Lithium iron phosphate coated lithium supplementing agent positive electrode material, preparation method thereof and lithium battery

Abstract

The invention provides a lithium iron phosphate coated lithium supplement agent positive electrode material and a preparation method thereof and a lithium battery, the lithium iron phosphate coated lithium supplement agent positive electrode material comprises an inner core, a middle layer, an outer layer and a carbon coating layer in sequence from inside to outside, the inner core comprises a lithium supplement agent, the middle layer comprises lithium cobalt oxide, and the lithium supplement agent comprises lithium nickelate. The lithium nickelate is used as the inner core, the lithium cobalt oxide is used as the middle layer, the lithium iron phosphate is used as the outer layer, and the outermost layer is the carbon coating layer from inside to outside in sequence, so that the gram volume, the conductivity and the stability of the positive electrode material are improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of batteries, in particular to a lithium phosphate-coated lithium supplement positive electrode material, a preparation method thereof and a lithium battery. BACKGROUND

[0002] The lithium phosphate positive electrode material has been widely applied in power batteries and energy storage fields due to its excellent safety, cycle life and environmental friendliness. However, the specific capacity of the lithium phosphate positive electrode material is low, and in particular, the intrinsic electronic conductivity and ion diffusion rate are poor, so that the rate performance and energy density of the lithium phosphate positive electrode material are difficult to meet the increasing market demand. Therefore, how to improve the specific capacity of the lithium phosphate positive electrode material has become a research focus. Patent CN116435501A discloses a method for preparing a composite material by mixing and coating lithium phosphate and a lithium supplement and then sintering, and the composite material can improve the specific capacity of the lithium phosphate. However, the lithium supplement itself has some defects, for example, the lithium-rich lithium nickelate has poor conductivity and poor rate performance, and the lithium-rich lithium ironate produces gas by decomposition, and these defects will cause the performance of the lithium phosphate combined with the lithium supplement to be poor. Therefore, it is of great scientific significance and commercial value to develop a new composite material which can not only maintain the intrinsic safety of the lithium phosphate but also significantly improve the specific capacity and comprehensive electrochemical performance of the lithium phosphate. SUMMARY

[0003] Therefore, the application provides a lithium phosphate-coated lithium supplement positive electrode material and a preparation method thereof and a lithium battery. The lithium phosphate-coated lithium supplement positive electrode material comprises, from inside to outside, a core, an intermediate layer, an outer layer and a carbon coating layer, the core comprises a lithium supplement, the intermediate layer comprises lithium cobaltate, and the lithium supplement comprises lithium nickelate. The lithium cobaltate is easy to decompose to produce oxygen, but has good conductivity, and the lithium nickelate can absorb oxygen, but has poor conductivity and poor rate performance. The lithium cobaltate and the lithium nickelate can improve the overall performance of the internal lithium-rich material in cooperation, the outer layer of the lithium phosphate effectively prevents the internal lithium-rich material from directly contacting the electrolyte, reduces the generation of side reactions, the outermost carbon coating layer improves the electronic conductivity and promotes the rapid transmission of electrons, and the shortcomings of poor conductivity of the lithium phosphate material are compensated.

[0004] The technical scheme of the application is implemented as follows: In a first aspect, the application provides a lithium phosphate-coated lithium supplement positive electrode material, which comprises, from inside to outside, a core, an intermediate layer, an outer layer and a carbon coating layer. The core comprises a lithium supplement, the intermediate layer comprises lithium cobaltate, and the lithium supplement comprises lithium nickelate.

[0005] The existing technology has the following problems: (1) The specific capacity of high specific capacity lithium supplement and the single coating of lithium iron phosphate can improve the specific capacity to a certain extent, but the defects of the lithium supplement inevitably lead to the deterioration of some electrical properties; (2) Carbon coating of lithium supplement can improve the conductivity of the material, but cannot fundamentally improve the intrinsic specific capacity of the material; (3) The current core-shell structure is mostly a simple coating, which fails to make full use of the synergistic effect between the materials of each layer.

[0006] This invention improves the specific capacity of the cathode material by setting a core and an intermediate layer. Both the core and the intermediate layer are lithium-rich materials, which can provide a high intrinsic specific capacity. The outer lithium iron phosphate layer has a stable voltage plateau in the early stage of charge and discharge, while the lithium-rich materials in the core and intermediate layer are activated at higher voltages, providing specific capacity. This makes the overall specific capacity of the composite material far exceed that of pure phase lithium iron phosphate.

[0007] The core structure of the lithium cobalt oxide in the middle layer is stable and has good lithium-ion conductivity, providing a stable framework and fast ion transport channels for the internal electrochemical reaction. The lithium cobalt oxide in the middle layer decomposes to produce oxygen, but has good conductivity, while the lithium nickel oxide in the core has poor conductivity, but can absorb oxygen. By coating the core and the middle layer, the overall performance of the internal lithium-rich material can be improved. The outer lithium iron phosphate layer and the middle lithium cobalt oxide layer together form a stable protective layer; lithium iron phosphate ensures the overall thermal stability and interfacial stability of the material, effectively preventing direct contact between the inner layer and the electrolyte, and reducing the occurrence of side reactions. The continuous carbon coating network greatly improves the electronic conductivity of the particle surface, promotes rapid electron transport, and makes up for the poor conductivity of lithium iron phosphate materials.

[0008] Based on the above technical solution, the outer layer further includes lithium iron phosphate.

[0009] Based on the above technical solution, the mass ratio of lithium cobalt oxide to lithium nickel oxide is further (0.5~2):1.

[0010] When the mass ratio of lithium cobalt oxide to lithium nickel oxide is less than the lower limit of 0.5:1, the proportion of lithium nickel oxide in the composite material is relatively low. Excessive lithium cobalt oxide cannot completely absorb the generated oxygen, leading to more side reactions between oxygen and the electrolyte, and increasing the risk of battery bulging and interface black spots. When the mass ratio of lithium cobalt oxide to lithium nickel oxide is greater than the upper limit of 2:1, the proportion of lithium nickel oxide in the composite material is relatively high. Since the specific capacity of lithium nickel oxide is half that of lithium cobalt oxide, excessive lithium nickel oxide results in a lower specific capacity, less lithium replenishment, and lower cycle retention rate in the composite lithium iron phosphate material.

[0011] In a second aspect, the present invention also provides a method for preparing a lithium iron phosphate coated lithium supplement cathode material, comprising the following steps: S1, mixing a first iron source or cobalt source with a first lithium source, a first carbon source and a lithium supplement, and performing a first sintering to obtain a composite material; S2. Disperse the composite material in a solvent, add an iron source, a phosphorus source, a reducing agent and a second lithium source, perform liquid-phase precipitation to obtain an intermediate product, and perform a second sintering on the intermediate product to obtain a precursor. S3. The precursor is mixed with the second carbon source and subjected to a third sintering to obtain the lithium iron phosphate coated lithium replenishing agent cathode material.

[0012] Based on the above technical solution, the mass ratio of iron source to composite material in step S2 is (150~400):200.

[0013] Based on the above technical solution, the mass ratio of the precursor to the second carbon source is further (95~99):(1~5).

[0014] Based on the above technical solution, further, the cobalt source in step S1 includes cobalt oxide, and the first lithium source includes lithium hydroxide; The molar ratio of Co in the cobalt source to Li in the first lithium source is (1.05~1.1):1.

[0015] Based on the above technical solution, the first carbon source in step S1 further includes glucose.

[0016] Based on the above technical solution, further, the mass of the first carbon source is 2 to 3 wt% of the mass of lithium cobalt oxide.

[0017] Based on the above technical solutions, the second carbon source further includes at least one of sucrose, glucose, and citric acid.

[0018] Without carbon coating, the material powder has high resistance, which leads to increased internal resistance, reduced energy efficiency, and poorer overall electrical performance in the prepared battery.

[0019] Based on the above technical solutions, the phosphorus source in step S2 further includes ammonium dihydrogen phosphate.

[0020] Based on the above technical solutions, the iron source in step S2 further includes at least one of ferrous sulfate and ferric phosphate.

[0021] Based on the above technical solution, the mass ratio of the precursor to the second carbon source is further (95~99):(1~5).

[0022] Based on the above technical solution, the first sintering further includes: sintering at 500℃~700℃ for 10~15h in an inert atmosphere.

[0023] Based on the above technical solution, the second sintering further includes: sintering at 300℃~500℃ for 2~5 hours in an inert atmosphere, and then sintering at 600℃~750℃ for 8~14 hours.

[0024] Based on the above technical solution, the third sintering further includes: sintering at 300℃~400℃ for 2~4 hours in an inert atmosphere, and then sintering at 600℃~750℃ for 6~12 hours.

[0025] Based on the above technical solution, the preparation method of the lithium replenishing agent further includes: mixing a lithium source and a nickel source, and sintering them to obtain the lithium replenishing agent; The lithium source includes at least one of lithium hydroxide, lithium oxide, and lithium carbonate, and the nickel source includes at least one of nickel hydroxide, nickel oxide, and nickel carbonate.

[0026] Based on the above technical solution, the sintering further includes: sintering at 700℃~850℃ for 10~15h in an oxygen or air atmosphere.

[0027] Based on the above technical solution, the molar ratio of Li in the lithium source to Ni in the nickel source is further (1~2.5):1.

[0028] Based on the above technical solutions, the reducing agent further includes ascorbic acid.

[0029] Thirdly, the present invention also provides a lithium battery, wherein the positive electrode material of the lithium battery is the lithium iron phosphate coated lithium replenishing agent positive electrode material.

[0030] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a lithium iron phosphate coated lithium supplement cathode material, its preparation method, and a lithium battery. By setting lithium nickel oxide as the core, lithium cobalt oxide as the intermediate layer, lithium iron phosphate as the outer layer, and a carbon coating layer as the outermost layer, the specific capacity, conductivity, and stability of the cathode material are improved through the synergistic effect of the core-intermediate-outer-carbon coating layer.

[0031] During charge and discharge, the lithium nickel oxide core is activated, providing specific capacity. Lithium cobalt oxide provides a stable framework and a fast ion transport channel; the lithium cobalt oxide in the middle layer decomposes to produce oxygen, which is absorbed by the lithium nickel oxide core, and the combination of the two improves the overall performance of the internal lithium-rich material; the middle and outer layers form a stable protective layer, and lithium iron phosphate effectively blocks direct contact between the interior and the electrolyte, reducing the generation of side reactions; the outermost carbon coating layer promotes rapid electron transport; thus significantly improving the specific capacity, conductivity, and stability of the cathode material, enabling the lithium battery using the cathode material to have both excellent discharge specific capacity and cycle performance. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] In the following specific implementation methods, unless otherwise specified, the experimental methods used are all conventional experimental methods, and the reagents used are all conventional reagents that can be obtained commercially.

[0034] Example 1 This embodiment provides a lithium iron phosphate coated lithium replenishing agent cathode material and its preparation method.

[0035] The preparation method includes the following steps: S1. Preparation of lithium nickelate core: 480g of lithium hydroxide and 927.1g of nickel hydroxide were mixed in a ball mill for 10h and sintered at 750℃ for 12h under an oxygen atmosphere to obtain Li2NiO2.

[0036] In lithium hydroxide (LiOH), the molar ratio of Li to Ni in nickel hydroxide (Ni(OH)2) is 2:1; S2, Intermediate layer lithium cobalt oxide coating: 118.16g lithium hydroxide, 378.9g cobalt oxide, 22.56g glucose and 752g Li2NiO2 prepared in step S1 were mixed in a ball mill for 8h and sintered at 650℃ for 12h under nitrogen atmosphere to obtain a composite material of Li6CoO4 coated with Li2NiO2.

[0037] The molar ratio of Li in lithium hydroxide (LiOH) to Co in cobalt oxide (Co2O3) is 1.08:1.

[0038] The mass ratio of Li6CoO4 to Li2NiO2 is 1:1.

[0039] The mass ratio of glucose to Li6CoO4 is 3%:1.

[0040] S3, Outer Lithium Iron Phosphate Coating: Dissolve 200g of the composite material prepared in step S2 in ethanol, and add 300g of ferrous sulfate, ammonium dihydrogen phosphate, lithium carbonate (Li:Fe:P = 1.05:1:1), and 422.69g of ascorbic acid. Using a liquid-phase precipitation method, uniformly coat the surface of the composite material prepared in step S2 with the lithium iron phosphate precursor.

[0041] The obtained lithium iron phosphate precursor was pre-sintered at 350℃ for 3h and then sintered at 700℃ for 10h to obtain the precursor of LNO@LFO@LFP material. S4. Carbon coating: Take 98g of the precursor of LNO@LFO@LFP material prepared in step S3 and 2g of sucrose, ball mill and mix for 4h, pre-sinter at 350℃ for 3h under nitrogen atmosphere, then heat to 700℃ for 6h, and obtain lithium iron phosphate cathode material after cooling.

[0042] Example 2 This embodiment provides a lithium iron phosphate coated lithium replenishing agent cathode material and its preparation method.

[0043] The preparation method includes the following steps: S1. Preparation of lithium nickelate core: 224.1g of lithium oxide and 927.1g of nickel hydroxide were mixed in a ball mill for 10h and sintered at 700℃ for 10h in air atmosphere to obtain Li2NiO2 material.

[0044] In this case, the molar ratio of Li in lithium oxide (Li2O) to Ni in nickel hydroxide (Ni(OH)2) is 1.5:1; S2, Intermediate layer lithium cobalt oxide coating: 57.34g lithium hydroxide, 189.1g cobalt oxide, 7.52g glucose and 752g Li2NiO2 material obtained in step S1 were mixed and ball-milled for 8h, and sintered at 500℃ for 10h under argon atmosphere to obtain Li6CoO4 coated Li2NiO2 composite material.

[0045] The molar ratio of Li in lithium hydroxide (LiOH) to Co in cobalt oxide (Co2O3) is 1.05:1.

[0046] The mass ratio of Li6CoO4 to Li2NiO2 is 0.5:1.

[0047] The mass ratio of glucose to Li6CoO4 is 2%:1.

[0048] S3, outer layer lithium iron phosphate coating: 200g of the Li6CoO4-coated Li2NiO2 composite material obtained in step S2 was dispersed in ethanol, and 150g of iron phosphate, ammonium dihydrogen phosphate, lithium carbonate (Li:Fe:P=1.05:1:1) and 422.69g of ascorbic acid were added. The lithium iron phosphate precursor was uniformly coated on the surface of the S2 composite material by liquid phase precipitation. The resulting product was pre-sintered at 500℃ for 3h and then sintered at 600℃ for 8h to obtain the precursor of LNO@LCO@LFP material.

[0049] S4. Carbon coating: Take 95g of the precursor of LNO@LCO@LFP material prepared in step S3 and 1g of glucose, ball mill and mix for 4h, pre-sinter at 300℃ for 2h under nitrogen atmosphere, then heat to 600℃ for 6h, and obtain lithium iron phosphate cathode material after cooling.

[0050] Example 3 This embodiment provides a lithium iron phosphate coated lithium replenishing agent cathode material and its preparation method.

[0051] The preparation method includes the following steps: S1. Preparation of lithium nickelate core: 923.63g of lithium carbonate and 927.1g of nickel hydroxide were mixed in a ball mill for 10h and sintered at 850℃ for 15h under an oxygen atmosphere to obtain Li2NiO2 material.

[0052] In this case, the molar ratio of Li in lithium carbonate (Li2CO3) to Ni in nickel hydroxide (Ni(OH)2) is 2.5:1; S2, Intermediate layer lithium cobalt oxide coating: 360.8g lithium hydroxide, 1136.1g cobalt oxide, 28.2g glucose and 752g Li2NiO2 obtained in step S1 were mixed and ball-milled for 8h, and sintered at 700℃ for 15h under nitrogen atmosphere to obtain a composite material of Li6CoO4 coated with Li2NiO2.

[0053] The molar ratio of Li in lithium hydroxide (LiOH) to Co in cobalt oxide (Co2O3) is 1.1:1.

[0054] The mass ratio of Li6CoO4 to Li2NiO2 is 1.5:1.

[0055] The mass ratio of glucose to Li6CoO4 is 2.5%:1.

[0056] S3, outer layer lithium iron phosphate coating: 200g of the composite material obtained in step S2 was dispersed in ethanol, and 400g of ferrous sulfate, ammonium dihydrogen phosphate, lithium carbonate (Li:Fe:P=1.05:1:1) and 422.69g of ascorbic acid were added. The lithium iron phosphate precursor was uniformly coated on the surface of the S2 composite material by liquid phase precipitation. The resulting product was pre-sintered at 300℃ for 5h and then sintered at 750℃ for 14h to obtain the precursor of LNO@LCO@LFP material.

[0057] S4. Carbon coating: Take 99g of the precursor of LNO@LCO@LFP material prepared in step S3 and 5g of citric acid, ball mill and mix for 4h, pre-sinter at 300℃ for 2h under nitrogen atmosphere, then heat to 600℃ for 6h, and obtain lithium iron phosphate cathode material after cooling.

[0058] Comparative Example 1 The difference between this comparative example and Example 1 is that it does not contain a lithium nickel oxide core.

[0059] Comparative Example 2 The difference between this comparative example and Example 1 is that it does not contain the intermediate layer of lithium cobalt oxide coating.

[0060] The steps include: S1, which is the same as step S1 in Example 1; S2. Dissolve 200g of Li2NiO2 prepared in step S1 in ethanol, add 300g of ferrous sulfate, ammonium dihydrogen phosphate, and lithium carbonate (Li:Fe:P = 1.05:1:1) and 422.69g of ascorbic acid. Using a liquid-phase precipitation method, uniformly coat the surface of the Li2NiO2 prepared in step S1 with the lithium iron phosphate precursor. Pre-sinter at 350℃ for 2h, then sinter at 700℃ for 8h to obtain the precursor of LNO@LFP material.

[0061] S3. Take 98g of the precursor of LNO@LFP material prepared in step S2 and 2g of sucrose, ball mill and mix for 4h, pre-sinter at 350℃ for 3h under nitrogen atmosphere, then heat to 700℃ for 6h, and obtain lithium iron phosphate cathode material after cooling.

[0062] Comparative Example 3 The difference between this comparative example and Example 1 is that this comparative example provides a method for preparing lithium iron phosphate.

[0063] Includes the following steps: 200g of iron phosphate, 50g of lithium carbonate, and 15g of glucose were mixed in pure water and milled. The resulting slurry was spray-dried and then sintered at 750℃ for 8 hours to obtain lithium iron phosphate.

[0064] Comparative Example 4 The difference between this comparative example and Example 1 is that the amount of lithium cobalt oxide is too small, and the mass ratio of lithium cobalt oxide to lithium nickel oxide is 0.1:1.

[0065] Comparative Example 5 The difference between this comparative example and Example 1 is that there is too much lithium cobalt oxide, and the mass ratio of lithium cobalt oxide to lithium nickel oxide is 10:1.

[0066] Application examples The lithium iron phosphate cathode materials, conductive agents, and binders prepared in Examples 1-3 and Comparative Examples 1-4 were mixed in a mass ratio of 8:1:1 and stirred in NMP to form a cathode slurry. The cathode slurry was uniformly coated onto carbon-coated aluminum foil and vacuum dried at 120°C for 8 hours. After drying, Φ12mm cathode sheets were cut and matched with Φ14mm lithium metal sheets. The electrolyte was a LiPF6+EC+PC+EMC system. Lithium-ion coin cells were assembled and charged and discharged at 0.1C between 2.5 and 4.05V. The charge-discharge specific capacity was measured. The test results are shown in Table 1 below.

[0067] Table 1

[0068] Table 1 shows that when using the lithium iron phosphate cathode materials prepared in Examples 1-3, the battery exhibits higher specific capacity and initial efficiency. Lithium nickel oxide has high impedance and low specific capacity; when the content of lithium nickel oxide in the composite material is high, the specific capacity and initial efficiency are also low. Lithium cobalt oxide has low impedance and high specific capacity; combining it with lithium iron phosphate can improve the specific capacity of the material. Comparative Example 2 does not contain lithium cobalt oxide, and the composite material prepared in Comparative Example 4 contains too much lithium nickel oxide. Due to the high resistance of lithium nickel oxide powder, the initial efficiency is low. Comparative Example 1 does not contain lithium nickel oxide, and the composite material prepared in Comparative Example 5 contains too much lithium cobalt oxide; the overall specific capacity of the material is slightly higher than that of pure lithium iron phosphate (compared to Comparative Example 3).

[0069] 2. The lithium iron phosphate cathode materials prepared in Examples 1-3 and Comparative Examples 1-4 are mixed with conductive agent (conductive carbon black) and binder (PVDF) at a mass ratio of 97:1:2. NMP is added and the mixture is stirred to form a uniform and stable cathode slurry. The cathode slurry is uniformly coated on the cathode current collector, dried and rolled to obtain the cathode sheet. Negative electrode sheet: The negative electrode active material is mixed with conductive agent (conductive carbon black), CMC and SBR in a mass ratio of 96.2:1:1.2:1.6. Deionized water is added and stirred to form a uniform and stable negative electrode slurry. The negative electrode slurry is uniformly coated on the negative electrode current collector (6μm thick copper foil), dried and rolled to obtain the negative electrode sheet. Battery assembly: Batteries were prepared by stacking, assembling, injecting electrolyte, forming, and capacity testing of the separator, negative electrode, and positive electrode in that order. The electrochemical performance of the lithium-ion batteries constructed with different positive electrode plates was tested, and the results are shown in Table 2 below.

[0070] Table 2

[0071] Table 2 shows that when the composite material contains little or no lithium nickel oxide, the gas produced by the decomposition of lithium cobalt oxide cannot be fully absorbed, resulting in a large amount of gas generated during battery storage, which poses a certain safety hazard. Conversely, when the composite material contains little or no lithium cobalt oxide, the overall specific capacity of the material is low, thus affecting the discharge specific capacity and cycle retention rate of the entire battery. Adjusting the ratio of lithium cobalt oxide to lithium nickel oxide until the gas produced by the decomposition of lithium cobalt oxide is exactly absorbed by lithium nickel oxide achieves the optimal specific capacity and storage performance of the battery.

[0072] In summary, this invention provides a lithium iron phosphate coated lithium replenishing agent cathode material, its preparation method, and a lithium battery. By setting lithium nickel oxide as the core, lithium cobalt oxide as the middle layer, lithium iron phosphate as the outer layer, and carbon coating layer as the outermost layer, the specific capacity, conductivity, and stability of the cathode material are significantly improved, enabling the lithium battery using the cathode material to have both excellent discharge specific capacity and cycle performance.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A lithium iron phosphate coated lithium replenishing agent cathode material, characterized in that, From the inside out, it includes a core, an intermediate layer, an outer layer, and a carbon coating layer. The core includes a lithium supplement, the intermediate layer includes lithium cobalt oxide, and the lithium supplement includes lithium nickel oxide.

2. The lithium iron phosphate coated lithium replenishing agent cathode material as described in claim 1, characterized in that, The outer layer comprises lithium iron phosphate.

3. The lithium iron phosphate coated lithium replenishing agent cathode material as described in claim 1, characterized in that, The mass ratio of lithium cobalt oxide to lithium nickel oxide is (0.5~2):

1.

4. The method for preparing a lithium iron phosphate coated lithium replenishing agent cathode material according to any one of claims 1 to 3, characterized in that, The process includes the following steps: S1, mixing a cobalt source with a first lithium source, a first carbon source and a lithium supplement, and performing a first sintering to obtain a composite material; S2. Disperse the composite material in a solvent, add an iron source, a phosphorus source, a reducing agent and a second lithium source, perform liquid-phase precipitation to obtain an intermediate product, and perform a second sintering on the intermediate product to obtain a precursor. S3. The precursor is mixed with the second carbon source and subjected to a third sintering to obtain the lithium iron phosphate coated lithium replenishing agent cathode material.

5. The preparation method according to claim 4, characterized in that, The mass ratio of iron source to composite material in step S2 is (150~400):

200.

6. The preparation method according to claim 4, characterized in that, The mass ratio of the precursor to the second carbon source is (95~99):(1~5).

7. The preparation method according to claim 4, characterized in that, The cobalt source in step S1 includes cobalt oxide, and the first lithium source includes lithium hydroxide. The molar ratio of Co in the cobalt source to Li in the first lithium source is (1.05~1.1):

1.

8. The preparation method according to claim 4, characterized in that, The first carbon source in step S1 includes glucose.

9. A lithium battery, characterized in that, The positive electrode material of the lithium battery is the lithium iron phosphate coated lithium replenishing agent positive electrode material as described in any one of claims 1 to 3.

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