Lithium Batteries, Lithium-Ion Batteries, and Lithium Polymer Batteries

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In the battery classification system, lithium batteries represent the broadest category, with lithium-ion batteries as a key subset, and lithium polymer batteries serving as an improved type of lithium-ion batteries. The three exhibit a clear hierarchical relationship of “general category – subset – improved type”. Specifically, the hierarchy can be divided as follows: Chemical Batteries (general category) → Lithium Batteries (subset) → Lithium-Ion Batteries (subtype) → Lithium Polymer Batteries (improved type of lithium-ion batteries). Additionally, lithium batteries also include other subtypes, such as lithium metal batteries. Due to their significant differences in characteristics, lithium-ion batteries and lithium polymer batteries are often still classified as parallel subcategories.

I. Core Definitions and Essential Properties of the Three Types

(I) Lithium Batteries

Lithium batteries are a general term for batteries that use lithium metal or lithium alloy as electrode materials and non-aqueous electrolyte solutions, rather than a single type of battery. Their core feature is relying on lithium-related electrochemical reactions to achieve energy output, mainly divided into two major categories:

• Primary lithium batteries (lithium primary batteries): Non-rechargeable. The negative electrode uses metallic lithium or lithium alloy, and the positive electrode uses solid active materials such as manganese dioxide and thionyl chloride. Electrical energy is generated through the dissolution and deposition of metallic lithium. They are commonly used in CR2032 button batteries, 3V special-purpose batteries for cameras, and military disposable battery packs.

• Secondary lithium batteries (rechargeable): Represented by lithium-ion batteries, they achieve charge-discharge cycles through the intercalation and deintercalation of lithium ions between the positive and negative electrodes, breaking away from the limitation of metallic lithium directly participating in the reaction. They are the mainstream battery type in fields such as consumer electronics and new energy vehicles.

(II) Lithium-Ion Batteries

Lithium-ion batteries are the core rechargeable category in the lithium battery family. Their core design is to avoid the problem of metallic lithium dendrites, relying on the migration of lithium ions between the positive and negative electrodes to complete energy conversion, without metallic lithium directly participating in the reaction process.

• Structural composition: The negative electrode is mostly graphite (partially combined with silicon-carbon or lithium titanate materials); the positive electrode commonly uses lithium cobalt oxide, lithium iron phosphate, ternary materials (NCM/NCA), etc.; the electrolyte is a lithium hexafluorophosphate carbonate organic solution; the separator adopts a PE/PP microporous membrane; the packaging form is mainly hard-shell (such as steel-shell or aluminum-shell batteries of models 18650 and 26650), with a small number of soft-pack forms.

• Key properties: They are recyclable charge-discharge batteries, with a cycle life usually ranging from 500 to 3000 times (depending on the positive electrode material, lithium iron phosphate has a longer life); the operating voltage is mostly 3.6-3.7V (3.2V for lithium iron phosphate); the energy density ranges from 150 to 280Wh/kg, affected by the chemical system and packaging method; a protection board must be used, as overcharging, over-discharging, and short circuits can cause permanent damage or even fire.

(III) Lithium Polymer Batteries

In essence, lithium polymer batteries are “soft-pack lithium-ion batteries” and are often regarded as an improved type of lithium-ion batteries. Due to the term “polymer” in their name, they are easily misunderstood as using solid polymer electrolytes. However, 99% of products on the market actually adsorb liquid electrolytes in gel separators (such as PVDF-HFP type) and then package them with aluminum-plastic film soft packs.

• Structural differences: Compared with traditional lithium-ion batteries (cylindrical/square-shell), the core differences lie in the shell and electrolyte form. The shell is made of aluminum-plastic film, which is lighter in weight, thinner in thickness, and can be made into irregular shapes; the electrolyte is in a gel state. Although it still relies on liquid ion conduction, the risk of electrolyte leakage is significantly reduced.

• Key properties: They support recyclable charge-discharge. The cycle life of ordinary products is 300-500 times, and high-end products can reach thousands of times; the energy density is 5-10% higher than that of lithium-ion batteries with the same material and steel shell. Some high-end models (such as enovbattery) have a gravimetric energy density of up to 320Wh/kg and a volumetric energy density of 400-600Wh/L; they have excellent discharge rates, capable of achieving 30-50C high-rate discharge, suitable for high-power demand scenarios; their shape and size can be customized, and they can be made into thin, curved, and other special forms, with higher space utilization.

II. Comparison of Core Differences Among the Three Types

(I) Charge-Discharge Characteristics

• Lithium batteries: Only lithium-ion batteries (including lithium polymer batteries) are rechargeable. Primary lithium batteries (such as CR2032 button batteries) are absolutely non-rechargeable. Forced charging will cause lithium dendrites to pierce the separator, leading to internal short circuits and high-temperature explosions. Experimental data shows that charging a CR2032 battery with a small current of 5V for 30 seconds can cause the shell temperature to exceed 150°C and the cover to burst.

• Lithium-ion batteries: Designed for repeated charge-discharge cycles, they have no memory effect, can be charged at any time without full discharge, have high charging efficiency, and can avoid the risk of abnormal charge-discharge when equipped with a protection board.

• Lithium polymer batteries, like lithium-ion batteries, are also rechargeable and exhibit no memory effect, maintaining the same charging characteristics. However, they have higher requirements for charging accuracy, and overcharging can easily cause battery swelling.

(II) Structure and Packaging

• Lithium batteries (primary type): Mostly in small packaging, such as button-type and small cylindrical shapes. The shell is mainly made of metal, with a simple structure and non-detachable design.

• Lithium-ion batteries: Mainly use hard-shell packaging (steel shell, aluminum shell), with relatively fixed shapes and sizes. Common types are cylindrical (18650, 21700) and square, with high standardization. Space utilization is limited by fixed sizes.

• Lithium polymer batteries: Use aluminum-plastic film soft-pack packaging, with no fixed shape or size. They can be customized into thin, irregular, or even curved forms according to application needs. Their space utilization is higher than that of lithium-ion batteries of the same size, and multi-layer combinations can be realized inside the cell to achieve high voltage (a single lithium-ion battery cell has a nominal voltage of 3.6V, and multiple cells need to be connected in series to achieve high voltage).

(III) Performance Parameters

Performance Dimension	Lithium Batteries (Primary Type)	Lithium-Ion Batteries	Lithium Polymer Batteries
Energy Density	270-300Wh/kg (extremely high)	150-280Wh/kg	180-300Wh/kg (up to 320Wh/kg for high-end models)
Operating Voltage	Approx. 3.0V	3.2-3.7V (depending on positive electrode material)	3.7V (4.2V when fully charged)
Cycle Life	1 time (non-recyclable)	500-3000 times	300-500 times (thousands of times for high-end models)
Self-Discharge Rate	Extremely low (90% remaining after 10 years of storage)	1-2% per month	Low (better than nickel-hydrogen batteries)
Weight	Lightweight for miniaturized products	2-4 times lighter than nickel-hydrogen and lead-acid batteries	Lighter than lithium-ion batteries of the same capacity

(IV) Safety

• Lithium batteries (primary type): There is no risk of abnormal charge-discharge. However, the properties of metallic lithium mean that there may still be safety hazards when subjected to impact or high temperatures. Moreover, if the non-rechargeable property is ignored, forced charging will cause a severe explosion.

• Lithium-ion batteries: The hard shell can resist certain physical damage. However, under high temperatures and high pressures, the shell may rupture, leading to the leakage of liquid electrolyte and causing combustion or explosion. A protection board is required to avoid risks.

• Lithium polymer batteries: They use gel electrolytes, so the risk of electrolyte leakage is low. The aluminum-plastic film shell will only break naturally under extreme conditions without explosion, resulting in relatively higher safety. However, overcharging, impact, and extreme temperatures should still be avoided.

(V) Cost and Application Scenarios

• Lithium batteries (primary type): Low production cost, but high long-term use cost due to non-recyclability. They are mainly used in low-power, one-time demand scenarios, such as button batteries (for remote controls, calculators), special-purpose batteries for cameras, and military emergency equipment.

• Lithium-ion batteries: Mature production process, high standardization, and low cost. They are suitable for scenarios sensitive to cost and requiring long-term cyclic use, such as laptops, smartphones, electric vehicles, industrial inspection drones, and agricultural plant protection equipment.

• Lithium polymer batteries: High customization level, complex production process, and high cost. They are suitable for scenarios with high requirements for weight, shape, and power, such as consumer-grade aerial photography drones, racing FPV drones, tablets, smart watches, and thin portable devices.

III. Practical Methods for Quickly Distinguishing the Three Types

• Check the markings: If “Li-ion”, “Lithium-ion”, “Li-Po”, or “rechargeable” is printed on the surface, it is a lithium-ion battery or lithium polymer battery. If “Primary battery” or “Do not recharge” is printed, it is a primary lithium battery.

• Check the voltage: A nominal voltage of 3.6V, 3.7V (or 3.2V for lithium iron phosphate) indicates a lithium-ion battery or lithium polymer battery. A nominal voltage of 3.0V indicates a primary lithium battery.

• Check the shape: Cylindrical or square hard-shell batteries such as models 18650 and 21700 are mostly lithium-ion batteries. Soft-pack thin or irregular-shaped batteries are mostly lithium polymer batteries. Button-shaped or small cylindrical batteries marked with “CR” (such as CR2032, CR123A) are primary lithium batteries.