Cycle life tests of mixed-technology cells

Pajda

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I have focused the previous three threads Cycle life tests of High Energy density cylindrical cells , Cycle life tests of High Power density cylindrical cells on a state-of-the-art particular Lithium-ion battery (LIB) technology, using small cylindrical formats with so-called ternary (NMC and NCA) cathodes and graphite-based (Gr.) anodes. The next step is to expand the scope to other interesting advanced battery technologies and try to compare them with existing results.

However, this step brings me to the literal comparison of apples with oranges (Btw, people who invent proverbs should consider their validity anywhere in the universe, because oranges do not normally grow in Central Europe, so we use pears instead :sneaky: ). Therefore, I would like to give a brief theory both for casual passers-by who have not had the opportunity to study this topic more and for those who use a different classification. Actually, I should have started with this a long time ago.

I think the clearest way to do this is to start with something what might be called: Pajda's hiearchical map of electrochemical accumulator technology. :) The hierarchy map shown here is limited to the most commonly used LIB technology, where the blue line shows example how to describe technology of a particular sample cell.
Pajda`s Hiearchy map.PNG
* In principle prismatic (hardcase) mechanical format allows the use of both jelly-roll and (Z)-stacking manufacturing technology. In practice, only jelly-roll technology is used. It is also common that several jelly-rolls are connected in parallel inside the big prismatic format cells.

Q&A session:

Q: What is the difference between intercalation and conversion principle?

Pajda's comment:
From an end-user perspective, this information is not crucial. However, it is essential for an academic discussions in „restaurant-type establishments“ that 99.9% of advanced battery production on the market today uses the intercalation principle, eg. lithium-ion batteries (LIB) or sodium-ion batteries (SIB). Emerging technologies, sometimes also called "post-lithium-ion batteries", in particular lithium-sulphur batteries (LSB) or solid-state batteries (SSB), are based on the conversion principle.

Intercalation vs. Conversion principle.PNG
This issue is nicely described in the figure above from this article Redirecting. I expect that the principle of intercalation will remain superior for some time in power density and particularly lifetime to the conversion principle. The reason for this bold statement is that during the intercalation phenomenon only the movement of ions occurs without the need of changes in the crystal structure of the intercalation anode active material. The main reason to consider the conversion principle, which suffer in real-world applications from problems of expansion of the anode active material during the chemical reaction (leading to its mechanical degradation with cycling) is that conversion active materials, typically lithium metal anode (LMA), promise theoretically significantly higher energy density than all previously known intercalation anode materials like carbon/graphite and LTO or NTO (N here stands for Niobium).

Q: What is the difference between High Energy (HE) and High Power (HP)?

Pajda's comment:
This issue is nicely described in the following table from this article Design Strategies for High Power vs. High Energy Lithium Ion Cells. The point is to achieve the best possible current path from the active material to the cell terminals by internal structure design. The weight (thickness) and porosity of the active material coating in combination with coating process have an important influence here. The low weight of the active material coating is essential for HP applications where it has a significant effect on the energy density (less active material in the cell). This, together with thicker current collectors is the main reason why HP cells have approximately 20% lower energy density than HE cells, both using the same active material. Another consequence of HP optimization is often a lower lifetime of the cell, both cyclic and calendar.

Table HP vs HE optimisation.png
Q: Where is Li-pol?

Pajda's comment:
In my opinion, this issue should be divided into two:

What Li-pol technology supposed to be? Historically, the most problematic component in all battery technologies has been the liquid electrolyte. The biggest practical concerns with liquid electrolytes for end-users are safety, limited operating temperature range and lifetime. One of the urban legends says that Li-pol technology was supposed to deliver a solid, or at least gel polymer electrolyte (GPE) in conjunction with the intercalation principle. As far as I know, this idea has never worked in practical applications. Currently, solid electrolytes are considered mostly with the conversion principle with lithium metal anodes as a solid-state batteries (SSB) technology.

What is in 99.9% sold today as Li-pol? From the technology point of view, it is a different mechanical format of the cell housing (pouch), coupled with a different approach to mechanical manufacturing process of the cell, the so-called “(Z)-stacking” and subsequent lamination. The crucial information is that pouch format cell uses the same intercalation principle, chemical compositions and HE/HP optimizations with liquid electrolytes as in other LIB/SIB mechanical formats.

Q: Why it is important to specify both cathode and anode material?

Pajda's comment:
Looking at the map on the LIB technology hierarchy, it is worth pointing out that the cathode and anode active materials listed here can be combined essentially arbitrarily. So, if we talk about NMC technology, we automatically mean with Gr. anode. However, NMC cathode is also often used with LTO anode. The combination of LFP with LTO also works, but in practice offers pathetic energy density.

For technical notation I use the pattern: cathode//anode. An example: NMC//Gr. The double forward slash is here used by me purely for practical reasons, where a single forward slash is often understood to mean "or" in the written text. Another problem with ambiguous notation is NMC//C, where C at the cathode means cobalt, whereas C at the anode means carbon. Btw., there is a lot of confusion about abbreviations in the battery business. A typical letter "S" in a given context can mean: Sulfur, Sodium or Solid-State :unsure:"

Another practical problem is to determine the actual composition of the active material in a given cell sample, especially at the cathode side. This information should be included in the mandatory document called: material safety datasheet (MSDS). Unfortunately, manufacturers are allowed to state here only that the cathode composition consists of “lithium metal transition oxide”, from which it is impossible to read whether it is an NMC or NCA composition.

Q: Why it is always good to specify Energy & P-rate rather than Capacity & C-rate?

Pajda's comment:
it's the different nominal voltage of different technologies. The difference between the nominal voltages of the ternary cathodes NMC and NCA is usually negligible. But if we enter the wild waters of other compositions, the nominal voltage starts to change drastically. At this point it should be mentioned that different nominal voltages affect both the energy and the actual power delivered. Thus, instead of the standard C-rate and CC discharging method, it would be correct to use P-rate and CP discharging method.

I'm going to stick with a combination of C-rate and CC discharging method with added both discharge Capacity&Energy graphs.
 
High Power Charging test (3C-3C continuous charge & discharge )

note: the test is performed at voltage ranges equvalent to 100% nominal capacity DoD

Test eqiupment:
- NEWARE BTS4000
- tested in room with relatively stable temperature 23 ±2 °C
- NEWARE four-wire cell fixture (20A version with "huge" golt plated contacts)
- 0.5mm Cu strips welded by Micro-TIG system with 4 mm2 load wires and 0.5 mm2 sense wires.

Remarks and comments:
- each 100th cycle is inserted datasheet nominal capacity test with 10s DCIR test

__
added Molicel INR21700-P50B (NMC//Gr., BTS4000 tester, Cu-strips), sample source: Vapcell
added Molicel INR21700-P45B (NMC//Gr., BTS4000 tester, Cu-strips), sample source: NKON
added LithiumWerks ANR26650m1b (LFP//Gr., BTS4000 tester, NEWARE fixture), sample source: NKON

added Molicel INR18650-P30B (NMC//Gr., BTS4000 tester, Cu-strips), sample source: NKON
added Tenpower INR18650-15SG (NMC//Gr., BTS4000 tester, NEWARE fixture), sample source: NKON
added LithiumWerks ANR18650m1b (LFP//Gr., BTS4000 tester, NEWARE fixture), sample source: ---
added HAKADI PLITR18650 (NMC//LTO, BTS4000 tester, NEWARE fixture), sample source: HAKADI
added HAKADI 18650P (*SIB, BTS4000 tester, NEWARE fixture), sample source: HAKADI

18650 size
"TRUE" 3C charge - 3C discharge
(charging with CC-CV method with 20 min cut-off time condition)

AiO_True-3C-3C_cycle_life_test@capacity.PNG
AiO_True-3C-3C_cycle_life_test@energy.PNG
AiO_True-3C-3C_cycle_life_test@DCIR10s.PNG


"STANDARD" 3C charge - 3C discharge
(charging with CC-CV method with ca C/10 cut-off current condition)


comming soon!
 
Last edited:
"Long Life" cycle life test
comparison of cells optimised for low cost & long life with modern HE/HP cells

Test eqiupment:
- ZKETECH EBC-X0510
- Neware BTS4000
- BF-2A four-wire cell fixture (10A version with Nickel plated contacts)
- tested in room with relatively stable temperature 23 ±2 °C

Remarks and comments:
- each 50th or 100th cycle is inserted datasheet nominal capacity test with 10s DCIR test
- minimal charging CV phase cut-off current is set to 100 mA due to the ZKETECH testers limitation
____
added DMEGC INR18650-26E to the chart (X0510 & BTS4000 tester), sample source: Tumich ES
added BAK N21700-50CG to the chart (X0510 & BTS4000 tester), sample source: BAK
added Molicel INR21700-P45B to the chart (X0510 & BTS4000 tester), sample source: Molicel

Long_cycle_life_test@capacity.PNG
Long_cycle_life_test@energy.PNG
Long_cycle_life_test@DCIR10s.PNG
 
Last edited:
small data update

3C-3C cycle
added Moli P50B, P45B (and another LFP sample from LithiumWerks/A123 in 26650 format)

- We can see that a true 20 minute fast charge (0-95% SoC) is not a problem for modern cells.
- Both, Moli P30 and P45 hit 60% SoH at about 1,300 cycles.
- Moli P50B so far shows that the only tax for higher capacity/energy density is much higher price
- For both LFP samples from LW, the first 1,000 cycles were only a warm-up lap, the same for LTO sample.

Long life
- DMEGC finished 4,000 cycles (btw. its test was launched on October 13, 2022)
- BAK CG begins to fade after 2,000 cycles
 
High Power Charging test (3C-3C continuous charge & discharge )

note: the test is performed at voltage ranges equvalent to 100% nominal capacity DoD

Test eqiupment:
- NEWARE BTS4000
- tested in room with relatively stable temperature 23 ±2 °C
- NEWARE four-wire cell fixture (20A version with "huge" golt plated contacts)
- 0.5mm Cu strips welded by Micro-TIG system with 4 mm2 load wires and 0.5 mm2 sense wires.

Remarks and comments:
- each 100th cycle is inserted datasheet nominal capacity test with 10s DCIR test

__
added Molicel INR21700-P50B (NMC//Gr., BTS4000 tester, Cu-strips), sample source: Vapcell
added Molicel INR21700-P45B (NMC//Gr., BTS4000 tester, Cu-strips), sample source: NKON
added LithiumWerks ANR26650m1b (LFP//Gr., BTS4000 tester, NEWARE fixture), sample source: NKON

added Molicel INR18650-P30B (NMC//Gr., BTS4000 tester, Cu-strips), sample source: NKON
added Tenpower INR18650-15SG (NMC//Gr., BTS4000 tester, NEWARE fixture), sample source: NKON
added LithiumWerks ANR18650m1b (LFP//Gr., BTS4000 tester, NEWARE fixture), sample source: ---
added HAKADI PLITR18650 (NMC//LTO, BTS4000 tester, NEWARE fixture), sample source: HAKADI
added HAKADI 18650P (*SIB, BTS4000 tester, NEWARE fixture), sample source: HAKADI

18650 size
"TRUE" 3C charge - 3C discharge
(charging with CC-CV method with 20 min cut-off time condition)


View attachment 358619
View attachment 358621
View attachment 358620

"STANDARD" 3C charge - 3C discharge
(charging with CC-CV method with ca C/10 cut-off current condition)


comming soon!
I didn't notice until now, but holy crap. The P50B doesn't give ANY crap about high power charging when it comes to IR.
It keeps trucking on and on.

With a much better charging algorithm than CCCV, it could probably truck on for a very long time at these power rates.
 
updated data for both 3C-3C Fast charging cycle-life and "long-life" in the first posts.

Fast charge:
-Molicel P50B shows slightly better cycle-life performance than P45B in fast charging cycle. I will continue with cycling to see if it can surpass the 1300 cycle mark where the P45B and P30B ended.

Long life:
- BAK CG50 was ended at 2500 cycles.
- Added Molice P45B to see how it performs in low power apps.
 
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