A multi-stage gradient biomimetic coupled lithium battery structure and a preparation method thereof

Abstract

This invention discloses a multi-level gradient biomimetic coupled lithium battery structure and its fabrication method, relating to the field of lithium battery technology. The battery structure includes an integrated sandwich unit, a biomimetic staggered stack, distributed biomimetic current collector tabs, and an integrated hot-pressed composite layer. The sandwich unit consists of gradient-mirror-matched positive and negative electrodes and a separator. The staggered stack structure disperses stress and improves stability, while the overall shape is regular and adaptable to standard casings. The distributed tabs homogenize current and reduce heat generation, and the hot-pressed composite layer forms an integrated whole. This invention solves the technical problems of poor adaptability, high interface impedance, and insufficient mechanical and thermal stability in existing battery structures. It is adaptable to multiple types of lithium battery systems, improves battery fast-charging capability, safety, reliability, and cycle life, and possesses extremely high industrialization and patent application value.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically to a multi-level gradient biomimetic coupling lithium battery structure and its preparation method, applicable to liquid lithium batteries, semi-solid lithium batteries and all-solid lithium batteries. Background Technology

[0002] Existing lithium batteries generally adopt traditional wound or stacked structures, which are poorly adapted to the three-dimensional gradient characteristics of multi-level gradient biomimetic composite electrodes and separators, resulting in the following technical defects: First, the bending stress concentration of the wound structure makes the three-dimensional gradient electrode skeleton prone to breakage and debris shedding, inducing the risk of micro-short circuits; Second, the uneven interlayer pressure and poor interface contact of the traditional stacked structure lead to high interface impedance and severe polarization, limiting fast charging performance; Third, the uneven wetting of the electrolyte between layers results in large concentration polarization and rapid capacity decay during cycling; Fourth, the concentrated current distribution of the electrode tabs leads to severe local heating and poor thermal stability; Fifth, the overall structure does not form an integrated biomimetic interconnection network, resulting in weak vibration and shock resistance, making it difficult to adapt to extreme operating conditions such as vehicle and energy storage applications. Currently, a small number of novel battery structure studies focus only on the optimization of stacking methods or tab designs in a single dimension, without systematically coupling designs for multi-level gradient biomimetic composite positive and negative electrodes and separators. This makes it impossible to achieve multi-dimensional synergistic optimization of structure, mechanics, and ion transport, resulting in poor industrial adaptability and difficulty in meeting the application requirements of high-safety, high-rate, and long-life lithium batteries. Summary of the Invention

[0003] Technical issues To address the shortcomings of existing technologies, this invention provides a multi-level gradient biomimetic coupled lithium battery structure and its preparation method. This solves the technical problems of poor compatibility between existing battery structures and multi-level gradient biomimetic composite electrodes / separators, high interface impedance, insufficient mechanical stability, poor thermal stability, weak cycle stability, and susceptibility to technological circumvention. It achieves deep coupling between the battery structure and three-dimensional gradient materials, thereby improving the battery's fast charging performance, safety and reliability, cycle life, and vibration and shock resistance. Technical solution A multi-level gradient biomimetic coupled lithium battery structure The multi-level gradient biomimetic coupled lithium battery structure includes an integrated sandwich unit, a biomimetic staggered stack, a distributed biomimetic current collector tab, and an integrated hot-pressed composite layer. The "bionic" described in this invention mimics the three-dimensional fiber interweaving, multi-level gradient pores, and layered and interlaced structural features naturally present in biological tissues (such as bones, tendons, and plant vascular bundles). This type of biological structure has the characteristics of high mechanical stability, directional material transport, and resistance to vibration and shock. This invention applies it to the design of lithium battery materials and structures to solve the technical pain points of poor adaptability and insufficient stability of existing technologies. The integrated sandwich unit is composed of a multi-level gradient biomimetic composite positive electrode, a multi-level gradient biomimetic coupling composite separator, and a multi-level gradient biomimetic composite negative electrode that are tightly bonded together in sequence. The gradient directions of the three components are strictly mirror-aligned to form a continuous channel for ion gradient transport. The overall thickness of the integrated sandwich unit is 80–200 μm, and the dimensional consistency tolerance is ≤ ±5 μm. The biomimetic staggered stack is composed of multiple integrated sandwich units stacked in a biomimetic staggered manner along the thickness direction; adjacent integrated sandwich units are staggered laterally by 10–30% and staggered longitudinally at a micro angle of 3–8°; the overall outer contour is kept regular and aligned during the stacking process, and the final stack is a standard cuboid shape; the number of stacking layers is 20–200, and the overall thickness of the stack is 2–40mm; The distributed biomimetic current collector adopts a multi-point distributed lead-out design, with positive and negative electrodes evenly distributed on both sides of the stack. The number of electrodes on each side is 2–4, and the electrode material is a titanium foil / copper foil biomimetic interwoven composite strip with a thickness of 50–200μm and a width of 5–20mm. An integrated hot-pressed composite layer is wrapped around the outside of the biomimetic staggered stack. The interfaces of each layer are tightly bonded through a hot-pressing process to form an integrated biomimetic interconnected whole. The hot-pressed composite layer is made of a high-temperature resistant insulating composite film with a thickness of 10–50 μm. Shell compatibility instructions: The battery structure of this invention has a standard cuboid shape, and its dimensions are compatible with existing mainstream lithium battery shells and module housings. It can be directly packaged and installed using conventional soft-pack aluminum-plastic film, square aluminum shells, or module trays without modifying existing production lines and layouts, making it highly adaptable to industrial applications. A method for fabricating a multi-level gradient biomimetic coupled lithium battery structure Fabrication of integrated sandwich unit: The multi-level gradient biomimetic composite positive electrode, the multi-level gradient biomimetic coupled composite separator, and the multi-level gradient biomimetic composite negative electrode are sequentially aligned and bonded together to ensure mirror matching of the gradient directions of the three; the integrated sandwich unit is obtained by pre-pressing using a low-temperature pre-pressing process with a pre-pressing temperature of 40–60℃, a pressure of 0.2–0.5MPa, and a holding time of 5–10min. Bionic staggered stacking: Multiple integrated sandwich units are stacked layer by layer with a lateral offset of 10–30% and a longitudinal micro-angle of 3–8°, maintaining the alignment of the outer contours throughout the process; the number of stacking layers is controlled to be 20–200, and the alignment accuracy of each unit is guaranteed to be ≤±1mm during the stacking process, resulting in a bionic staggered stack. Distributed tab welding: 2–4 distributed biomimetic current collector tabs are welded to both ends of the biomimetic staggered stack; ultrasonic welding process is used, with a welding power of 800–1500W and a welding time of 0.5–2s, to ensure that the tabs are firmly connected to the electrode current collector and the contact resistance is ≤5mΩ. Integrated hot-pressing composite: The biomimetic staggered stacked body after welding the tabs is covered with a high-temperature resistant insulating composite film and placed in a hot-pressing device for overall hot-pressing composite; the hot-pressing temperature is 80–120℃, the pressure is 0.5–1.5MPa, and the holding time is 10–30min, which eliminates the gaps between layers, strengthens the interface bonding, and forms an integrated biomimetic interconnected whole. Packaging and testing: The battery structure after hot-pressing composite is side-sealed and then tested for insulation, internal resistance, capacity and mechanical stability. Defective products are rejected to obtain the finished product of multi-level gradient biomimetic coupling lithium battery structure. Beneficial effects The integrated sandwich unit achieves mirror alignment of the positive, negative, and negative gradient directions, constructs a continuous ion gradient transport channel, significantly reduces interface impedance and concentration polarization, and significantly improves battery fast charging performance. The biomimetic staggered stacking structure effectively disperses interlayer stress through lateral misalignment and longitudinal micro-angle staggered design, improves vibration and impact resistance, avoids the breakage and debris of the three-dimensional gradient electrode skeleton, and eliminates the risk of micro short circuits from the root; at the same time, it maintains a regular overall shape and is compatible with standard housings and module installations. Distributed biomimetic current collector tabs achieve uniform current distribution, eliminate local current concentration and hot spots, reduce polarization and heat generation, and improve battery thermal stability and safety reliability. The integrated hot-pressing composite process allows the interfaces of each layer to be tightly bonded, forming an integrated biomimetic interconnected whole, which improves the overall structure and mechanical stability, and is suitable for extreme working conditions such as vehicle and energy storage. The structural design is compatible with liquid, semi-solid, and all-solid lithium battery systems. When used with multi-level gradient biomimetic composite positive and negative electrodes and separators, it can achieve a synergistic increase in battery performance. The manufacturing process adopts mature stacking, welding, and hot pressing technologies. The process is controllable, compatible with existing mass production lines, and has high product consistency, making it extremely valuable for industrial applications.

Claims

1. A multi-level gradient biomimetic coupled lithium battery structure, characterized in that, The system comprises an integrated sandwich unit, a biomimetic staggered stack, distributed biomimetic current collector tabs, and an integrated hot-pressed composite layer. The integrated sandwich unit is composed of a multi-level gradient biomimetic composite positive electrode, a multi-level gradient biomimetic coupling composite separator, and a multi-level gradient biomimetic composite negative electrode sequentially bonded together, with the gradient directions mirror-aligned, and the unit thickness is 80–200 μm. The biomimetic staggered stack is composed of multiple integrated sandwich units that are staggered laterally by 10–30% and longitudinally at a micro-angle of 3–8°, maintaining a regular outer contour during the stacking process, with 20–200 stacked layers. The distributed biomimetic current collector tabs are distributed at multiple points on both end faces, with 2–4 tabs on each side, and are made of titanium foil / copper foil biomimetic interwoven composite strips. The integrated hot-pressed composite layer covers the outside of the stack and is a high-temperature resistant insulating composite film.

2. The multi-level gradient biomimetic coupled lithium battery structure according to claim 1, characterized in that, The dimensional consistency tolerance of the integrated sandwich unit is ≤ ±5μm.

3. The multi-level gradient biomimetic coupled lithium battery structure according to claim 1, characterized in that, The distributed biomimetic current collector tabs are 50–200 μm thick and 5–20 mm wide.

4. The multi-level gradient biomimetic coupled lithium battery structure according to claim 1, characterized in that, The thickness of the integrated hot-pressed composite layer is 10–50 μm.

5. A method for fabricating a multi-level gradient biomimetic coupled lithium battery structure, characterized in that, Includes the following steps: (1) Align and bond the multi-level gradient biomimetic composite positive electrode, separator and negative electrode, and pre-press at low temperature of 40–60℃ and 0.2–0.5MPa to prepare an integrated sandwich unit; (2) Multiple integrated sandwich units are staggered laterally by 10–30% and stacked longitudinally at a micro-angle of 3–8°, maintaining a regular outer contour throughout the process, to obtain a biomimetic staggered stacked body; (3) Weld 2–4 distributed biomimetic current collector tabs to both ends of the stack; (4) Cover with a high-temperature resistant insulating composite film, and hot-press composite at 80–120℃ and 0.5–1.5MPa to form an integrated whole; (5) Packaging and testing to obtain the finished battery structure.

6. The preparation method according to claim 5, characterized in that, Low-temperature pre-compression and heat preservation time: 5–10 min.

7. The preparation method according to claim 5, characterized in that, The electrode tabs are welded using ultrasonic welding with a power of 800–1500W and a time of 0.5–2s.

8. The preparation method according to claim 5, characterized in that, The overall hot-pressing composite insulation time is 10–30 minutes.