How Lithium Polymer Batteries are Made

Contributors: Nate
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Great Power Batteries

As part of the 2014 China trip, I got the chance to tour one of our battery manufactures. Robert was kind enough to give me a tour of Great Power Battery and to hook me up with one of the material engineers that works there. The following is a rough step-by-step of how LiPo batteries are manufactured.

Grounds at GPB

Great power has a multi-building campus outside of Zhuhai, China.

Robert and Nathan

Robert was nice enough to pick me up from the port of Zhuhai (pronounced chew-high) and give me a tour of the facility.

Step by step graph

A quick step-by-step process of how LiPos are manufactured!

Safety uniforms

It was really neat to see the complexity of the uniforms and safety gear for the different positions along the assembly process.

Electrode Preparation

Mixing machine

The material that will be coated on to the anode and cathode is mixed.


Large rolls of raw materials are loaded into the coating machine. I think this is aluminum.

Coating machine

A thin layer of the slurry of carbon and lithium material is applied in large square swaths onto the metal terminal material.


In a continuous fashion, the material is fed through an oven to cure the slurry onto the terminal. This room was probably 20m (65ft) long and pretty toasty.

Anode coming out of the oven

There was two lines running continuously. One was the anode (I believe this is customarily aluminum) and one line was the cathode (copper). I remember this as a-a and c-c (copper is for cathode). Seen above is the never ending strip of copper with the carbon slurry cured in squares coming out of the oven. These squares will be cut and folded in the next few steps so don’t be fooled into thinking they are making cells quite that big. Yet.

Copper rolls

Lots of lots of raw electrodes ready for trimming.

Thinning Machine

This machine smashes the electrode like a pasta machine. In effect, making the sheets much thinner so that they can be folded more times.

LiPo cutting machine

Cutting the large sheets to proper width.

Electrode Creation

Electrode Creation

These machines take the rolls of electrodes, attach a terminal or tab, cut them to the proper length, and a whole bunch of other things I can’t quite discern.

LiPo Battery Anode Preparation

Here’s a video of the machines in glorious action.

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And there’s a ton of them.

LiPo Battery Terminal Welding

Here’s a close up of the tab welding.

Machine to combine electrodes

Once a pile of a given anode type is made, it is brought together with a pile of the cathode of the same size. A semi-permeable membrane is inserted between the layers, and the three strips are then folded together many times.

The above machine is a semi-automatic machine. It requires the operator to insert and line up the two electrodes, but it does the rest.

LiPo Battery Inner Cell Wrapping

Here’s a video of the machine wrapping a cell.

LiPo Battery Cell Wrapping

Above is a close-up of the folding or wrapping of the layers.

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And when you’re done you have the layers folded many times and taped.

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Multiply the lines, and you can see how this factory produces 750,000 units a month.

LiPo Battery Massive Wrapping Machine

Above is a more automated wrapping machine. This level of automation makes me giddy. How do you build something like that and keep it running without constant tweaking?! Amazing.

Forming and Electrolyte

Machine to cut and create the battery form

In a separate room, the housing is made.

A rough square outline

These machines cut, form, and create the slightly flexible but protective housing for the inner electrodes and electrolyte polymer. I believe this material is a type of plastic or PVC.

Insertion of electrodes into housing

The electrodes are then inserted between the protective housing and thermally welded together on three sides. The fourth side is left open for squirting in the electrolyte.

Cell in housing

Electrodes in their housing.

Electrolyte insertion

In a carefully controlled environment the electrolyte is pumped into the cell. This part of the manufacturing floor is tightly controlled for humidity and temperature. The fume chamber is even more carefully controlled.

Electrolyte lines

Multiple lines going at the same time. The final step of this line is thermally welding the fourth side of the battery to contain the electrolyte and seal the battery.


Charging with wing

Once sealed, we can now call this thing a battery. This is the first charging cycle. You can see the plastic clips that clamp down on the exposed tabs. The small wing left on the battery is there to collect any electrolyte or gas that is pushed out during this first cycle.

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Multiply by a lot of chargers.

Floor of battery chargers

And then fill an entire floor.

Compressing batteries

After their first charge is complete, the cells are strongly compressed. They told me “6 million pounds,” but orders of magnitude often get mangled in translation. Let’s call it a lot.

Compressed Lipo batteries

Air quickly degrades and causes problems with the battery chemistry. The heavy compression helps force out any remaining air from the cells.

Battery oven

I failed to get the exact amount of time or temperature, but the batteries bake compressed for a few hours.

Cutting off excess

The next step is to remove any excess electrolyte that has been forced out of the main cell and into the side pillow. If you’ve ever smelled a puffed or ‘sweet’ smelling battery, you know what this room smells like. Once the electrolyte is removed, the cell is trimmed.

A single lipo cell

At the end of all this, you have a battery. Technically, this is a single cell because the protection circuit and termination is still required.

Lot of cells

Again, scale is important to remember. Every portable device we play with: tablets, cell phones, shavers, e-cigarettes, RC helicopers, etc. have a LiPo battery. Great power manufactures tens of thousands of cells a day.

Battery Creation

Soldering on protection circuit

The protection circuit prevents the LiPo cell from being over charged (bad things happen when the cell is pushed past 4.3V), under charged (the cell can be harmed if pulled below about 2.8V), and short-circuit (shorting the positive and negative terminals together). If any of these triggers occur, the protection circuit very quickly disconnects the cell from the terminals.

Bettery with terminals

Above, we finally have a formal battery with taped-in protection circuit (the yellow kapton tape) and positive and negative terminal wires (sans connector).

Large tablet battery

Dozens of different models of batteries were all over the factory. Above was a larger battery for a tablet.

Dual cell battery

I found this battery particularly intriguing. I’ve never seen a two part battery. Perhaps the dual cell allows for the battery pack to bend? Large cell goes under the keyboard and small cell behind the screen? I couldn’t get more information about this one, but it does make me think about differently about battery options.

A line of battery workers

Each different battery model had their own line of employees.

Multiple lines of battery manufacturing

Multiply by many lines.

Cylindrical Coverings

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On a different line Lithium Iron Phosphate batteries (LiFePO4) were being made. I was told the process is nearly the same, so I didn’t get as many photos. Because “lithium iron phosphate cells are much harder to ignite in the event of mishandling” they are considered the ‘safer’ battery compared to LiPo batteries. I’m not entirely convinced, but LiFePO4 batteries are finding their way into many rechargeable vehicle applications. Watch out for the nominal 3.2V (instead of 3.7V for LiPos), but if you’re making a massive battery pack of cells in series, 3.2V doesn’t really matter.

Lithium Iron Phosphate Cell Covering

This machine would take bare cells and automatically cut and slip on the heat shrink label. The loose cells then entered a 4 foot heat tunnel. I just love the sound in this video.

Labeled LiFePO4 Battery

After exiting the oven, a AA sized battery complete with heat shrink label.

Battery Testing

After asking so many questions and taking so many photos the materials engineering was really getting into showing me around. I don’t think I was much like their average tour. Excitedly, the engineer asked me if I would like to see the test chamber - YES!

Battery testing cage

On a different floor of the building a caged room housed eight machines of medieval torture. QC and failure testing is a part of every batch of batteries produced during the day.

Oven test chamber

They quickly offered me access and I hesitantly entered. Above is the oven that pushes batteries to their eventual demise.

Battery Crush Tester

The aptly named ‘battery crush tester’ takes a cell and squeezes the sides laterally until it fails.

Puncture tester

The puncture tester is composed of a 10kg mass with a 10mm diameter rod at the end of it. The test pulls this mass 1m into the air and thrusts it down into the flat face of the cell. The engineer fired this one with an astounding thud that caught me off guard. It’s a lot of force.

Needle stake machine

The stake test. Can we poke it until it ignites?

Fold testing machine

The fold test. This presses the cell down onto a length of triangular steel that causes the cell to fold at gnarly angles. Needless to say the carnage was epic and the chambers were covered in the soot of failed cells.

Burned out lipo batteries

A few cells after their voyage.

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Once they reach the end of the test, the cells are decomposed, unrolled, and the failure vector evaluated. Overall I was impressed with the level of undertaking and verification.

Big Batteries

The final stop on the tour was is a room far from the others, on the opposite end of the building.

Very large battery packs

This is where the very large battery packs are built and tested. I was told these are used to power an electric bus.

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Imagine what you could do with 49V at 40,000mAh. The largest packs were 100Ah. That’s nearly 5000Wh! Incredible stuff.

Resources and Going Further

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