Method for preparing cobalt-free layered positive electrode material by using li + / h + exchange

Abstract

A method for preparing a cobalt-free layered positive electrode material. The method comprises the following steps: adding a metal sulfate solution, a precipitant solution and a complexing agent solution dropwise into an ammonia solution for a precipitation and complexation reaction, so as to obtain a precursor; and mixing the precursor and a lithium source, and sequentially performing first calcination and second calcination, so as to obtain a cobalt-free layered positive electrode material, wherein the temperature of the first calcination is lower than the temperature of the second calcination, and metal sulfates in the metal sulfate solution are at least two non-cobalt transition metal sulfates. Low-temperature pre-calcination is performed to fully exchange a hydrogen-oxygen precursor with a lithium source, so as to form a metastable intermediate, thereby laying the foundation for forming a good cobalt-free layered structure.

Description

A method using Li + / H + Method for preparing cobalt-free layered positive electrode material by exchange

[0001] This application is filed with the China Patent Office on March 7, 2024, with application number CN202410263401.X and the name of the invention being “A Method of Using Li + / H + The entire contents of the Chinese patent application entitled "Method for preparing cobalt-free layered positive electrode materials by exchange" are incorporated herein by reference. Technical Field

[0002] This application belongs to the technical field of positive electrode materials and specifically relates to a method for + / H + A method for preparing cobalt-free layered cathode materials by exchange. Background Art

[0003] Lithium nickel cobalt manganese oxide (NCM) cathode materials are widely used in electric vehicles and portable electronic devices due to their high specific capacity. However, due to the environmental problems of cobalt mining and the continuous rise in the price of cobalt elements, the exploration of cobalt-free high-nickel layered cathode materials has begun. Therefore, the synthesis of high-nickel cobalt-free layered cathode materials has attracted much attention and is of great importance.

[0004] The sintering synthesis reaction of existing cobalt-free layered cathode materials is inherently complex. 2+ After 750℃, it will be oxidized to trivalent in large quantities, and the Ni(OH)6 octahedron will decompose to form a broken (asymmetric) (Ni 2+ )O 6-x Octahedron and H2O, accompanied by high concentration of oxygen vacancies, Li + Too late to fit into the empty space, Ni 2+ From the unstable (Ni 2+ )O 6-x The octahedron moves to the Li layer, forming a serious Li / Ni mixed arrangement, so it is necessary to sinter at a higher crystallization temperature (≥850℃) and oxygen atmosphere, which causes Li / O loss, and because the metastable intermediates in the sintering synthesis process are + The influence of metal ion diffusion will cause different degrees of internal pores in the particles. At the same time, Li / O loss and Li + , uneven diffusion of metal ions will also cause different degrees of Li / Ni mixing, and then the overall secondary particles will have different Li + Poor diffusion ability, capacity performance and cycle stability. Summary of the Invention

[0005] The purpose of this application is to provide a method for utilizing Li + / H+ The method for preparing cobalt-free layered cathode materials by exchange can promote the + / H + exchange and form a good layered structure (I (003) / I (104) >1.2), thereby making the obtained cobalt-free layered cathode material have large charge and discharge capacity and good cycle stability.

[0006] In order to achieve the above objectives, this application provides the following technical solutions:

[0007] This application provides a method of using Li + / H + The method for preparing a cobalt-free layered cathode material by exchange comprises the following steps:

[0008] adding a metal sulfate solution, a precipitant solution, and a complexing agent solution dropwise into an ammonia solution to carry out a precipitation and complexation reaction to obtain a hydroxide precursor;

[0009] The hydroxide precursor and the lithium source are mixed, and pre-sintered and crystallized in sequence to obtain the cobalt-free layered positive electrode material; the pre-sintering temperature is lower than the crystallization temperature;

[0010] The metal sulfates are at least two non-cobalt transition metal sulfates.

[0011] Preferably, the metal sulfate includes a mixed salt of nickel sulfate and manganese sulfate, or a mixed salt of nickel sulfate, manganese sulfate and ferrous sulfate, or a mixed salt of nickel sulfate, manganese sulfate and titanium sulfate.

[0012] Preferably, the mixed salt of nickel sulfate and manganese sulfate contains 2+ and Mn 2+ The molar ratio is 8-9.5:0.5-2;

[0013] The mixed salt of nickel sulfate, manganese sulfate and ferrous sulfate contains 2+ 、Mn 2+ and Fe 2+ The molar ratio is 8-9.5:0.45-1.95:0.05-0.5;

[0014] The mixed salt of nickel sulfate, manganese sulfate and titanium sulfate contains 2+ 、Mn 2+ and Ti 2+ The molar ratio is 8~9.5:0.45~1.95:0.05~0.5.

[0015] Preferably, the concentration of the metal sulfate solution is 1.8 to 2 mol / L;

[0016] The precipitant in the precipitant solution includes sodium hydroxide and / or potassium hydroxide; the concentration of the precipitant solution is 4 to 6 mol / L;

[0017] The complexing agent in the complexing agent solution includes ammonium hydroxide; the concentration of the complexing agent solution is 4 to 10 mol / L;

[0018] The concentration of the ammonia solution is 0.5 to 2 mol / L;

[0019] The volume ratio of the metal sulfate solution, the precipitant solution, the complexing agent solution and the ammonia solution is 100-300:100-300:50-200:2590-2900.

[0020] Preferably, the droplet acceleration rate of the metal sulfate solution is 0.4 to 0.8 mL / min; the droplet acceleration rate of the precipitant solution is 0.4 to 0.8 mL / min; and the droplet acceleration rate of the complexing agent solution is 0.2 to 0.4 mL / min.

[0021] Preferably, the temperature of the precipitation complexation reaction is 50-60° C., and the reaction time is 20-60 h.

[0022] Preferably, the molar ratio of the hydroxide precursor to the lithium source is 1:1.05-1.2.

[0023] Preferably, the pre-sintering temperature is 150-300° C., and the holding time is 6-10 hours; the pre-sintering is performed under oxygen, air or vacuum conditions.

[0024] Preferably, the crystallization temperature is 810-850° C., and the holding time is 12-20 h; and the crystallization is carried out under an oxygen atmosphere.

[0025] This application provides a method of using Li + / H + The method for preparing a cobalt-free layered positive electrode material by exchange includes the following steps: adding a metal sulfate solution, a precipitant solution, and a complexing agent solution to an ammonia solution to perform a precipitation and complexation reaction to obtain a hydroxide precursor; mixing the hydroxide precursor with a lithium source, and sequentially performing pre-sintering and crystallization to obtain the cobalt-free layered positive electrode material; the pre-sintering temperature is lower than the crystallization temperature; the metal sulfate is at least two types of non-cobalt transition metal sulfates. In the present application, under the joint action of the precipitant and the complexing agent, metal ions are simultaneously precipitated to reach an atomic level under the competition of the complexation reaction and the precipitation and complexation reaction to obtain a hydroxide precursor; after mixing with the lithium source, the hydroxide precursor M(OH)2 is pre-sintered at a low temperature to reduce the H + Li +The metastable intermediates are fully exchanged to form a good cobalt-free layered structure, which lays the foundation for the formation of a good cobalt-free layered structure; and then crystallization is carried out at a higher crystallization temperature to form a good layered structure (I (003) / I (104) >1.2), and finally the obtained cobalt-free layered cathode material has the advantages of large charge and discharge capacity and good cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG1 is a SEM image of the precursor of NM in Example 1;

[0027] FIG2 is a high-magnification local SEM image of the NM precursor in Example 1;

[0028] FIG3 is a SEM image of the NM layered structure cathode material in Example 1;

[0029] FIG4 is a high-magnification local SEM image of the NMT precursor in Example 1;

[0030] FIG5 is a low-magnification wide-area SEM image of the NMT precursor in Example 1;

[0031] FIG6 is a high-magnification local SEM image of the NMT layered structure cathode material in Example 1;

[0032] FIG7 is a low-magnification wide-area SEM image of the NMT layered structure cathode material in Example 1;

[0033] FIG8 is an XRD pattern of the NM precursor and the NM cathode material in Example 1;

[0034] FIG9 is an XRD pattern of the NM positive electrode materials in Example 1, Comparative Example 1 and Comparative Example 2;

[0035] FIG10 is an XRD pattern of the positive electrode materials NM, NMT and NMF in Example 1;

[0036] FIG11 is a local view of peak 003 in FIG10 ;

[0037] FIG12 is a cycle performance curve of the battery assembled with the NMF positive electrode material in Example 1 and Comparative Example 1;

[0038] FIG13 is an XRD pattern of the positive electrode materials NM, NMT and NMF in Example 2;

[0039] FIG14 is an XRD pattern of the positive electrode materials NM, NMT and NMF in Example 3;

[0040] FIG15 is an XRD pattern of the positive electrode materials NM, NMT and NMF in Comparative Example 1;

[0041] FIG16 is an XRD pattern of the positive electrode materials NM, NMT and NMF in Example 4;

[0042] FIG17 is an XRD pattern of the positive electrode materials NM, NMT and NMF in Comparative Example 3;

[0043] FIG18 is a cycle performance curve of a battery assembled with the positive electrode material obtained in Example 4. DETAILED DESCRIPTION

[0044] This application provides a method of using Li + / H + The method for preparing a cobalt-free layered cathode material by exchange comprises the following steps:

[0045] adding a metal sulfate solution, a precipitant solution, and a complexing agent solution dropwise into an ammonia solution to carry out a precipitation and complexation reaction to obtain a hydroxide precursor;

[0046] The hydroxide precursor and the lithium source are mixed, and pre-sintered and crystallized in sequence to obtain the cobalt-free layered positive electrode material; the pre-sintering temperature is lower than the crystallization temperature;

[0047] The metal sulfates are at least two non-cobalt transition metal sulfates.

[0048] In this application, unless otherwise specified, all preparation raw materials are commercially available products well known to those skilled in the art.

[0049] In the present application, a metal sulfate solution, a precipitant solution and a complexing agent solution are added dropwise to an ammonia solution to carry out a precipitation and complexing reaction to obtain a precursor.

[0050] In the present application, the metal sulfate is at least two of non-cobalt transition metal sulfates. In the present application, the metal sulfate preferably includes a mixed salt of nickel sulfate and manganese sulfate, wherein Ni 2+ and Mn 2+ The molar ratio of is preferably 8-9.5:0.5-2.

[0051] In the present application, the metal sulfate preferably includes a mixed salt of nickel sulfate, manganese sulfate and ferrous sulfate, wherein Ni 2+ 、Mn 2+ and Fe 2+ The molar ratio of is preferably 8-9.5:0.45-1.95:0.05-0.5.

[0052] In the present application, the metal sulfate preferably includes a mixed salt of nickel sulfate, manganese sulfate and titanium sulfate, wherein Ni 2+ 、Mn 2+ and Ti 2+The molar ratio of is preferably 8-9.5:0.45-1.95:0.05-0.5.

[0053] In the present application, the concentration of the metal sulfate solution is preferably 1.8 to 2 mol / L.

[0054] In the present application, the precipitant in the precipitant solution preferably includes sodium hydroxide and / or potassium hydroxide; the concentration of the precipitant solution is preferably 4 to 6 mol / L.

[0055] In the present application, the complexing agent in the complexing agent solution preferably includes ammonium hydroxide; and the concentration of the complexing agent solution is preferably 4 to 10 mol / L.

[0056] In the present application, the concentration of the ammonia solution is preferably 0.5 to 2 mol / L. In the present application, the volume ratio of the metal sulfate solution, the precipitant solution, the complexing agent solution and the ammonia solution is preferably 100 to 300: 100 to 300: 50 to 200: 2590 to 2900.

[0057] Before the dropwise addition, the present application also preferably includes preheating the ammonia solution, and the preheating temperature is preferably the same as the temperature of the precipitation complexation reaction.

[0058] In the present application, the droplet acceleration rate of the metal sulfate solution is preferably 0.4 to 0.8 mL / min; the droplet acceleration rate of the precipitant solution is preferably 0.4 to 0.8 mL / min; and the droplet acceleration rate of the complexing agent solution is preferably 0.2 to 0.4 mL / min.

[0059] In the present application, the dropwise addition is preferably carried out under a nitrogen atmosphere and stirring; the stirring speed is preferably 700 to 1000 rpm. In the present application, the pH value is preferably controlled to be maintained at 11.2 to 11.8 during the dropwise addition.

[0060] In the present application, the temperature of the precipitation complexation reaction is preferably 50-60°C, and the reaction time is preferably 20-60 hours. In the present application, the precipitation complexation reaction is preferably carried out under a nitrogen atmosphere with stirring; the stirring speed is preferably 600-800 rpm. In the present application, the pH value during the precipitation complexation reaction is preferably maintained at 11.2-11.8.

[0061] In the present application, during the precipitation-complexation reaction, metal ions are simultaneously precipitated to achieve atomic-level mixing to obtain a hydroxide precursor under the competition of the complexation reaction and the precipitation-complexation reaction. The process mainly includes two steps: crystal nucleation and crystal growth:

[0062] After the precipitation complexation reaction, the present application also preferably includes filtering, washing and drying the obtained precipitate; the drying conditions are preferably: drying in an oven at 80-100° C. for 12-24 hours.

[0063] In the present application, when the metal sulfate is a mixed salt of nickel sulfate and manganese sulfate, the chemical composition of the hydroxide precursor is preferably Ni 0.8 Mn 0.2 (OH) 2; When the metal sulfate is a mixed salt of nickel sulfate, manganese sulfate and ferrous sulfate, the chemical composition of the hydroxide precursor is preferably Ni 0.8 Mn 0.15 Fe 0.05 (OH) 2; When the metal sulfate is a mixed salt of nickel sulfate, manganese sulfate and titanium sulfate, the chemical composition of the hydroxide precursor is preferably Ni 0.8 Mn 0.15 Ti 0.05 (OH)2.

[0064] After obtaining the hydroxide precursor, the present application mixes the hydroxide precursor with a lithium source, and sequentially performs pre-sintering and crystallization to obtain the cobalt-free layered positive electrode material.

[0065] In the present application, the lithium source preferably includes one or more of lithium hydroxide, lithium carbonate, lithium nitrate, and lithium sulfate. In the present application, the molar ratio of the hydroxide precursor to the lithium source is preferably 1:1.05-1.2. In the present application, the mixing method is preferably grinding.

[0066] In the present application, the pre-sintering temperature is preferably 150-300° C., more preferably 230-250° C.; the holding time is preferably 6-10 h; and the pre-sintering is preferably carried out under oxygen, air or vacuum conditions.

[0067] This application is pre-sintered at low temperature, Mn 2+ / Fe 2+ / Ti 3+ is preferentially oxidized, so Mn 2+ (OH)6 / Fe 2+ (OH)6 / Ti 3+ (OH)6 octahedron transforms to Mn 4+ O6 / Fe 3+ O6 / Ti 4+ O6 octahedron, making the H of the hydroxide precursor M(OH)2 + Li + Fully exchange to form a metastable intermediate (Ni 2+ )(OH) 2-x (Mn 4+ / Fe3+ / Ti 4+ )(OLi) x , laying the foundation for the formation of a good cobalt-free layered structure.

[0068] In the present application, the crystallization is performed by directly heating the material without cooling after the pre-sintering.

[0069] In the present application, the crystallization temperature is preferably 810-850° C., more preferably 820-830° C.; the holding time is preferably 12-20 h; and the crystallization is preferably carried out under an oxygen atmosphere.

[0070] In the present application, when the metal sulfate is a mixed salt of nickel sulfate and manganese sulfate, the pre-sintering temperature is preferably 250°C, and the crystallization temperature is preferably 850°C; when the metal sulfate is a mixed salt of nickel sulfate, manganese sulfate and ferrous sulfate, the pre-sintering temperature is preferably 230°C, and the crystallization temperature is preferably 810°C; when the metal sulfate is a mixed salt of nickel sulfate, manganese sulfate and titanium sulfate, the pre-sintering temperature is preferably 250°C, and the crystallization temperature is preferably 830°C.

[0071] The present invention is crystallized at a relatively high temperature to form a good layered structure (I (003) / I (104) >1.2).

[0072] In the present application, when the metal sulfate is a mixed salt of nickel sulfate and manganese sulfate, the chemical composition of the cobalt-free layered cathode material is preferably LiNi 0.8 Mn 0.2 O2 (NM); When the metal sulfate is a mixed salt of nickel sulfate, manganese sulfate and ferrous sulfate, the chemical composition of the cobalt-free layered positive electrode material is preferably LiNi 0.8 Mn 0.15 Fe 0.05 When the metal sulfate is a mixed salt of nickel sulfate, manganese sulfate and titanium sulfate, the chemical composition of the cobalt-free layered cathode material is preferably LiNi 0.8 Mn 0.15 Ti 0.05 O2(NMT).

[0073] The present invention uses a coprecipitation method to prepare cobalt-free secondary particles of hydroxide, which are formed by agglomeration of nano-sheet-shaped primary particles and have a layered crystal structure. It is beneficial to the Li in the sintering process (i.e. the whole process of pre-sintering and crystallization). + Diffusion and Li + / H +Second, the hydroxide precursor will disintegrate into a layered structure at high temperature, decomposing into a spinel or rock salt structure oxide, which blocks the Li + / H + Therefore, the present invention mixes the precursor with the lithium source and pre-sinters it at a low temperature, so as to quickly and evenly form cobalt-free layered material seed crystals in the particles, which helps the subsequent high-temperature crystallization of the particle block. Third, due to the high oxygen concentration, a large amount of Ni(OH)2 will decompose into NiO with a rock salt structure, resulting in a layered structure. Collapse, so this application uses oxygen atmosphere, air atmosphere or vacuum atmosphere in the low temperature pre-firing stage. + / H + Exchange, cobalt-free layered materials can form a good layered structure at high crystallization temperature and show excellent cycle performance.

[0074] In order to further illustrate the present application, the following is a method of utilizing Li provided by the present application in conjunction with the accompanying drawings and embodiments. + / H + The methods for preparing cobalt-free layered positive electrode materials by exchange are described in detail, but they should not be understood as limiting the scope of protection of this application.

[0075] Example 1

[0076] Mix ammonia water and 2.5L pure water in a reactor and stir evenly to form a 1mol / L ammonia solution as the base solution;

[0077] Prepare 300mL of 2mol / L metal sulfate solution (NM: Ni 2+ / Mn 2+ =8 / 2, NMF:Ni 2+ / Mn 2+ / Fe 2+ =8 / 1.5 / 0.5, NMT: Ni 2+ / Mn 2+ / Ti 3+ =8 / 1.5 / 0.5); prepare 300mL of 5mol / L NaOH solution as a precipitant solution; prepare 200mL of 10mol / L ammonium hydroxide solution as a complexing agent solution;

[0078] The temperature of the bottom liquid was heated to 50°C, and nitrogen was introduced into the reactor;

[0079] The metal sulfate solution, precipitant solution, and complexing agent solution were pumped into the reactor at a rate of 0.4 mL / min, 0.4 mL / min, and 0.2 mL / min, respectively, using a high-precision peristaltic pump, and the stirring rate was set to 800 rpm. The pH value was maintained at 11.5-11.8 during the addition process, and the addition was continued for 15 hours.

[0080] After the addition was completed, the stirring rate was set to 700 rpm, the pH value was maintained at 11.5-11.8, and the temperature of the mixed liquid in the reactor was maintained at 50°C. The reaction was carried out under these conditions for 45 hours. The obtained precipitate was filtered and washed, and then dried in an oven at 80°C for 12 hours to obtain a brown hydroxide precursor.

[0081] The hydroxide precursor and LiOH were mixed and ground evenly (the molar ratio of the hydroxide precursor to LiOH was 1:1.05); the mixture was pre-sintered at a pre-sintering temperature and air atmosphere (NM: 250°C, NMT: 250°C, NMF: 230°C) for 6 hours, and then the temperature was continued to be raised to the crystallization temperature (NM: 850°C, NMT: 830°C, NMF: 810°C) without annealing, and kept warm for 12 hours in an O2 atmosphere to obtain positive electrode materials NM, NMT and NMF, respectively.

[0082] Example 2

[0083] Positive electrode materials NM, NMT and NMF were prepared respectively in the manner of Example 1, except that the atmosphere of the first calcination was adjusted to an oxygen atmosphere.

[0084] Example 3

[0085] Positive electrode materials NM, NMT and NMF were prepared respectively in the manner of Example 1, except that the atmosphere of the first calcination was adjusted to a vacuum atmosphere.

[0086] Example 4

[0087] The positive electrode materials NM, NMT and NMF were prepared respectively in the manner of Example 1, except that LiOH was replaced by Li2CO3. The pre-sintering temperature of the three positive electrode materials was 230°C, and the crystallization temperature was 810°C.

[0088] Comparative Example 1

[0089] Positive electrode materials NM, NMT and NMF were prepared respectively in the manner of Example 2, except that the pre-sintering temperature was adjusted to 500°C.

[0090] Comparative Example 2

[0091] The positive electrode materials NM, NMT and NMF were prepared respectively in the manner of Example 2, except that no pre-sintering was performed.

[0092] Comparative Example 3

[0093] The positive electrode materials NM, NMT and NMF were prepared respectively in the manner of Example 4, except that the pre-sintering temperature was 500° C. and the entire sintering atmosphere was oxygen.

[0094] Performance Testing

[0095] Test Example 1

[0096] The cathode material obtained in Example 1 was subjected to a scanning electron microscope test, and the obtained SEM test images are shown in Figures 1 to 7, wherein Figure 1 is an SEM image of the NM precursor, Figure 2 is a high-magnification local SEM image of the NM precursor, Figure 3 is an SEM image of the NM layered structure cathode material, Figure 4 is a high-magnification local SEM image of the NMT precursor, Figure 5 is a low-magnification wide-area SEM image of the NMT precursor, Figure 6 is a high-magnification local SEM image of the NMT layered structure cathode material, and Figure 7 is a low-magnification wide-area SEM image of the NMT layered structure cathode material;

[0097] As can be seen from Figures 1 to 7, the precursor of the cobalt-free layered cathode material is a spherical secondary particle formed by the agglomeration of nano-sheet-shaped primary grains. After the precursor is mixed with the lithium source and sintered, the spherical secondary particles are still maintained and the primary particles are polyhedral. The material particle size is 4 to 10 μm, and the size is uniform and dispersed.

[0098] Test Example 2

[0099] The positive electrode materials obtained in the embodiment and the comparative example were subjected to X-ray diffraction test, and the obtained XRD patterns are shown in the figure;

[0100] 8 is an XRD diagram of the NM precursor and NM positive electrode material obtained in Example 1. It can be seen from FIG8 that the coprecipitation method prepared a layered The structure is cobalt-free precursor, and the precursor is mixed with a certain proportion of lithium source and then sintered to obtain α-NaFeO2 type Cobalt-free cathode materials with layered structures;

[0101] FIG9 is an XRD diagram of the NM positive electrode materials obtained in Example 1, Comparative Example 1 and Comparative Example 2, wherein “without pre-sintering” is Comparative Example 2, “pre-sintering at high temperature” is Comparative Example 1, and “with low temperature pre-sintering” is Example 1. As can be seen from FIG9 , under the same high temperature sintering conditions, the (006) / (012) peak and (018) / (110) peak of the XRD diffraction peak of the cobalt-free positive electrode material without the pre-sintering stage do not show obvious splitting, and the intensity ratio of the (003) peak to the (104) peak is only 0.57, which is much smaller than 1.2, indicating that it does not form a layered structure. The I of the cobalt-free positive electrode material pre-sintered at high temperature is (003) / I (104) The ratio is 1.12<1.2, indicating that it does not form a good layered structure, while the cobalt-free cathode material I pre-sintered at low temperature (003) / I (104)The ratio is 1.21>1.2. Compared with the first two, the low-temperature Li / H exchange promotes the formation of layered structure, forming a good cobalt-free layered structure cathode material.

[0102] FIG10 is an XRD pattern of the positive electrode materials NM, NMT and NMF obtained in Example 1, and FIG11 is a local view of the 003 peak. It can be seen from FIG10 and FIG11 that the low-temperature pre-calcination of NM, NMT and NMF in an air atmosphere inhibits the disintegration of the layered structure of the hydrogen and oxygen precursors and promotes Li / H exchange to form a metastable intermediate that has been converted into a layered structure. In the later high-temperature insulation process, it is converted into a good layered structure (I (003) / I (104) >1.2), and the lattice parameter c of NM, NMF, and NMT increases in sequence;

[0103] FIG13 is an XRD pattern of the positive electrode materials NM, NMT and NMF obtained in Example 2. FIG13 shows that NM, NMT and NMF are pre-calcined at low temperature in an oxygen atmosphere. During the Li / H exchange, the oxygen atmosphere accelerates the disintegration of the layered hydrogen and oxygen precursors, and the Li / H exchange is insufficient. Therefore, the layered structure formed is more highly arranged than the Li / Ni mixed structure of Example 1 (I (003) / I (104) The ratio is lower than that of Example 1);

[0104] FIG14 is an XRD pattern of the positive electrode materials NM, NMT and NMF obtained in Example 3. FIG14 shows that NM, NMT and NMF are pre-sintered at low temperature in a vacuum atmosphere and then kept at high temperature for the highest degree of Li / Ni mixing (I (003) / I (104) The ratio is the lowest relative to Example 1 and Example 2).

[0105] FIG15 is an XRD pattern of the positive electrode materials NM, NMT and NMF obtained in Comparative Example 1. FIG15 shows that NM, NMT and NMF do not undergo Li / H exchange during high temperature pre-sintering (500° C.) due to the rapid disintegration of the quasi-layered hydrogen and oxygen precursors. Therefore, no metastable intermediates that can promote the transformation to a layered structure are formed, resulting in no good layered structure being formed during the high temperature sintering stage (I (003) / I (104) <1.2).

[0106] FIG16 is an XRD diagram of the positive electrode materials NM, NMT and NMF obtained in Example 4. As can be seen from FIG16 , the Li + / H + Even if the lithium source is replaced by LiOH with Li2CO3 (~723℃), which requires a higher melting point, a good layered structure (I (003) / I(104) >1.3) Cobalt-free cathode materials are beneficial for Li + / H + The exchange preparation of cobalt-free positive electrode materials is close to industrial production.

[0107] FIG17 is an XRD diagram of the positive electrode materials NM, NMT and NMF obtained in Comparative Example 3. As can be seen from FIG17 , compared with Example 4, the high temperature pre-calcination causes the layered structure of the hydrogen and oxygen precursor to disintegrate rapidly and miss the early Li + / H + Even if the sintering atmosphere is high-purity oxygen, the NM and NMT do not form a good layered structure (I (003) / I (104) <1.2).

[0108] Test Example 3

[0109] The NMF cathode materials obtained in Example 1 and Comparative Example 1 were assembled into batteries and the electrochemical performance was tested. The assembly process was as follows: 1. The cathode material, PVDF, and conductive carbon black were dissolved in NMP and mixed evenly to form a cathode slurry; 2. The cathode material was evenly coated on aluminum foil, dried, and rolled to obtain a cathode sheet (load mass 3.5-6 g / cm 2 ), 3. Assemble the positive electrode shell, positive electrode sheet, diaphragm, negative electrode, metal gasket, and spring negative electrode shell into a button battery in a glove box;

[0110] The obtained cycle performance curve is shown in FIG12 , where the “cobalt-free layered material with Li / H exchange” is Example 1 and the “cobalt-free layered material without Li / H exchange” is Comparative Example 1. As can be seen from FIG12 , at 0.1C, >180 mAh·g can be released. -1 The specific capacity and the charge and discharge capacity retention rate are >85% after 100 cycles.

[0111] The NM, NMF, and NMT cathode materials obtained in Example 4 were assembled into batteries and their electrochemical performance was tested. The assembly process was as follows: 1. The cathode material, PVDF, and conductive carbon black were dissolved in NMP and mixed evenly to form a cathode slurry; 2. The cathode material was evenly coated onto aluminum foil, dried, and rolled to form a cathode sheet (load mass 3.5-6 g / cm2); 3. The cathode shell, cathode sheet, separator, anode, metal gasket, and spring-formed anode shell were assembled into a button cell in a glove box;

[0112] The obtained cycle performance curve is shown in Figure 18. When the lithium source is replaced with Li2CO3 and Li / H exchange is used at a crystallization temperature of 810℃, NM, NMF, and NMT can all release more than 180mAh·g at 0.1C. -1The first-week discharge capacity of NMF and NMT is slightly lower than that of NM, but the capacity retention rate is significantly improved.

[0113] Although the above embodiment provides a detailed description of the present application, it is only a part of the embodiments of the present application, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present application.

Claims

1. A method of utilizing Li + / H + The method for preparing a cobalt-free layered cathode material by exchange is characterized in that: The following steps are involved: adding a metal sulfate solution, a precipitant solution, and a complexing agent solution dropwise into an ammonia solution to carry out a precipitation and complexation reaction to obtain a hydroxide precursor; The hydroxide precursor and the lithium source are mixed, and pre-sintered and crystallized in sequence to obtain the cobalt-free layered positive electrode material; the pre-sintering temperature is lower than the crystallization temperature; The metal sulfates are at least two non-cobalt transition metal sulfates.

2. The preparation method according to claim 1, characterized in that The metal sulfate includes a mixed salt of nickel sulfate and manganese sulfate, or a mixed salt of nickel sulfate, manganese sulfate and ferrous sulfate, or a mixed salt of nickel sulfate, manganese sulfate and titanium sulfate.

3. The preparation method according to claim 2, characterized in that The mixed salt of nickel sulfate and manganese sulfate contains 2+ and Mn 2+ The molar ratio is 8-9.5:0.5-2; The mixed salt of nickel sulfate, manganese sulfate and ferrous sulfate contains 2+ 、Mn 2+ and Fe 2+ The molar ratio is 8-9.5:0.45-1.95:0.05-0.5; The mixed salt of nickel sulfate, manganese sulfate and titanium sulfate contains 2+ 、Mn 2+ and Ti 2+ The molar ratio is 8~9.5:0.45~1.95:0.05~0.

5.

4. The preparation method according to claim 1, characterized in that The concentration of the metal sulfate solution is 1.8 to 2 mol / L; The precipitant in the precipitant solution includes sodium hydroxide and / or potassium hydroxide; the concentration of the precipitant solution is 4 to 6 mol / L; The complexing agent in the complexing agent solution includes ammonium hydroxide; the concentration of the complexing agent solution is 4 to 10 mol / L; The concentration of the ammonia solution is 0.5 to 2 mol / L; The volume ratio of the metal sulfate solution, the precipitant solution, the complexing agent solution and the ammonia solution is 100-300:100-300:50-200:2590-2700.

5. The preparation method according to claim 1 or 4, characterized in that The droplet acceleration rate of the metal sulfate solution is 0.4-0.8 mL / min; the droplet acceleration rate of the precipitant solution is 0.4-0.8 mL / min; and the droplet acceleration rate of the complexing agent solution is 0.2-0.4 mL / min.

6. The preparation method according to claim 1, characterized in that The temperature of the precipitation complexation reaction is 50-60° C., and the reaction time is 20-60 hours.

7. The preparation method according to claim 1, characterized in that The molar ratio of the hydroxide precursor to the lithium source is 1:1.05-1.

2.

8. The preparation method according to claim 1, characterized in that The pre-sintering temperature is 150-300° C., and the heat preservation time is 6-10 hours. The pre-sintering is carried out under oxygen, air or vacuum conditions.

9. The preparation method according to claim 1, characterized in that The crystallization temperature is 810-850° C., and the holding time is 12-20 hours; the crystallization is carried out under an oxygen atmosphere.

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