Method for preventing charge / discharge degradation of secondary batteries by reusing dendrites

Abstract

In secondary batteries where dendrites form, repeated charging and discharging amplifies dendrite degradation, leading to an accumulation of capacity loss. Beyond a certain point of degradation, a short circuit can occur at the electrodes, posing a fire hazard. Solving this problem is an urgent issue for rechargeable batteries, which are widely used. This invention provides a charge / discharge method that recombines dendrites in secondary batteries to prevent capacity degradation. [Solution] By discharging a secondary battery that generates dendrites and then changing the charging current value in a 360-degree 3-axis direction during charging, and maintaining this state while charging, the dendrites settle on the upper surface and detach on the lower surface, efficiently separating and accumulating the dendrites and recombining them through charging. Repeating the above prevents a decrease in the design capacity. See Figure 1.

Description

[Technical Field]

[0001] Charge and discharge method for secondary batteries [Background Art]

[0002] Secondary batteries that degrade due to dendrite formation require replacement due to capacity reduction caused by dendrite deposition These dendrites may cause short-circuits and fire hazards, which is also a serious social problem Various methods for suppressing dendrites have been proposed Development is mainly focused on dendrite suppression, and dendrites are notably prone to form on lithium metal electrodes Using carbon materials as the negative electrode avoids dendrite formation and achieves high reliability For dendrite suppression, various approaches have been investigated including functional additives, use of different elements, adjustment of electrolyte concentration, and all-solid-state batteries and various other suppression methods have been tested In the prior art, no information has been found that allows dendrite consumption and electrode restoration [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application No. Hei 3-342306 Title of the Invention: Charging method for lithium secondary battery Characteristics of the prior patent: Pulse charging breaks dendrites to prevent short-circuits and enable long-term use. Improvements of the present patent: By adding a separation and bonding process for dendrites through temperature change and sedimentation effect, dead lithium can be reused during recharging, enabling capacity recovery and state maintenance [Patent Document 2] Japanese Patent Publication No. 2007-267559 (P2007-267559A) Title of Invention: Charging Method for Secondary Batteries Features of Prior Patent: A charging method that charges with a constant current and efficiently stops full charging using voltage as a determining factor. Improvements of the Present Patent: The charging standard is based on the standard specifications of the charging mechanism, and the storage method during charging is changed to create dendrite separation and dead lithium settling action, efficiently separating and combining deteriorated parts, and a charging method that recovers capacity and avoids danger. [Patent Document 3] Japanese Patent Publication No. 2007-259602 (P2007-259602A) Title of Invention: Charging device and charging method for lithium-ion secondary battery Features of prior patent: A charging and discharging method using a charge / discharge circuit utilizing constant current and constant voltage with grounding. Improvements of this patent: A charging and discharging method that utilizes dendrite separation and the settling action of dead lithium to achieve efficient capacity recovery and avoid hazards. [Non-patent literature]

[0004] [Non-Patent Document 1] Paper Title: Dendrite-free alkali-metal electrodeposition from contact-ion-pair state induced by mixing alkaline earth cation DOI:10.1016 / j.xcrp.2022.100907 Tohoku University Graduate School of Engineering / Faculty of Engineering Characteristics of prior literature: Controlling the reaction rate and deposition morphology of lithium and sodium metal anodes by using polyvalent cation salts as additives. Improvements of this patent: Without using additives, a process of dendrite separation and dead lithium sedimentation is created through state transfer in lithium batteries, enabling efficient recombination of degraded lithium during charging, capacity recovery, and state maintenance. [Overview of the project] [Problems that the invention aims to solve]

[0005] For the negative electrode material of a rechargeable battery, metal negative electrodes have the highest charge capacity density. Its practical application is expected from the perspective of improving energy density. When alkali metal element negative electrodes are stacked, dendrites (tree-like crystals) are formed. The electrode area decreases, reducing battery capacity. The dendrite layers penetrate the separator and reach the positive electrode, posing a fire hazard. A carbon material negative electrode is used, which is expected to have an inhibitory effect. However, a fundamental solution has not been reached, and it has become a pressing social issue. To effectively utilize renewable energy and secure resources, it can be used for a long period of time. Battery development is necessary. [Means for solving the problem]

[0006] Conventional secondary battery technology has faced the challenge of degradation due to dendrites. It had remained unresolved for a long time. This invention aims to solve the problem by applying a three-step technology. This solution was successful. This addresses the problems inherent in conventional technologies, such as the causes of degradation, the risk of fire, and the need to ensure long-term capacity. In contrast, this technology brings about groundbreaking improvements and establishes a next-generation technological foundation. Normally, dendrites are developed for their inhibitory effect. There is a lack of thinking that makes reuse possible. Instead of stopping the increase, temporarily restoring the increase would increase the usable area. Furthermore, it enables high functionality. As a result of implementing the above, we observed a wide variety of effects.

[0007] We discovered that improvements could be made by performing multiple processing steps in the preliminary stages. Rechargeable products (products with an active control chip) can be used repeatedly. Identify the direction of degradation and repeat the same operation, charging and discharging, even knowing it will be difficult. The system repeatedly undergoes state changes, and charging is performed in the direction that causes the current value to increase during the initial charge. An upward trend can be an indicator of improvement in deterioration. From the above results, charging promotes the expansion of dendrites, which is "heating" Stopping charging enables contraction, i.e., "cooling" Metal fatigue (cracks) are formed by expansion and contraction, enabling dendrite fracture State movement enables sedimentation of dead lithium on the upper surface and detachment on the lower surface When a current is applied to the sedimented and accumulated material, a dissolution effect occurs and the material is recombined Thereby, the orientation in which the charging current value increases during initial charging is identified Sedimentation on the upper surface and detachment on the lower surface are enabled, thereby consuming dendrites Favorable charging efficiently restores the electrode When charging is favorable, charging is completed when the current value decreases Since the capacity is limited with a single restoration Capacity recovery is performed through repeated sedimentation-detachment-charging processes The capacity recovery value after recovery can be predicted by the battery surface area An increase in the current value can be achieved by 3-axis 360-degree movement When the battery plane is placed horizontally, sedimentation is enabled in the upward direction, and detachment is enabled in the downward direction 1st step: sedimentation, 2nd step: detachment, 3rd step: increase (combination) of the current value during initial charging (hereinafter referred to as the 3 steps) By repeating this operation, the deterioration that would have originally accumulated is efficiently consumed Capacity recovery is enabled, and in addition, dendrite consumption, which was impossible in the past, is enabled However, it is impossible to prevent deterioration, and in order to maintain a safe operating range By repeatedly performing the three steps alternately, long-term capacity is secured There is no information indicating that restoration is possible in the prior art In the future, by widely publicizing information that restoration is possible, capacity reduction and deterioration can be prevented Fire accidents can be avoided in advance [Advantageous Effects of the Invention]

[0008] By repeating the three steps, deterioration is reset and long-term capacity can be secured By detecting increases in current values ​​during charging, it becomes possible to prevent degradation before it occurs.

[0009] The range of possible improvements, where 3 steps constitute one process, can be easily predicted. By measuring the charging capacity, the next improvement timing can be predicted, reducing the number of times the process needs to be performed.

[0010] Previously, charging methods that avoided full charging were recommended. It is possible to fully charge the device and increase its available power.

[0011] By stabilizing the electrodes, the electrode area during charging is restored. This technology is expected to suppress heat generation during power transfer and minimize power loss due to heat generation.

[0012] Achieving a full charge enables continuous power connection. Fully charging ensures sufficient battery capacity. Charging is stopped, and only the power used for operating the device is consumed, thus reducing power consumption. When the charger is disconnected, it can always be fully charged, ensuring continuous operation time.

[0013] By enabling full charging, the BMS (Battery Management System) This makes simplification possible. By changing the BMS settings, system lock during over-discharge can be avoided. It can be reused even under conditions of over-discharge due to long-term storage. This reduces the balancing (averaging when using multiple batteries) required by the BMS function.

[0014] This is expected to ensure the safety of metal electrodes (lithium metal electrodes) and avoid potential hazards. Lithium metal electrodes are expected to have 10 times the capacity of carbon electrodes. If lightweight and high-capacity designs can be achieved, it may be possible to make EVs weigh as much as gasoline-powered cars.

[0015] There is no information indicating that it is possible to restore it using conventional technology. By widely publicizing that it is recoverable This makes it possible to prevent deterioration in advance and avoid fire accidents caused by deterioration.

[0016] Maintaining the charging capacity makes full charging possible. This allows the single-charge capacity of an EV to be maintained while reducing the number of charging cycles. The regenerative charging capacity will also increase. This is expected to alleviate congestion at EV charging stations. Maintaining capacity reduces the amount of battery waste, eliminating the need for resource recycling. [Brief explanation of the drawing]

[0017] [Figure 1] This represents the movement of dendrites inside the battery. 1 indicates detachment downwards from the electrode, and 2 indicates sinking after reversal. Charging causes alternating rupture, detachment, sinking, and bonding, gradually consuming the dendrites, and the bonding restores capacity. Complex degradation other than rotation utilizes a 360-degree 3-axis system. [Figure 2] In the case of a cylindrical battery powered from an AC outlet and with an ammeter measuring the current rise, the recovery process is completed by rotating the battery, measuring the current rise, continuing to charge it, stopping the charging, and then repeating the rotation until the current rises uniformly and the current value becomes 0mA. [Modes for carrying out the invention]

[0018] Under normal circumstances, the effective means of bonding is unknown. The conclusion was reached after repeated cycle tests. To recombine dendrites in a secondary battery Reducing the dendritic layer is the most effective approach. We devised a process for breaking and bonding dendrites. The fracture process utilizes the expansion and contraction caused by changes in charging temperature. The joining process utilizes inversion of the broken pieces. The lower surface detaches, while the upper surface accumulates through a sinking effect, enabling bonding through charging. The charging process is performed simultaneously with the detachment and settling process, and the charging current is measured. When you move the surface where the current value increases in the initial stages of charging upwards... We were able to enable the processes of fracture, separation, settlement, and joining simultaneously. The directions of upward movement are intricately intertwined during deterioration. It is possible to ascend in 360 degrees on 3 axes. However, it is not possible to process all deteriorated materials in a single step. When the upper surface settles and bonds, separation is progressing on the lower surface, making bonding impossible. By repeatedly performing the reversal process during and after charging, recovery bonding is made possible. Increase the usable area to prevent a decrease in design capacity. Immediately after charging, it expands due to heat, and cooling is necessary to utilize its contraction. Another method is to pause charging for a certain period of time. Repeat until the amount of degraded material that can be detached decreases. The above describes the restoration process; complete restoration is complete. Because the degradation rate due to the increased capacity over a certain period of time is slowed down. Determine the execution capacity and then execute the recovery process. For portable devices such as smartphones, charge them by alternating between the front and back sides for continuous use. Maintaining its condition prevents deterioration. [Examples]

[0019] Embodiment using CC-CV charging (Constant Current - Constant Voltage) This invention implements the charging action between the charging termination voltage (4.2V) and the discharging termination voltage (2.75V), enabling efficient prevention and recovery of capacity degradation. To explain charging and discharging more clearly, I purchased a brand new battery. The reason for using new products is to avoid the fact that deterioration conditions differ depending on how they are used. I purchased a new tablet PC battery and measured the current value after replacement. I used the current values ​​from the computer's battery report. The initial value in Table 1 below is the self-discharge value at the time of purchase (55%). When charged to the charging stop voltage using normal charging, 99% (number 1) is considered a full charge. The key to determining whether charging has stopped is to read the change in current value, and the decision can also be made after 7 hours have passed. After that, it was discharged to 3% (number 2) under normal consumption and the first recovery charge was performed, resulting in 33516mWh (number 3), showing an increase of 783mWh. The second time, it was discharged to 2% (number 4) and the recovery charge was performed. It is 35758mWh (number 5), an increase of 2242mWh. The third charge was 2% discharge (number 6), and the recovery charge was 36883mWh (number 7). The value was 1125mWh, and under subsequent use, the value at full charge did not change. Numbers 8 and above represent figures from two months later, before the restoration process was carried out. A recovery process capacity of around 2000mAh is appropriate. The important point to note is that when it stops at the initial full charge, it's not because it's fully charged, but because the voltage level has stopped. After cooling, measuring the initial charging current increase process again showed that the electrodes were stable. The required voltage decreases, making recharging possible. The cooling, expansion, and inversion process is repeated again to consume the degraded dendrites. Current value increase is possible in a 360-degree range across three axes. Skipping the cooling process and recharging is not the best approach from the perspective of expansion and contraction. This means that after charging overnight, you can leave it and use it during the day. A more effective method is to reverse the charge at a later date. By enabling capacity increases beyond the design capacity, recombination is possible. The evidence in this case was effectively executed. Note that poor performance due to inability to flow the solution at low temperatures is not covered. [Table 1]

[0020] The above describes charging and discharging at high capacity. I'm including this because smartphones are generally used to effectively utilize this feature. The one to use is Smartphone, USB A-type 5V charger, USB charging cable, USB type ammeter When charging a used smartphone, it's advantageous if the battery level is low. When charging normally, reverse the charging position by 180 degrees from the position used during the previous charge. Since long-term degradation is expected to result in layering, it is more effective to frequently use reverse charging. However, a certain amount of normal charging is effective in the sense that it provides stimulation. When seeking rapid improvement in long-term degraded products, it is effective to use an ammeter to find the initial increase in charging current, observe the situation for 15 seconds to 1 minute, alternately reverse the process to find the point where the current increases, maintain the increasing state, and if it stops, reverse it again. Holding the charge at the point where the initial increase is high is effective. Ascent is possible in 360 degrees on 3 axes. In a good charging state, the current value drops to zero, indicating a uniform state. The next time you charge it, you'll be able to maintain its condition by reversing the cycle every other day. Full charging becomes possible, and the average charging rate conserves the charge for the next use. It is effective for the battery you have on hand. [Industrial applicability]

[0021] Preventing battery capacity degradation in EV batteries Prevents range degradation and enables long-term use. Because the capacity that can be charged at once is maintained. This will help alleviate congestion at EV charging stations.

[0022] Practical application of lithium metal electrode batteries This will enable a tenfold increase in capacity compared to lithium carbon batteries. Making EVs lighter and enabling longer-distance travel beyond gasoline levels. Accelerating the spread of electric vehicles

[0023] Households that can generate their own electricity can reduce the amount of electricity they buy back. It will become possible to sell surplus electricity in the long term. It has the advantage of not requiring battery replacement.

[0024] The spread of battery storage systems is accelerating, and the demand for renewable energy is increasing. Therefore, a future without nuclear or thermal power plants is predicted.

Claims

[Claim 1] A method for preventing degradation in a secondary battery in which dendrites are generated, When a secondary battery is in a state where it can be charged and discharged, (1) While changing the orientation of the secondary battery in the three-axis 360-degree direction, It detects a posture in which the charging current value increases during the initial stages of charging. The process of charging in that position, (2) After charging stops, search again for a position in which the current value increases, The process of repeating the above charging, (3) Due to the temperature rise associated with the charging and discharging and changes in posture, Expand the dendrite, Cooling during the cessation of charging and discharging generates metal stress. The process of breaking down the dendrites, (4) The upper fragment of the dendrite that has broken due to the change in posture will sink, The process of detaching the lower fragment, (5) A step of recombining the broken fragments by recharging the settled material. Features that include A method for preventing degradation of secondary batteries by reusing dendrites.

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