Electrode material and preparation method thereof, battery monomer, battery device and power utilization device

Abstract

The invention provides a battery monomer, an electrode material, a preparation method of the electrode material, a battery device and a power utilization device. The battery monomer comprises an electrode plate and an electrolyte, the electrode plate comprises a current collector and an electrode film layer arranged on the current collector, the electrode film layer comprises an electrode material, the electrode material comprises an electrode active material and a modified group, the modified group comprises one or more of cyano, phenyl ester group and sulfate radical, and the modified group is dispersed in the electrode film layer. The modified groups are grafted on the surface of the electrode active material, so that the stability of the surface structure of the electrode active material can be effectively improved, the interface film forming effect of the electrode active material and electrolyte is optimized, and the capacity, the first effect, the cycle performance and the high-temperature storage performance of a battery monomer are further improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to an electrode material and its preparation method, a battery cell, a battery device, and an electrical device. Background Technology

[0002] With the popularization and development of new energy vehicles, developing high-energy-density lithium-ion batteries to improve the range of vehicles is currently the main development and application direction of power battery products.

[0003] Currently, the main strategies for improving the energy density of cathode materials in lithium-ion batteries include: using high-operating-voltage cathode active materials represented by lithium nickel manganese oxides (such as LiNi0.5Mn1.5O4, abbreviated as LNMO), or using high-capacity cathode active materials represented by nickel-rich oxides (LiNixCoyMnzO2, x+y+z=1, abbreviated as NCM). Compared with LNMO, NCM has a higher capacity under normal charge and discharge conditions and is becoming the most promising high-energy-density lithium-ion battery material for practical applications.

[0004] However, under working conditions, the surface stability of the positive electrode active material particles is poor, especially in the lithium nickel cobalt manganese oxide system with high nickel content. The CEI film at the positive electrode electrolyte interface cannot effectively prevent the positive electrode active material particles from contacting the electrolyte, thereby continuously causing serious side reactions and eroding the surface active centers.

[0005] Therefore, there is an urgent need for an effective technical solution to improve the surface stability of positive electrode active material particles in lithium-ion batteries under working conditions, thereby improving the overall electrochemical performance and cycle performance of lithium-ion batteries. Summary of the Invention

[0006] This application provides an electrode material and its preparation method, a battery cell, a battery device, and an electrical device, which improves the surface stability of the electrode material under working conditions.

[0007] The first aspect of this application provides a battery cell including an electrode sheet and an electrolyte. The electrode sheet includes a current collector and an electrode film layer disposed on the current collector. The electrode film layer includes an electrode material, which includes an electrode active material and a modifying group. The modifying group includes one or more of cyano, phenyl ester, and sulfate groups, and the modifying group is dispersed in the electrode film layer.

[0008] By grafting the aforementioned modified groups onto the surface of the electrode active material, the modified groups are more stable on the surface of the electrode active material than through physical encapsulation. Therefore, the prepared electrode film can simultaneously contain both the modified groups and the electrode active material. When the battery cell is in operation, the modified groups can still form a stable connection with the surface of the electrode active material through chemical bonding. Compared to traditional CEI films, they are less likely to dissolve in the electrolyte and migrate. Thus, the modified groups can continuously stabilize the crystal structure of the electrode active material, allowing more active ions to return to the positive electrode during discharge. Therefore, even if the content of the electrode active material is reduced due to the inclusion of these modified groups, the battery cell can still maintain a high initial efficiency. Simultaneously, it can optimize the interfacial film formation between the electrode active material and the electrolyte. On one hand, the modified groups can interact with PF6… - The reaction inhibits the generation of HF and water, reduces the etching of the surface of the positive electrode active material, improves the stability of the CEI film formed during cycling, and allows the CEI film to play a better role. On the other hand, when the modified groups have a high redox potential, they can also participate in film formation to optimize the ion transport capability of the interfacial film, which is beneficial to improving the capacity, first efficiency, cycle performance and high temperature storage performance of the battery cell.

[0009] In any embodiment of the first aspect, the electrode is a positive electrode.

[0010] In any embodiment of the first aspect, the electrode active material is a positive electrode active material, which is selected from one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0011] In any embodiment of the first aspect, the positive electrode active material includes one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, and lithium manganese oxide, and the molar percentage of nickel in the lithium nickel cobalt manganese oxide is 50% to 95% of the nickel, manganese and cobalt elements, and is further optionally 80% to 95%.

[0012] In any embodiment of the first aspect, the mass content of the modified group in the electrode film layer is 0.05% to 2.5%, optionally 0.05% to 1%. When the mass content of the modified group is within the above range, its role in stabilizing the surface structure of the positive electrode active material can be fully utilized, while mitigating the impact of the addition of the modified group on the specific capacity and conductivity.

[0013] In any embodiment of the first aspect, the electrolyte comprises a solvent and a lithium salt, wherein the solvent comprises one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, ethyl acetate, and fluoroethylene carbonate, and the lithium salt comprises one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0014] A second aspect of this application provides an electrode material comprising an electrode active material and a modifying group, wherein the modifying group is grafted onto the surface of the electrode active material, and the modifying group comprises one or more of cyano, alkoxy, and sulfate groups.

[0015] In any embodiment of the second aspect, the electrode active material is a positive electrode active material, which is selected from one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0016] In any embodiment of the second aspect, the positive electrode active material includes one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, and lithium manganese oxide, and the molar proportion of nickel in the lithium nickel cobalt manganese oxide is 50% to 95% of the total nickel, manganese and cobalt elements, and may be further selected as 80% to 95%.

[0017] In any embodiment of the second aspect, the electrode material further includes one or more of methyl and methylene groups.

[0018] In any embodiment of the second aspect, the mass content of the modified group in the electrode material is 0.05% to 2.5%, and optionally 0.05% to 1%.

[0019] A third aspect of this application provides a method for preparing an electrode material, comprising: mixing a material including an electrode active material, a free radical initiator, and a slurry solvent to obtain a mixed slurry, wherein the free radical initiator includes a modifying group, and the modifying group includes one or more of cyano, phenyl ester, and sulfate groups; decomposing the free radical initiator in the mixed slurry to obtain free radical groups, wherein the free radical groups include the modified groups; and grafting the free radical groups onto the surface of the electrode active material to obtain the electrode material.

[0020] In any embodiment of the third aspect, the slurry solvent includes one or more of N-methylpyrrolidone, dimethylacetamide, and dimethylformamide.

[0021] In any embodiment of the third aspect, the free radical initiator is decomposed by heating, light exposure, or radiation.

[0022] In any embodiment of the third aspect, the free radical initiator includes one or more of azo initiators, organic peroxide initiators, and inorganic peroxide initiators.

[0023] In any embodiment of the third aspect, the azo initiator includes one or more of azobisisoheptanenitrile, azobisisobutyronitrile, azobisisovaleratenitrile, azoisobutylcyanoformamide, and azobiscyclohexylformitrile.

[0024] In any embodiment of the third aspect, the organic peroxide initiator includes one or more of tert-butyl peroxide and benzoyl peroxide.

[0025] In any embodiment of the third aspect, the inorganic peroxide initiator includes one or more of potassium persulfate and ammonium persulfate.

[0026] In any embodiment of the third aspect, the free radical initiator includes an azo initiator, and the mixed slurry is heated to the decomposition temperature of the free radical initiator to decompose the free radical initiator in the mixed slurry.

[0027] In any embodiment of the third aspect, the slurry is stirred while being heated, optionally at a stirring speed of 1000 rpm / min to 2000 rpm / min.

[0028] In any embodiment of the third aspect, the mass ratio of the free radical initiator to the electrode active material is from 0.05:99.95 to 2.5:97.5, and optionally from 0.05:99.95 to 1:99.

[0029] In any embodiment of the third aspect, the electrode active material is a positive electrode active material, which includes one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0030] In any embodiment of the third aspect, the positive electrode active material includes one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, and lithium manganese oxide, and the molar proportion of nickel in the lithium nickel manganese cobalt oxide is 50% to 95% of the total nickel, manganese and cobalt elements, and may be further selected as 80% to 95%.

[0031] A fourth aspect of this application provides a battery device comprising any one of the battery cells of the first aspect.

[0032] The fifth aspect of this application provides an electrical device, including any of the battery cells in the first aspect and any of the battery devices in the fourth aspect, wherein the battery cells or battery devices are used to store or provide electrical energy. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0035] Figure 2 yes Figure 1 An exploded view of a battery cell according to one embodiment of this application is shown.

[0036] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0037] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0038] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0039] Figure 6 This is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to one embodiment of this application.

[0040] The accompanying drawings are not drawn to scale.

[0041] Explanation of reference numerals in the attached figures:

[0042] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Casing; 52 Electrode assembly; 53 End cap. Detailed Implementation

[0043] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0044] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the electrode materials, their preparation methods, battery cells, and electrical devices of this application. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0045] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0047] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0048] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0049] Unless otherwise specified, the terms "comprising" and "including" as used in this application are open-ended. For example, "comprising" and "including" may mean that other components not listed may also be included or contained.

[0050] Unless otherwise specified, the term "or" is inclusive in this application. For example, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0051] [Electrode Materials]

[0052] As mentioned above, effectively improving the surface stability of active material particles is crucial for enhancing the electrochemical and cycle performance of battery cells.

[0053] In existing technologies, both positive and negative electrode active materials often improve their surface stability through surface coating modification. Surface coating modification not only needs to consider the stability of the coating material in the electrolyte but also needs to meet the requirements of active ion transport and electron conduction. More importantly, the particle size of electrode active materials is not uniform, making it quite difficult to form a coating material of uniform and appropriate thickness on the particle surface. Using electrolyte film-forming additives is also a common strategy to improve the surface stability of electrode active materials. However, the surface stability of positive electrode active material particles is poor, especially in lithium nickel cobalt manganese oxide systems with high nickel content. The CEI film at the positive electrode electrolyte interface cannot effectively prevent the contact between the positive electrode active material particles and the electrolyte, thus continuously causing serious side reactions and eroding the surface active centers, resulting in extremely limited improvement in the cycle performance of the battery cell. Furthermore, if a strategy of simply increasing the amount of electrolyte additives is to provide more effective protection for the electrode active materials, it will inevitably lead to a decrease in the content of other components in the electrolyte, adversely affecting the overall performance of the battery cell.

[0054] Therefore, the first embodiment of this application provides an electrode material, including an electrode active material and a modifying group, wherein the modifying group is grafted onto the surface of the electrode active material, and the modifying group includes one or more of cyano, phenyl ester, and sulfate groups.

[0055] By grafting the aforementioned modified groups onto the surface of the electrode active material, the modified groups are more stable on the surface of the electrode active material than through physical encapsulation. Therefore, the prepared electrode film can simultaneously contain both the modified groups and the electrode active material. When the battery cell is in operation, the modified groups can still form a stable connection with the surface of the electrode active material through chemical bonding. Compared to traditional CEI films, they are less likely to dissolve in the electrolyte and migrate. Thus, the modified groups can continuously stabilize the crystal structure of the electrode active material, allowing more active ions to return to the positive electrode during discharge. Therefore, even if the content of the electrode active material is reduced due to the inclusion of these modified groups, the battery cell can still maintain a high initial efficiency. Simultaneously, it can optimize the interfacial film formation between the electrode active material and the electrolyte. On one hand, the modified groups can interact with PF6… - The reaction inhibits the generation of HF and water, reduces the etching of the surface of the positive electrode active material, improves the stability of the CEI film formed during cycling, and allows the CEI film to play a better role. On the other hand, when the modified groups have a high redox potential, they can also participate in film formation to optimize the ion transport capability of the interfacial film, which is beneficial to improving the capacity, first efficiency, cycle performance and high temperature storage performance of the battery cell.

[0056] In some embodiments, the aforementioned electrode active material is a positive electrode active material, selected from one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. When the positive electrode active material is in a delithiation state, transition metal ions on the surface of the aforementioned positive electrode active material may dissolve and migrate into the electrolyte, or they may migrate into the Li... + Vacancy migration and occupation cause irreversible phase transitions in the positive electrode active material, affecting the cycle performance of the secondary battery. When modified using the aforementioned modifying groups, the modifying groups can react with transition metal ions such as Co. 3+ The formation of a stable lattice structure for the positive electrode active material through coordination can significantly improve its power performance and cycle stability.

[0057] In some embodiments, the positive electrode active material includes one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, and lithium manganese oxide, wherein the molar percentage of nickel in the lithium nickel cobalt manganese oxide is 50%-95%, and more preferably 80%-95%. Lithium nickel cobalt manganese oxide is widely recognized as a promising positive electrode active material for lithium-ion power batteries. A higher molar percentage of nickel among the transition metal elements results in higher specific capacity and energy density. However, it is also necessary to overcome the stability decrease caused by increased nickel content, especially in strong oxidizing environments. 4+ The formed CEI film is soluble in commonly used electrolyte systems. However, the unstable CEI film at the interface is unable to effectively prevent particles from contacting the electrolyte, thus continuously causing severe side reactions and erosion of the surface active sites. Modified groups can be directionally anchored on the surface of the positive electrode active material, forming coordination structures with transition metal ions, thereby effectively stabilizing the surface structure and reacting with PF6 in the lithium salt before the electrolyte. - The reaction inhibits the production of HF and water in the electrolyte.

[0058] The aforementioned positive electrode active material can be used alone or in combination of two or more. For example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 At least one of the following: ) and its modified compounds.

[0059] In some embodiments, the electrode material further includes one or more of methyl and methylene groups. The methyl and methylene groups are introduced simultaneously with the modification groups, and multiple tests have shown that the presence of small amounts of methyl and methylene groups does not affect the performance of the positive electrode active material.

[0060] In some embodiments, the mass content of the modified group in the electrode material is 0.05% to 2.5%. The mass content of the modified group within the above range can not only give full play to its role in stabilizing the surface structure of the positive electrode active material, but also mitigate the impact of the addition of the modified group on the specific capacity and conductivity.

[0061] In some embodiments, the mass content of the modified group in the electrode material can be selected as 0.05% to 1%. The modified group can stabilize the crystalline structure of the positive electrode active material, thus allowing more active lithium to be re-intercalated into the positive electrode during discharge. Even with a reduced loading of the positive electrode active material, the initial efficiency / capacity can still be increased.

[0062] [Preparation methods for electrode materials]

[0063] The second embodiment of this application provides a method for preparing an electrode material. The method includes: mixing materials including an electrode active material, a free radical initiator, and a slurry solvent to obtain a mixed slurry, wherein the free radical initiator includes a modifying group, and the modifying group includes one or more of cyano, phenyl ester, and sulfate groups; decomposing the free radical initiator in the mixed slurry to obtain free radical groups, wherein the free radical groups include the modified groups; and grafting the free radical groups onto the surface of the electrode active material to obtain the electrode material.

[0064] The above preparation method utilizes the pyrolysis mechanism of free radical initiators. The free radicals obtained from the pyrolysis attack the surface of the electrode active material, attaching free radical groups, including modified groups, to the surface of the electrode active material. Surface grafting can significantly improve the interaction strength between the modified groups and the surface of the electrode active material, preventing them from moving with the electrolyte during secondary battery operation, thereby improving the surface stability of the electrode active material.

[0065] In some embodiments, the slurry solvent includes one or more of N-methylpyrrolidone, dimethylacetamide, and dimethylformamide, to dissolve the electrode active material and free radical initiator in the slurry solvent and mix them thoroughly.

[0066] In some embodiments, heating, light exposure, or radiation can be used to decompose the free radical initiator. The initiation method can be selected according to the type and activity of the free radical initiator.

[0067] In some embodiments, the free radical initiator includes one or more of azo initiators, organic peroxide initiators, and inorganic peroxide initiators.

[0068] Both azo initiators and organic peroxide initiators can generate highly reactive free radicals through free radical initiator cleavage reactions. These modified groups attack the surface of the positive electrode active material in the form of free radicals, thus firmly grafting onto the material. Furthermore, both azo initiators and organic peroxide initiators are commonly used free radical initiators, readily available, and possess high initiator efficiency.

[0069] In some embodiments, the free radical initiator includes azo initiators. Heating the mixed slurry to the decomposition temperature of the free radical initiator decomposes the initiator in the mixed slurry. Based on differences in decomposition activation energy, free radical initiators can be classified into high-temperature initiators, medium-temperature initiators, and low-temperature initiators. Most azo initiators belong to the medium-temperature category, with decomposition temperatures ranging from 40°C to 110°C. In some embodiments, the azo initiator includes one or more of azobisisobutyronitrile (ABVN), azobisisobutyronitrile (AIBN), azobisisovalerate (AMBN), and azoisobutylcyanoformamide (CABN). To improve the decomposition rate, heating the mixed slurry to approximately the corresponding decomposition temperature can effectively enhance the decomposition efficiency. For example, the decomposition temperature of azobisisobutyronitrile is around 51°C, that of azobisisobutyronitrile is around 65°C, and that of azoisobutylcyanoformamide is around 104°C.

[0070] In some embodiments, the organic peroxide initiator includes one or more of tert-butyl peroxide (BPB) and benzoyl peroxide (BPO).

[0071] In some embodiments, the inorganic peroxide initiator includes one or more of potassium persulfate and ammonium persulfate.

[0072] The aforementioned organic / inorganic peroxide initiators can also have their decomposition rate increased by heating.

[0073] In some embodiments, the slurry is stirred while being heated. Optionally, the stirring speed is 1000 rpm / min to 2000 rpm / min. The free radical initiator decomposes to generate free radicals. Stirring allows the electrode active material in the slurry to come into full contact with the free radicals and also facilitates the escape of gases (such as N2) generated during decomposition, reducing the probability of reverse reactions and further improving reactivity. Furthermore, a stirring speed of 1000 rpm / min to 2000 rpm / min can effectively increase the reaction rate of free radical groups grafted onto the surface of the electrode active material.

[0074] In some embodiments, the mass ratio of the free radical initiator to the electrode active material is from 0.05:99.95 to 2.5:97.5. Initiator decomposition may lead to induced decomposition or a cage-like effect, resulting in reduced initiator efficiency. Different types of initiators have varying initiator efficiencies; therefore, those skilled in the art can flexibly adjust the amount of free radical initiator added within the above range, referring to the initiator efficiency. Of course, a smaller mass ratio of free radical initiator to electrode active material means a higher mass content of electrode active material in the electrode sheet, which is more beneficial for improving the specific capacity of the electrode sheet. In some embodiments, the above mass ratio can be selected from 0.05:99.95 to 1:99.

[0075] The electrode active material used in the above preparation method can be any of the electrode active materials provided in the first embodiment, which will not be described in detail here.

[0076] [Battery cell]

[0077] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0078] The battery cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, etc., and the embodiments of this application are not limited to this.

[0079] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator positioned between the positive and negative electrodes. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits while allowing active ions to pass through.

[0080] The third embodiment of this application provides a battery cell including an electrode sheet and an electrolyte. The electrode sheet includes a current collector and an electrode film layer disposed on the current collector. The electrode film layer includes an electrode material, which includes an electrode active material and a modifying group. The modifying group includes one or more of cyano and alkoxy sulfate groups, and the modifying group is dispersed in the electrode film layer.

[0081] The aforementioned modified groups are located within the electrode film layer along with the electrode active material, and can modify the surface of the electrode active material through chemical bonds. When the battery cell is in operation, the modified groups can still form a stable connection with the surface of the electrode active material through chemical bonding, making them difficult to dissolve in the electrolyte and migrate. Therefore, the modified groups can continuously stabilize the crystal structure of the electrode active material, while also optimizing the interfacial film formation between the electrode active material and the electrolyte, thereby improving the battery cell's capacity, initial efficiency, cycle performance, and high-temperature storage performance.

[0082] The electrode material described above can be selected from any one of the electrode materials in the first embodiment, and will not be described in detail here.

[0083] [Positive electrode plate]

[0084] In some embodiments, the aforementioned electrode sheet is a positive electrode sheet. When the electrode sheet is a positive electrode sheet, the electrode film layer is a positive electrode film layer. The modified groups coexist with the positive electrode active material particles in the positive electrode film layer of the positive electrode sheet, playing a role in stabilizing the surface of the positive electrode active material and participating in the formation of the CEI film.

[0085] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium phosphates include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM)211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Modified compounds refer to substances obtained by modification methods such as doping or coating based on the above-mentioned substances.

[0086] In some embodiments, the modifying group includes a cyano group, with the cyano group having a mass content of 0.05% to 3% in the electrode film, optionally 0.05% to 1%. The cyano group within the above mass content range forms a covalent bond with the surface of the positive electrode active material, making it difficult to dissolve in the electrolyte and leave the surface of the positive electrode active material. Simultaneously, it can absorb HF and water generated in the electrolyte, reducing the reaction between HF and the surface of the positive electrode active material, further improving cycle performance. The cyano group also has a high redox potential, preferentially undergoing oxidation before the electrolyte, thus participating in the formation of the CEI film. For cobalt-containing positive electrode active materials, the cyano group can stabilize the positive electrode lattice by forming coordination with Co on the surface of the positive electrode active material.

[0087] The mass content of cyano groups in the electrode film can be determined by X-ray photoelectron spectroscopy (XPS). The determination can be performed as follows: Take the un-liquefied positive electrode sheet, scrape off the powder, and perform XPS test. The characteristic peak of cyano group (N element) is located at 400 eV.

[0088] A positive electrode typically includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the aforementioned electrode material.

[0089] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0090] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0091] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0092] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0093] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0094] [Electrolytes]

[0095] In some embodiments, the battery cell also includes a liquid electrolyte (electrolyte), comprising an electrolyte salt and a solvent, which acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements.

[0096] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0097] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0098] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the battery cell, such as additives that improve the overcharge / fast charge performance of the battery cell, additives that improve the high-temperature performance of the battery cell, and additives that improve the low-temperature performance of the battery cell.

[0099] [Negative electrode plate]

[0100] In some embodiments, the negative electrode can be a negative electrode sheet, and the negative electrode sheet can include a negative current collector.

[0101] As an example, the negative electrode current collector can be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0102] As an example, the negative electrode sheet may include a negative current collector and a negative active material disposed on at least one surface of the negative current collector.

[0103] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0104] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0105] In some embodiments, the negative electrode can be made of foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. When foamed metal is used as the negative electrode sheet, the surface of the foamed metal may or may not contain a negative electrode active material.

[0106] As an example, negative electrode active materials can be filled or / and deposited within the negative electrode current collector.

[0107] In some embodiments, the negative electrode film layer may optionally include a binder. As an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0108] In some embodiments, the negative electrode film may optionally include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0109] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0110] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0111] [Isolation Component]

[0112] In some embodiments, the electrode assembly further includes an isolator disposed between the positive and negative electrodes.

[0113] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0114] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a single component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0115] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and to isolate the positive and negative electrodes.

[0116] [Structure of the electrode assembly]

[0117] The electrode assembly can be a wound structure, a stacked structure, or a hybrid structure of wound and stacked.

[0118] In some embodiments, the electrode assembly is a wound structure. The positive electrode and the negative electrode are wound into a wound structure.

[0119] In some implementations, the electrode assembly is a stacked structure.

[0120] As an example, multiple positive and negative electrode plates can be set, and multiple positive and multiple negative electrode plates can be stacked alternately.

[0121] As an example, multiple positive electrode sheets can be set, and negative electrode sheets are folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0122] As an example, both the positive and negative electrode sheets are folded to form multiple stacked folded segments.

[0123] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0124] As an example, the separator can be continuously arranged between any adjacent positive or negative electrode plates by folding or rolling.

[0125] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0126] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0127] [shell]

[0128] In some embodiments, the battery cell may include a casing. The casing may be a steel casing, an aluminum casing, a plastic casing (such as a polypropylene casing), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum-plastic film, etc. In some embodiments, the casing may be a sealed structure or a non-sealed structure. As an example, when the casing is a non-sealed structure, the casing serves to protect the electrode assembly, and a sealing bag is included between the casing and the electrode assembly to encapsulate the electrode assembly and electrolyte. Specifically, the sealing bag may be a bag-shaped insulating component or an aluminum-plastic film. When the casing is a sealed structure, it is used to encapsulate components such as the electrode assembly and electrolyte.

[0129] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations.

[0130] In some embodiments, the housing includes an end cap and a housing, the housing having an opening, and the end cap covering the opening. The housing may have one or more openings. The end cap may also have one or more.

[0131] In some embodiments, at least one electrode terminal is provided on the housing, and the electrode terminal is electrically connected to the tab. The electrode terminal can be directly connected to the tab, or it can be indirectly connected to the tab through a current collector. The electrode terminal can be provided on the end cap or on the housing.

[0132] In some embodiments, a pressure relief mechanism is provided on the casing. The pressure relief mechanism is used to release the internal gas of the battery cell.

[0133] As an example, the internal pressure or temperature of a battery cell is actuated to release the internal pressure or temperature when it reaches a predetermined threshold. When the internal pressure or temperature of the battery cell reaches the predetermined threshold, the pressure relief mechanism is activated or a weak structure in the pressure relief mechanism is broken, thereby forming an opening or channel for the internal pressure or temperature to be released. The threshold design varies depending on the design requirements. The threshold may depend on the materials of one or more of the positive electrode, negative electrode, electrolyte, and separator in the battery cell.

[0134] As an example, the pressure relief mechanism can be integrally molded with the housing.

[0135] As an example, the pressure relief mechanism can also be separately installed and connected to the housing.

[0136] The term "actuation" as used in this application refers to the activation or actuation of the pressure relief mechanism to a certain state, thereby releasing the internal pressure and temperature of the battery cell. The actions of the pressure relief mechanism may include, but are not limited to: movement of components within the mechanism to form an exhaust channel, rupture, breakage, tearing, or opening of at least a portion of the mechanism, etc. When the pressure relief mechanism is activated, the high-temperature, high-pressure substances inside the battery cell are discharged as waste from the activated portion. This method allows for pressure and temperature relief of the battery cell under controllable pressure or temperature, thereby preventing potentially more serious accidents.

[0137] In some embodiments, when the housing is a non-sealed structure, the pressure relief mechanism can be configured as a through hole for venting gas inside the battery cell.

[0138] The emissions from battery cells mentioned in this application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode plates, fragments of separators, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0139] Figure 1 The example shown is a square-structured battery cell 5.

[0140] In some implementations, refer to Figure 2 The outer casing may include a housing 51 and an end cap 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the end cap 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 via a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0141] [Battery Device]

[0142] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0143] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0144] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0145] Figure 3 This is battery module 4 as an example. (See reference...) Figure 3 In the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other way. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0146] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0147] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0148] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module into the housing. Alternatively, the battery cell assembly can be housed in a housing by directly fixing multiple battery cells to the housing.

[0149] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0150] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0151] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0152] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0153] The technical solutions described in this application are applicable to various electrical devices that use individual battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft. As for the aforementioned electrical devices, individual battery cells, battery modules, or battery packs can be selected according to their usage requirements.

[0154] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of individual battery cells, a battery pack or battery module can be used.

[0155] [Example]

[0156] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0157] The preparation methods of the negative electrode, separator, and electrolyte are the same in all embodiments and comparative examples. Therefore, for the sake of brevity, the same contents are given first. For the preparation method of the positive electrode, please refer to the description in each embodiment and comparative example.

[0158] Preparation of negative electrode sheet:

[0159] The negative electrode active material, conductive agent, dispersant, binder, and thickener were dissolved in deionized water at a mass ratio of 96.2:0.8:1.8:1.2 and mixed evenly to obtain a negative electrode slurry. This slurry was then uniformly coated on both sides of the negative electrode current collector copper foil, followed by drying, cold pressing, and slitting to obtain the negative electrode sheet. The negative electrode active material was artificial graphite, the conductive agent was carbon black, the binder was styrene-butadiene rubber, and the thickener was sodium carboxymethyl cellulose.

[0160] Preparation of the diaphragm:

[0161] A polyethylene film with a thickness of 7 μm was used as the base film for the separator. Ceramic particles and polyvinylidene fluoride (PVDF) binder were sprayed onto the base film one after the other.

[0162] Electrolyte preparation:

[0163] Ethylene carbonate, diethyl carbonate, and dimethyl carbonate were mixed in a volume ratio of 1:1:1. LiPF6 was then dissolved in this solution to obtain an electrolyte. The concentration of LiPF6 in this electrolyte was 1 mol / L.

[0164] Example 1

[0165] Preparation of cathode materials:

[0166] LiNi, the positive electrode active material 0.95 Co 0.03 Mn 0.02 O2 and azobisisoheptanenitrile were dissolved in N-methylpyrrolidone at a mass ratio of 99.9:0.1 to form a mixed slurry. The mixture was stirred at a speed of 1800 rpm / min. At the same time, the slurry was heated to 55°C to decompose the azobisisoheptanenitrile, producing cyano radicals and nitrogen gas. The cyano radicals were grafted onto the surface of the positive electrode active material as a modifying group. The nitrogen gas escaped. The positive electrode active material with cyano radical grafted on the surface was used as the positive electrode material. The mass content of the modifying group in the positive electrode material was about 0.1%.

[0167] Preparation of the positive electrode sheet:

[0168] The above-mentioned positive electrode material, conductive carbon black, conductive agent acetylene black, binder polyvinylidene fluoride (PVDF) and solvent N-methylpyrrolidone (NMP) are dissolved in the mass ratio of 96.5:1:1:1.5 and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is then uniformly coated on one side of the positive electrode current collector aluminum foil, and then dried, cold-pressed and slit to obtain the positive electrode sheet.

[0169] Example 2

[0170] Preparation of cathode material: The cathode active material LiNi 0.95 Co 0.03 Mn 0.02 O2 and benzoyl peroxide were dissolved in N-methylpyrrolidone at a mass ratio of 99.9:0.1 to form a mixed slurry. The mixture was stirred at a speed of 1800 rpm / min, and the slurry was heated to 72°C to decompose benzoyl peroxide and generate phenyl ester free radicals. The phenyl ester free radicals were grafted onto the surface of the positive electrode active material as a modifying group. The positive electrode active material with phenyl ester grafts on the surface was used as the positive electrode material. The mass content of the modifying group in the positive electrode material was about 0.1%.

[0171] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0172] Example 3

[0173] Preparation of cathode material: The cathode active material LiNi 0.95 Co 0.03 Mn 0.02 O2 and potassium persulfate were dissolved in N-methylpyrrolidone at a mass ratio of 99.9:0.1 to form a mixed slurry. The mixture was stirred at a speed of 1800 rpm / min. At the same time, the slurry was heated to 80°C to decompose the potassium persulfate and generate sulfate free radicals. The sulfate free radicals were grafted onto the surface of the positive electrode active material as a modifying group. The positive electrode active material with sulfate grafted onto its surface was used as the positive electrode material. The mass content of the modifying group in the positive electrode material was about 0.1%.

[0174] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0175] Example 4

[0176] Preparation of cathode material: The cathode active material LiNi 0.95 Co 0.03 Mn 0.02 O2 and azobisisobutyronitrile are dissolved in N-methylpyrrolidone at a mass ratio of 99.95:0.05 to form a mixed slurry. The mixture is stirred at a speed of 1800 rpm / min. At the same time, the slurry is heated to 55°C to decompose the azobisisobutyronitrile, producing cyano radicals and nitrogen gas. The cyano radicals are grafted onto the surface of the positive electrode active material as a modifying group. The nitrogen gas escapes. The positive electrode active material with cyano radical grafted on the surface is used as the positive electrode material. The mass content of the modifying group in the positive electrode material is about 0.05%.

[0177] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0178] Example 5

[0179] Preparation of cathode material: The cathode active material LiNi 0.95 Co 0.03 Mn 0.02 O2 and azobisisoheptanenitrile were dissolved in N-methylpyrrolidone at a mass ratio of 99.7:0.3 to form a mixed slurry. The mixture was stirred at a speed of 1800 rpm / min. At the same time, the slurry was heated to 55°C to decompose the azobisisoheptanenitrile, producing cyano radicals and nitrogen gas. The cyano radicals were grafted onto the surface of the positive electrode active material as a modifying group. The nitrogen gas escaped. The positive electrode active material with cyano radical grafted on the surface was used as the positive electrode material. The mass content of the modifying group in the positive electrode material was about 0.3%.

[0180] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0181] Example 6

[0182] Preparation of cathode material: The cathode active material LiNi 0.95 Co 0.03 Mn 0.02 O2 and azobisisoheptanenitrile are dissolved in N-methylpyrrolidone at a mass ratio of 99.5:0.5 to form a mixed slurry. The mixture is stirred at a speed of 1800 rpm / min. At the same time, the mixed slurry is heated to 55°C to decompose the azobisisoheptanenitrile, generating cyano radicals and nitrogen gas. The cyano radicals are grafted onto the surface of the positive electrode active material as a modifying group. The nitrogen gas escapes. The positive electrode active material with cyano radical grafted on the surface is used as the positive electrode material. The mass content of the modifying group in the positive electrode material is about 0.5%.

[0183] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0184] Example 7

[0185] Preparation of cathode material: The cathode active material LiNi 0.95 Co 0.03 Mn 0.02 O2 and azobisisoheptanenitrile are dissolved in N-methylpyrrolidone at a mass ratio of 99:1 to form a mixed slurry. The mixture is stirred at a speed of 1800 rpm / min. At the same time, the mixed slurry is heated to 55°C to decompose the azobisisoheptanenitrile, producing cyano radicals and nitrogen gas. The cyano radicals are grafted onto the surface of the positive electrode active material as a modifying group. The nitrogen gas escapes. The positive electrode active material with cyano radical grafted on the surface is used as the positive electrode material. The mass content of the modifying group in the positive electrode material is about 1%.

[0186] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0187] Example 8

[0188] Preparation of cathode material: The cathode active material LiNi 0.95 Co 0.03 Mn 0.02 O2 and azobisisoheptanenitrile are dissolved in N-methylpyrrolidone at a mass ratio of 98:2 to form a mixed slurry. The mixture is stirred at a speed of 1800 rpm / min. At the same time, the mixed slurry is heated to 55°C to decompose the azobisisoheptanenitrile, producing cyano radicals and nitrogen gas. The cyano radicals are grafted onto the surface of the positive electrode active material as a modifying group. The nitrogen gas escapes. The positive electrode active material with cyano radical grafted on the surface is used as the positive electrode material. The mass content of the modifying group in the positive electrode material is about 2%.

[0189] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0190] Example 9

[0191] Preparation of cathode material: The cathode active material LiNi 0.95 Co 0.03 Mn 0.02 O2 and azobisisoheptanenitrile are dissolved in N-methylpyrrolidone at a mass ratio of 97.5:2.5 to form a mixed slurry. The mixture is stirred at a speed of 1800 rpm / min. At the same time, the slurry is heated to 55°C to decompose the azobisisoheptanenitrile, producing cyano radicals and nitrogen gas. The cyano radicals are grafted onto the surface of the positive electrode active material as a modifying group. The nitrogen gas escapes. The positive electrode active material with cyano radical grafted on the surface is used as the positive electrode material. The mass content of the modifying group in the positive electrode material is about 2.5%.

[0192] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0193] Example 10

[0194] Preparation of cathode material: The cathode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 and azobisisobutyronitrile are dissolved in N-methylpyrrolidone at a mass ratio of 99.95:0.05 to form a mixed slurry. The mixture is stirred at a speed of 1800 rpm / min. At the same time, the slurry is heated to 55°C to decompose the azobisisobutyronitrile, producing cyano radicals and nitrogen gas. The cyano radicals are grafted onto the surface of the positive electrode active material as a modifying group. The nitrogen gas escapes. The positive electrode active material with cyano radical grafted on the surface is used as the positive electrode material. The mass content of the modifying group in the positive electrode material is about 0.05%.

[0195] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0196] Example 11

[0197] Preparation of cathode material: The cathode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 and azobisisoheptanenitrile were dissolved in N-methylpyrrolidone at a mass ratio of 99.9:0.1 to form a mixed slurry. The mixture was stirred at a speed of 1800 rpm / min. At the same time, the slurry was heated to 55°C to decompose the azobisisoheptanenitrile, producing cyano radicals and nitrogen gas. The cyano radicals were grafted onto the surface of the positive electrode active material as a modifying group. The nitrogen gas escaped. The positive electrode active material with cyano radical grafted on the surface was used as the positive electrode material. The mass content of the modifying group in the positive electrode material was about 0.1%.

[0198] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0199] Example 12

[0200] Preparation of cathode material: The cathode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 and azobisisoheptanenitrile were dissolved in N-methylpyrrolidone at a mass ratio of 99.7:0.3 to form a mixed slurry. The mixture was stirred at a speed of 1800 rpm / min. At the same time, the slurry was heated to 55°C to decompose the azobisisoheptanenitrile, producing cyano radicals and nitrogen gas. The cyano radicals were grafted onto the surface of the positive electrode active material as a modifying group. The nitrogen gas escaped. The positive electrode active material with cyano radical grafted on the surface was used as the positive electrode material. The mass content of the modifying group in the positive electrode material was about 0.3%.

[0201] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0202] Example 13

[0203] Preparation of cathode material: The cathode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 and azobisisoheptanenitrile are dissolved in N-methylpyrrolidone at a mass ratio of 99.5:0.5 to form a mixed slurry. The mixture is stirred at a speed of 1800 rpm / min. At the same time, the mixed slurry is heated to 55°C to decompose the azobisisoheptanenitrile, generating cyano radicals and nitrogen gas. The cyano radicals are grafted onto the surface of the positive electrode active material as a modifying group. The nitrogen gas escapes. The positive electrode active material with cyano radical grafted on the surface is used as the positive electrode material. The mass content of the modifying group in the positive electrode material is about 0.5%.

[0204] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0205] Example 14

[0206] Preparation of cathode material: The cathode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 and azobisisoheptanenitrile are dissolved in N-methylpyrrolidone at a mass ratio of 99:1 to form a mixed slurry. The mixture is stirred at a speed of 1800 rpm / min. At the same time, the mixed slurry is heated to 55°C to decompose the azobisisoheptanenitrile, producing cyano radicals and nitrogen gas. The cyano radicals are grafted onto the surface of the positive electrode active material as a modifying group. The nitrogen gas escapes. The positive electrode active material with cyano radical grafted on the surface is used as the positive electrode material. The mass content of the modifying group in the positive electrode material is about 1%.

[0207] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0208] Example 15

[0209] Preparation of cathode material: The cathode active material LiNi 0.6 Co 0.2 Mn 0.2 O2 and azobisisobutyronitrile are dissolved in N-methylpyrrolidone at a mass ratio of 99.95:0.05 to form a mixed slurry. The mixture is stirred at a speed of 1800 rpm / min. At the same time, the slurry is heated to 55°C to decompose the azobisisobutyronitrile, producing cyano radicals and nitrogen gas. The cyano radicals are grafted onto the surface of the positive electrode active material as a modifying group. The nitrogen gas escapes. The positive electrode active material with cyano radical grafted on the surface is used as the positive electrode material. The mass content of the modifying group in the positive electrode material is about 0.05%.

[0210] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0211] Example 16

[0212] Preparation of cathode material: The cathode active material LiNi 0.6 Co 0.2 Mn 0.2 O2 and azobisisoheptanenitrile were dissolved in N-methylpyrrolidone at a mass ratio of 99.9:0.1 to form a mixed slurry. The mixture was stirred at a speed of 1800 rpm / min. At the same time, the slurry was heated to 55°C to decompose the azobisisoheptanenitrile, producing cyano radicals and nitrogen gas. The cyano radicals were grafted onto the surface of the positive electrode active material as a modifying group. The nitrogen gas escaped. The positive electrode active material with cyano radical grafted on the surface was used as the positive electrode material. The mass content of the modifying group in the positive electrode material was about 0.1%.

[0213] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0214] Example 17

[0215] Preparation of cathode material: The cathode active material LiNi 0.6 Co 0.2 Mn 0.2 O2 and azobisisoheptanenitrile were dissolved in N-methylpyrrolidone at a mass ratio of 99.7:0.3 to form a mixed slurry. The mixture was stirred at a speed of 1800 rpm / min. At the same time, the slurry was heated to 55°C to decompose the azobisisoheptanenitrile, producing cyano radicals and nitrogen gas. The cyano radicals were grafted onto the surface of the positive electrode active material as a modifying group. The nitrogen gas escaped. The positive electrode active material with cyano radical grafted on the surface was used as the positive electrode material. The mass content of the modifying group in the positive electrode material was about 0.3%.

[0216] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0217] Example 18

[0218] Preparation of cathode material: The cathode active material LiNi 0.6 Co 0.2 Mn 0.2 O2 and azobisisoheptanenitrile are dissolved in N-methylpyrrolidone at a mass ratio of 99.5:0.5 to form a mixed slurry. The mixture is stirred at a speed of 1800 rpm / min. At the same time, the mixed slurry is heated to 55°C to decompose the azobisisoheptanenitrile, generating cyano radicals and nitrogen gas. The cyano radicals are grafted onto the surface of the positive electrode active material as a modifying group. The nitrogen gas escapes. The positive electrode active material with cyano radical grafted on the surface is used as the positive electrode material. The mass content of the modifying group in the positive electrode material is about 0.5%.

[0219] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0220] Example 19

[0221] Preparation of cathode material: The cathode active material LiNi 0.6 Co 0.2 Mn 0.2 O2 and azobisisoheptanenitrile are dissolved in N-methylpyrrolidone at a mass ratio of 99:1 to form a mixed slurry. The mixture is stirred at a speed of 1800 rpm / min. At the same time, the mixed slurry is heated to 55°C to decompose the azobisisoheptanenitrile, producing cyano radicals and nitrogen gas. The cyano radicals are grafted onto the surface of the positive electrode active material as a modifying group. The nitrogen gas escapes. The positive electrode active material with cyano radical grafted on the surface is used as the positive electrode material. The mass content of the modifying group in the positive electrode material is about 1%.

[0222] Preparation of the positive electrode sheet: This example is the same as Example 1.

[0223] Comparative Example 1

[0224] No surface modification is performed on the positive electrode active material; instead, LiNi is directly mixed at a mass ratio of 96.5:1:1:1.5. 0.95 Co 0.03 Mn 0.02 O2, conductive carbon black, conductive acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is then uniformly coated on one side of the positive electrode current collector aluminum foil, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0225] Comparative Example 2

[0226] No surface modification is performed on the positive electrode active material; instead, LiNi is directly mixed at a mass ratio of 96.5:1:1:1.5. 0.8 Co 0.1 Mn0.1 O2, conductive carbon black, conductive acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is then uniformly coated on one side of the positive electrode current collector aluminum foil, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0227] Comparative Example 3

[0228] No surface modification is performed on the positive electrode active material; instead, LiNi is directly mixed at a mass ratio of 96.5:1:1:1.5. 0.6 Co 0.2 Mn 0.2 O2, conductive carbon black, conductive acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is then uniformly coated on one side of the positive electrode current collector aluminum foil, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0229] [Testing Method]

[0230] XPS method for characterizing modified groups in electrode films:

[0231] X-ray photoelectron spectroscopy (XPS) can be used. Take the un-liquefied positive electrode sheet, scrape off the powder, and determine the mass content of modified groups in the electrode film layer by XPS. With the help of peak position analysis and peak splitting analysis, XPS can determine the element type and chemical state of the element, and at the same time quantitatively obtain the atomic percentage (at.%) of elements (C, N, O, S, etc.), and determine the presence, type and content of modified groups.

[0232] In the modified groups included in the above embodiments, the characteristic peak of the cyano group is located near 400 eV (N element), the characteristic peak of the phenyl ester group is located near 531 eV (phenyl ester), and the characteristic peak of the sulfate group is located near 168 eV (S element).

[0233] Battery cell capacity testing:

[0234] At 25°C, the battery cell is charged at a constant current of 0.5C to the charging cutoff voltage V1, then charged at a constant voltage of 3.8V until the current is less than 0.05C, and then discharged at a constant current of 0.5C to the discharge cutoff voltage V2 to obtain the discharge capacity at 0.5C (unit: mAh), where C is the nominal capacity of the battery cell.

[0235] Cycle capacity retention determination of individual battery cells:

[0236] (1) At 45°C, charge the battery cell at a constant current of 0.33C to the charging cutoff voltage V1, then charge it at a constant voltage of V1 to a current of 0.05C. After standing for 5 minutes, discharge it at 1.0C to the discharge cutoff voltage V2 and record the discharge capacity C0.

[0237] (2) Charge the battery cell at a constant current of 1.0C to the charging cutoff voltage V1, let it stand for 5 minutes, and then discharge it at 1.0C to the discharge cutoff voltage V2. Record the discharge capacity C1.

[0238] Repeat step (2) above 500 times, and record the discharge capacity C of the battery cell after the 500th cycle. 500 Capacity retention rate P 500 =C 500 / C0×100%.

[0239] Methods for testing initial coulomb efficiency:

[0240] At 25℃, the formed battery cells were charged at a constant current rate of 0.33C (CC) to the charging cutoff voltage V1, and then charged at a constant voltage rate of V1 (CV) to a current of 0.05C. After standing for 10 minutes, the charging capacity was recorded. Then, the cells were discharged at a constant current rate of 0.33C (DC) to the discharge cutoff voltage V2, and the discharge capacity was recorded. The initial coulombic efficiency = discharge capacity / charging capacity × 100%.

[0241] Determination of remaining capacity retention rate at 100% SOC high-temperature storage:

[0242] The battery cells were placed in a 25°C constant temperature chamber and left to stand for 30 minutes to allow them to reach a constant temperature of 25°C. They were then charged at a constant current of 1C to the charging cutoff voltage V1, and then charged at a constant voltage to 0.05C. Finally, they were discharged at a constant current of 1C to the discharge cutoff voltage V2. The discharge capacity was recorded as the initial capacity C. i Then, charge at a constant current of 1C to the charging cutoff voltage V1, and then charge at a constant voltage to 0.05C. Transfer the battery cells to a 60℃ constant temperature chamber for storage for 15 days, then transfer them to a 25℃ constant temperature chamber, let them stand for 60 minutes, and then discharge at a constant current of 1C to the discharge cutoff voltage V2. Record the discharge capacity as the remaining capacity C. j The remaining capacity retention rate of a single battery cell is calculated using the following formula: Remaining capacity retention rate at 100% SOC high-temperature storage = C j / C i ×100%. In this application, the remaining capacity retention rate after 90 days of storage at 60°C is used as an indicator to evaluate the high-temperature storage performance of a single battery cell at 100% SOC.

[0243] Depending on the composition of the positive electrode active material, the charge / discharge cutoff voltage of a single battery cell varies. Table 1 shows the positive electrode active material composition and the corresponding charge / discharge cutoff voltage values.

[0244] Table 1 Positive electrode active material <![CDATA[Charging cut-off voltage V1]]> <![CDATA[Discharge cut-off voltage V2]]> <![CDATA[LiNi 0.95 What 0.03 Mn 0.02 O2]]> 4.25 2.5 <![CDATA[LiNi 0.8 What 0.1 Mn 0.1 O2]]> 4.25 2.8 <![CDATA[LiNi 0.6 What 0.2 Mn 0.2 O2]]> 4.4 2.8

[0245] By measuring the performance of the battery cells in the above embodiments and comparative examples, and comparing them in groups, the technical effects of different implementation methods of this application can be evaluated. The specific results and analysis are presented below:

[0246] Examples 1-3 utilize different free radical initiators to react the positive electrode active material LiNi 0.95 Co 0.03 Mn 0.02 Different modified groups were grafted onto the O2 surface, and the mass ratio of free radical initiator to positive electrode active material was 0.1:99.9. Table 2 shows the performance comparison of the battery cells in Examples 1-3 and Comparative Example 1.

[0247] Table 2

[0248] The first-efficiency and high-temperature storage capacity retention rates of the battery cells in Examples 1-3 are close to those of Comparative Example 1, and the capacity and cycle capacity retention rates are better than those of Comparative Example 1, indicating that the addition of modified groups is beneficial to improving the energy density and cycle performance of the battery cells.

[0249] The examples in Table 3 all use LiNi. 0.95 Co 0.03 Mn 0.02 The difference between using O2 as the positive electrode active material and cyano as the modifying group lies in the different mass ratios of free radical initiator to positive electrode active material during the preparation of the positive electrode material in each embodiment. Additionally, Comparative Example 1 was used as a blank control group. Specific parameters representing the battery cell performance are shown in Table 3. For simplicity, the mass content of the modifying group in the positive electrode material in Table 3 is simply referred to as "modified group mass content".

[0250] The results in Table 3 show that with the increase of mass ratio, the initial coulombic efficiency, capacity, cycle capacity, and high-temperature storage capacity retention of the battery cell all improve. Considering that increasing the amount of modified groups would reduce the proportion of the positive electrode active material in the positive electrode active layer, the results show that the initial coulombic efficiency of the battery cell did not decrease as a result. Furthermore, with the increase of mass ratio and the introduction of a higher mass content of modified groups, the cycle capacity retention rate was significantly and continuously improved. This reflects that the introduction of modified groups is beneficial to stabilizing the structure of the positive electrode active material, reducing the loss of the positive electrode active material during cycling, and enabling the battery cell to achieve improved capacity utilization and cycle stability.

[0251] Table 3

[0252] The examples in Table 4 all use LiNi 0.8 Co 0.1 Mn 0.1 The difference between using O2 as the positive electrode active material and cyano as the modifying group lies in the different mass ratios of free radical initiator and positive electrode active material during the preparation of the positive electrode material in each embodiment. In addition, Comparative Example 2 is used as a blank control group. The specific parameters representing the performance of the battery cell are shown in Table 4. For the sake of simplicity, the mass content of the modified group in the positive electrode material in Table 4 is simply referred to as "modified group mass content".

[0253] Table 4

[0254] The mass content of modified groups in the cathode material of Example 10 is very low, and the improvement of various performance parameters of the battery cell compared with Comparative Example 2 is small. However, the performance parameters of the battery cells of Examples 11 to 14 are all improved compared with Comparative Example 2, especially the cycle capacity retention rate is significantly improved.

[0255] The examples in Table 5 all use LiNi. 0.6 Co 0.2 Mn 0.2 The difference between using O2 as the positive electrode active material and cyano as the modifying group lies in the different mass ratios of free radical initiator and positive electrode active material during the preparation of the positive electrode material in each embodiment. In addition, Comparative Example 3 is used as a blank control group. The specific parameters representing the performance of the battery cell are shown in Table 5. For the sake of simplicity, the mass content of the modified group in the positive electrode material in Table 5 is simply referred to as "modified group mass content".

[0256] Table 5

[0257] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, comprising an electrode sheet and an electrolyte, wherein the electrode sheet comprises a current collector and an electrode film layer disposed on the current collector, the electrode film layer comprises an electrode material, the electrode material comprises an electrode active material and a modifying group, the modifying group comprising one or more of cyano, phenyl ester, and sulfate groups, the modifying group being dispersed in the electrode film layer.

2. The battery cell according to claim 1, wherein, The electrode sheet is a positive electrode sheet.

3. The battery cell according to claim 1 or 2, wherein, The electrode active material is a positive electrode active material, which is selected from one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. Optionally, the positive electrode active material includes one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, and lithium manganese oxide, and the molar proportion of nickel in the lithium nickel cobalt manganese oxide among nickel, manganese and cobalt is 50% to 95%, and more preferably 80% to 95%.

4. The battery cell according to any one of claims 1 to 3, wherein, The modified groups have a mass content of 0.05% to 2.5% in the electrode film, and can be selected as 0.05% to 1%.

5. The battery cell according to any one of claims 1 to 4, wherein, The electrolyte comprises a solvent and a lithium salt. The solvent comprises one or more of ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, ethyl acetate, and fluoroethylene carbonate. The lithium salt comprises one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

6. An electrode material comprising an electrode active material and a modifying group, wherein the modifying group is grafted onto the surface of the electrode active material, and the modifying group comprises one or more of cyano, alkoxy, and sulfate groups.

7. The electrode material according to claim 6, wherein, The electrode active material is a positive electrode active material, which is selected from one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. Optionally, the positive electrode active material includes one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, and lithium manganese oxide, and The nickel element in the lithium nickel cobalt manganese oxide has a molar percentage of 50% to 95% in nickel, manganese and cobalt elements, and can be further selected as 80% to 95%.

8. The electrode material according to claim 6 or 7, wherein, The electrode material also includes one or more of methyl and methylene groups.

9. The electrode material according to any one of claims 6 to 8, wherein, The modified group has a mass content of 0.05% to 2.5% in the electrode material, and can be optionally 0.05% to 1%.

10. A method for preparing an electrode material, wherein, The preparation method includes: A mixed slurry is obtained by mixing materials including electrode active materials, free radical initiators, and slurry solvents. The free radical initiator includes a modifying group, which includes one or more of cyano, phenyl ester, and sulfate groups. The free radical initiator in the mixed slurry is decomposed to obtain free radical groups, including the modified groups, and the free radical groups are grafted onto the surface of the electrode active material to obtain the electrode material.

11. The preparation method according to claim 10, wherein, The slurry solvent includes one or more of N-methylpyrrolidone, dimethylacetamide, and dimethylformamide.

12. The preparation method according to claim 10 or 11, wherein, The free radical initiator is decomposed by heating, light exposure, or radiation.

13. The preparation method according to any one of claims 10 to 12, wherein, The free radical initiator includes one or more of azo initiators, organic peroxide initiators, and inorganic peroxide initiators; Optionally, the azo initiator includes one or more of azobisisoheptanenitrile, azobisisobutyronitrile, azobisisovaleratenitrile, azoisobutylcyanoformamide, and azobiscyclohexylformitrile; Optionally, the organic peroxide initiator includes one or more of tert-butyl peroxide and benzoyl peroxide; Optionally, the inorganic peroxide initiator includes one or more of potassium persulfate and ammonium persulfate.

14. The preparation method according to claim 13, wherein, The free radical initiator includes an azo initiator. The mixed slurry is heated to the free radical initiator decomposition temperature to decompose the free radical initiator in the mixed slurry. Optionally, the mixture is stirred while being heated, and more preferably, the stirring speed is 1000 rpm / min to 2000 rpm / min.

15. The preparation method according to any one of claims 10 to 14, wherein, The mass ratio of the free radical initiator to the electrode active material is 0.05:99.95 to 2.5:97.5, and can be selected as 0.05:99.95 to 1:

99.

16. The preparation method according to any one of claims 10 to 15, wherein, The electrode active material is a positive electrode active material, which includes one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. Optionally, the positive electrode active material includes one or more of lithium nickel cobalt manganese oxide, lithium cobalt oxide, and lithium manganese oxide, and the molar proportion of nickel in the lithium nickel manganese cobalt oxide is 50% to 95% of the total nickel, manganese, and cobalt elements, and is further optionally 80% to 95%.

17. A battery device comprising a plurality of battery cells according to any one of claims 1 to 5.

18. An electrical device comprising a battery cell according to any one of claims 1 to 5, or a battery device according to claim 17, wherein the battery cell or the battery device is used to store or provide electrical energy.

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