March 14, 2024
Why Lithium Batteries Lose Power Over Time: Understanding the Self-Discharge Rate
Have you ever wondered why the power of mobile phones, laptops or other devices using lithium batteries will inexplicably decrease even if they are not used for a long time? This is actually a phenomenon called “self-discharge”, which is a normal physical and chemical process that exists in all batteries. Understanding the self-discharge rate of lithium batteries can not only help us better manage batteries, but also effectively extend the life of batteries (explore lithium battery life). This article will explore in depth the principles, influencing factors, and countermeasures of lithium battery self-discharge, as well as how to minimize the losses caused by self-discharge rate in daily life.
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What Is the Self-Discharge Rate of Lithium Batteries?
Self-discharge refers to the phenomenon that the amount of electricity stored in a battery spontaneously and gradually decreases when it is idle without any external circuit connected. The self-discharge rate is usually expressed as a percentage of power lost per month. For example, if a lithium battery has a self-discharge rate of 3% per month, then the battery will have a 3% reduction in power after one month without any external load.
It should be emphasized that self-discharge is an inherent characteristic of all types of batteries (including lithium-ion, lead-acid, nickel-metal hydride, etc.). There is no “zero self-discharge” battery, but the self-discharge rate of different battery chemistry systems is different.
Self-discharge Rate of Different Types of Batteries
| Battery Type | Monthly Self-Discharge Rate (%) | Typical Applications |
|---|---|---|
| Li/CFx (Energy Type) | ~0% | Long-term storage (medical, aerospace equipment) |
| LFP (Lithium Iron Phosphate) | 1–3% | Electric vehicles, energy storage, backup power |
| Standard Lithium-ion | 2–5% | Consumer electronics |
| NiMH (Standard) | 20–30% | Power tools, emergency devices |
| NiMH (Low Self-Discharge) | 1–2% | Low-maintenance backup power |
| NiCd (Nickel-Cadmium) | 15–30% | Industrial equipment (phasing out) |
| Lead-acid | 5–15% | Vehicle starting, UPS systems |
As can be seen from the above table, different types of lithium batteries have different self-discharge rates. Lithium iron phosphate (LiFePO4 ) batteries usually have a lower self-discharge rate of between 1%-3%, while ordinary lithium-ion batteries are between 2%-5%.
Why Do Lithium Batteries Self-Discharge?
The self-discharge of lithium batteries is a complex process, which is affected by many factors and can be roughly summarized into the following three aspects:
Inevitable Chemical Side Reactions (Normal Self-Discharge)
- Growth and Dissolution of SEI film
- Oxidation/Reduction of Electrolyte
- Impurity Reactions in Active Materials
Internal Micro Short Circuits (Caused by Manufacturing Defects or Aging)
- Diaphragm Defects
Tiny pinholes, impurities or weak points on the diaphragm may cause tiny electronic conduction (micro short circuit) between the positive and negative electrodes after charge and discharge cycles or long-term storage, directly causing charge leakage. This is the main cause of abnormally high self-discharge. In addition, although the diaphragm prevents electron conduction at a macro level and only allows ions to pass through. At the micro level, the electrode material itself or the conductive agent network may form an extremely weak electron leakage path through the electrolyte.
- Dendrite Penetration
In batteries that are overcharged, charged at low temperatures or severely aged, lithium metal may be unevenly deposited on the negative electrode surface to form dendrites. Sharp dendrites may penetrate the diaphragm, connect the positive and negative electrodes, and cause lithium battery internal short circuits.
- Metal Dust During the Manufacturing Process
Metal dust introduced during the production process (such as that generated when cutting electrodes) may also cause micro short circuits if it remains between the electrodes or diaphragms. Absolute dust-free production is impossible. When the dust is not enough to pierce the diaphragm and cause the positive and negative electrodes to short-circuit, its impact on the battery is not significant; but when the dust is serious enough to pierce the diaphragm, the impact on the battery will be very obvious.
Temperature Effect
Temperature is one of the most critical influencing factors. The higher the temperature, the faster the rate of all chemical reactions that lead to self-discharge (SEI film evolution, electrolyte decomposition, impurity reaction, etc.), and the self-discharge rate rises sharply. Therefore, long-term storage of batteries should be carried out at low temperatures (but avoid freezing).
Impact of Lithium Battery Self-Discharge
- Capacity loss: The most direct impact, the battery’s available capacity is reduced.
- Voltage drop: The open circuit voltage decreases with storage time.
- Accelerated aging: Side reactions during self-discharge (such as continued growth of SEI) consume active lithium and electrolyte, which is itself an aging mechanism.
- Difficulty in estimating the state of charge: Self-discharge makes it complicated to accurately judge the remaining power based on voltage alone.
- Safety risks (extreme cases): Abnormally high self-discharge (such as severe internal micro-short circuits) may cause the battery temperature to rise and even cause thermal runaway in lithium batteries.
- Battery damage: For batteries that have been stored for a long time, if self-discharge causes the power to be exhausted to too low a voltage (deep discharge), it may also cause irreversible capacity loss, causing permanent deterioration of the battery and shortening the battery life.
How to Deal With Lithium Battery Self-Discharge?
Knowing the causes and effects of lithium battery self-discharge, we can take corresponding measures to slow down self-discharge and extend the life of the battery:
- Optimize battery design and materials: Improve the stability of the SEI film, develop electrolytes and high-purity materials with stronger oxidation resistance, and improve the quality of the diaphragm. This mainly depends on the technical research and development of battery manufacturers.
- Control storage conditions: This is a key factor that users can control.
- Temperature: The most important! Try to store the battery at low temperature (such as 10°C-25°C, avoid below 0°C). High temperature will significantly accelerate the self-discharge rate.
- Charge state: When storing for a long time, charge the battery to a medium charge state (such as 40%-60%). A fully charged state will accelerate the oxidation of the electrolyte by the positive electrode, and a completely empty state may cause the negative electrode to be over-discharged and damaged. Avoid long-term storage in a fully charged or completely exhausted state.
- Regular recharge: For batteries that have been idle for a long time, the voltage/SOC should be checked regularly, and when the power is too low, appropriate charging (such as charging to 50%) should be performed to avoid deep discharge and damage to the battery. It is recommended to check the power every 3-6 months and recharge in time.
- Avoid harsh use environments: Avoid harsh environments such as overcharging, over-discharging, high temperature, and humidity, which will accelerate battery aging and self-discharge.
- Buy batteries from regular channels: Choose batteries purchased from well-known brands (explore TYCORUN 73V 30Ah semi-solid battery for electric motorcycle) and regular channels, the quality is more guaranteed, and can effectively avoid abnormal self-discharge caused by manufacturing defects.
How to Minimize Lithium Battery Self-Discharge in Daily Life?
- Electronic devices that are not used for a long time: Charge to about 50%, turn off and store in a cool and dry place.
- Power tool batteries: Also charge to half-charged state and store, avoid high temperature environment.
- Vehicle batteries: If the vehicle is parked for a long time, it is recommended to disconnect the negative pole of the battery to reduce power loss. If it cannot be disconnected, start the vehicle regularly to charge the battery.
- Mobile power (power bank): Charge to half-charged and store, check the power regularly and recharge.
Conclusion
The self-discharge of lithium batteries is an inevitable phenomenon, but by understanding its principles and influencing factors, we can take effective measures to slow down self-discharge rate and extend the life of the battery. In daily life, paying attention to storage conditions, checking the power regularly, and avoiding harsh use environments can minimize the losses caused by self-discharge. Understanding the principle of lithium battery self-discharge can help optimize battery use and storage strategies, extend battery life, and avoid safety hazards. With this knowledge, you can better protect your batteries and make them serve you longer.
FAQ
What is battery self-discharge rate?
Battery self-discharge rate refers to how quickly a battery loses its charge when not in use. It varies depending on battery type, temperature, age, and storage conditions.
Which battery type has the lowest self-discharge rate?
Lithium-ion and LiFePO4 batteries typically have the lowest self-discharge rates, often less than 3% per month. In contrast, NiMH and NiCd batteries can lose 20% or more in the same time frame.
How does temperature affect battery self-discharge?
Higher temperatures accelerate chemical reactions inside the battery, increasing the self-discharge rate. Storing batteries in cool, dry environments helps reduce this effect.
Can self-discharge be completely avoided?
No, self-discharge is a natural chemical process in all batteries. However, it can be minimized through proper storage, regular maintenance, and choosing low self-discharge battery chemistries.
How can I reduce the self-discharge of my batteries during storage?
To minimize battery self-discharge:
- Store in a cool, dry place (15–25°C)
- Avoid full charge or full depletion before long-term storage
- Use storage-friendly chemistries like LiFePO4 or low self-discharge NiMH
- Disconnect batteries from devices when not in use
Who we are
TYCORUN is a leading company in the battery swap industry, focusing on the research and development and manufacturing of battery swap stations and lithium-ion batteries. We are committed to providing efficient and sustainable energy solutions for electric two-wheeled vehicles such as electric motorcycles, electric tricycles, and electric scooters (explore battery swapping vs charging station).
With deep industry experience, TYCORUN focuses on serving urban areas with strong demand for electric two-wheeled vehicles, especially in cities with broad market potential in different countries and regions. We continue to increase R&D investment, actively promote the innovation and upgrading of battery technology, and continuously expand the network layout of battery swap stations.
TYCORUN’s battery swap station design is convenient and efficient, and the user experience is excellent. Our lithium-ion batteries are known for their high energy density, long battery life and excellent performance, and are suitable for a variety of electric two-wheeled vehicles. At the same time, we also provide advanced software solutions to help users achieve real-time monitoring and intelligent management of battery status, and comprehensively improve operational efficiency and user satisfaction.
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Willow is a materials engineer with a Master’s degree in Materials Science and Engineering, specializing in lithium-ion battery materials and energy storage technologies.
Her work focuses on EV battery swapping solutions, battery innovation, and new energy industry trends, aiming to translate research insights into practical applications for sustainable transportation.
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