5 benefits of Lithium-Ion Batteries over Lithium-Polymer Batteries

In the ever-evolving landscape of energy storage technology, lithium-based batteries have emerged as the frontrunners, offering efficient and compact power solutions for a wide range of applications. Among these, lithium-ion (Li-ion) batteries and lithium-polymer (LiPo) batteries have established themselves as prominent choices for energy storage and power delivery for various industries. While both possess distinct advantages, this article will shed light on the numerous benefits of lithium-ion batteries and explain why they often outshine their lithium-polymer counterparts.

First, Let's talk about the Lithium-ion battery:
Lithium-Ion Batteries:

Lithium-ion batteries, often abbreviated as Li-ion batteries, are a popular and versatile form of rechargeable energy storage. They have become the go-to choice for numerous applications due to their impressive energy density, reliability, and adaptability. These batteries consist of lithium compounds as their cathodes, offering a range of advantages that make them the preferred choice for powering a wide array of modern devices and systems.

Advantages of Lithium-Ion Batteries:

1. High Energy Density: Lithium-ion batteries store a significant amount of energy relative to their size and weight, making them ideal for portable electronics and electric vehicles.
2. Longevity: They have an extended lifespan with a high number of charge-discharge cycles, reducing the need for frequent replacements and minimizing waste.
3. Safety Features: Li-ion batteries are equipped with protection circuits and thermal controls, making them inherently safer and less prone to overheating or short-circuits.
4. Efficiency: These batteries have a lower self-discharge rate, meaning they can retain their charge for longer periods when not in use, making them an energy-efficient choice.
5. Versatility: Lithium-ion batteries can be designed to suit a wide range of applications, from small, compact cells for smartphones to large battery packs for electric vehicles, offering adaptability to various needs and devices.

Now, what is actually a lithium-polymer battery?

Lithium-polymer batteries, often referred to as LiPo batteries, but since they contain no polymers, should be referred as Lithium Pouch.
it is a sub category of Lithium Ion cells, only difference is that they are packed inside an aluminum package.
Almost all chemistries related to Lithium, can also be packed in pouch casing.
this means that not all pouch cells are the same.
they may contain very high end and expensive chemistries – usually for pre- mass production and state of the art EV batteries – will be very difficult to obtain these cells.
Our focus here, is for the common LiPo cells offered to the industry.

When we refer to Lithium Ion in our professional jargon, we generally refer to cells manufactured in metallic cylindrical or prismatic shape.
most known is the 18650 and 21700 which are 18mm and 21mm diameter respectively cylinder shaped cells with 65mm and 70 mm height respectively.

While they have their merits, LiPo batteries are known for specific characteristics and applications that set them apart from their lithium-ion counterparts. Understanding these distinctive features is key to appreciating their value in certain scenarios.

Advantages of LiPo Batteries:

1. Flexibility in Shape: Lithium-polymer batteries are more flexible in terms of shape and size compared to lithium-ion batteries. This versatility allows them to fit into unconventional spaces and find use in devices with unique form factors.
2. Lightweight Design: LiPo batteries are usually lightweight, making them a preferred choice for applications where weight considerations are paramount, such as in drones and radio-controlled models.
3. High Discharge Rates: These batteries are capable of delivering high discharge rates (20C~90C!), making them well-suited for applications that require rapid energy release, like racing drones and remote-controlled vehicles.
   Typically have high nominal voltage (typically 3.8V / cell ) to support the high current for longer time.
4. Enhanced Power Density: LiPo batteries offer a slightly higher power density, which means they can deliver a burst of power more quickly. This characteristic is valuable in scenarios where immediate, high-energy output is necessary.
5. Seams easy to assemble: it is tempting for un-skilled in battery design - hardware companies to work with LiPo, because it is relatively simple to solder wires to it.
   this is not recommended, though, since applying so much heat on the aluminum electrode may damage the cell structure.

While LiPo batteries might not match the overall versatility and safety of lithium-ion batteries, their unique set of advantages makes them a valuable choice for specific applications where their characteristics align with the requirements of the device or system at hand.

Disadvantages of Lithium-Pouch Batteries:

1. Swelling: Everybody who ever worked with LiPo cells, know what we mean.
   the structure and packaging of the pouch cells, is subjected to swelling, when the cell gets inflated and no more functioning. Sometime it can happen to a fresh cell, who was poorly manufactured or held in bad storage conditions. It may happen to a battery pack that passed all inspections and deployed to the customer.
2. Manufacturers are generally either 2^nd and 3^rd Tier manufacturers. The premium and 1^st tier cell manufacturers, will usually use pouch for their special chemistries which are not available for the industry. The cell to be used for the industry are usually cylindrical and prismatic shape with hard metallic shape.
3. Longevity in peak performance: The datasheets are usually stretching the cells ability and not conservative.
   A standard LiPo cell that support 30C discharge rates, probably allow 50-100 cycles which is fine for a consumer drone that is dedicated to hobby and consumer use, but not for an industrial / military Drone that needs to perform for a warranted period.
4.  Thermal performance: unlike cylindrical cells, LiPo cells don’t have a centralized thermal heat sink. This means that in a structure of cells in series, it will be difficult to clear the heat off the battery pack evenly. This will create a clear un balance embedded in the battery pack design. Will lead to lose of capacity and swelling.

But, now let’s see why the lithium-ion batteries will be the best choice for your application:

1. Manufactures:

The premium manufacturers such as: Samsung SDI, Panasonic, LG ext. are offering the industry their cylindrical and prismatic cells in competitive prices, allowing verified and tested specifications, no swelling and most importantly, batches are very much sorted.
Meaning the cells are very very similar in voltage and internal impedance.
A battery designer cannot stress the importance of a balanced battery pack enough, it carries a lot of weight to the long term performance of the battery pack.

2. Durability and Longevity:

Li-ion batteries have proven to be more durable and long-lasting than LiPo batteries. Because of the very well sorted batches and the good solid structure of the cells, you may count on them to reach the promised cycle life and deliver the promised performance.
Very crucial when building your product warranty and longevity around such an important component like batteries. It is much more noticeable when ramping up production.

3. Safety:

Safety is a paramount concern in battery technology. Li-ion batteries have a well-established safety record and are equipped with features such as protection circuits and thermal controls to minimize the risk of overheating and short-circuits. LiPo batteries, on the other hand, are known for their susceptibility to swelling and a higher risk of fire or explosion if punctured, overcharged, or damaged. Many LiPo cells out there don’t follow the UL1604 directive for cell safety.

4. Thermal behavior.

The cylindrical and prismatic shapes of Li Ion cells, offer ways to assemble the battery pack in a way that the thermal design is even, and able to manage the heat more efficiently.
it is true when aiming to have an even thermal design, but more importantly, when aiming to cool or heat the battery pack externally.

5. Power delivery

The cylindrical and prismatic shapes of Li Ion cells, offer ways to split and deliver the high power out of the battery pack, especially when aiming to deliver >100A currents like you often see in Drones and LEVs.

In conclusion, while lithium-pouch batteries have their own set of advantages, lithium-ion batteries often emerge as the preferred choice for many applications due to their superior energy density, longevity, safety features and efficiency. As technology continues to advance, Li-ion batteries are likely to maintain their prominence as a reliable and efficient energy storage solution that powers the present and shapes the future.

Embrace the future of energy storage as we highlight the key reasons why lithium-ion batteries are powering the present and shaping the sustainable energy landscape of tomorrow.