BU-206: Li-polymer Battery: Substance or Hype?

Find out why lithium-polymer is so popular.

The polymer hype of the early 2000s is still going strong, but most users cannot distinguish between a regular Li-ion and one with polymer architecture. While many people identify the term “polymer” as a “plastic,” polymers range from synthetic plastics to natural biopolymers and proteins that are from a fundamental biological structure.

Lithium-polymer differs from other battery systems in the type of electrolyte used. The original polymer design dating back to the 1970s used a solid (dry) polymer electrolyte that resembles a plastic-like film. This insulator allows the exchange of ions (electrically charged atoms) and replaces the traditional porous separator that is soaked with electrolyte. A solid polymer has a poor conductivity at room temperature and the battery must be heated to 60C (140F) and higher to enable current flow. The much anticipated “true plastic battery” promised in the early 2000s did not materialize as the conductivity could not be attained at ambient temperature.

To make the modern Li-polymer battery conductive at room temperature, gelled electrolyte has been added. All Li-ion polymer cells today incorporate a micro porous separator with some moisture. Li-polymer can be built on many systems, such as Li-cobalt, NMC, Li-phosphate and Li-manganese, and is not considered unique battery chemistry. Most Li-polymer packs are for the consumer market and are based on Li-cobalt.

With gelled electrolyte added, what is the difference between a normal Li ion and Li ion polymer? As far as the user is concerned, lithium polymer is essentially the same as lithium-ion. Both systems use identical cathode and anode material and contain a similar amount of electrolyte. Li-polymer is unique in that a micro porous electrolyte replaces the traditional porous separator. Li-polymer offers slightly higher specific energy and can be made thinner than conventional Li-ion, but the manufacturing cost is higher by 10–30 percent.

Li-polymer cells also come in a flexible foil-type case (polymer laminate or pouch cell) that resembles a food package. While a standard Li-ion needs a rigid case to press the electrodes together, Li-polymer uses laminated sheets that do not need compression. A foil-type enclosure reduces the weight by more than 20 percent over the classic hard shell. Thin film technology liberates design as the battery can be made into any shape, fitting neatly into stylish mobile phones and laptops. Li-polymer can also be made very slim to resemble a credit card. [BU-301a: Types of Battery Cells]

Charge and discharge characteristics of Li-polymer are identical to other Li-ion systems and do not require a special charger. Safety issues are also similar in that protection circuits are needed. Gas buildup during charge can cause some prismatic and pouch cells to swell and equipment manufacturers must make allowances for expansion. Li-polymer in a foil package may be less durable than Li-ion in the cylindrical package.

Solid Electrolyte with Lithium-metal Batteries

Research with the solid electrolyte (SE) continues and attempts are made by using metallic lithium as anode material. Solid lithium has a higher energy density than in modified lithium-ion form, but lithium anodes have been tried before and battery manufacturers were forced to discontinue production because of safety issues. Lithium tends to form metal filaments, or dendrites, that cause short circuits. Scientists are trying to overcome this invasion by using specially designed separators and other remedies.

The key objectives for the so-called “solid state lithium ion battery” are achieving sufficient conductivity at room temperature and below and delivering a high enough cycle count, a weak point with most new battery designs. Prototypes of the solid state lithium ion only reach 100 cycles. Targeted applications are load leveling for renewable energy source and fulfilling the need for personal transportation in cars that are non-polluting, charge in minutes and do not prompt range anxiety. Commercialization can take 10 years or longer. 

Last Updated 2/20/2015

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On December 22, 2010 at 6:32pm
Lachlan wrote:

Do we have to wait until 2005 for a Li-polymer battery?

Perhaps this web page needs updating.

On January 6, 2011 at 9:44am
Ike wrote:

Lachlan, agree with you. Li-Po batteries come nowadays as standard in various products, such as new Nokia E Series phones… so it’s hardly “experimental” tech any more.

On January 27, 2011 at 11:51am
RIKK wrote:

li-pos are lighter than li-ion, it is a huge advantage in rc hobby.

On February 11, 2011 at 5:30pm
Ray Koosha wrote:

Li-Poly cells are aimed at minimizing the effect of swelling as compared to their Li-Ion counterparts.

On September 8, 2011 at 8:57am
Ken W. wrote:

Can you address the new (least least to me) LiFePO4 (Lithium Iron Phosphate) batteries. There does not appear to be any chargers available for these batteries. They can only be charged in the solar lights in which they are installed.

On October 3, 2011 at 2:36am
Andrew wrote:

Ken, LiFePO4 batteries can be charged with any constant current/constant voltage (CC/CV) power source like laboratory power sources. Just set the voltage to 3.6V and limit the current to something like 0.2C-1C (where C is cell capacity). As soon as current drops to 0.01C or less, it’s finished.

Also most contemporary RC chargers can charge LiFePO4.

On November 7, 2011 at 7:36am
Mark wrote:

“Also most contemporary RC chargers can charge LiFePO4.”


On January 23, 2012 at 3:23am
Pieter Borst wrote:

Is it right that Ion-polymere batterys has to be installed - saved or stored
in a certain position as some recomment -horizontal or vertical ??
I ask to excuse my “english”—I’m Dutch .
Grs Pieter.

On March 9, 2012 at 5:07am
Kevin Middleton wrote:

Think this site might need updating a bit,I’ve been using Li Po batteries in my model aircraft for years.

On April 11, 2012 at 6:13am
John Norman wrote:

I have to keep my llithium polymer batteries outside, and they could be there, unused for several months during winter.. Are they likely to be damaged when temperatures fall below zero???
The batteries are used for flying model aircraft.
Thank you

On May 27, 2012 at 4:48pm
Ron Xiu wrote:

Pieter Borst, lipo battery can use and store in any position. They are fully seal so electrolyte does not spill.

On May 30, 2012 at 11:25am
Dennis Staley wrote:

I’m new to LiPo (8 mos.) and have done all the research possible to get the most out of my new investments.  I use them in R/C aircraft, and have been very careful in the balancing-charging procedure.  Each of my four 3-cell (11.1V) packs have been used carefully and not discharged below 40% of capacity (11.43V).  However, all four packs have gradually increased in “puffiness”, which occurs during flight and not during charging.  The packs are always moderately cool to the touch after flying and charging, but the puffiness seems to increase regardless.  The manufacturer (Park Zone) states they should be discarded when puffiness occurs, but the hobby shop manager says they are just fine, and compared to the ones HE uses, their puffiness is minimal.  His will almost ROLL down a slight incline!  He also flies his batteries until there is a reduction in available power, while I time my flights and land BEFORE the voltage is below the 40% recommended minimum.  I’ve not seen any “technical” information or advice on this phenomenon, and would welcome knowledgeable opinions.

On June 6, 2012 at 5:55pm
sunnyzeng wrote:

LiPo batteries will share a larger market share in future, and will be widely used on differents kinds of difital products. we are li-ion and liPo batteries manufacturer,and at present we are develop liPo battery market

On June 9, 2012 at 9:19am
Dennis Staley wrote:

I was notified that sunnyzeng had entered a response to my question regarding LiPo packs expanding (puffing out) because of expanding gas leaking from the cells.  Does sunnyzeng mean his company is “developing LiPo battery market” by making the batteries with a short life span and therefore a built-in obsolescence?
Let me make my question more to-the-point:  What degree (or measurement) of “puffiness” makes a LiPo pack dangerous for continued use?

On October 10, 2012 at 6:37am
Srinivas Raj.G wrote:

What are the Layers of Lithium ion and Applications ?

On February 18, 2013 at 3:28pm
Paul Vigushin wrote:

I am looking for an expert in LiPo batteries to consult with on a fire claim.  Please send e-mail to paul@pv-law.com.

On April 3, 2013 at 9:46pm
Ariyan wrote:

poor me, my limited brain still couldn’t decide that Li-Po is substance or just hype? my temporary conclusion is, Li-Po is made to replace Li-ion, because it has same energy with Li-ion but Li-po is lighter, smaller (or can be made in small form), but it’s poor conductivity made Li-Po easy to hot than Li-Ion that’s why it needs a gel to cool it, but it made Li-Po more fragile becuase it’s gel can be change to other form (or puffiness like Denis Staley above said) if the battry is dropped, or hard pressed, so that’s why many phone manufacture still use Li-Ion battery, because Li-ion still more efficient and economical than Li-Po, my new BlackBerry Z10 is one of them.. CMIIW (sorry for my poor english i’m Indonesian)

On April 22, 2013 at 8:35pm
Hari wrote:

Guys I need some basic knowledge . help me

I bought a smartphone last week and it is written “Polymer Battery” on the battery
You can view the image of battery in below links:



But whenever i typed ” polymer battery” in google, the results brought only about lithium polymer battery ....(including this site)
I can’t find a single site which speaks about polymer battery ,, everywhere it is Lithium Polymer ..

So my doubt is , Are polymer battery and lithium polymer battery same ?

Is the term POLYMER BATTERY is another name to mention lithium Polymer (LiPo) battery ? OR Both lithium Polymer and Polymer battery are Different ?

On May 2, 2013 at 3:19pm
Mads wrote:

“Charge and discharge characteristics of Li-polymer are identical to other Li-ion systems and do not require a special charger”

Needs to be precizes that there’s no need for separate charger exactly between Li-Ion and LiPo batteries. smile
At first time reading this it makes a sense as if LiPos can be charged with NiCd battery charger also, which is extremely dangerous attempt.

On June 16, 2013 at 11:24am
matt wrote:

I wanted to answer Hary’s question. I’m not 100% sure but I’d say I’m 95% sure that the batteries you bought are LiPo’s.
Whoever wrote simply: Polymer battery, did so because he/she thought it sufficient because consumers that pay attention to that type of thing would know what they were getting. Also, who know’s? Maybe he/she figured it would be obvious since there’s no such thing as a polymer battery.

On July 26, 2013 at 12:34am
Michael wrote:

Is it possible to use multiple 12v Li-polymer car starter batteries in series (total 72V) in a continuous duty cycle, such as an electric propulsion system without overheating?

On October 28, 2013 at 2:02am
randy wrote:

it seems common to have prismatic/polymer in parallel configuration. but, is it common to put them in series? or how about series and parallel combination?
is there a reason why there are more cylindrical Li-ion batteries in series than Li-ion Polymer in series?


On November 23, 2013 at 6:47pm
Heiko wrote:

A friend of mine is an rc model car racer and he says LiPo batteries are a blessing. 15 years ago they were having problems with just a standard racing distance of 20 rounds (I believe, sorry if I’m wrong) while nowadays with LiPo batteries they could go for the double distance, if they wanted.
Batteries used to be the one weak link in rc racing, but with LiPo batteries all that went away and the models could theoretically have more power than what you can actually get down on the street.

On February 19, 2014 at 11:32pm
nishant sharma wrote:


On June 2, 2014 at 2:29am
Ramakrishna Rao wrote:

Can Li-Po batteries be taper charged? I.e. charge a 1000 mAH battery at 250 mA when 6.2V, 120 mA at 7.4V and 50 mA at 8.0 volt and stop charging at 8.4V

On June 28, 2014 at 8:19am
Ray wrote:

Ramakrishna Roa, yes my charger does it.

On July 20, 2014 at 11:06pm
Gary wrote:

I have noticed my lipo batteries seem to take twice as long to charge once the temperature drops to single figures. I use then in an RC model they last about ten minutes but take and hour and a half to charge.

On August 22, 2014 at 10:41pm
dave . M wrote:

To whom ever is in charge of this website ; do you know that there is an advertisement of pornographic material on the right of your website with a very dirty pictures of Gay porn?

Is this what you get paid for? ,. it may O.K for you but you should consider the reality that some people might find it disturbing !?!.

Dave Manning

On August 29, 2014 at 2:46am
Prachi Agrawal wrote:

Could you provide a comparison between solid state lithium-ion batteries and standard lithium-ion batteries that have a liquid electrolyte?

On October 29, 2014 at 12:21pm
Kathleen O'Connor wrote:

New personal vaping tech is pushing battery capabilities.

I’m still looking for current data on the progression of the Li-Po’s for use in personal vaping devices. Claims of better performance and of course flexibility of shape area big plus. What else should I know; what milestone should I wait for.

Example: http://www.sourcingelectricals.com/3-7V1850mAh-li-polymer-battery-10113003/

On January 16, 2015 at 5:37pm
Jon D wrote:

Does anyone have experience with potting lipo batteries with a foil type pouch?  I know swelling during charging and discharging can be an issue, but first encasing the battery in a compressible material would mitigate that.  Otherwise, are there any other safety concerns or techniques that might help?

On January 19, 2015 at 2:16pm
Gerard Campeau wrote:

We have an application for a Battery in an most high temperature Environment . 90% humidity and 100F to 140 F . 12V at 2 Ah can anybody suggest the best and most economic battery and source. Qty about 200to 2000 units to start.

On February 28, 2015 at 2:28pm
Shelli wrote:

I’m looking for a replacement battery for my MacBook Pro, and am faced with the decision regarding lithium-ion, or Li-Po.  The prior battery got very warm, and finally puffed out, so I’m a little confused, do the Li-Po’s run cooler?  Or warmer?

Oh, and Dave Manning:  Ever heard of “clickstream data?”