Batteries containing lithium, such as the rechargeable batteries used in mobile phones, laptops, and electric vehicles, play a vital role in our daily lives. Consequently, research into lithium battery technology is one of the key areas of scientific innovation today. This has led to the widespread use of terms such as “lithium battery,” “lithium-ion battery,” and “lithium metal battery.” However, are these terms interchangeable?
Both lithium-metal batteries and lithium-ion batteries are types of lithium-based batteries. This article will explore these two types’ key differences in detail.
Understanding Lithium-ion Batteries
A lithium-ion battery is a secondary (rechargeable) battery that moves lithium ions (Li+) between the positive and negative electrodes. Lithium ions (Li+) are inserted into and extracted from the electrodes throughout the charge and discharge cycle. During charging, lithium ions are extracted from the positive electrode and transferred to the negative electrode through the electrolyte. This results in the negative electrode becoming enriched with lithium. The reverse occurs during discharge.
Components of a Lithium-ion Battery
A. Positive Electrode (Cathode)
The active material used in the positive electrode is typically lithium manganese oxide, lithium cobalt oxide, lithium nickel manganese cobalt oxide (commonly referred to as ternary material), etc. A ternary material or a combination of ternary material and lithium manganese oxide is often used for electric bicycles. Pure lithium manganese oxide and lithium iron phosphate are becoming less common due to factors such as their relatively large size, lower performance, or higher cost. The current collector for the positive electrode typically uses aluminum foil with a thickness of 10-20 micrometers.
B. Separator
The separator is a specially designed polymer film with a microporous structure. It allows the passage of lithium ions but prevents the passage of electrons.
C. Negative Electrode (Anode)
The negative electrode current collector is made of electrolytic copper foil with a thickness ranging from 7 to 15 micrometers.
D. Organic Electrolyte
The electrolyte is typically a carbonate-based solvent in which lithium hexafluorophosphate is dissolved. Lithium polymer batteries, on the other hand, use a gel electrolyte.
E. Battery Case
Lithium batteries are available in various forms, including steel cases (square cases are rare), aluminum cases, nickel-plated iron cases (common in cylindrical batteries), and aluminum laminate film (used in pouch cells). The battery cap serves as the positive and negative terminals of the battery.
How Lithium-ion Batteries Work
Lithium-ion batteries use a carbon-based material as the negative electrode and a lithium-containing compound as the positive electrode. Importantly, lithium metal is not involved; only lithium ions are.
Lithium-ion batteries rely on the process of lithium-ion intercalation and deintercalation at the electrodes. In simple terms, lithium ions move in and out of the electrodes during charging and discharging. Electrons also move in sync with the lithium ions, a process that manifests as intercalation or deintercalation within the electrodes.
Lithium ions are released from the positive electrode when the battery is charging and moving through the electrolyte to the negative electrode. The graphite used for the negative electrode has a layered structure rich in micropores. The lithium ions that reach the negative electrode are inserted into these pores. The more lithium ions that are inserted, the higher the battery’s state of charge.
For more details on battery manufacturing and innovation, please refer to our Top LiPo Batteries for Drones Guide.
Battery Capacity and Discharge Process
When charging a lithium-ion battery, lithium ions move from the positive electrode to the negative electrode, embedding in the carbon layer structure. The number of lithium ions transferred determines the charging capacity of the battery.
When the battery is discharged (i.e., when the battery is in use), the lithium ions embedded in the carbon layer of the negative electrode are released and return to the positive electrode. A higher discharge capacity indicates more lithium ions returning to the positive electrode.
Typically, the charging current for lithium-ion batteries is set between 0.2C and 1C. The larger the current, the faster the charging process. However, faster charging generates more heat. Charging with excessively high current can prevent the battery from reaching its full capacity because its electrochemical reactions require time to complete. Just as haste makes waste, pouring beer too quickly creates excessive foam, affecting its taste.
Advantages of Lithium-Ion Batteries
A. High Voltage
A single lithium-ion battery cell has an operating voltage of 3.7-3.8V (3.2V for lithium iron phosphate batteries), which is three times the voltage of nickel-cadmium and nickel-metal hydride batteries.
B. Energy Density
The actual energy density of lithium-ion batteries is approximately 555Wh/kg, with a specific capacity of the material exceeding 150mAh/g (3-4 times larger than nickel-cadmium batteries and 2-3 times higher than nickel-metal hydride batteries), reaching approximately 88% of the theoretical value.
C. Long Cycle Life
Lithium-ion batteries can typically be used for more than 500 cycles; some can exceed 1,000 cycles. Lithium iron phosphate batteries can be used for more than 2,000 cycles. Low current discharge devices can effectively extend battery life, enhancing product competitiveness.
D. Safety
Lithium-ion batteries are environmentally friendly and do not have a “memory effect,” which affects some other battery types, such as nickel-cadmium batteries. Metallic lithium, the predecessor to lithium-ion batteries, was prone to short circuits due to lithium dendrite formation. Lithium-ion batteries, however, do not have this issue. In addition, lithium-ion batteries do not contain cadmium, lead, or mercury, which are harmful to the environment.
E. Low Self-Discharge Rate
After one month of storage at room temperature, a fully charged lithium-ion battery has a self-discharge rate of approximately 2%. This is far lower than the 25-30% self-discharge rate of nickel-cadmium batteries and the 30-35% self-discharge rate of nickel-metal hydride batteries.
F. Fast Charging
Lithium-ion batteries can reach over 80% of their rated capacity after being charged at 1C for 30 minutes. Lithium iron phosphate batteries only need 10 minutes to reach 90% of their rated capacity.
G. Wide Operating Temperature Range
Lithium-ion batteries can operate in a temperature range of -25°C to 45°C. With advancements in electrolytes and cathode materials, this range is expected to expand to -40°C to 70°C.
Disadvantages of Lithium-Ion Batteries
A. Decay
Unlike other rechargeable batteries, the capacity of lithium-ion batteries gradually decreases. This decay process is affected by usage frequency and temperature, leading to a decrease in capacity or an increase in internal resistance.
B. Recycling Rate
Due to various factors, approximately 1% of newly manufactured lithium-ion batteries are sent for recycling.
C. Prone to Overcharging
Overcharging lithium-ion batteries can cause excessive lithium ions to embed permanently in the lattice structure, preventing their subsequent release and reducing battery life.
D. Prone to Over-Discharging
Over-discharging causes the electrodes to release too many lithium ions, leading to lattice structure collapse and shortened battery life.
What is a Lithium Metal Battery?
A lithium metal battery (LMB) is a type of battery that uses metallic lithium as the negative electrode (anode). The positive electrode material can vary, including substances such as oxygen, elemental sulfur, or metal oxides. Lithium metal batteries function similarly to standard dry-cell batteries, generating electrical energy through the oxidation of metallic lithium. Compared to lithium-ion batteries, lithium metal batteries theoretically have a higher energy density, making them a subject of great interest.
Lithium Metal Batteries: An Overview
Lithium metal batteries are primary batteries and, therefore, non-rechargeable.
Why Choose Lithium Metal Batteries?
Lithium metal batteries offer significantly higher energy density than other types of batteries, such as dry-cell batteries, because they use metallic lithium as an electrode. This makes them an ideal power source for devices requiring long-lasting power, including portable devices like cameras.
What is a Lithium Metal Battery?
A lithium metal battery is a primary (non-rechargeable) battery that uses pure metallic lithium as an anode. These batteries are known for their high energy density and long shelf life, making them well-suited for applications needing a compact, reliable, and long-lasting power source.
Key Features of Lithium Metal Batteries:
- High Energy Density: Lithium metal batteries have exceptionally high energy density, allowing them to store more electrical energy in a smaller and lighter package than other battery types, such as alkaline or zinc batteries.
- Non-Rechargeable: These primary batteries are non-rechargeable and must be replaced when depleted.
- Voltage: Lithium metal batteries typically have a voltage of approximately 3.0V, significantly higher than most other primary batteries, like alkaline batteries (1.5V).
- Long Shelf Life: These batteries can last for 10-15 years if stored properly, making them ideal for devices requiring long-term power and infrequent replacement.
- Low Self-Discharge Rate: Lithium metal batteries have an extremely low self-discharge rate, meaning they lose very little energy when not in use, extending their shelf life.
Common Applications:
- Medical Devices: Pacemakers, hearing aids
- Consumer Electronics: Watches, calculators, remote controls
- Military and Aerospace: Used for their high energy density and reliability in extreme conditions
- Backup Systems: Memory backup for computers and other electronic devices
- Safety and Security Devices: Smoke detectors, emergency beacons
Safety Considerations:
- Thermal Instability: Lithium metal is highly reactive and can lead to thermal runaway and fire if damaged or mishandled.
- Transportation Restrictions: Due to safety concerns, there are restrictions on the transportation of lithium metal batteries, especially by air.
Lithium Metal vs. Lithium-Ion Batteries
The main difference between lithium metal and lithium-ion batteries lies in their design and functionality. Lithium metal batteries are primary (non-rechargeable), while lithium-ion batteries are rechargeable and designed for multiple charge cycles.
Lithium Metal Batteries:
Lithium metal batteries work similarly to traditional dry-cell batteries. They use lithium metal as an electrode and generate electrical energy through the corrosion or oxidation of the metallic lithium. Once depleted, they are no longer usable and cannot be recharged.
Lithium-Ion Batteries:
On the other hand, lithium-ion batteries use lithium cobalt oxide as the positive electrode and carbon as the negative electrode. These batteries have an electrolyte in the middle, forming a channel for free ions. A separator divides the positive and negative electrodes to prevent short circuits. During charging, lithium ions migrate from the positive electrode to the negative electrode, where they are stored within the carbon structure. During discharge, the ions return to the positive electrode, completing the cycle.
In summary, the key difference between lithium-ion and lithium-metal batteries is that lithium-ion batteries use Li+ ions as the charge carriers.
Batteries using lithium metal as an electrode are classified as lithium metal batteries.
Understanding Lithium Metal Batteries
Lithium metal batteries are a type of rechargeable battery closely related to lithium-ion batteries but with significant differences. Lithium ions (Li+) migrate through an electrolyte during charge and discharge cycles in both types. However, lithium metal batteries use lithium metal as the anode material, whereas lithium-ion batteries use compounds like graphite. Strictly speaking, lithium metal batteries can be considered a special subset of lithium-ion batteries.
In scientific literature, the term “lithium-ion battery” often refers to non-lithium metal versions, while “lithium metal battery” refers to those using a lithium metal electrode. This distinction clarifies the differences in their charging/discharging mechanisms and materials.
- Lithium-ion battery: Lithium exists as Li+ ions that move between electrodes during charging and discharging. The electrode materials undergo redox reactions to facilitate this process.
- Lithium metal battery: Lithium metal undergoes oxidation and reduction (redox) during charge and discharge, changing its chemical state. This is a key difference from traditional lithium-ion batteries, where the lithium remains ionic.
In some contexts, the broader term “lithium battery” encompasses both lithium metal and lithium-ion batteries, as they rely on lithium-based components.
Summary
After decades of development, lithium-ion batteries are now a mature technology in the market, powering a wide range of devices, from smartphones to electric vehicles. Meanwhile, lithium metal batteries have become a key focus of scientific research due to their potential for high energy density. However, their widespread commercialization is still years away due to challenges such as dendrite growth and, in the case of lithium-sulfur batteries, the polysulfide shuttle effect and inherent safety concerns.
Despite these obstacles, significant investments are being made in lithium metal batteries due to their superior energy density. For example, lithium metal has a specific capacity as an anode material that is more than 11 times that of graphite-based lithium-ion battery anode materials (C6Li). This makes lithium metal batteries a promising candidate for next-generation energy storage.
However, some issues still need to be overcome. Lithium metal is highly reactive, and during charging, it can form dendrites that cause short circuits. Safety is another concern, especially given lithium’s reactivity with oxygen and moisture. Nevertheless, ongoing research is promising, and with continued scientific advancements, lithium metal batteries may soon revolutionize the energy storage field, making our devices lighter and increasing the range of electric vehicles. If you’re curious about different types of batteries, check out our Difference Between Lithium Polymer vs. Lithium Batteries guide for more insights.
