-resolution transmission electron microscope, corresponding to the (111) crystal plane or other verified crystal planes of Li3PO4.

[0023] In one example of the present invention, elements B and P are enriched and distributed in a region of 1 to 50 nm from the particle surface, and the gradient distribution is shown to gradually decrease with increasing depth by XPS depth profiling and TOF-SIMS depth analysis; wherein, the gradient depth is preferably 1 to 30 nm.

[0024] In one example of the present invention, the cathode material maintains an α-NaFeO2 type layered structure with a space group of R-3m, and the main phase structure of the matrix is ​​not destroyed after modification. Preferably, the original sample has a space group of 1.26 and the modified sample has a space group of 1.68.

[0025] In one example of the present invention, the lithium-containing component, boron-containing component, and phosphorus-containing component are Li2O, B2O3, and Li3PO4, respectively, and the molar ratio of the feed is (2-4):(5-7):(0.3-2). Preferably, it is (2-3):(6-6.5):(0.5-2); more preferably, it is 3:6:1.

[0026] According to a second aspect of the present invention, a method for preparing a positive electrode material as described above includes the following steps: S10: Provides layered LiNi 0.6 Co 0.2 Mn 0.2 O2 matrix materials; S20: Weigh Li2O, B2O3 and Li3PO4 according to a predetermined ratio and disperse them in a solvent to form a modified precursor system; S30: Combine the modified precursor system with layered LiNi 0.6 Co 0.2 Mn 0.2O2 matrix material is mixed and evenly distributed; S40: After solvent removal and heat treatment, the layered LiNi... 0.6 Co 0.2 Mn 0.2 The composite interface layer is formed in situ on the surface of the O2 matrix material.

[0027] This preparation method achieves a multi-functional synergy that is difficult to achieve with simple Li3PO4 coating, simple boron-containing layer or general doping + coating by constructing a two-level composite interface structure of "crystalline Li3PO4 / boron-containing amorphous dual-phase outer layer + B / P near-surface gradient control layer". The continuous outer coating layer prepared by this method can serve as a stable physical / chemical dual interface, reducing direct contact between the electrolyte and the positive electrode active material, and inhibiting interfacial side reactions and the dissolution of transition metals. The preparation method enriches and shallowly penetrates B and P elements near the surface, which can pin and regulate the surface lattice, reduce Li / Ni cation mixing, and maintain the stability of the layered structure. The composite interface layer formed by this preparation method can also reduce surface residual alkali, improve surface chemical state, and withstand low-temperature Li + Transport kinetics were optimized to improve the material's capacity, rate performance, and cycle stability at low temperatures; the preferred sample achieved a discharge specific capacity of 154.21 mAh g⁻¹ in the 10th cycle at -20°C and 0.2C. -1 It was significantly better than the original sample and the key control group; This preparation method, by setting up control samples with only Li3PO4 coating, only boron layer, and B / P physical mixture, can further prove that the present invention is not a simple splicing of existing technologies, but has unexpected advantages under low temperature conditions.

[0028] In one example of the present invention, in step S20, the solvent is anhydrous ethanol; the stirring time is 0.5 to 2 hours; and the mixing time of the matrix particles and the precursor system is 0.5 to 2 hours.

[0029] In one example of the present invention, in step S40, during solvent removal and heat treatment, the drying temperature is 80–120°C, preferably 100°C; the drying time is 8–16 h, preferably 12 h; and the heating rate is 3–10°C / min. -1 .

[0030] In one example of the present invention, the heat treatment temperature is 450–550°C, preferably 500°C; the holding time is 8–12 h, preferably 10 h; the heat treatment atmosphere is oxygen or an oxygen-enriched atmosphere, and the gas flow rate is 20–100 mL / min. -1 The preferred gas flow rate is 50 mL / min. -1 .

[0031] In one example of the present invention, based on 100g of LiNi0.6Co0.2Mn0.2O2 matrix material, the amounts of Li2O, B2O3 and Li3PO4 added are 0.432g, 2.012g and 0.556g, respectively.

[0032] According to a third aspect of the present invention, a positive electrode sheet is prepared from the low-temperature high-performance positive electrode material described above.

[0033] According to a fourth aspect of the present invention, a lithium-ion battery includes the positive electrode sheet described above. Example 1

[0034] S10: Take layered LiNi 0.6 Co 0.2 Mn 0.2 100g of O2 matrix material will be used as the matrix for subsequent modification. The matrix material can be prepared in-house or sourced commercially.

[0035] S20: Weigh the lithium-containing component, boron-containing component, and phosphorus-containing component according to the molar ratio of Li2O:B2O3:Li3PO4=3:6:1; based on 100g of NCM622 matrix material, the amount of Li2O, B2O3, and Li3PO4 added is 0.432g, 2.012g, and 0.556g, respectively; add the above raw materials to anhydrous ethanol and stir for 1h to form a uniformly dispersed modified precursor system.

[0036] S30: Add NCM622 matrix particles to the precursor system and continue stirring or ball milling for 1 hour to ensure that the modified precursor is uniformly attached to the particle surface. S40: Then dry at 100℃ for 12 hours, and then at 3℃ for 1 minute. -1 The temperature was raised to 500℃ and kept at that temperature for 10 hours in an oxygen or oxygen-enriched atmosphere to obtain NCM@LBLP2 cathode material.

[0037] As shown in Figure 1, all samples maintained the α-NaFeO2 type layered structure with space group R-3m, indicating that the modification treatment did not destroy the main phase structure of the matrix material.

[0038] As shown in Figure 2, the modified particles still maintain the spherical secondary particle morphology, without obvious agglomeration and breakage. A continuous coating layer is formed on the surface of the material, and the internal layered NCM lattice remains intact. The average thickness of this continuous coating layer is about 9.82±1.25nm. At the same time, there are boron-containing amorphous regions in the coating layer, and a crystalline-amorphous dual-phase composite coating structure has been successfully constructed.

[0039] As shown in Figure 3, the proportion of low-valence Ni species decreased and the proportion of high-valence Ni species increased in the modified sample; the area ratio of Li2CO3-related peaks on the material surface decreased significantly; B1s and P2p test results showed that stable boron- and phosphorus-containing species existed on the material surface, verifying the successful construction of the composite interface layer. Further Ar... + XPS depth analysis showed that B and P had strong signals in the near-surface region of the material, which gradually weakened with increasing etching depth. Weak signals could still be detected in deeper regions, indicating that B and P were mainly enriched in the near-surface region of the material and a small amount of infiltration into the shallow inner layer occurred.

[0040] As shown in Figure 4, the redox peak potential difference of the original NCM sample was 1.1 V, while the peak potential difference of the modified sample decreased to 0.72 V, indicating that the electrode polarization of the modified material was significantly reduced; the Li in the modified sample + The diffusion coefficient is generally around 10. -13 ~10 -11 cm 2 ・s -1 This represents an improvement of one order of magnitude compared to the original sample, validating the effect of the composite interface layer on Li. + Significant improvement in transport dynamics.

[0041] As shown in Figure 5, the modified samples were fabricated into positive electrode sheets and assembled into lithium-ion half-cells. Electrochemical performance tests were conducted within a test voltage window of 2.5–4.5 V and a test temperature of -20 °C. At a 0.2 C rate, the lithium-ion battery assembled with this positive electrode material exhibited a discharge specific capacity of 154.2 mAh·g⁻¹ on the 10th cycle. -1 It is significantly superior to the original NCM's 85.29mAh·g -1 Meanwhile, it exhibits the best average discharge voltage, rate performance, and cycle stability. At -20℃ and a current density of 0.2C, its initial reversible discharge specific capacity reaches 154.29mAh / g, and after 300 cycles, its discharge specific capacity still reaches 134.33mAh / g, with a capacity retention rate of 87.06%.

[0042] As shown in Figure 6, to enhance the evidence strength of the gradient layer, it is preferable to further supplement the TOF-SIMS depth distribution. The corresponding result should be written as: the characteristic signals of B and P are significantly enriched within 1~80nm from the surface and show a continuous attenuation trend; the test conditions are Cs + The sputtering rate is 0.84 nm / s, the sputtering time is 0~1400 s, and the corresponding depth is 0~1176 nm. Example 2

[0043] S10: Take layered LiNi 0.6 Co 0.2 Mn 0.2 100g of O2 matrix material will be used as the matrix for subsequent modification. The matrix material can be prepared in-house or sourced commercially.

[0044] S20: Weigh the lithium-containing component, boron-containing component, and phosphorus-containing component according to the molar ratio of Li2O:B2O3:Li3PO4=3:6.5:0.5; based on 100g of NCM622 matrix material, the amount of Li2O, B2O3, and Li3PO4 added is 0.448g, 2.262g, and 0.289g, respectively; add the above raw materials to anhydrous ethanol and stir for 1h to form a uniformly dispersed modified precursor system.

[0045] S30: Add NCM622 matrix particles to the precursor system and continue stirring or ball milling for 1 hour to ensure that the modified precursor is uniformly attached to the particle surface. S40: Then dry at 100℃ for 12 hours, and then at 3℃ for 1 minute. -1 The temperature was raised to 500℃ and kept at that temperature for 10 hours in an oxygen atmosphere to obtain NCM@LBLP1 cathode material.

[0046] The samples in this example all maintained the α-NaFeO2 layered structure with space group R-3m, indicating that the modification treatment did not damage the main phase structure of the matrix material. At -20℃ and a current density of 0.2C, the initial reversible discharge specific capacity reached 148.43 mAh / g, and after 300 cycles, the discharge specific capacity still reached 125.28 mAh / g, with a capacity retention of 84.4%. Example 3

[0047] The raw materials were weighed according to the molar ratio of Li2O:B2O3:Li3PO4=2:6:2, and NCM@LBLP3 was prepared according to the same dispersion, mixing, drying and heat treatment steps as in Example 2.

[0048] S10: Take layered LiNi 0.6 Co 0.2 Mn 0.2 100g of O2 matrix material will be used as the matrix for subsequent modification. The matrix material can be prepared in-house or sourced commercially.

[0049] S20: Weigh the lithium-containing component, boron-containing component, and phosphorus-containing component according to the molar ratio of Li2O:B2O3:Li3PO4=2:6:2; based on 100g of NCM622 matrix material, the amount of Li2O, B2O3, and Li3PO4 added is 0.253g, 1.768g, and 0.979g, respectively; add the above raw materials to anhydrous ethanol and stir for 1h to form a uniformly dispersed modified precursor system.

[0050] S30: Add NCM622 matrix particles to the precursor system and continue stirring or ball milling for 1 hour to ensure that the modified precursor is uniformly attached to the particle surface. S40: Then dry at 100℃ for 12 hours, and then at 3℃ for 1 minute. -1 The temperature was raised to 500℃ and kept at that temperature for 10 hours in an oxygen atmosphere to obtain NCM@LBLP3 cathode material.

[0051] The samples in this example all maintained the α-NaFeO2 layered structure with space group R-3m, indicating that the modification treatment did not damage the main phase structure of the matrix material. At -20℃ and a current density of 0.2C, the initial reversible discharge specific capacity reached 142.68 mAh / g, and after 300 cycles, the discharge specific capacity still reached 120.31 mAh / g, with a capacity retention of 84.32%. Example 4

[0052] To demonstrate that this invention is not a simple extension of a single phosphate coating, a control group with only Li3PO4 coating was set up. Using NCM622 as the matrix, only Li3PO4 precursor or other equivalent phosphorus sources were added, and the total coating amount, drying regime, and heat treatment regime were controlled to be as consistent as possible with Embodiment 1.

[0053] S10: Take layered LiNi 0.6 Co 0.2 Mn 0.2 100g of O2 matrix material will be used as the matrix for subsequent modification. The matrix material can be prepared in-house or sourced commercially.

[0054] S20: The amount of Li3PO4 added is 3g per 100g NCM622 matrix material; the above raw materials are added to anhydrous ethanol and stirred for 1h to form a uniformly dispersed modified precursor system.

[0055] S30: Add NCM622 matrix particles to the precursor system and continue stirring or ball milling for 1 hour to ensure that the modified precursor is uniformly attached to the particle surface. S40: Then dry at 100℃ for 12 hours, and then at 3℃ for 1 minute. -1 The temperature was raised to 500℃ and kept at that temperature for 10 hours in an oxygen atmosphere. The resulting sample was named NCM@Li3PO4.

[0056] The samples in this example all maintained the α-NaFeO2 layered structure with space group R-3m, indicating that the modification treatment did not damage the main phase structure of the matrix material. At -20℃ and a current density of 0.2C, its initial reversible discharge specific capacity reached 115.68 mAh / g, and after 300 cycles, its discharge specific capacity still reached 71.35 mAh / g, with a capacity retention of 61.67%. Example 5

[0057] To demonstrate that the biphase outer layer formed after introducing the P component has an effect distinct from that of a single boron-containing surface layer, a boron-only control group was set up. Using NCM622 as the matrix, only B2O3 or other equivalent boron-containing precursors were added, and control samples were prepared under comparable conditions of total coating amount and heat treatment regime.

[0058] S10: Take layered LiNi 0.6 Co 0.2 Mn 0.2 100g of O2 matrix material will be used as the matrix for subsequent modification. The matrix material can be prepared in-house or sourced commercially.

[0059] S20: Based on 100g of NCM622 matrix material, the amount of Li2O and B2O3 added is 0.530g and 2.470g respectively (Li2O:B2O3 molar ratio 1:2, total coating amount 3wt%); the above raw materials are added to anhydrous ethanol and stirred for 1h to form a uniformly dispersed modified precursor system.

[0060] S30: Add NCM622 matrix particles to the precursor system and continue stirring or ball milling for 1 hour to ensure that the modified precursor is uniformly attached to the particle surface. S40: Then dry at 100℃ for 12 hours, and then at 3℃ for 1 minute. -1 The temperature was raised to 500℃ and kept at that temperature for 10 hours in an oxygen atmosphere. The resulting sample was named NCM@LBO.

[0061] The samples in this example all maintained the α-NaFeO2 layered structure with space group R-3m, indicating that the modification treatment did not damage the main phase structure of the matrix material. At -20℃ and a current density of 0.2C, the initial reversible discharge specific capacity reached 132.4 mAh / g, and after 300 cycles, the discharge specific capacity still reached 112.32 mAh / g, with a capacity retention of 84.84%. Example 6

[0062] To eliminate the possibility of accidental performance improvements from simple physical mixing, a B / P physical mixing control group was set up. The control group used the same total addition amount as in Example 1, but did not follow the reaction pathway that could form a biphase outer layer and a gradient layer in situ, or used a post-mixing method to construct an in-situ composite layer.

[0063] The Li3PO4-coated sample from Example 4 and the LBO-coated sample from Example 5 were physically mixed at a mass ratio of 1:4.4 and manually ground in an agate mortar for 30 minutes to obtain a physical mixture control sample, named NCM@LBO+LPO-Mix.

[0064] The samples in this example all maintained the α-NaFeO2 layered structure with space group R-3m, indicating that the modification treatment did not damage the main phase structure of the matrix material. At -20℃ and a current density of 0.2C, the initial reversible discharge specific capacity reached 125.64 mAh / g, and after 300 cycles, the discharge specific capacity still reached 86.52 mAh / g, with a capacity retention of 68.8%.

[0065] The foregoing description, with reference to preferred embodiments, details an exemplary embodiment of the low-temperature high-performance cathode material, its preparation method, and its application proposed in this invention. However, those skilled in the art will understand that various modifications and alterations can be made to the above specific embodiments without departing from the concept of this invention, and various combinations can be made to the various technical features and structures proposed in this invention without exceeding the protection scope of this invention, which is determined by the appended claims.

Claims

1. A low-temperature high-performance cathode material, characterized in that, include: Layered LiNi 0.6 Co 0.2 Mn 0.2 O2 matrix particles and formed in the layered LiNi 0.6 Co 0.2 Mn 0.2 A composite interface layer on the surface of O2 matrix particles; the composite interface layer is formed in situ by surface reaction and heat treatment of lithium-containing, boron-containing and phosphorus-containing components, and includes an outer continuous coating layer and a near-surface regulation layer located between the outer continuous coating layer and the matrix particles; wherein, the outer continuous coating layer contains both crystalline Li3PO4 phase and boron-containing amorphous phase, and the near-surface regulation layer is a shallow region enriched with B and P elements and distributed in a gradient decreasing towards the interior of the matrix.

2. The low-temperature high-performance cathode material according to claim 1, characterized in that, The average thickness of the outer continuous coating layer is 5–12 nm, wherein the crystalline Li3PO4 phase exhibits lattice fringes of 0.30–0.35 nm under a high-resolution transmission electron microscope.

3. The low-temperature high-performance cathode material according to claim 1, characterized in that, The cathode material maintains an α-NaFeO2 type layered structure with a space group of R-3m, and the main phase structure of the matrix is ​​not destroyed after modification.

4. The low-temperature high-performance cathode material according to claim 1, characterized in that, The lithium-containing component, boron-containing component, and phosphorus-containing component are Li2O, B2O3, and Li3PO4, respectively, and the molar ratio of the feed is (2-4):(5-7):(0.3-2).

5. A method for preparing the cathode material according to any one of claims 1 to 4, characterized in that, Includes the following steps: S10: Provides layered LiNi 0.6 Co 0.2 Mn 0.2 O2 matrix materials; S20: Weigh Li2O, B2O3 and Li3PO4 according to a predetermined ratio and disperse them in a solvent to form a modified precursor system; S30: Combine the modified precursor system with layered LiNi 0.6 Co 0.2 Mn 0.2 O2 matrix material is mixed and evenly distributed; S40: After solvent removal and heat treatment, the layered LiNi... 0.6 Co 0.2 Mn 0.2 The composite interface layer is formed in situ on the surface of the O2 matrix material.

6. The method for preparing the cathode material according to claim 5, characterized in that, In step S20, the solvent is anhydrous ethanol; the stirring time is 0.5~2h; and the mixing time between the matrix particles and the precursor system is 0.5~2h.

7. The method for preparing the cathode material according to claim 5, characterized in that, In step S40, the drying temperature is 80–120°C; the drying time is 8–16 h; and the heating rate is 3–10°C / min. -1 .

8. The method for preparing the cathode material according to claim 5, characterized in that, The heat treatment temperature is 450–550℃; the holding time is 8–12 h; the heat treatment atmosphere is oxygen or oxygen-enriched atmosphere, and the gas flow rate is 20–100 mL / min. -1 .

9. A positive electrode sheet, characterized in that, It is prepared from the low-temperature high-performance cathode material as described in any one of claims 1 to 4.

10. A lithium-ion battery, characterized in that, Includes the positive electrode sheet as described in claim 9.

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