Lithium titanate material, lithium titanate negative electrode, battery and dynamic impedance matching management method

Abstract

The invention relates to the technical field of batteries, in particular to a lithium titanate material, a lithium titanate negative electrode, a battery and a dynamic impedance matching management method, and the lithium titanate material can be used for preparing the negative electrode of the battery. The preparation method of the lithium titanate material comprises the following steps: mixing titanium oxide, lithium carbonate and a niobium source, adding an alcohol solvent, carrying out ball milling, and then carrying out spray drying to prepare precursor microspheres; sintering the precursor microspheres in a protective atmosphere; the preparation method of the negative electrode comprises the following steps: coating slurry on a negative electrode current collector by adopting a gradient coating process so as to sequentially form a first coating layer and a second coating layer along the thickness direction of the negative electrode current collector; wherein the solid content of the slurry for coating the first coating layer is larger than that of the slurry for coating the second coating layer, so that the porosity of the first coating layer is smaller than that of the second coating layer. The negative electrode prepared from the lithium titanate material can ensure a relatively high capacity retention ratio in long-term circulation of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a lithium titanate material, a lithium titanate negative electrode, a battery and a dynamic impedance matching management method. BACKGROUND

[0002] The lithium titanate battery has the advantages of long cycle life (up to 10,000 times or more), excellent fast charging performance (10-20 minutes to full charge), good low temperature performance (normal charging and discharging at -30℃), etc., and has been widely used in new energy vehicles, energy storage power stations and other fields.

[0003] The lithium titanate battery provided by the related art needs to perform "grouping" operation on a large number of battery monomers in the production process, that is, monomers with high consistency in parameters such as capacity, internal resistance and voltage are selected to form a battery, so as to avoid the imbalance of charging and discharging caused by the difference between monomers, and to avoid the performance degradation, bulging, and even fire and other safety problems of the battery.

[0004] However, the lithium titanate battery provided by the related art will still have the problem of consistency decrease due to the difference in the aging speed of monomers in long-term cycling, thereby reducing the overall life of the battery. SUMMARY

[0005] The purpose of the present application is to provide a lithium titanate material, a lithium titanate negative electrode, a battery and a dynamic impedance matching management method, which can be used to prepare a negative electrode of a battery, and can maintain good consistency in long-term cycling, that is, can ensure a high capacity retention rate in long-term cycling; and the dynamic impedance matching management method can further ensure that the battery maintains good consistency in long-term cycling.

[0006] The present application is implemented as follows: In a first aspect, the present application provides a lithium titanate material and a preparation method of a lithium titanate negative electrode material, comprising: mixing titanium oxide, lithium carbonate and niobium source, adding alcohol solvent for ball milling, and then spray drying to obtain precursor microspheres; sintering the precursor microspheres under a protective atmosphere.

[0007] In an optional embodiment, the mass of the niobium source accounts for 0.3-0.7wt% of the total mass of the titanium oxide and the lithium titanate.

[0008] In an optional embodiment, the sintering temperature is 800-900℃.

[0009] In a second aspect, the present application provides a lithium titanate negative electrode and a preparation method of a lithium titanate negative electrode, comprising: mixing the lithium titanate material of any one of the preceding embodiments with an adhesive to obtain a slurry; The slurry is coated on the negative current collector by gradient coating process to form a first coating layer and a second coating layer along the thickness direction of the negative current collector; wherein the solid content of the slurry for coating the first coating layer is greater than the solid content of the slurry for coating the second coating layer, so that the porosity of the first coating layer is less than the porosity of the second coating layer.

[0010] In an optional embodiment, the solid content of the slurry for coating the first coating layer is 60±5%; and the solid content of the slurry for coating the second coating layer is 40±5%.

[0011] In an optional embodiment, the porosity of the first coating layer is 10-15%; and the porosity of the second coating layer is 25-35%.

[0012] In a third aspect, the present application provides a battery, which comprises the lithium titanate material of any one of the preceding embodiments, or the lithium titanate negative electrode of any one of the preceding embodiments.

[0013] In an optional embodiment, the surface of the positive current collector of the battery is embedded with copper micro-networks with a line width of 40-60 μm and an opening rate of 35-45%.

[0014] In an optional embodiment, the tab of the battery is connected by elastic conductive glue.

[0015] In a fourth aspect, the present application provides a dynamic impedance matching management method for managing the battery of any one of the preceding embodiments. The dynamic impedance matching management method comprises: detecting real-time state parameters of the battery, and calculating the internal impedance of the battery according to the real-time state parameters; in the case where the calculated internal impedance does not meet the preset impedance, controlling the battery with greater active equalization current to perform energy transfer, and / or, heating or cooling the battery.

[0016] The present application has the following advantages: The lithium titanate material provided by the embodiments of the present application, when prepared, by calcining the precursor microspheres, makes Nb 5+ substitute part of Ti 4+ enter the spinel lattice (space group F d3m ), introduces oxygen vacancies, and improves the lithium ion diffusion coefficient to 4×10 -8 ~6×10 - 8 cm 2 / s, which is 120%-180% higher than that of the undoped material, so as to improve the consistency of the material.

[0017] The lithium titanate negative electrode provided by the embodiment of the present application comprises the aforementioned lithium titanate material, the lithium titanate material itself has good consistency, and can maintain a high capacity retention rate after long-term cycling; meanwhile, when the negative electrode material is coated with slurry, gradient coating is adopted, so that the porosity of the first coating layer close to the negative electrode current collector is smaller than that of the second coating layer far from the negative electrode current collector, that is, the first coating layer can be used as a compaction zone to ensure the mechanical strength of the negative electrode current collector, and the second coating layer can be used as a loose zone to facilitate the infiltration and storage of electrolyte when the negative electrode is used in a battery, thereby reducing the lithium ion migration impedance difference.

[0018] The battery provided by the embodiment of the present application comprises the aforementioned lithium titanate material or lithium titanate negative electrode, and the battery still has a good capacity retention rate after long-term cycling.

[0019] The dynamic impedance matching management method provided by the embodiment of the present application is used for managing the aforementioned battery, and can real-time regulate and control the running state of the battery to improve the capacity retention rate of the battery after long-term cycling. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0021] Figure 1 SEM micrograph of the mesoporous microspheres of lithium titanate powder of the present disclosure. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely. The specific conditions are not specified in the embodiments, and are carried out according to conventional conditions or manufacturer's recommended conditions. The reagents or instruments used are not specified by the manufacturer, and are conventional products that can be purchased on the market.

[0023] The lithium titanate battery provided by the related art needs to perform "grouping" operation on a large number of battery monomers in the production process, that is, the monomers with high consistency in parameters such as capacity, internal resistance and voltage are selected to form a battery, so as to avoid the imbalance of charging and discharging caused by the difference between monomers, and to avoid the safety problems such as performance degradation, bulging and even fire of the battery.

[0024] However, the inventors have found that the "grouping" operation needs to be screened by capacity, internal resistance and voltage (consistency requirement ±3% or less), which takes 30% to 40% of the overall production cycle, and the qualified rate is only 85% to 90%, resulting in high cost.

[0025] More importantly, even if "matching", the lithium titanate battery provided by the related art still has the problem of consistency decline due to the difference in the aging speed of single cells in long-term cycles, reducing the overall life of the battery; the reason is that lithium titanate nanoparticles are prone to agglomeration, the particle size deviation is often > 15%, and the capacity dispersion is expanded with the number of cycles (after 1000 cycles > 10%) due to the difference in the utilization rate of active substances in the cycle.

[0026] In order to improve the above problems, the present disclosure provides a lithium titanate material which can be used to prepare the negative electrode of a battery, which can maintain good consistency in long-term cycles, that is, can ensure a high capacity retention rate in long-term cycles. At the same time, the present disclosure also provides a dynamic impedance matching management method for managing the battery to ensure that the battery maintains good consistency in long-term cycles.

[0027] The preparation method of the lithium titanate material provided by the present disclosure includes: Mixing titanium oxide (TiO2), lithium carbonate (Li2CO3) and niobium source (for example: di-niobium pentoxide, Nb2O5), adding alcohol solvent for ball milling, and then spray drying to obtain precursor microspheres; Sintering the precursor microspheres under a protective atmosphere to obtain mesoporous microsphere lithium titanate powder (SEM micro-morphology diagram as shown in Figure 1 ).

[0028] By calcining the precursor microspheres, Nb 5+ substitutes part of Ti 4+ into the spinel lattice (space group F d3m ), introduces oxygen vacancies, and improves the lithium ion diffusion coefficient to 4×10 -8 ~6×10 -8 cm 2 / s, which is 120%~180% higher than that without doping, and does not need to be "matched", which can also improve the consistency of the material.

[0029] The inventors have found that the lithium titanate material of the present disclosure, through its preparation process, realizes material and structure optimization, so that the single cell capacity deviation is ≤3%, and the internal resistance deviation is ≤5mΩ; the initial capacity difference of the battery prepared by using the lithium titanate material as the negative electrode is ≤1.5%, the capacity consistency after 5000 cycles is > 98%, and the capacity retention rate is > 90%.

[0030] Moreover, the lithium titanate material of the present disclosure does not need to be "matched", which can improve the production efficiency (roughly can improve the efficiency by 40%), and can improve the utilization rate of the material (roughly can be improved to more than 98%), and the comprehensive cost can be reduced by 20~30%.

[0031] Optionally, the mass of the niobium source accounts for 0.3-0.7wt% of the total mass of the titanium oxide and the lithium titanate, for example, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, etc., which is not specifically limited herein.

[0032] Optionally, the molar ratio of Li and Ti is 0.85±0.05, for example, 0.80, 0.85, 0.90, etc., which is not specifically limited herein.

[0033] Optionally, the alcohol solvent includes ethanol, methanol, etc., which is not specifically limited herein.

[0034] Optionally, the rotation speed of the ball milling is 300-500r / min, for example, 300r / min, 400r / min, 500r / min, etc., which is not specifically limited herein.

[0035] Optionally, the inlet air temperature of the spray drying is 200-250℃ (for example, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, etc., which is not specifically limited herein), and the exhaust air temperature is 80-120℃ (for example, 80℃, 90℃, 100℃, 110℃, 120℃, etc., which is not specifically limited herein).

[0036] Optionally, the protective atmosphere of the sintering includes but is not limited to argon atmosphere.

[0037] Optionally, the temperature of the sintering is 800-900℃, for example, 800℃, 820℃, 850℃, 880℃, 900℃, etc., which is not specifically limited herein.

[0038] It should be noted that the time of the sintering is not specifically limited, including but not limited to 5h, 6h, 7h.

[0039] Optionally, after the sintering and cooling, the product can be crushed and sieved.

[0040] Optionally, the particle size of the prepared precursor microspheres is 10-20μm, for example, 10μm, 12μm, 15μm, 18μm, 20μm, etc., which is not specifically limited herein.

[0041] Optionally, the mesopore size of the prepared precursor microspheres is 2-5nm, for example, 2nm, 3nm, 4nm, 5nm, etc.; the specific surface area is 80-100m 2 / g, for example, 80m 2 / g, 85m 2 / g, 90m 2 / g, 95m 2 / g, 100m 2 / g, etc., which is not specifically limited herein; the size deviation of the particles is less than 5%.

[0042] The present disclosure also provides a lithium titanate negative electrode, a preparation method thereof comprising: Mixing the lithium titanate material and the binder to obtain a slurry; Coating the slurry on the negative electrode current collector by gradient coating to form a first coating layer and a second coating layer along the thickness direction of the negative electrode current collector; wherein the solid content of the slurry for coating the first coating layer is greater than the solid content of the slurry for coating the second coating layer, so that the porosity of the first coating layer is less than the porosity of the second coating layer.

[0043] The lithium titanate material itself has good consistency and can maintain a high capacity retention rate after long-term cycling; at the same time, when the slurry is coated, gradient coating is adopted, so that the porosity of the first coating layer close to the negative electrode current collector is less than the porosity of the second coating layer away from the negative electrode current collector, that is, the first coating layer can be used as a compaction zone to ensure the mechanical strength of the negative electrode current collector, and the second coating layer can be used as a loose zone to facilitate the infiltration and storage of electrolyte when the negative electrode is used in a battery, thereby reducing the impedance difference of lithium ion migration.

[0044] Optionally, the solid content of the slurry for coating the first coating layer is 60±5%, for example, 55%, 60%, 65%, etc., which is not limited herein; the solid content of the slurry for coating the second coating layer is 40±5%, for example, 35%, 40%, 45%, etc., which is not limited herein.

[0045] Optionally, the porosity of the first coating layer is 10-15%, for example, 10%, 12%, 15%, etc., which is not limited herein; the porosity of the second coating layer is 25-35%, for example, 25%, 28%, 30%, 32%, 35%, etc., which is not limited herein.

[0046] It should be noted that the amount of lithium titanate negative electrode material and binder used to prepare the slurry can be selected as needed, for example, 90:10, 95:5, 88:12, etc.

[0047] It should also be noted that when the first coating layer and the second coating layer are formed by coating, different amounts of organic solvents can be mixed into the slurry to achieve this.

[0048] Optionally, the binder is selected similarly to related technologies, for example, PVDF binder (polyvinylidene fluoride binder) can be selected; correspondingly, the organic solvent is also selected similarly to related technologies, for example, NMP (N-methyl pyrrolidone) can be selected.

[0049] Optionally, after the first coating layer and the second coating layer are prepared, the electrode piece can also be rolled and cut.

[0050] Optionally, the negative current collector can be a copper foil, which is not specifically limited herein.

[0051] The battery provided by the present disclosure uses the aforementioned lithium titanate negative material, and still has a good capacity retention rate after long-term cycling.

[0052] Optionally, the surface of the positive current collector of the battery is embedded with copper micro-networks with a line width of 40-60 μm (for example, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, etc., which are not specifically limited herein) and an opening rate of 35-45% (for example, 35%, 38%, 40%, 42%, 45%, etc., which are not specifically limited herein). In this way, a transverse current shunt network can be formed, so that the surface current density deviation is <5%.

[0053] Optionally, the tab of the battery is connected by elastic conductive glue. Through gradient coating of the lithium titanate negative electrode and use of the elastic conductive glue, self-balancing of the battery structure can be achieved. The elastic conductive glue can adapt to displacement to achieve compensation of ±0.2 mm.

[0054] Optionally, the elastic conductive member can be a silicone rubber conductive adhesive containing silver-coated copper particles (silver layer thickness: 50-100 nm, for example, isotropic conductive adhesive specified in QC / T1127-202X, silver-coated copper filler content is recommended to be ≥70%, and the base glue is a high-temperature curing rubber), and the conductivity is >10 4 S / cm, which can adapt to thermal expansion displacement of ±0.2 mm, maintain a contact resistance of <5 mΩ, and maintain a module static pressure difference of <5 mV.

[0055] It should be noted that the positive material, electrolyte, and related technology of the battery are similar, and are not specifically limited herein.

[0056] It should also be noted that the battery of the present disclosure can be used in new energy vehicles, energy storage systems, etc., and has strong compatibility.

[0057] The present disclosure also provides a dynamic impedance matching management method for the above-mentioned battery, which comprises: detecting real-time state parameters of the battery, calculating the internal impedance of the battery according to the real-time state parameters; in the case where the calculated internal impedance does not meet the preset impedance, controlling the battery with a larger active balancing current to perform energy transfer, and / or heating or cooling the battery.

[0058] The management method can real-time regulate the running state of the battery to improve the capacity retention rate of the battery after long-term cycling.

[0059] The inventors have further found that the management method can real-time regulate and compensate the battery, and the battery still maintains a good capacity retention rate (capacity retention rate ≥ 80%) after 10,000 cycles.

[0060] It should be noted that the dynamic impedance matching management method of the present disclosure can also match a management system, which can integrate high-frequency monitoring and high-power active balancing to compensate for cycle differences in real time.

[0061] The hardware architecture of the above management system includes: a double-channel monitoring chip is configured for each single battery, wherein the voltage sampling accuracy is ±1mV, the temperature sampling frequency is 1kHz, and the sampled data is uploaded to the central controller through the CAN bus.

[0062] The above management system is also configured with an active balancing module, which uses an array of MOSFETs to form a bidirectional balancing circuit, and the balancing current can reach 15-25A, the response time in the fast charging (10C) stage is <10ms, and the instantaneous voltage difference is suppressed to <10mV.

[0063] Therefore, the core of the dynamic impedance matching management method of the present disclosure is a closed-loop management system through "monitoring + intelligent decision-making (i.e., real-time regulation according to the detected real-time state of the battery) + active balancing".

[0064] Among them, the monitoring can be continuously detected by a high-frequency sensor, such as the voltage, current, temperature and other parameters of the battery cell, so as to calculate the internal impedance of the battery (the impedance of the cell will dynamically change with temperature, aging degree, and charging and discharging rate) according to the detected real-time parameters using the intelligent algorithm built-in the management system.

[0065] Optionally, the detection frequency of the high-frequency sensor is 1kHz, that is, the voltage, current, temperature and other parameters of the battery cell are collected and calculated once every 1ms, and the regulation and control decision is made according to the collection and calculation results (i.e., real-time regulation and control).

[0066] Optionally, the "controlling the battery with larger active balancing current to perform energy transfer in the case that the calculated internal impedance does not meet the preset impedance" specifically includes: driving a powerful active balancing current (such as 20A energy) to perform energy transfer in the case that the calculated internal impedance does not meet the preset impedance, that is, the management system can transfer a current of up to 20A from one cell to another. This process not only has extremely high efficiency and speed, but also effectively deals with the inconsistency problem of large-capacity packs (i.e., actively matches the state of the cells and suppresses inconsistency).

[0067] It should be noted that the process of driving a strong active balancing current to transfer energy is to control the on-off of the switching device arranged on the active balancing circuit to realize accurate energy transfer; wherein the management system can be configured to make a judgment every 1 ms (i.e. every 1 ms to determine whether energy transfer is needed), and issue refrigeration according to the judgment result to control the on-off of the switching device arranged on the active balancing circuit to realize energy transfer.

[0068] Optionally, the above-mentioned "heating or cooling the battery in the case that the calculated internal impedance does not meet the preset impedance" specifically includes: when the temperature of the battery cell is detected to be as low as-20℃, starting the heater configured for the battery to heat the battery cell.

[0069] It should be understood that at low temperature, the internal resistance of the lithium titanate battery will increase sharply, and lithium precipitation will occur during charging, causing safety hazards, therefore, it is necessary to ensure that the temperature of the battery cell is not too low.

[0070] Correspondingly, in the dynamic impedance matching management method of the present disclosure, a safe charging / discharging target temperature is matched, for example: greater than or equal to 5℃.

[0071] Optionally, the above-mentioned "heating or cooling the battery in the case that the calculated internal impedance does not meet the preset impedance" specifically further includes: calculating a dynamic heating rate according to the current temperature, target temperature, battery pack heat capacity and current power of the heater of the detected battery cell, and controlling the heating time of the heater, and / or controlling the real-time power of the heater at different positions, to ensure that the temperature difference between all battery cells in the battery is ≤1.5℃. In this way, the problem of local overheating can be improved, and uniform and safe heating can be achieved.

[0072] The present disclosure will be further described in detail below in combination with embodiments.

[0073] Embodiment 1 1. Synthesis of high-consistency lithium titanate material TiO2 (purity 99.9%), Li2CO3 (Li / Ti molar ratio 0.85) and Nb2O5 (0.5wt% of Nb2O5 based on the total mass of the titanium oxide and the lithium titanate) were mixed in proportion, ball-milled in ethanol for 8 hours (rotation speed 500r / min), spray dried (inlet temperature 250℃, exhaust temperature 120℃) to obtain precursor microspheres; the microspheres were sintered at 850℃ for 6 hours in an argon atmosphere, crushed and sieved after cooling to obtain mesoporous microspherical lithium titanate powder.

[0074] 2. Self-balancing electrode preparation • Anode: Lithium titanate powder mixed with PVDF binder at a ratio of 90:10, added with NMP to make slurry, coated on copper foil using gradient coating process (the solid content of the first coating layer close to the copper foil current collector is 60%, and the solid content of the second coating layer away from the copper foil current collector is 40%), and then cut after rolling; • Cathode: ternary material (NCM) mixed with conductive carbon black and PVDF at a ratio of 92:5:3 to make slurry, coated on aluminum foil containing copper micro mesh (line width is 60 μm, and opening rate is 35%), and then cut after rolling.

[0075] 3. Single cell assembly The single cell (anode-separator-cathode) is assembled using the lamination process, electrolyte (1 mol / L LiPF6 in EC:DMC=1:1) is injected, and then the cell is packaged and formed (0.1C charging to 2.5V, standing for 2 hours).

[0076] 4. Formation of the module without preparation The single cells are arranged in a honeycomb array (the gap is filled with heat-conducting silicone grease with a thermal conductivity of 5 W / mK), the tabs are connected by laser welding and elastic conductive glue, and the integrated monitoring chip and active balancing module are integrated.

[0077] Example 2 The difference between Example 2 and Example 1 is the synthesis of high-consistency lithium titanate material and the preparation of self-balancing electrodes, and the other processes refer to Example 1.

[0078] 1. Synthesis of high-consistency lithium titanate material TiO2 (purity 99.9%), Li2CO3 (Li / Ti molar ratio 0.80), and Nb2O5 (0.3wt% of Nb2O5 based on the total mass of the titanium oxide and the lithium titanate) are mixed in proportion, ball milled in ethanol for 10 hours (rotation speed 300 r / min), and spray dried (inlet temperature 200°C, exhaust temperature 80°C) to obtain precursor microspheres; the microspheres are sintered at 800°C for 7 hours in an argon atmosphere, crushed and sieved after cooling, to obtain mesoporous lithium titanate powder.

[0079] 2. Preparation of self-balancing electrodes • Anode: Lithium titanate powder mixed with PVDF binder at a ratio of 90:10, added with NMP to make slurry, coated on copper foil using gradient coating process (the solid content of the first coating layer close to the copper foil current collector is 65%, and the solid content of the second coating layer away from the copper foil current collector is 35%), and then cut after rolling; • Cathode: ternary material (NCM) mixed with conductive carbon black and PVDF at a ratio of 92:5:3 to make slurry, coated on aluminum foil containing copper micro mesh (line width is 60 μm, and opening rate is 35%), and then cut after rolling.

[0080] Example 3 Example 3 is different from Example 1 in that the high-consistency lithium titanate material synthesis and self-balanced electrode preparation, other processes refer to Example 1.

[0081] 1. High-consistency lithium titanate material synthesis TiO2 (purity 99.9%), Li2CO3 (Li / Ti molar ratio 0.90) and Nb2O5 (the mass of Nb2O5 accounts for 0.7wt% of the total mass of the titanium oxide and the lithium titanate) were mixed in proportion, ball-milled in ethanol for 9 hours (rotation speed 400 r / min), spray dried (inlet air temperature 220℃, exhaust air temperature 100℃) to obtain precursor microspheres; the microspheres were sintered at 900℃ for 5 hours in an argon atmosphere, crushed and sieved after cooling, to obtain mesoporous microspheres of lithium titanate powder.

[0082] 2. Self-balanced electrode preparation • Negative electrode: lithium titanate powder was mixed with PVDF binder in a ratio of 90:10, NMP was added to prepare a slurry, which was coated on a copper foil using a gradient coating process (the solid content of the first coating layer close to the copper foil current collector was 55%, and the solid content of the second coating layer away from the copper foil current collector was 45%), and then cut after rolling; • Positive electrode: ternary material (NCM) was mixed with conductive carbon black and PVDF in a ratio of 92:5:3 to prepare a slurry, which was coated on an aluminum foil containing copper micro-mesh (line width 60μm, opening rate 35%), and then cut after rolling.

[0083] Comparative Example 1 Comparative Example 1 is different from Example 1 in that when preparing the lithium titanate material, the sintering temperature is 700℃; other processes refer to Example 1.

[0084] Comparative Example 2 Comparative Example 2 is different from Example 1 in that when preparing the lithium titanate material, the sintering temperature is 1000℃; other processes refer to Example 1.

[0085] Comparative Example 3 Comparative Example 3 is different from Example 1 in that when preparing the negative electrode, only one coating layer is coated on the copper foil current collector, and the solid content of the coating layer is 60%; other processes refer to Example 1.

[0086] The capacity retention rates of the batteries of Examples 1-3 and Comparative Examples 1-3 were detected after 3000 cycles, 5000 cycles and 10000 cycles (test method refers to GB / T 31484-2015), and the results are shown in Table 1.

[0087] Table 1

[0088] As can be seen from Table 1, as in Comparative Examples 1 and 2, the sintering temperature is lower or higher than the sintering temperature of the present disclosure, which will result in a decrease in the cycle capacity retention rate; and as in Comparative Example 3, only one layer is coated, and the gradient pore distribution of the present disclosure is not formed, which will also result in a decrease in the cycle capacity retention rate.

[0089] In summary, the lithium titanate material of the present application can be used to prepare the negative electrode of the battery, which can maintain good consistency in long-term cycling, i.e., can ensure a high capacity retention rate in long-term cycling; and the dynamic impedance matching management method can further ensure that the battery maintains good consistency in long-term cycling.

[0090] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A lithium titanate material, characterized in that, The preparation method of the lithium titanate anode material includes: Precursor microspheres were prepared by mixing titanium dioxide, lithium carbonate and niobium source, adding alcohol solvent and ball milling, and then spray drying. The precursor microspheres were sintered under a protective atmosphere.

2. The lithium titanate material according to claim 1, characterized in that, The niobium source accounts for 0.3 to 0.7 wt% of the total mass of the titanium oxide and the lithium titanate.

3. The lithium titanate material according to claim 1, characterized in that, The sintering temperature is 800~900℃.

4. A lithium titanate anode, characterized in that, The method for preparing the lithium titanate anode includes: The lithium titanate material according to any one of claims 1-3 is mixed with an adhesive to prepare a slurry; A gradient coating process is used to coat the slurry onto the negative electrode current collector to sequentially form a first coating layer and a second coating layer along the thickness direction of the negative electrode current collector; wherein, the solid content of the slurry coating the first coating layer is greater than the solid content of the slurry coating the second coating layer, so that the porosity of the first coating layer is less than the porosity of the second coating layer.

5. The lithium titanate anode according to claim 4, characterized in that, The slurry used for coating the first coating layer has a solid content of 60±5%; the slurry used for coating the second coating layer has a solid content of 40±5%.

6. The lithium titanate anode according to claim 4, characterized in that, The porosity of the first coating layer is 10-15%; the porosity of the second coating layer is 25-35%.

7. A battery, characterized in that, The battery comprises the lithium titanate material according to any one of claims 1-3, or the lithium titanate anode according to any one of claims 4-6.

8. The battery according to claim 7, characterized in that, The surface of the positive electrode current collector of the battery is embedded with a copper micromesh with a linewidth of 40~60μm and an opening rate of 35~45%.

9. The battery according to claim 7, characterized in that, The battery tabs are connected by elastic conductive adhesive.

10. A dynamic impedance matching management method, characterized in that, For use in managing the battery as described in any one of claims 7-9; The dynamic impedance matching management method includes: The real-time state parameters of the battery are detected, and the internal impedance of the battery is calculated based on the real-time state parameters; If the calculated internal impedance does not meet the preset impedance, the battery with the larger active balancing current is controlled to transfer energy, and / or the battery is heated or cooled.

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