Batteries
Contents
Objectif
- obtenir des batteries au prix le plus bas possible, impliquant probablement un assemblage maison de cellules
- acquérir des connaissances dans le domaine des batteries, faire les choses selon les normes en vigueur, ne pas compromettre la sécurité
Applications
Batteries Lithium-ion
https://en.wikipedia.org/wiki/Lithium-ion_battery
Handheld electronics mostly use LIBs based on lithium cobalt oxide (LiCoO2), which offers high energy density, but presents safety risks, especially when damaged.
Lithium iron phosphate (LiFePO4), Lithium ion manganese oxide battery (LMnO or LMO) and lithium nickel manganese cobalt oxide (LiNiMnCoO2 or NMC) offer lower energy density, but longer lives and inherent safety. Such batteries are widely used for electric tools, medical equipment and other roles. NMC in particular is a leading contender for automotive applications.
Lithium nickel cobalt aluminum oxide (LiNiCoAlO2 or NCA) and lithium titanate (Li4Ti5O12 or LTO) are specialty designs aimed at particular niche roles.
http://batteryuniversity.com/learn/article/types_of_lithium_ion
While Li-aluminum (NCA) is the clear winner by storing more capacity than other systems, this only applies to specific energy.
In terms of specific power and thermal stability, Li-manganese (LMO) and Li-phosphate (LFP) are superior.
Li-titanate (LTO) may have low capacity but this chemistry outlives most other batteries in terms of life span and also has the best cold temperature performance.
Sélection
| caracteristics | NMC | LiFePO4 | LTO |
|---|---|---|---|
| nominal voltage [V] | 3.6, 3.7 | 3.2, 3.3 | 2.4 |
| typical operating range [V/cell] | 3.0–4.2 or higher | 2.5–3.65 | 1.8–2.85 |
| Specific energy (capacity) [Wh/kg] | 150–220 | 90–120 | 70–80 |
| Charge (C-rate) typical | 0.7–1 C; Charge current above 1C shortens battery life. | 1 C | 1 C; 5C maximum |
| charges to [V] | 4.2, some go to 4.3 | 3.65 | 2.85 |
| Charge time [h], typical | 3 | 3 | |
| Discharge (C-rate) | 1 C; 2 C possible on some cells | 1 C, 25 C on some cells; 40 A pulse (2 s) | 10 C possible, 30 C 5 s pulse |
| Discharge cut-off voltage [V] | 2.5 | 2.5 (lower that 2 V causes damage) | 1.8 |
| Cycle life (related to depth of discharge, temperature) | 1000–2000 | 1000–2000 | 3000–7000 |
| Thermal runaway temperature [°C], typical | 210 | 270 | |
| Thermal runaway, others | High charge promotes thermal runaway | Very safe battery even if fully charged | One of safest Li-ion batteries |
| Applications | E-bikes, medical devices, EVs, industrial | Portable and stationary needing high load currents and endurance | UPS, electric powertrain (Mitsubishi i-MiEV, Honda Fit EV), solar-powered street lighting |
| Comments | Provides high capacity and high power. Serves as Hybrid Cell. Favorite chemistry for many uses; market share is increasing. | Very flat voltage discharge curve but low capacity. One of safest Li-ions. Used for special markets. Elevated self-discharge. | Long life, fast charge, wide temperature range but low specific energy and expensive. Among safest Li-ion batteries. |
de côté
LMO et NCA, mis en commentaire
Formes
Li-ion cells (as distinct from entire batteries) are available in various shapes, which can generally be divided into four groups:
- Small cylindrical (solid body without terminals, such as those used in laptop batteries)
- Large cylindrical (solid body with large threaded terminals)
- Pouch (soft, flat body, such as those used in cell phones)
- Prismatic (semi-hard plastic case with large threaded terminals, such as vehicles' traction packs)
https://en.wikipedia.org/wiki/Lithium_polymer_battery
A lithium polymer battery, or more correctly lithium-ion polymer battery (abbreviated variously as LiPo, LIP, Li-poly and others), is a rechargeable battery of lithium-ion technology in a pouch format. Unlike cylindrical and prismatic cells, LiPos come in a soft package or pouch, which makes them lighter but also less rigid.
[...] "polymer" refers more to a "polymer casing" (that is, the soft, external container) rather than a "polymer electrolyte". While the design is usually flat, and lightweight, it is not truly a polymer cell, since the electrolyte is still in liquid form, although it may be "plasticized" or "gelled" through a polymer additive.
LiFePO4
http://batteryuniversity.com/learn/article/types_of_lithium_ion
high current rating and long cycle life, besides good thermal stability, enhanced safety and tolerance if abused.
LiFePO4 is more tolerant to full charge conditions and is less stressed than other lithium-ion systems if kept at high voltage for a prolonged time. As a trade-off, the lower voltage of 3.2 V/cell reduces the specific energy to less than that of LMO. With most batteries, cold temperature reduces performance and elevated storage temperature shortens the service life, and LiFePO4 is no exception. LiFePO4 has a higher self-discharge than other Li-ion batteries, which can cause balancing issues with aging.
Four cells in series produce 12.8 V, a similar voltage to six 2 V lead acid cells in series. Vehicles charge lead acid to 14.4 V (2.4 V/cell) and maintain a topping charge. With four LiFePO4 cells in series, each cell tops at 3.6 V, which is the correct full-charge voltage. At this point, the charge should be disconnected but the topping charge continues while driving. LiFePO4 is tolerant to some overcharge; however, keeping the voltage at 14.4 V for a prolonged time, as most vehicles do on a long drive, could stress LiFePO4. Cold temperature operation starting could also be an issue with LiFePO4 as a starter battery.
LiFePO4 has excellent safety and long life span but moderate specific energy and elevated self-discharge.
LiNiMnCoO2 / NMC
http://batteryuniversity.com/learn/article/types_of_lithium_ion
Similar to LMO, these systems can be tailored to serve as Energy Cells or Power Cells. For example, NMC in an 18650 cell for moderate load condition has a capacity of about 2800 mAh and can deliver 4 A to 5 A; NMC in the same cell optimized for specific power has a capacity of only about 2000 mWh but delivers a continuous discharge current of 20 A. A silicon-based anode will go to 4000 mAh and higher but at reduced loading capability and shorter cycle life. Silicon added to graphite has the drawback that the anode grows and shrinks with charge and discharge, making the cell mechanically unstable.
NMC is the battery of choice for power tools, e-bikes and other electric powertrains. The cathode combination is typically one-third nickel, one-third manganese and one-third cobalt, also known as 1-1-1. This offers a unique blend that also lowers the raw material cost due to reduced cobalt content. Another successful combination is NMC with 5 parts nickel, 3 parts cobalt and 2 parts manganese. Further combinations using various amounts of cathode materials are possible. New electrolytes and additives enable charging to 4.4 V/cell and higher to boost capacity
NMC has good overall performance and excels on specific energy. This battery is the preferred candidate for the electric vehicle and has the lowest self-heating rate.
There is a move towards NMC-blended Li-ion as the system can be built economically and it achieves a good performance. The three active materials of nickel, manganese and cobalt can easily be blended to suit a wide range of applications for automotive and energy storage systems (EES) that need frequent cycling. The NMC family is growing in its diversity.
Li4Ti5O12 / LTO
http://batteryuniversity.com/learn/article/types_of_lithium_ion
LTO has a nominal cell voltage of 2.4 V, can be fast charged and delivers a high discharge current of 10 C, or 10 times the rated capacity. The cycle count is said to be higher than that of a regular Li-ion. LTO is safe, has excellent low-temperature discharge characteristics and obtains a capacity of 80% at –30°C. However, the battery is expensive and at 65 Wh/kg the specific energy is low, rivalling that of NiCd. LTO charges to 2.8 V/cell, and the end of discharge is 1.8 V/cell.
Typical uses are electric powertrains, UPS and solar-powered street lighting.
LTO excels in safety, low-temperature performance and life span. Efforts are being made to improve the specific energy and lower cost.
de côté
LMO et NCA, mis en commentaire
Modèles de location
Puisque c'est un modèle commercial qui est pratiqué (en particulier s'agissant de certains véhicules électriques), il vaudrait la peine de le décrire/comprendre afin d'en tenir compte et de ne pas passer à côté de solutions économiquement intéressantes.
