CN117691104A

CN117691104A - Positive electrode active material, method for preparing same, secondary battery, and device

Info

Publication number: CN117691104A
Application number: CN202311693710.2A
Authority: CN
Inventors: 曲晓丹; 孟宪慧
Original assignee: Weilai Battery Technology Anhui Co ltd
Current assignee: Weilai Battery Technology Anhui Co ltd
Priority date: 2023-12-06
Filing date: 2023-12-06
Publication date: 2024-03-12

Abstract

The present application relates to a positive electrode active material, a method of preparing the same, a secondary battery, and a device. The positive electrode active material comprises primary particles, wherein the primary particles comprise a core body and a coating layer, the coating layer is arranged on the surface of the core body and is in a continuous layer shape, and the primary particles comprise Li element, ni element and Al element; the coating coefficient T of the Al element in the primary particles satisfies the following conditions: t is more than or equal to 10 and less than or equal to 40,wherein, the mass percentage content of Al in primary particles accounting for all other metal elements except Li is Al when tested by XPS under the condition of 0 second of sputtering etching time _XPS0 The method comprises the steps of carrying out a first treatment on the surface of the The XPS is adopted to test under the condition of sputtering etching time of 180 seconds, and the mass percentage content of Al in primary particles accounting for all other metal elements except Li is Al _XPS1 The method comprises the steps of carrying out a first treatment on the surface of the The mass percentage of Al in the primary particles accounting for all other metal elements except Li is Al by adopting an ICP test _ICP The method comprises the steps of carrying out a first treatment on the surface of the In the spectrum of the primary particles tested by XPS, ni is in the range of 848 eV-868 eV of binding energy ²⁺ Peak area of (2)Ni ³⁺ Peak area of (2)Thereby, the cycle performance is improved.

Description

Positive electrode active material, method for preparing same, secondary battery, and device

Technical Field

The present application relates to the field of energy storage. Specifically, the present application relates to a positive electrode active material, a method of preparing the same, a secondary battery, and a device.

Background

Lithium ion batteries are important energy storage solutions in the fields of electronic equipment, electric automobiles and the like. The improvement of the energy density of the positive electrode side of the lithium ion battery mainly depends on three methods: high voltage, high compaction, high nickel, wherein the high nickel multi-element positive electrode active material exhibits high discharge capacity due to its considerable electron transferable number, thereby meeting the requirement of high energy density. Voltage decay of the multi-component high nickel positive electrode active material is caused by structural degradation and interfacial instability between the positive electrode and electrolyte, and these deleterious surface behaviors include: surface structure reconstruction, stress induced cracking, electrolyte decomposition, transition metal dissolution and surface chemical instability. The surface structure and chemical properties play an important role in determining the structure and interface stability, adjusting the reversibility of lithium ion intercalation/deintercalation at the interface and affecting the dynamic behavior of the interface reaction in the charge/discharge process. The coating of the positive electrode active material can improve the structural stability and electrochemical performance of the positive electrode active material by reducing the direct contact area between the positive electrode active material and the electrolyte.

However, the current secondary battery and device have yet to be improved.

Disclosure of Invention

The inventor finds that the multi-element positive electrode active material is synthesized by using excessive lithium to solve the problem of cation mixing discharge in the prior art, and the residual lithium is in an island shape after one-time sinteringThe multi-element positive electrode active material shows that partial residual lithium still exists in a partial residual lithium-rich area on the surface after coating and secondary sintering processes, the metal oxide in the non-residual lithium-rich area does not fully undergo lithiation reaction, the coating still exists in discrete island-shaped particles, and lithium in a robbed structure leads to collapse of a layered structure so as to lead to Ni ²⁺ The content of (c) is increased, and a uniform coating effect is not achieved. That is, in the prior art, when the coating modification is performed on the positive electrode active material, it is difficult to achieve a uniform coating effect due to the in-situ lithiation coating due to the non-uniformity of the residual lithium of the positive electrode active material. In view of the shortcomings of the prior art, the application provides a positive electrode active material, a preparation method thereof, a secondary battery and a device. According to the method, the Al element is introduced into the coating layer of the primary particles of the positive electrode active material, and the coating coefficient of the Al element is controlled, so that a continuous, uniform and compact layered coating layer (such as an aluminum lithium compound) can be formed on the surface of the core body, namely, the high coverage rate fast ion conductor coating is realized on the surface of the core body, the direct contact between the core body and the electrolyte is effectively avoided, the side reaction between the core body and the electrolyte is reduced, and the structural stability and the dynamic performance of the positive electrode active material are improved.

The application provides a positive electrode active material, which comprises primary particles, wherein the primary particles comprise a core body and a coating layer, the coating layer is arranged on the surface of the core body and is in a continuous layer shape, and the primary particles comprise Li element, ni element and Al element; the coating coefficient T of the Al element in the primary particles meets the following conditions: t is more than or equal to 10 and less than or equal to 40,

wherein, an X-ray photoelectron spectrometer is adopted for testing under the condition of sputtering etching time of 0 second, the mass percentage content of Al in the primary particles accounting for all other metal elements except Li is Al _XPS0 ；

Testing under the condition of sputtering etching time of 180 seconds by adopting an X-ray photoelectron spectrometer, wherein Al in the primary particles accounts for the components except LiThe mass percentage content of all other metal elements is Al _XPS1 ；

The inductively coupled plasma spectrometer is adopted for testing, wherein the mass percentage of Al in the primary particles accounting for all other metal elements except Li is Al _ICP ；

In a spectrum of the primary particles tested by an X-ray photoelectron spectrometer under the sputtering etching time of 0 second, ni is in the range of 848 eV-868 eV of binding energy ²⁺ Peak area of (2)Ni ³⁺ Peak area of +.>

The application also provides a preparation method of the positive electrode active material, which comprises the following steps:

Mixing a Ni-containing precursor, lithium salt and a first compound containing an element A, and performing first sintering treatment to obtain a first sintered material; wherein a comprises at least one of Zr, sr, Y, nb, sb, na, mg, ba, ti, si, sn, V, P, W and Mo;

mixing the first sintering material with deionized water to obtain a first mixture;

and mixing a second compound containing element Al with the first mixture, and obtaining the positive electrode active material through a second sintering treatment.

The present application also provides a secondary battery including the positive electrode active material described above or the positive electrode active material formed by the above-described preparation method.

The present application also provides an apparatus comprising the secondary battery as described above.

The beneficial effects of this application are:

according to the method, the Al element is introduced into the coating layer of the primary particles of the positive electrode active material, so that a passivation film is formed on the surface of the positive electrode, the problem of corrosion caused by contact between the positive electrode body and the acid electrolyte is effectively avoided, the positive electrode can maintain a complete layered structure, and further, a good Li ion transmission channel can be maintained at the later period of circulation, so that excellent DCR performance and circulation performance are shown; and by controlling the coating coefficient of the Al element, a continuous, uniform and compact lamellar coating layer (such as an aluminum lithium compound) can be formed on the surface of the nuclear body, namely, the high coverage rate fast ion conductor coating is realized on the surface of the nuclear body, so that the direct contact between the nuclear body and electrolyte is effectively avoided, and the structural stability and the dynamic performance of the positive electrode active material are further improved. Thus, based on the above improvements, the positive electrode active material of the present application has at least one of the following advantages: the DCR (resistance) performance, cycle performance and capacity retention rate of the secondary battery using the positive electrode active material are improved.

Description of the drawings:

FIG. 1 is a scanning electron microscope image of a prior art positive electrode active material;

FIG. 2 shows Ni2P peaks in XPS spectrum of a positive electrode active material according to the prior art _3/2 Is a graph of the peak and curve fitting of (a).

Fig. 3 is a cross-sectional scanning electron microscope image of a positive electrode active material according to an embodiment of the present application.

FIG. 4 is a drawing showing Ni peak Ni2P in XPS spectrum of a positive electrode active material according to an embodiment of the present application _3/2 Is a graph of the peak and curve fitting of (a).

Detailed Description

For simplicity, this application discloses only a few numerical ranges specifically. However, any lower limit may be combined with any upper limit to form a range not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and any upper limit may be combined with any other upper limit to form a range not explicitly recited. Furthermore, each separately disclosed point or individual value may itself be combined as a lower limit or upper limit with any other point or individual value or with other lower limit or upper limit to form a range not explicitly recited.

Unless otherwise indicated, terms used in the present application have well-known meanings commonly understood by those skilled in the art. Unless otherwise indicated, the numerical values of the parameters set forth in this application may be measured by various measurement methods commonly used in the art (e.g., may be tested according to the methods set forth in the examples of this application).

The list of items to which the term "at least one of," "at least one of," or other similar terms are connected may mean any combination of the listed items. For example, if items a and B are listed, the phrase "at least one of a and B" means only a; only B; or A and B. In another example, if items A, B and C are listed, then the phrase "at least one of A, B and C" means only a; or only B; only C; a and B (excluding C); a and C (excluding B); b and C (excluding A); or A, B and C. Item a may comprise a single component or multiple components. Item B may comprise a single component or multiple components. Item C may comprise a single component or multiple components.

The present application is further described below in conjunction with the detailed description. It should be understood that these specific embodiments are presented by way of example only and are not intended to limit the scope of the present application.

1. Positive electrode active material

The application provides a positive electrode active material, which comprises primary particles, wherein the primary particles comprise a core body and a coating layer, the coating layer is arranged on the surface of the core body and is in a continuous layer shape, and the primary particles comprise Li element, ni element and Al element;

The coating coefficient T of the Al element in the primary particles meets the following conditions: t is more than or equal to 10 and less than or equal to 40,

wherein, an X-ray photoelectron spectrometer (XPS) is adopted for testing under the condition of sputtering etching time of 0 second, the mass percentage content of Al in the primary particles accounting for all other metal elements except Li is Al _XPS0 The method comprises the steps of carrying out a first treatment on the surface of the Testing under the condition of sputtering etching time of 180 seconds by adopting an X-ray photoelectron spectrometer, wherein the Al in the primary particles accounts for the mass percent of all other metal elements except LiThe specific content is Al _XPS1 The method comprises the steps of carrying out a first treatment on the surface of the The primary particles are tested by an Inductively Coupled Plasma (ICP) spectrometer, wherein the mass percentage of Al in all other metal elements except Li is Al _ICP The method comprises the steps of carrying out a first treatment on the surface of the In a spectrum of the primary particles tested by an X-ray photoelectron spectrometer under the sputtering etching time of 0 second, ni is in the range of 848 eV-868 eV of binding energy ²⁺ Peak area of (2)Ni ³⁺ Peak area of +.>

In some embodiments, the primary particles comprise Li _a Ni _b Co _c Mn _d Al _e A _f O _x Wherein a is more than or equal to 0.95 and less than or equal to 1.3,0.5 and less than or equal to b is more than or equal to 0.96,0 and less than or equal to c is more than or equal to 0.35,0 and less than or equal to d is more than or equal to 0.35,0 and less than or equal to 0.05, f is more than or equal to 0 and less than or equal to 0.05,2 and less than or equal to x is more than or equal to 2.2, and b+c+d+e+f=1. A includes at least one of Zr, sr, Y, nb, sb, na, mg, ba, ti, si, sn, V, P, W and Mo.

In some embodiments, a is 0.95, 0.97, 0.99, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, or any value therebetween. In some embodiments, b is 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, 0.96, or any value therebetween. In some embodiments, 0.6.ltoreq.b.ltoreq.0.96. In some embodiments, c is 0, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, or any value therebetween. In some embodiments, 0.ltoreq.c.ltoreq.0.2. In some embodiments, d is 0, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, or any value therebetween. In some embodiments, e is 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, or any value therebetween. In some embodiments, f is 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, or any value therebetween. In some embodiments, x is 2, 2.05, 2.1, 2.15, 2.2, or any value therebetween.

In some embodiments, the coating coefficient T of the Al element in the primary particles satisfies: t is more than or equal to 10 and less than or equal to 40. In some embodiments, the coating coefficient T of the Al element in the primary particles is 18, 20, 30, 40, 50, 60 or any value therebetween. In some embodiments, 15.ltoreq.T.ltoreq.40. The coating coefficient of the Al element indicates the coating degree of Al on primary particles, so that even coating of the element Al on the surface of the core body can be realized by controlling the coating coefficient T of the Al element, namely, a continuous, even and compact layered coating layer (such as an aluminum lithium compound) is formed on the surface of the core body, namely, high coverage rate fast ion conductor coating is realized on the surface of the core body, direct contact between the core body and electrolyte is effectively avoided, and the structural stability and the dynamic performance of the positive electrode active material are further improved. When the coating coefficient T of the Al element is too small, the coverage rate of the compound containing the Al element in the coating layer is lower, and the isolation effect on side reaction is smaller, so that poor circulation and DCR increase are shown; when the coating coefficient T of the Al element is too large, the coverage rate of the compound containing the Al element in the coating layer is higher, and the Li is influenced ⁺ The deintercalation, thereby affecting the capacity and rate performance of the battery.

In some embodiments, XPS is used at a sputter etch time of 0 secondsThe mass percentage of Al in all metal elements except Li in the primary particles is tested to be Al _XPS0 ，2.5％≤Al _XPS0 Less than or equal to 6 percent. In some embodiments, al _XPS0 Is 2.5%, 3%, 3.5%, 4%, 4.1%, 4.2%, 4.5%, 5%, 5.5%, 6% or any value therebetween. In some embodiments, 4.1% Al _XPS0 Less than or equal to 6 percent. The XPS was tested at a sputter etching time of 0 seconds, and the Al content on the surface of the primary particles could be tested. When Al is _XPS0 Too small, the content of Al element in the coating layer on the surface of the primary particles is low, and the effect of protecting the positive electrode is poor; when Al is _XPS0 Too large, the content of Al element in the coating layer on the surface of the primary particles is high, and the deintercalation of Li ions is affected, so that the capacity and the rate performance of the battery are affected.

In some embodiments, XPS is used for testing at a sputter etching time of 180 seconds, wherein the primary particles comprise Al in all other metal elements except Li in percentage by mass _XPS1 ，0.1％≤Al _XPS1 Less than or equal to 2 percent. In some embodiments, al _XPS1 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2% or any value therebetween. In some embodiments, 0.2% Al _XPS1 Less than or equal to 1.5 percent. The XPS is tested at 180 seconds of sputter etching time, so that the content of Al element in the primary particles, that is, the content of Al element in a certain depth of the primary particles, for example, the content of corresponding Al in the coating layer of the primary particles, can be tested. When Al is _XPS1 Too small, indicating no enrichment of Al at a certain depth; when Al is _XPS1 Too large, it is indicated that the Al-related coverage depth is high or that the Al-capping agent is still present in a large particle state.

In some embodiments, the primary particles are tested by ICP, and the mass percentage of Al in all other metal elements except Li is Al _ICP ，0.01％≤Al _ICP Less than or equal to 0.2 percent. In some embodiments, al _ICP 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.12%, 0.15%, 0.18%, 0.2% or any value in between. In some embodiments, 0.1% Al _ICP Less than or equal to 0.2 percent. The ICP test can test the Al content of the primary particles as a whole. When Al is _ICP Too small, the coating source is insufficient, and a complete coating film cannot be formed effectively, namely a layered coating layer cannot be formed; when Al is _ICP Too large can result in a relatively high level of inactive materials, affecting overall capacity performance.

In some embodiments, the primary particles have a binding energy in the range of 848eV to 868eV, ni in a spectrum tested by XPS at a sputter etch time of 0 seconds ²⁺ Peak area of (2)Ni ³⁺ Peak area of +.> In some embodiments, the->70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 99%, 99.5% or any value therebetween. In some embodiments of the present invention, in some embodiments,ni2p having binding energy in the range of 850eV to 870eV _3/2 After peak separation and curve fitting, ni is obtained ²⁺ Corresponding peak and Ni ³⁺ Corresponding peak separation, ni ²⁺ The corresponding peak dividing area isNi ³⁺ The corresponding peak area is +.>In some embodimentsIn the mode, the specific mode of carrying out peak separation and curve fitting is not particularly limited, and Ni can be obtained only by realizing the method according to the map ²⁺ Corresponding peak and Ni ³⁺ The peak position correction may be performed, for example, by setting the c—c peak of the C1s spectrum to 284.6eV in the XPS spectrum; then, using PHI MultiPak software, the peak Ni2p of the Ni bonding portion at the position where the binding energy is 848eV to 868eV was measured _3/2 According to Ni ²⁺ Peak position about 853.2ev, ni ³⁺ Peak separation and curve fitting are carried out under the condition of about 855.2eV peak position to obtain Ni ²⁺ Peak area and Ni ³⁺ Peak area. />Can characterize Ni in primary particles ³⁺ The proportion of which, the value reflects the degree of consumption of structural lithium, < >>The control of the values in the above range is advantageous in that the positive electrode active material has suitable dynamic properties, and the positive electrode active material can have good rate performance while maintaining a stable structure. When->Too small, can lead to inactive Ni ²⁺ Too large a content ratio results in a positive electrode active material having low Li ⁺ Diffusion coefficient, finally, the multiplying power performance of the positive electrode active material is deteriorated; when->Too large results in poor stability of the layered structure of the coating layer, resulting in too fast a DCR growth rate.

In some embodiments, the coating layer has a thickness of 10nm to 50nm. In some embodiments, the thickness of the coating is 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, or any value therebetween. In some embodiments, the coating layer has a thickness of 20nm to 30nm.

In some embodiments, the coating layer is present in an amount of 0.1wt% to 4wt% based on the total mass of the primary particles. In some embodiments, the coating layer is present in an amount of 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, or any value therebetween, based on the total mass of the primary particles.

In some embodiments, the Dv50 of the positive electrode active material is 2um to 8um. In some embodiments, the Dv50 of the positive electrode active material is 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8.0 μm, or any value in between. In some embodiments, the cathode active material has a Dv50 of 2.5 μm to 4.5 μm. The Dv50 is a particle size corresponding to a cumulative volume distribution percentage of the positive electrode active material of 50%, for example, obtained by a laser particle size measurement. The positive electrode active material includes primary particles, a quasi-single crystal or spherical agglomerate formed by agglomeration of the primary particles. The primary particles (primary particles) are crystals having a particle diameter in the range of 0.2 μm to 8 μm and containing no grain boundaries, and the crystallographic orientation thereof is substantially uniform throughout the inside.

In summary, the positive electrode active material of the present application has at least one of the following advantages: the DCR (resistance) performance, cycle performance and capacity retention rate of the secondary battery using the positive electrode active material are improved.

2. Preparation method of positive electrode active material

S100: mixing a Ni-containing precursor, lithium salt and a first compound containing an element A, and performing first sintering treatment to obtain a first sintered material; wherein a comprises at least one of Zr, sr, Y, nb, sb, na, mg, ba, ti, si, sn, V, P, W and Mo;

s200: mixing the first sintering material with deionized water to obtain a first mixture;

s300: and mixing a second compound containing element Al with the first mixture, and obtaining the positive electrode active material through a second sintering treatment.

In some embodiments, the first calcination treatment is at a temperature of 700 ℃ to 960 ℃ for a time of 8 hours to 15 hours. In some embodiments, the temperature of the first calcination treatment is 700 ℃, 750 ℃, 800 ℃, 850 ℃, 900 ℃, 950 ℃, 960 ℃, or any value therebetween, for a time of 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, or any value therebetween.

In some embodiments, the step of mixing the first frit and deionized water comprises: deionized water is mixed with the first sintering material in a spray state. Therefore, trace moisture is introduced before the coating process (mixed with the first sintering material in a spray state), the purpose of uniform residual lithium is achieved by premixing the multi-element positive electrode primary sintering material (the first sintering material) first, a uniform lithium source is provided for lithiation of a subsequent coating, and further high coverage rate and fast ion conductor coating is achieved on the surface of a nuclear body, the problems of high residual alkali and poor cycle performance caused by unstable surface of primary particles are effectively avoided, the formed continuous layered coating can avoid direct contact between the nuclear body and electrolyte, side reaction between the nuclear body and electrolyte is reduced, and further the structural stability and dynamic performance of a positive electrode active material are improved, and the problems of short cycle life and poor dynamic performance of a lithium ion battery are solved.

In some embodiments, the second calcination treatment is at a temperature of 350 ℃ to 550 ℃ for a time of 8 hours to 15 hours. In some embodiments, the temperature of the second calcination treatment is 300 ℃, 350 ℃, 400 ℃, 450 ℃, 500 ℃, 550 ℃ or any value therebetween for a time of 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h or any value therebetween. Before the second calcination treatment, a trace amount of water is introduced (mixed with the first sintering material in a spray state) to premix the first sintering material, so that uniform residual lithium can be realized, and a uniform lithium source is provided for the lithiation of the subsequent coating. Further, if the residual lithium is not subjected to homogenization treatment (mixed with the first sintering material in a spray state), al source particles still exist in large-particle-size island particles in the non-lithium-rich aggregation area during the second calcination treatment, the interface of the core body cannot be effectively covered, and thus a continuous layered coating layer cannot be formed, part of structural lithium is consumed, and the coating coefficient T of Al element in the primary particles cannot meet the above range value, so that direct contact between the core body and the electrolyte is caused, side reaction is generated between the core body and the electrolyte, and further the structural stability and the kinetic performance of the positive electrode active material are affected.

In some embodiments, the Ni-containing precursor includes Ni _g Co _h Mn _i (OH) ₂ G is more than or equal to 0.5 and less than or equal to 0.96,0, h is more than or equal to 0.3, i is more than or equal to 0 and less than or equal to 0.4, and g+h+i=1. In some embodiments, g is 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, 0.96, or any value therebetween. In some embodiments, h is 0, 0.1, 0.15, 0.2, 0.25, 0.3, or any value therebetween, and i is 0, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, or any value therebetween.

In some embodiments, the lithium salt comprises Li ₂ CO ₃ And LiOH.

In some embodiments, the first compound comprises at least one selected from the group consisting of carbonates, oxides, fluorides, hydroxides of Zr, sr, Y, nb, sb, na, mg, ba, ti, si, sn, V, P, W, mo.

In some embodiments, the second compound comprises AlOOH, al (OH) ₂ 、Al ₂ O ₃ 、Al(OH) ₃ 、Al ₂ (SO4) ₃ And Al (NO) ₃ ) ₃ At least one of them.

In some embodiments, the mass ratio of the Ni-containing precursor, the lithium salt, and the first compound is 1: (0.3-0.6): (0.001-0.02). In some embodiments, the mass ratio of the Ni-containing precursor, the lithium salt, and the first compound is 1:0.3:0.001, 1:0.4:0.001, 1:0.5:0.001, 1:0.6:0.001, 1:0.3:0.01, 1:0.3:0.02, 1:0.4:0.01, 1:0.5:0.01, 1:0.6:0.01, 1:0.4:0.02, 1:0.5:0.02, 1:0.6:0.02 or any value in between.

In some embodiments, the mass ratio of the first frit to the deionized water is 1: (0.02-0.4). In some embodiments, the mass ratio of the first frit to the deionized water is 1:0.03, 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.04 or any value in between.

In some embodiments, the mass ratio of the first mixture, the second compound is 1: (0.0005 to 0.01). In some embodiments, the mass ratio of the first mixture, the second compound is 1:0.0005, 1:0.001, 1:0.005, 1:0.008, 1:0.01 or any value in between.

3. Secondary battery

The present application also provides a secondary battery including the positive electrode active material described above or the positive electrode active material formed by the above-described preparation method. Thus, the device may have all of the features and advantages of the positive electrode active material or the preparation method described above, and will not be described herein.

In some embodiments, the secondary battery is coated with a positive electrode tab, a negative electrode tab, and an electrolyte. The positive electrode plate comprises a positive electrode current collector and a positive electrode active material arranged on the positive electrode current collector, wherein the positive electrode active material comprises the positive electrode active material or the positive electrode active material formed by the preparation method.

In some embodiments, the positive electrode active material layer further includes a binder and a conductive material. The binder enhances the bonding of the positive electrode active material particles to each other and also enhances the bonding of the positive electrode active material to the current collector. In some embodiments, the binder comprises: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, an ethyleneoxy-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, or the like. In some embodiments, the conductive material comprises: carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based material is selected from natural graphite, synthetic graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

In some embodiments, the positive electrode current collector may employ a metal foil or a composite current collector. For example, aluminum foil may be used. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, or the like) on a polymer substrate.

In some embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode active material disposed on the negative electrode current collector, the negative electrode active material including the silicon-based material, or a mixture of the silicon-based material and at least one material selected from a carbon-based material, a tin-based material, a phosphorus-based material, and metallic lithium. In some embodiments, the silicon-based material comprises at least one of silicon, a silicon alloy, a silicon oxygen compound, and a silicon carbon compound, the carbon-based material comprises at least one of graphite, soft carbon, hard carbon, carbon nanotubes, and graphene, the tin-based material comprises at least one of tin, a tin oxide, and a tin alloy, and the phosphorus-based material comprises phosphorus and/or a phosphorus-carbon composite. Based on the mass of the anode active material, the mass percentage content of the silicon-based material is 0-30%. The mass percentage content of the silicon-based material is 0%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 25%, 30% or any value therebetween, based on the mass of the anode active material. Based on the mass of the anode active material, the mass percentage content of the silicon-based material is 0-5%. Based on the mass of the anode active material, the mass percentage content of the silicon-based material is 0-15%.

In some embodiments, the anode active material layer further includes a binder and a conductive agent. In some embodiments, the binder comprises: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, an ethyleneoxy-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, or the like. In some embodiments, the conductive agent comprises: carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based material is selected from natural graphite, synthetic graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

In some embodiments, the negative electrode current collector includes: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or any combination thereof.

In some embodiments, the electrolyte includes a lithium salt, a solvent, and an additive.

In some embodiments, the lithium salt comprises lithium hexafluorophosphate (LiPF ₆ ) Lithium tetrafluoroborate (LiBF) ₄ ) At least one of lithium trifluorosulfonyl (LiTf), lithium bis (fluorosulfonyl) imide (LiLiFeSI), lithium trifluoromethanesulfonate (trifluoromethanesulfonyl) (perfluorobutylsulfonyl) imide (LiNFSI), lithium bis (pentafluoroethylsulfonyl) imide (LiBETI), lithium bis (fluoromalonic acid) borate (LiBFMB), lithium bis (LiBOB) oxalate, lithium difluorooxalato borate (LiDFOB), lithium difluorodioxalate phosphate, and lithium 4, 5-dicyano-2- (trifluoromethyl) imidazole (LiTDI).

In some embodiments, the lithium salt is present in an amount of 4% to 25% by mass based on the mass of the electrolyte. In some embodiments, the mass percent content of lithium salt is 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or any value therebetween. In some embodiments, the lithium salt is present in an amount of 6% to 18% by mass.

In some embodiments, the solvent comprises at least one of a chain carbonate and a cyclic carbonate.

In some embodiments, the chain carbonate is selected from at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylethyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, and fluoro chain carbonate. In some embodiments, the cyclic carbonate comprises at least one of ethylene carbonate, propylene carbonate, and butylene carbonate. In some embodiments, the organic solvent further comprises a non-fluorinated carboxylic ester selected from at least one of methyl formate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and gamma-butyrolactone.

In some embodiments, the solvent is present in an amount of 40% to 80% by mass based on the mass of the electrolyte. In some embodiments, the solvent is 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80% by mass or any value therebetween. In some embodiments, the solvent is present in an amount of 50% to 70% by mass.

In some embodiments, the additive comprises at least one of Vinylene Carbonate (VC), ethylene carbonate, tris (trimethylsilane) phosphate (TMSP), tris (trimethylsilane) borate (TMSB), succinonitrile, adiponitrile, glutaronitrile, and hexanetrinitrile. In some embodiments, the additive further comprises at least one of Methylene Methylsulfonate (MMDS), ethylene ethyldisulfonate, 1, 3-propane sultone (1, 3-PS), 1-propylene-1, 3-sultone (PST), 1, 4-butane sultone (1, 4-BS), vinyl sulfate (DTD), 4-methyl ethylene sulfate (PCS), 4-ethyl ethylene sulfate (PES), 4-propyl ethylene sulfate (pegst), propylene sulfate (TS), ethylene sulfite (DTO), dimethyl sulfite (DMS), and diethyl sulfite (DES).

In some embodiments, the additive is present in an amount of 0.05% to 10% by mass based on the mass of the electrolyte. In some embodiments, the additive is present in an amount of 0.05%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10% by mass or any value therebetween. In some embodiments, the additive is present in an amount of 0.1% to 5% by mass.

In some embodiments, a separator is provided between the positive and negative electrode sheets to prevent shorting. The materials and shape of the release film that can be used in the embodiments of the present application are not particularly limited, and can be any of the techniques disclosed in the prior art. In some embodiments, the separator comprises a polymer or inorganic, etc., formed from a material that is stable to the electrolyte of the present application.

For example, the release film may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer comprises at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric or a polypropylene-polyethylene-polypropylene porous composite membrane can be selected.

The surface treatment layer is provided on at least one surface of the base material layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or may be a layer formed by mixing a polymer and an inorganic substance.

The inorganic layer includes inorganic particles including at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate, and a binder. The binder includes at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene.

The polymer layer contains a polymer, and the material of the polymer comprises at least one of polyamide, polyacrylonitrile, acrylic polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride and poly (vinylidene fluoride-hexafluoropropylene).

In some embodiments, the method of manufacturing the secondary battery includes providing an electrode assembly, injecting a liquid, packaging, and forming. In some embodiments, the temperature of the formation is 40 ℃ to 50 ℃, e.g., 41 ℃, 42 ℃, 43 ℃, 44 ℃, 45 ℃, 46 ℃, 47 ℃, 48 ℃, or 49 ℃.

In some embodiments, the forming comprises: charging to 4.25V at a current of 0.05C under a condition of a temperature of 40-50 ℃, for example 45 ℃, a pressure of 150-250 kgf, for example 210kgf, standing for 60min, then charging to 4.25V at 0.1C, and then discharging to 3.0V at 0.2C.

In some embodiments, the secondary battery is a lithium secondary battery or a sodium secondary battery. In some embodiments, lithium secondary batteries include, but are not limited to: lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries, or lithium ion polymer secondary batteries.

In some embodiments, the secondary battery may include an outer package, which may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The exterior package of the secondary battery may also be a pouch type pouch, for example. The soft bag can be made of one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

In some embodiments, the shape of the secondary battery is not particularly limited, and may be cylindrical, square, or any other shape.

In some embodiments, the present application also provides a battery module. The battery module includes the secondary battery described above. The battery module of the present application employs the above-described secondary battery, and thus has at least the same advantages as the secondary battery. The number of secondary batteries contained in the battery module of the present application may be plural, and the specific number may be adjusted according to the application and capacity of the battery module.

In some embodiments, the present application also provides a battery pack including the above battery module. The number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

4. Device and method for controlling the same

The present application also provides an apparatus comprising at least one of the above secondary battery, battery module, and battery pack. Thus, the device may have all of the features and advantages of the secondary battery, the battery module, or the battery pack described above, which are not described herein.

In some embodiments, the apparatus includes, but is not limited to: electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric storage systems, and the like. In order to meet the high power and high energy density requirements of the device for the secondary battery, a battery pack or a battery module may be employed.

In other embodiments, the device may be a cell phone, tablet, notebook, or the like. The device is generally required to be light and thin, and a secondary battery can be used as a power source.

Examples and comparative examples

Example 1

The preparation steps of the positive electrode active material are as follows: (1) Preparation of Ni by coprecipitation method _0.90 Co _0.05 Mn _0.05 (OH) ₂ Precursor, ni _0.90 Co _0.05 Mn _0.05 (OH) ₂ Precursor, liOH H ₂ O and dopant nano ZrO ₂ The mass ratio is 1:0.4714:0.004, and then carrying out primary sintering treatment at 780 ℃ to prepare a first sintering material; (2) The method comprises the steps of (1) mixing a first sintering material and deionized water according to a mass ratio of 1:0.025, and mixing deionized water in a spray state with the primary sintering material prepared in the step (1) in an industrial mixer for 10min to obtain a first mixture; (3) mixing the first mixture and aluminum hydroxide according to a mass ratio of 1:0.001, adding aluminum hydroxide into the first mixture of the step (2), and mixing for 20min in an industrial mixer to obtain a second mixture. (4) Mixing the second mixtureAnd (3) placing the material in an oxygen atmosphere, and sintering the material for 10 hours at the temperature rising speed of 2 ℃/min to the target temperature of 450 ℃ to obtain the anode active material.

The preparation steps of the positive pole piece are as follows: the positive electrode active material, CNT (conductive carbon nano tube)/Super-P (conductive carbon black) and the binder polyvinylidene fluoride PVDF are prepared according to the weight ratio: CNT/Super-P: pvdf=95: (2.0/1.0): 2, in N-methyl pyrrolidone NMP, fully homogenizing, coating on an aluminum current collector with the thickness of 12 mu m, and then drying, rolling, hot-pressing and the like to obtain the positive electrode plate.

The preparation steps of the negative electrode plate are as follows: the negative electrode active material silicon oxide (SiOx, x is more than or equal to 0.5 and less than or equal to 1.5) -graphite compound (Si/C=5:95), conductive agent acetylene black, binder styrene-butadiene rubber SBR, thickener sodium carboxymethyl cellulose CMCNa and polyacrylic acid PAA according to the weight ratio of 95:2:1.5:1: and 0.5, adding the mixture into deionized water, fully homogenizing the mixture, coating the mixture on an 8 mu m thick copper current collector, and then drying, rolling, hot-pressing and the like to obtain the negative electrode plate.

Preparation of electrolyte: in an argon-filled glove box (H) ₂ O＜0.1ppm，O ₂ < 0.1 ppm), lithium salt LiPF ₆ The mixed solution fully dissolved in EC/DEC/EMC (ethylene carbonate/diethyl carbonate/methylethyl carbonate) =25/20/55 was prepared as a 1mol/L solution.

Isolation film: adopts a PP/PE/PP (polypropylene/polyethylene/polypropylene) three-layer composite isolating film.

Preparation of lithium ion secondary battery: the positive electrode plate, the isolating film (PP/PE/PP three-layer composite film) and the negative electrode plate are sequentially overlapped layer by layer, the isolating film is positioned between the positive electrode plate and the negative electrode plate, a bare cell is obtained by winding, the bare cell is placed in a punched aluminum plastic film soft package shell, the prepared electrolyte is injected after the bare cell is fully dried, the battery is placed at 45 ℃ for 48 hours and is subjected to high-temperature clamp formation (the formation condition is that the temperature is 45 ℃, the pressure is 210kgf and the current is 0.05C, the battery is charged to V1 and is placed for 60 minutes, then the battery is charged to V1 at 0.1C, then the battery is discharged to 2.5V at 0.2C, wherein the high-nickel positive electrode (such as ternary 8 series and ternary 9 series) is v1=4.2V, and the medium-nickel positive electrode (such as ternary 5 series, ternary 6 series and ternary 7 series) is v1=4.4V, and the battery is repeatedly subjected to three times and secondary sealing, and conventional capacity division is carried out.

Comparative example 1

The other steps in comparative example 1 were the same as in example 1, except that the positive electrode active material was prepared in the following steps:

the preparation steps of the positive electrode active material are as follows: the preparation steps of the positive electrode active material are as follows: (1) Preparation of Ni by coprecipitation method _0.90 Co _0.05 Mn _0.05 (OH) ₂ Precursor, ni _0.90 Co _0.05 Mn _0.05 (OH) ₂ Precursor, liOH H ₂ O and dopant nano ZrO ₂ The mass ratio is 1:0.4714:0.004, and then carrying out primary sintering treatment at 780 ℃ to prepare a first sintering material; (2) according to the mass ratio of the first sintering material to the aluminum hydroxide of 1:0.001, adding aluminum hydroxide into the first mixture of the step (1), and mixing for 20min in an industrial mixer to obtain a first mixture. (3) And placing the first mixture under the condition of oxygen atmosphere, raising the temperature rising speed of 2 ℃/min to the target temperature of 450 ℃ and sintering for 10 hours to perform second sintering treatment, thus obtaining the positive electrode active material.

Examples 2 to 8 and comparative examples 2 to 3

Examples 2 to 8 were carried out by adjusting the type of Ni-containing precursor, the mass ratio of the first sinter to the sprayed deionized water, the type of charge of the clad material, the mass ratio of the core to the charge of the clad material, etc. on the basis of example 1, and comparative examples 2 to 3 were carried out by adjusting the type of Ni-containing precursor, the type of charge of the clad material, the mass ratio of the core to the charge of the clad material, etc. on the basis of comparative example 1, and specific adjustment measures and detailed data are shown in table 1.

Test method

1. Capacity retention test

The prepared lithium ion secondary battery is charged to V1 at a constant current of 1C rate at 25 ℃, and then is charged to a constant voltage until the current is less than 0.05C. After 5 minutes of rest, discharge to 2.5V at 1C rate, wherein high nickel positive electrode: v1=4.2v, medium nickel positive electrode: v1=4.4v, and the initial discharge capacity was recorded. The lithium ion secondary battery was charged and discharged 300 times by the above method, and the discharge capacity of each time was recorded. Capacity retention rate of the lithium ion secondary battery at 25 ℃ for 300 cycles=300 th discharge capacity/initial discharge capacity×100%.

2. Impedance (DCR) test

Discharging the lithium ion battery to 2.5V at the constant current of 1C at the temperature of 25+/-2 ℃, charging to V1 at the constant current of 0.5C, and charging to 0.05C at the constant voltage under the constant voltage of V1, wherein the high-nickel anode: v1=4.2v, medium nickel positive electrode: v1=4.4v, then 1C constant current discharge to 50% soc, standing for 60min, recording voltage U1 after standing, then 2C constant current discharge for 10s, recording voltage U2 after discharging, 2C current recording as I, standing for 60min. Calculating the discharge DCR (impedance) of the battery at 50% SOC according to the formula DCR= (U1-U2)/I; the DCR tested according to the flow is marked as DCR0 before the cyclic test, and the DCR tested according to the flow is marked as DCR1 after the cyclic test is repeated for a certain number of times, and the DCR increment rate is (DCR 1-DCR 0)/DCR 0;

3. X-ray photoelectron spectrometer (XPS) test

Discharging the lithium ion battery to 2.5V at the current of 0.1C, and dismantling the lithium ion battery in a glove box filled with argon to obtain the electrode plate. Cutting the obtained electrode plate into a test sample with the size of 8mm multiplied by 8mm, soaking and cleaning for half an hour by using a low-boiling point dimethyl carbonate DMC solvent, after the test sample is completely dried, pasting the test sample on a sample table of XPS, enabling the surface of the negative electrode active material layer, which is far away from a current collector, to face upwards, and measuring under the condition of not being exposed to the atmosphere. The specific test conditions and steps are as follows:

using single crystal spectral alkα rays, data at a sputter etch time of 0 seconds or 180 seconds was selected using 1000X 1750 μm ellipse form output of 10KV and 22mA for the X-ray point, 284.8eV for neutral carbon C1s, and 3-point smoothing, peak area measurement, background subtraction and peak synthesis for data processing such as peak differentiation, to calculate atoms for each component.

4. Inductively coupled plasma emission spectrometer (ICP) testing

Disassembling the lithium ion battery in a protective atmosphere, taking out the electrode pole piece, cleaning and soaking the disassembled electrode pole piece by DMC, removing electrolyte remained on the surface of the pole piece, and eliminating the influence of the electrolyte. After the DMC solvent volatilizes, electrode plate powder is collected for later use in subsequent ICP testing. Specifically, about 0.05g (accurate to 0.00001 g) of the sample is weighed into a 50mL beaker, 8.0mL of 1+1 hydrochloric acid is added, the mixture is heated and dissolved at a low temperature on an electric furnace, 5 drops of hydrogen peroxide and a small amount of water are added after the sample is basically dissolved, and the mixture is taken down and cooled after being heated until the solution does not generate small bubbles. Transfer to volume in 100mL volumetric flask, measure using ICP instrument while blank experiments were performed.

5. Capacity recovery rate

Constant current charging is carried out to V1 at the rate of 1C before storage, and then constant voltage charging is carried out to the current of less than 0.05C. After standing for 5 minutes, the discharge capacity C0 was recorded by discharging to 2.5V at a 1C rate. After 30 days of storage at 60 ℃, the battery is taken out and placed to normal temperature (more than 4 h), discharged to 2.5V at 1C multiplying power, the record holding capacity C1 is then charged to V1 at 1C multiplying power with constant current, and then the constant voltage is charged to current less than 0.05C. After 5 minutes of rest, discharge to 2.5V at 1C rate, wherein high nickel positive electrode: v1=4.2v, medium nickel positive electrode: the discharge capacity was recorded by v1=4.4v, and thus the charge-discharge cycle 3 was taken as an average value C2 of the discharge capacity of three times, and the capacity recovery rate after 30 days of storage at 60 ℃ was (C0-C2)/C0.

6. Electrolyte consumption rate test

Weighing the total mass M1 of the battery before liquid injection and the total mass M2 of the battery after liquid injection to obtain the liquid injection amount M3=M2-M1; charging and discharging the battery; the prepared lithium ion secondary battery is charged to V1 at a constant current of 1C rate under the condition of 25 ℃, then is charged to a current of less than 0.05C at a constant voltage, is kept stand for 5 minutes, and is discharged to a high nickel anode at the 1C rate: v1=4.2v, medium nickel positive electrode: v1=4.4v, and the lithium ion secondary battery was charge-discharge cycled 300 times by the above method. After battery cycling, the battery mass M4 is weighed. And disassembling the battery, taking out electrolyte in the battery, adding a solvent into the disassembled battery to soak and clean the battery so as to remove the electrolyte, heating the disassembled battery, and weighing the mass M5 of the disassembled battery after the solvent volatilizes. The remaining amount m6=m4-M5 of the electrolyte after the battery cycle was calculated, and the electrolyte consumption rate = (M3-M6)/m3×100% after the battery was cycled 300 turns at 25 ℃.

7. Discharge gram Capacity test

Taking 4 parallel samples of the prepared secondary batteries, charging the secondary batteries to V1 voltage at the room temperature of 25 ℃ with constant current of 0.33C multiplying power, and charging the secondary batteries to current lower than 0.05C under the constant voltage condition of V1 to enable the secondary batteries to be in the full-charge state of V1. Then, constant current discharge was performed at 0.33C rate for 2.5V to obtain discharge capacity. Discharge gram capacity at 0.33C rate = discharge capacity/active mass, with high nickel positive electrode: v1=4.2v, medium nickel positive electrode: v1=4.4v.

Test results

TABLE 2

As can be seen from examples 1 to 8 and comparative examples 1 to 3, the present application facilitates the formation of a passivation film on the surface of the positive electrode by introducing Al element into the coating layer of the primary particles of the positive electrode active material, which effectively avoids the problem of corrosion caused by the contact of the positive electrode body with the acidic electrolyte, so that the positive electrode can maintain a complete layered structure, and further can maintain a good Li ion transport channel in the late cycle stage, thereby exhibiting excellent DCR performance and cycle performance; and by controlling the coating coefficient of the Al element, a continuous, uniform and compact lamellar coating layer can be formed on the surface of the nuclear body, namely, the high coverage rate fast ion conductor coating is realized on the surface of the nuclear body, the direct contact between the nuclear body and electrolyte is effectively avoided, and the structural stability and the dynamic performance of the positive electrode active material are further improved. Thus, based on the above improvements, the positive electrode active material of the present application has at least one of the following advantages: the DCR performance, cycle performance and capacity retention rate of the secondary battery using the positive electrode active material are improved.

As is clear from comparative examples 1 to 7 and comparative example 1, the coating layer on the surface of the positive electrode active material core body was island-shaped, and when Al _XPS0 Too low,When the coating coefficient of the Al element is too low, the coverage rate of the compound containing the Al element in the coating layer is low, the isolation effect on side reaction is small, the electrolyte consumption rate of the battery is further increased, the capacity retention rate is reduced, the impedance of the battery is increased, and the capacity recovery rate is poor.

As is clear from comparative examples 1 to 7 and comparative example 2, although the coating layer on the surface of the positive electrode active material core body is layered, when the coating coefficient of Al element is too high, and thus the electrolyte consumption rate of the battery increases, the coverage of the Al element-containing compound in the coating layer is high, affecting Li ⁺ The deintercalation further results in reduced discharge gram capacity and poor capacity recovery rate.

As is clear from comparative examples 1 to 7 and comparative example 3, although the coating layer on the surface of the positive electrode active material core was in the form of a layer, when Al _XPS0 Too high, al _XPS1 Too high, al _ICP Too high,When the coating coefficient of the Al element is too low, the coverage rate of the compound containing the Al element in the coating layer is low, the isolation effect on side reaction is small, and further the discharge gram capacity of the battery is reduced and the electrolyte consumption rate is increased.

Fig. 1 is a scanning electron microscopic view of the positive electrode active material of comparative example 1, in which the coating layer on the surface of the core body is seen to be island-shaped.

FIG. 2 is a Ni peak Ni2P in XPS spectrum of the positive electrode active material of comparative example 1 _3/2 Is a graph of the peak and curve fitting of (a).

Fig. 3 is a cross-sectional scanning electron microscope image of the positive electrode active material according to example 1 of the present application, from which it is seen that the coating layer of the surface of the core body is in a continuous layer.

FIG. 4 is a Ni peak Ni2P in XPS spectrum of the positive electrode active material according to example 1 of the present application _3/2 Is a graph of the peak and curve fitting of (a).

While certain exemplary embodiments of the present application have been illustrated and described, the present application is not limited to the disclosed embodiments. Rather, one of ordinary skill in the art will recognize that certain modifications and changes may be made to the described embodiments without departing from the spirit and scope of the present application, as described in the appended claims.

Claims

1. A positive electrode active material characterized in that the positive electrode active material includes primary particles including a core body and a coating layer which is provided on a surface of the core body and is continuous in a layer shape, the primary particles including Li element, ni element, and Al element;

The test is carried out by adopting an X-ray photoelectron spectrometer under the condition of sputtering etching time of 180 seconds, wherein the mass percentage content of Al in the primary particles accounting for all other metal elements except Li is Al _XPS1 ；

2. The positive electrode active material according to claim 1, wherein the primary particles include Li _a Ni _b Co _c Mn _d Al _e A _f O _x Wherein a is more than or equal to 0.95 and less than or equal to 1.3,0.5 and less than or equal to b is more than or equal to 0.96,0 and less than or equal to c is more than or equal to 0.35,0 and less than or equal to d is more than or equal to 0.35,0 and less than or equal to 0.05, f is more than or equal to 0 and less than or equal to 0.05,2 and less than or equal to x is more than or equal to 2.2, and b+c+d+e+f=1. A includes at least one of Zr, sr, Y, nb, sb, na, mg, ba, ti, si, sn, V, P, W and Mo.

3. The positive electrode active material according to claim 1 or 2, wherein 15.ltoreq.t.ltoreq.40.

4. The positive electrode active material according to claim 1 or 2, wherein 2.5% or less of Al _XPS0 Less than or equal to 6 percent; and/or, al is more than or equal to 0.1 percent _XPS1 Less than or equal to 2 percent; and/or, al is more than or equal to 0.01 percent _ICP Less than or equal to 0.2 percent; and/or the number of the groups of groups,

5. the positive electrode active material according to claim 4, wherein 4.1% or less of Al _XPS0 Less than or equal to 6 percent; and/or, al is more than or equal to 0.2 percent _XPS1 Less than or equal to 1.5 percent; and/or, al is more than or equal to 0.1 percent _ICP Less than or equal to 0.2 percent; and/or the number of the groups of groups,

6. the positive electrode active material according to claim 2, wherein b.ltoreq. 0.96,0.ltoreq.c.ltoreq.0.2; and/or

The thickness of the coating layer is 10 nm-50 nm; and/or

The mass percentage content of the coating layer is 0.1-4wt% based on the total mass of the primary particles; and/or

The Dv50 of the positive electrode active material is 2-8 um.

7. A method for preparing a positive electrode active material, comprising:

8. The method according to claim 7, wherein the first calcination treatment is performed at a temperature of 700 to 960 ℃ for a time of 8 to 15 hours; and/or

The step of mixing the first sinter and deionized water comprises the steps of: mixing deionized water with the first sintering material in a spray state; and/or

The temperature of the second calcination treatment is 350-550 ℃ and the time is 8-15 h; and/or

The Ni-containing precursor includes Ni _g Co _h Mn _i (OH) ₂ G is more than or equal to 0.5 and less than or equal to 0.96,0, h is more than or equal to 0.3, i is more than or equal to 0 and less than or equal to 0.4, and g+h+i=1; and/or

The lithium salt comprises Li ₂ CO ₃ And LiOH; and/or

The first compound comprises at least one selected from the group consisting of a carbonate, an oxide, a fluoride, and a hydroxide of Zr, sr, Y, nb, sb, na, mg, ba, ti, si, sn, V, P, W, mo; and/or

The second compound comprises AlOOH, al (OH) ₂ 、Al ₂ O ₃ 、Al(OH) ₃ 、Al ₂ (SO4) ₃ And Al (NO) ₃ ) ₃ At least one of (a)Seed; and/or

The mass ratio of the Ni-containing precursor, the lithium salt and the first compound is 1: (0.3-0.6): (0.001-0.02); and/or

The mass ratio of the first sintering material to the deionized water is 1: (0.02-0.4); and/or

The mass ratio of the first mixture to the second compound is 1: (0.0005 to 0.01).

9. A secondary battery comprising the positive electrode active material according to any one of claims 1 to 6 or the positive electrode active material formed by the production method according to any one of claims 7 to 8.

10. An apparatus comprising the secondary battery according to claim 9.