A lithium ion battery and a preparation method thereof

Abstract

The application discloses a lithium ion battery and a preparation method thereof. The positive electrode material contains boron elements, and the distribution amount of the element B meets the following characteristics: the content of boron in the positive electrode material is less than or equal to 20% of the total mass of boron elements, the content of boron elements in the negative electrode is less than or equal to 20% of the total mass of boron elements, and the content of B elements in the electrolyte is greater than or equal to 60% of the total mass of boron elements. The method improves the accumulation orientation of the transition metal layer, improves the charge density distribution of oxygen elements, cooperatively improves the stability of the negative electrode SEI film, reduces the electrolyte consumption and metal dissolution, and improves the mechanical compression resistance.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a lithium-ion battery and its preparation method. Background Technology

[0002] Lithium-ion batteries, as the most promising energy storage devices, are widely used in consumer electronics, pure electric vehicles, hybrid vehicles, and smart grids. Lithium cobalt oxide, due to the limitations of delithiation caused by structural phase transitions, has an actual usable capacity of about half its theoretical capacity. Furthermore, factors such as cobalt reserves, the environmental hazards of cobalt, and humanitarian mining restrict its application in high-end markets such as pure electric vehicles and high-power power tools. Currently, ternary materials are gradually being used to replace lithium cobalt oxide in lithium batteries, further expanding the application market for lithium-ion batteries and reducing their operating costs. Based on the different elements incorporated into the cathode material, it can be mainly divided into two categories: lithium nickel cobalt manganese oxide (NCM) and lithium nickel cobalt aluminum oxide (NCA). Among them, high-nickel lithium nickel cobalt manganese oxide (LiNi1-x-yCoxMnyO2, abbreviated as NCM) cathode materials with hexagonal α-NaFeO2 layered structure have the characteristics of low cost, easy preparation, environmental friendliness, and high energy density, which can meet people's requirements for high energy density. However, the expansion and contraction of individual grains in ternary materials, especially ultra-high nickel ternary materials (Ni≥83%), during charge and discharge processes can cause cracks on the secondary sphere surface and even grain disintegration, further deteriorating the structural stability of the cathode material and reducing battery safety. Existing technologies use different valence states Single-element doping or coating can improve the structural stability of the cathode, thereby enhancing the applicability and safety of the battery. However, traditional doping and coating methods have not truly solved the interfacial stability of the cathode, further leading to the dissolution of transition metal elements and continuous consumption of electrolyte. In addition, the dissolved transition metal elements undergo reduction reactions during battery discharge and precipitate as "zero-valent" transition metal elements on the negative electrode side. These elements have the ability to catalyze the cracking of electrolyte and solid electrolyte membrane, continuously consuming electrolyte in the cell and generating flammable gases, reducing the cell's capacity and safety. Simple doping and coating have not solved the problem of effective distribution of target elements and have not effectively solved the problems of electrolyte consumption and cathode grain boundary breakage in the cell.

[0003] Patent CN110867580A discloses a method for preparing lithium nickel cobalt manganese oxide single crystal cathode material by doping with strontium. The method involves uniformly mixing and sintering lithium carbonate and strontium hydroxide precursor powder to obtain single crystal NCM523. However, the Sr element is not activated and does not form a distributed and concentrated structure, which cannot solve the problems of cell cycle life and stability.

[0004] Patent CN109713297A discloses a primary particle orientation cathode material and its preparation method. It uses a doping method with a specific crystal type guiding agent to change the orientation of the 003 crystal plane of the cathode, thereby reducing the stress concentration caused by the shrinkage and expansion of the crystal and extending the battery life. However, it is difficult to achieve a uniform distribution of doping elements. The uneven distribution of elements will inevitably lead to stress concentration in the material grains, and the goal of improving the cathode material cannot be achieved.

[0005] Patent CN103840148A discloses a method for preparing multi-component composite lithium-ion battery cathode materials through secondary sintering. It uses doping elements and transition metal salts to mix together to obtain a doped precursor. After sintering and coating, a more stable cathode material is obtained. The elements are uniformly distributed inside the precursor to form a co-precipitated precursor, which solves the problem of uniform element distribution. However, the secondary sintering and coating does not effectively solve the problem of element distribution. The stress concentration problem between grains still exists. In addition, after cell activation, it cannot be guaranteed that the elements can meet the specific distribution, thus solving the problem of electrolyte consumption.

[0006] Patent CN107895793B discloses a lithium battery cathode material coated with tungsten-doped boride and its preparation method. The patent first dissolves tungsten source in water, sprays it into a mixture of ternary precursor and lithium source, stirs and dries it to obtain a mixture, then calcines it at high temperature to obtain a tungsten-doped ternary cathode, and finally coats the tungsten-doped ternary cathode with MgB2 to obtain a lithium battery cathode material coated with tungsten-doped boride. However, traditional doping and coating cannot ensure that the elements are effectively concentrated in various components of the cell, making it difficult to exert the multiple synergistic effects of the elements, and also does not have the effect of reducing electrolyte consumption. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a lithium-ion battery material and its preparation method, which employs a multi-element modified cathode material to achieve a more concentrated distribution of elements within the battery. This reduces electrolyte decomposition during use and enhances the stability between the electrolyte and the positive and negative electrodes.

[0008] To address the above problems, the present invention provides the following technical solution:

[0009] A lithium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive electrode material containing boron. The distribution of boron in the positive electrode material meets the following characteristics: the boron content in the positive electrode material is ≤20% of the total mass of boron; the boron content in the negative electrode is ≤20% of the total mass of boron; and the boron content in the electrolyte is ≥60% of the total mass of boron.

[0010] Preferably, the positive electrode material further contains a metallic element M, wherein M is one or more of the elements Zr, Ti, Ce, La, Mg, Al, W, Mo, Nb, Ba, and Ta.

[0011] Preferably, the distribution of metal element M meets the following characteristics: the content of metal element M in the positive electrode material is ≥ 80% of the total mass of metal element M, the content of metal element M in the negative electrode is ≤ 10% of the total mass of metal element M, and the content of metal element M in the electrolyte is ≤ 10% of the total mass of metal element M.

[0012] Preferably, the positive electrode material is one or more of NCM, NCA, NM, and NC.

[0013] Preferably, the cathode material is NCM, and the structure of the cathode material is: Li[(Ni 1-x-y-z Co x Mn y M z )]B η O 2-3η Wherein, 0.01≤x≤0.1, 0.01≤y≤0.1, 0.001≤z≤0.05, 0.01≤η≤0.2, and M is one or more of the elements Zr, Ti, Ce, La, Mg, Al, W, Mo, Nb, Ba, and Ta.

[0014] Preferably, the electrolyte is a carbonate-based solvent electrolyte.

[0015] Preferably, the negative electrode material is graphite or a composite graphite material mixed with 1-2% silicon (such as silicon suboxide).

[0016] Preferably, the diaphragm is a ceramic-coated diaphragm.

[0017] This invention also provides a method for preparing the above-mentioned battery material, comprising the following steps:

[0018] 1) Element modifiers including metal M and element B are added into the bulk phase of the cathode material or enriched on the surface of the material by sintering. After calcination is completed and cooled to room temperature, the material is crushed by roller crushing and sieved to obtain a multi-element modified cathode material.

[0019] 2) The obtained multi-element modified positive electrode material is prepared into a positive electrode, which is combined with a negative electrode, a separator, and an electrolyte to form a battery cell. Through a voltage differential growth formation process, the effective elements in the multi-element modifier are activated and distributed and enriched in the main material of the battery cell to achieve a stable interface and reduce electrolyte consumption.

[0020] In some preferred embodiments of the present invention, to achieve the objective of the present invention, the method for preparing the positive electrode material is as follows:

[0021] The precursor and lithium salt were mixed evenly according to the elemental molar ratio, and then a modifier containing metal M and B elements was added. After mixing evenly, the mixture was calcined, pulverized and sieved in an oxygen-enriched kiln at an appropriate temperature to obtain a multi-element modified cathode material.

[0022] Preferably, the molar ratio of lithium salt to precursor transition metal element is in the range of 0.99-1.05.

[0023] Preferably, the calcination temperature range is 600-800℃, and the calcination time is 8-18h. In some preferred embodiments of the present invention, the cathode material can also be prepared by a secondary sintering method, which is as follows: the precursor and lithium salt are mixed evenly according to the elemental molar ratio, calcined, pulverized, and sieved in a kiln to obtain a pretreated cathode material, then a modifier containing metal M and B elements is added, and after further mixing evenly, the mixture is sintered, pulverized, and sieved in a kiln to obtain a multi-element modified cathode material.

[0024] Preferably, the secondary roasting temperature range is 300-600℃.

[0025] Preferably, the first roasting time is 8-18 hours and the second roasting time is 5-10 hours.

[0026] Modifiers include, but are not limited to, borates or borate compounds of elements such as Zr, Ti, Ce, Co, Mg, Al, W, Mo, Nb, Ba, and Ta, such as NbB2, TaB2, ZrB2, SrB4O7, BaB6, and SrB6, in various forms of one or more borates or borates.

[0027] The molar ratio of the precursor to the modifier is 0.9-0.99:0.001-0.05.

[0028] The voltage differential growth formation process in step 2) specifically refers to the voltage increasing to 3.95V at a constant rate of V1 for the first time at high temperature, the first rest and elimination of electrochemical polarization, and the initial activation of the effective elements in the multi-element modifier.

[0029] After polarization elimination, it is charged again at a constant rate of V2 to a cutoff voltage of 4.25 to 4.5V, rests again, and fully activates the effective elements in the multi-element modifier, causing them to be distributed and enriched at the interface of the positive electrode, electrolyte, and negative electrode.

[0030] Preferably, the high-temperature formation temperature is 40–60℃.

[0031] Preferably, the initial charging rate V1 is 0.1–2.0 V / h;

[0032] Preferably, the initial rest period is 2–4 hours;

[0033] Preferably, the recharge rate V2 is 0.05–0.5 V / h;

[0034] The preferred rest period is 6 to 12 hours.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] This invention involves doping the positive electrode material with metallic and non-metallic elements (B), distributing them on the surface and at grain boundaries. After the material is assembled into a battery cell and activated, the target elements in the multi-element modification are activated and distributed and concentrated in the positive electrode, negative electrode, and electrolyte. This stabilizes the crystal structure and the SEI film, while mitigating the damage to the acidic electrolyte environment caused by hydrogen fluoride from trace water, reducing electrolyte consumption, improving the stability of the negative electrode solid electrolyte film, and increasing the interfacial stability between the positive electrode and the electrolyte.

[0037] By adding metallic element M and non-metallic element B to the cathode material and through an activation process, the effective elements M and B are concentratedly distributed in the electrolyte, negative electrode, and positive electrode portions of the battery cell. The distribution of non-metallic element B improves the stability of the electrolyte and the stability of the solid electrolyte film at the negative electrode interface. The distribution of metallic element M enhances the toughness of the material structure. At the same time, the small amount of non-metallic element B in the cathode material facilitates the formation of covalent bonds with oxygen atoms on its surface, improving the toughness of the cathode material itself, enhancing the material's processing performance and cycle stability. The synergistic effect of multi-element distributed enrichment can not only significantly alleviate the cracking phenomenon of crystal particles, but also reduce the oxidative decomposition of the electrolyte, reduce the amount of electrolyte consumed in the battery cell, and further expand the application scenarios and service life of lithium-ion batteries. Attached Figure Description

[0038] Figure 1 This is a cross-sectional electron microscope and schematic diagram of the positive electrode material in Embodiment 1 of the present invention after being cycled at 45°C for 500 cycles;

[0039] Figure 2 This is a cross-sectional electron microscope and schematic diagram of the cathode material of Comparative Example 1 of the present invention after being cycled at 45°C for 500 cycles.

[0040] Figure 3 This is the XRD pattern of the cathode material in Embodiment 1 of the present invention.

[0041] Example 1

[0042] (1) The NCM precursor and lithium hydroxide monohydrate were mixed evenly at an elemental molar ratio of 1.03 and sintered in a kiln at 800℃ for 10 h to obtain the intermediate NCM cathode material.

[0043] (2) Add 98g of the cathode material and 1.52g of the multi-element modifier SrB6 from step 1 above according to the molar ratio of NCM:SrB6 = 0.99:0.01. After mixing evenly, calcine at 500℃ for 10h, crush and sieve to obtain the NCM cathode material modified with the metal element strontium and the non-metal element boron.

[0044] (3) The positive electrode material, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) prepared above were mixed in a mass ratio of 95:2:3 to form a positive electrode slurry. The positive electrode slurry was uniformly coated on the current collector aluminum foil at 90% of the negative electrode capacity; after drying at 120°C, it was cold-pressed; then the edges were trimmed, cut into pieces, and slit, and dried under vacuum at 120°C for 2 hours to form the positive electrode of the lithium-ion battery.

[0045] (4) Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed uniformly at a mass ratio of EC:EMC = 30:70 to form the electrolyte; graphite is used as the negative electrode active material, and the separator is a double-sided ceramic coated separator. The battery positive electrode, negative electrode, separator, and electrolyte are assembled into a 5Ah soft-pack cell. Under a constant temperature environment of 45℃, the assembled cell is charged to 3.95V at a rate of 1.0V / h, then rested for 2 hours to eliminate electrochemical polarization, and then charged to 4.25V at a rate of 0.2V / h. After resting for another 10 hours, the formation process is completed, which thoroughly activates the target elements to be distributed and enriched in the electrolyte, negative electrode, and positive electrode materials, which can significantly reduce the electrolyte consumption.

[0046] like Figure 1 As shown in the schematic diagram, the modification of the cathode material with multi-component modifiers alters the material's appearance morphology, and the multi-component modification reduces the surface energy of the primary particles, thereby changing the crystal orientation of the primary particles, further mitigating excessive delithiation and reducing the severity of the irreversible H2-H3 phase transition. Figure 1 shows a cross-sectional electron microscope image of the cathode material from Example 1 of this invention after 500 cycles at 45°C. The image shows no obvious cracks extending to the surface of the particles.

[0047] Figure 2 The cross-sectional electron microscope in the image shows the cathode material of Comparative Example 1 of this patent. After undergoing the same 500 cycles at 45°C as the cathode material of Example 1, it is evident that stress concentration leads to the appearance of a large number of fine lines, and even causes the crystal to disintegrate and break. The comparison of the two images further proves that reducing the contraction / expansion between the anisotropy of primary particles can significantly improve the stability of the material interface, thereby extending the service life and safety of the battery cell. Figure 3The XRD pattern shows that after modification, the cathode material still has no impurity peaks at 003, 101, 006 / 012, 104, 015, 017, 018 / 110, and 113. The multi-element modification did not produce any extra impurity peaks, proving that the modified cathode material still has a good layered structure. In addition, the 006 / 012 and 018 / 110 peaks are clearly separated, indicating that the cation mixing degree of the material is low. This shows that the multi-element modifier, within a suitable range, did not cause damage to the layered structure of the material itself.

[0048] The battery material of this invention can not only alleviate the grain boundary stress during the charging and discharging process of the positive electrode material, but also reduce electrolyte consumption and extend the battery cell life. The electrolyte retention of the battery cell is used to represent the electrolyte consumption during the battery cell cycle, as shown in Table 1. After the battery was disassembled after 500 cycles at 45°C, the electrolyte content was measured and the electrolyte retention and retention rate were calculated. The mass of electrolyte consumed by the lithium-ion battery material of this invention is significantly compared with the battery material consumption of Example 1, which again proves that the lithium-ion battery with the specific modification element distribution of this invention can alleviate the stress concentration between crystals, reduce the occurrence of side reactions, reduce electrolyte consumption, and extend the battery cell life.

[0049] A 5Ah battery cell was assembled using a multi-element modified positive electrode material, a graphite negative electrode, a double-sided ceramic-coated separator, and a high-voltage electrolyte. After formation, the effective element distribution in the modifier was activated. The battery cell was disassembled after a 45°C high-temperature cycling test, and the remaining electrolyte mass was measured. A fresh battery cell that had undergone formation and was fully discharged was also disassembled. The disassembled positive and negative electrode portions were washed with NMP and collected. The modifier content in the disassembled positive and negative electrodes and the electrolyte was analyzed using ICP-OES, and the percentage distribution of metallic element M and non-metallic element B in the battery cell was calculated. The test results of the multi-element distribution of the battery cell components are detailed in Table 2. The comparative test results of Example 1 and Example 2 demonstrate that the effective distribution of metallic element M and non-metallic element B in this patent can indeed reduce electrolyte consumption and improve the cycle stability of the battery cell.

[0050] The results show that the battery material of this application significantly improves the electrolyte consumption of the battery cell. At the same time, the formation method described in this patent effectively and thoroughly activates the metal element M and the non-metal element B and distributes them to the electrolyte, positive electrode, negative electrode and other components, thereby enhancing the stability of the battery cell and extending its service life.

[0051] Example 2

[0052] 1) The same method as in Example 1 was used, except that the molar ratio of the precursor and lithium hydroxide monohydrate was adjusted to 1.50 and the calcination temperature was 770°C.

[0053] 2) Add 98g of the cathode material and 1.54g of the multi-element modifier NbB2 from step 1 above according to the molar ratio of NCM:NbB2 = 0.985:0.015. After mixing evenly, calcine at 600℃ for 10h, crush and sieve to obtain the NCM cathode material modified with the metallic element niobium and the non-metallic element boron.

[0054] 3) Using the same electrolyte and separator as in Example 1, the positive electrode material of this example is prepared using the same method as step (3) in Example 1. Graphite containing 1% silicon is used as the negative electrode material and assembled into a 5Ah soft-pack cell. Under a constant temperature environment of 40°C, the assembled cell is charged to 3.95V at a rate of 2.0V / h. After the cell rests for 4 hours to eliminate electrochemical polarization, it is charged to 4.30V at a rate of 0.05V / h. After resting for another 6 hours, the formation process is completed, which thoroughly activates the target elements to be distributed and enriched in the electrolyte, negative electrode, and positive electrode material. This can significantly reduce the electrolyte consumption, and the effect is no less than that of Example 1.

[0055] Example 3

[0056] 1) The same method as in Example 1 was used, except that the molar ratio of the precursor and lithium hydroxide monohydrate was adjusted to 1.00 and the calcination temperature was 790°C.

[0057] 2) Add 98g of the cathode material and 1.91g of the multi-element modifier TaB2 from step 1 above according to the molar ratio of NCM:TaB2 = 0.99:0.01. After mixing evenly, calcine at 450℃ for 5h, crush and sieve to obtain the NCM cathode material modified with the metallic element tantalum and the non-metallic element boron.

[0058] 3) Using the same electrolyte and separator as in Example 1, the positive electrode material of this example is prepared using the same method as step (3) in Example 1. Graphite containing 0.5% silicon is used as the negative electrode and assembled into a 5Ah soft-pack cell. Under a constant temperature environment of 50°C, the assembled cell is charged to 3.95V at a rate of 0.5V / h. After the cell rests for 2 hours to eliminate electrochemical polarization, it is charged to 4.4V at a rate of 0.1V / h. After resting for 7 hours again, the formation process is completed, which thoroughly activates the target elements to be distributed and enriched in the electrolyte, negative electrode, and positive electrode material. This can significantly reduce the electrolyte consumption, and the effect is no less than that of Example 1.

[0059] Example 4

[0060] 1) Using the same method as in Example 1, except that the molar ratio of the precursor and lithium hydroxide monohydrate was adjusted to 1.02, the calcination temperature was 760°C, and the multi-element modifier was 1.01g of BaB6, all other parameters were the same to obtain a barium metal and boron non-metal NCM cathode material.

[0061] 2) Using the same electrolyte, negative electrode, and separator as in Example 1, and using the same method as step (3) in Example 1, the positive electrode material of this example is prepared. The positive electrode material, negative electrode, separator, and electrolyte are assembled into a 5Ah soft-pack battery cell. Under a constant temperature environment of 60℃, the assembled battery cell is charged to 3.95V at a rate of 2.0V / h. After the battery cell rests for 3h to eliminate electrochemical polarization, it is charged to 4.5V at a rate of 0.5V / h. After resting for 12h again, the formation process is completed, which thoroughly activates the target elements to be distributed and enriched in the electrolyte, negative electrode, and positive electrode material. This can significantly reduce the electrolyte consumption, and the effect is no less than that of Example 1.

[0062] Comparative Example 1

[0063] The cathode material was obtained in the same manner as in Example 1. Except that no multi-component modifier was used, the cell assembly and testing conditions were the same as in Example 1. The main difference is that the activation method was to charge the cell at room temperature of 25°C with a constant current of 0.5C to the cutoff voltage of 4.25V. The testing of the other cells was the same as in Example 1. For specific test results, please refer to other parts of this patent.

[0064] Comparative Example 2

[0065] The positive electrode material was obtained in the same manner as in Example 1. The cell assembly and testing conditions were the same as in Example 1. However, the cell activation adopted the traditional constant current and constant voltage activation method. The main difference is that the activation method is to charge the cell at room temperature of 25°C with a constant current of 0.5C until the cutoff voltage of 4.25V. The testing of the other cells is the same as in Example 1. For specific test results, please refer to other parts of this patent.

[0066] Table 1 shows that various positive electrode materials, negative electrodes, electrolytes, and separators prepared using the examples and comparative examples were assembled into battery cells. After a voltage differential growth formation process, the battery cells with different positive electrode materials were subjected to 500 cycles of 1C / 1C charge / discharge at 45°C in a constant temperature chamber under a cutoff voltage of 2.7-4.25V. The battery cells were then disassembled, and the remaining electrolyte mass was tested to obtain the electrolyte retention amount and electrolyte retention percentage. The electrolyte retention amount in this patent embodiment is significantly improved. In addition, the rapid reduction of electrolyte during battery cell cycling is a major factor contributing to the degradation of battery cell lifespan. This patent reduces the electrolyte consumption rate through specific element distribution, further increasing the battery lifespan and improving the economy and applicability of the battery cell.

[0067] Table 1. Changes in electrolyte mass after 500 cycles at 45℃

[0068] name Initial electrolyte mass / g Electrolyte mass after cycling / g Liquid retention rate / % Example 1 16.0 13.8 86.3 Example 2 16.0 13.8 86.3 Example 3 16.0 14.2 88.7 Example 4 16.0 13.9 86.8 Comparative Example 1 16.0 7.1 44.4 Comparative Example 2 16.0 8.5 53.2

[0069] Table 2 Percentage of Modifying Elements Distributed in Cell Components

[0070] Element types positive electrode / % Electrolyte / % negative electrode / % Example 1 Metal element M 91 5 4 nonmetallic element B 7 90 3 Example 2 Metal element M 96 3 1 nonmetallic element B 6 92 2 Example 3 Metal element M 81 14 5 nonmetallic element B 10 80 10 Example 4 Metal element M 95 4.5 0.5 nonmetallic element B 10 85 5 Comparative Example 1 Metal element M / / / nonmetallic element B / / / Comparative Example 2 Metal element M 99.98 0.01 0.01 nonmetallic element B 70 20 10

[0071] This invention discloses a method for preparing a lithium-ion battery that reduces electrolyte consumption. The method modifies the ternary material with borides or borate compounds of relevant metal elements to improve the surface morphology distribution of the material and reduce the reaction surface energy of nanoparticles to form a preferred crystal structure. The preferred crystal orientation is used to slow down the phase transition caused by cycling. The distributed enrichment of functional elements can reduce the amount of electrolyte consumed, delay material aging, and increase cycle capacity and cell life.

[0072] By introducing metallic element M and non-metallic element B in a single step, and through a formation activation process, the effective elements M and B are concentratedly distributed in the electrolyte, negative electrode, and positive electrode portions of the battery cell. The distribution of non-metallic element B improves the stability of the electrolyte and the stability of the solid electrolyte film at the negative electrode interface. The distribution of metallic element M enhances the toughness of the material structure. At the same time, the small amount of non-metallic element B distributed in the positive electrode material facilitates the formation of covalent bonds with oxygen atoms on its surface, improving the toughness of the positive electrode material itself, enhancing the material's processing performance and cycle stability. The distributed enrichment of elements can not only significantly alleviate the cracking phenomenon of crystal particles, but also reduce the oxidative decomposition of the electrolyte, reduce the amount of electrolyte consumed in the battery cell, and further expand the application scenarios and service life of lithium-ion batteries.

[0073] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A lithium ion battery material, characterized in that, The battery includes a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode includes a positive electrode material containing boron element, the distribution amount of element B meets the following characteristics: the content of boron in the positive electrode material is less than or equal to 20% of the total mass of boron element, the content of boron element in the negative electrode is less than or equal to 20% of the total mass of boron element, and the content of B element in the electrolyte is greater than or equal to 60% of the total mass of boron element; The positive electrode material further contains metal element M, wherein M is one or more of Zr, Ti, Ce, La, Mg, Al, W, Mo, Nb, Ba and Ta; The distribution amount of metal element M meets the following characteristics: the content of metal element M in the positive electrode material is greater than or equal to 80% of the total mass of metal element M, the content of metal M in the negative electrode is less than or equal to 10% of the total mass of metal element M, and the content of metal M in the electrolyte is less than or equal to 10% of the total mass of metal element M.

2. The battery material of claim 1, wherein, The positive electrode material is one or more of NCM, NCA, NM and NC.

3. The battery material of claim 2, wherein, The positive electrode material is NCM.

4. The battery material of claim 1, wherein, The structure of the positive electrode material is: Li[(Ni 1-x-y- z Co x Mn y M z )]B η O 2-3η , wherein, 0.01≤x≤0.1, 0.01≤y≤0.1, 0.001≤z≤0.05, 0.01≤η≤0.2, in addition, M is one or more of Zr, Ti, Ce, La, Mg, Al, W, Mo, Nb, Ba, Ta elements.

5. The battery material of any one of claims 1-4, wherein, The electrolyte is a carbonate solvent electrolyte.

6. The battery material of any one of claims 1-4, wherein, The negative electrode material is graphite or a composite graphite material containing 1-2% of silicon.

7. The battery material of any one of claims 1-4, wherein, The separator is a ceramic coated separator.

8. The method of claim 1-7, wherein, The method includes the following steps: 1) adding a modifier containing metal M and element B into the bulk phase of the positive electrode material or enriching it on the surface of the material by sintering, crushing and sieving after cooling to room temperature after calcination to obtain a multi-element modified positive electrode material; 2) preparing the obtained multi-element modified positive electrode material into a positive electrode, combining it with a negative electrode, a separator and an electrolyte to form a battery cell, and activating the effective element distribution of the multi-element modifier in the main material of the battery cell through a voltage equal difference increasing formation process; The modifier is a boride or a boric acid compound of Zr, Ti, Ce, Co, Mg, Al, W, Mo, Nb, Ba and Ta; The voltage equal difference increasing formation process in step 2) specifically refers to increasing the voltage at a constant V1 rate to 3.95V at high temperature for the first time; After polarization elimination, charge again at a constant rate V2 to a cut-off voltage of 4.25-4.5V.

9. The battery material preparation method of claim 8, wherein, The modifier is selected from NbB2, TaB2, ZrB2, SrB4O7, BaB6 and SrB6.

10. The battery material preparation method of claim 8, wherein, The preparation method of the positive electrode material is as follows: uniformly mixing a precursor and a lithium salt according to the element mole ratio, adding a modifier containing metal M and B element, continuously mixing uniformly, and then roasting, crushing and sieving at a proper temperature in an oxygen-rich kiln to obtain a multi-element modified positive electrode material.

11. The battery material preparation method of claim 10, wherein, The mole ratio of the precursor to the modifier is 0.9-0.99:0.001-0.

05.

12. The battery material preparation method of claim 8, wherein, High-temperature formation temperature: 40-60℃.

13. The battery material preparation method of claim 8, wherein, First charging rate V1: 0.1-2.0V / h.

14. The battery material preparation method of claim 8, wherein, First rest time: 2-4h.

15. The battery material preparation method of claim 8, wherein, Second charging rate V2: 0.05-0.5V / h.

16. The battery material preparation method of claim 8, wherein, Second rest time: 6-12h.

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