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What Is the Difference Between Lithium and NiMH Batteries? 

 September 19, 2021

By  Phil Borges

There are several different kinds of batteries that can be used for multiple purposes. Some of these include rechargeable batteries such as lithium and nickel-metal hydride (NiMH) batteries.

Lithium and NiMH batteries mainly differ from each other on the basis of the elements that they are composed of. These can then also determine their other distinctions such as rate of self-discharge, cost, energy density, capacity, recharging times, safety, applications and their impact on the environment, among others.

You can learn more about each of these differences by reading the next section that details everything you should know about these batteries.

Difference Between NiMH and Lithium-Ion Batteries

Let’s take a look at the main differences between these two batteries.

Composition

Lithium-ion batteries include a compound (that includes lithium) at the positive electrode and an ion such as graphite at the negative electrode. There can be several variations in this composition in terms of the compounds present at the cathode as well as the materials that make up the electrolyte.

NiMH batteries have a nickel-based compound (nickel oxide hydroxide) at the cathode or positive electrode and an alloy at the anode or negative electrode that can absorb hydrogen. The electrolyte is alkaline in nature.

These compositions tend to determine the other characteristics of each of these batteries, such as their energy density, capacity, cost, discharge rate and more.

Self-Discharge Rate

Rechargeable batteries have a tendency of losing some of their efficiency as time passes by due to normal losses that take place during the electrochemical reactions frequently taking place in the batteries. This can take place even if the batteries are not connected.

For lithium-ion batteries, the self-discharge rate is only 1-2% per month. With time, however, this rate tends to go on increasing along with several external unfavorable conditions such as extreme temperatures, high humidity, damage and more, if any.

The self-discharge rate for NiMH batteries can go up to 2.9% per month, which is a bit higher than lithium-ion batteries. The higher rate for these is nearly 30% per month.

Recharging

Recharging takes around an hour for both lithium-ion and NiMH batteries as long as you do it with an authentic and compatible charger. This can, of course, vary depending on the size and capacity of the batteries.

Lithium-ion batteries claim to not exhibit a memory effect, which refers to a phenomenon in which batteries lose some of their effectiveness if you keep recharging them at a small discharge level.

However, research has found that they experience this issue as well, just like NiMH batteries do.

Further, NiMH batteries have more charging cycles than lithium-ion batteries, with the former going up to 2,000 and the latter up to 1,200.

Cost

NiMH batteries tend to be more affordable as compared to lithium-ion batteries as the latter makes use of a lot more expensive elements and processes in terms of manufacturing.

Further, lithium-ion batteries also have a lot more detail in terms of their control and regulation as compared to NiMH batteries.

Size

Lithium-ion batteries tend to be smaller in size as compared to NiMH batteries, while also being much lighter in weight. Lighter batteries generally have a higher energy density.

However, while NiMH batteries come in common sizes, the sizes of lithium-ion batteries usually depend on the manufacturers. This makes the size vary significantly and may not always come in standard sizes.

Energy Density

When it comes to rechargeable batteries, energy density refers to how much charge a battery holds in each gram. Lithium-ion batteries have a much higher density as compared to NiMH batteries, holding anywhere between 250 and 700 watts per hour.

In comparison, NiMH batteries hold around 150-300 watts per hour.

This energy density tends to be determined by compounds, electrolytes and ions or other elements that form these batteries.

This high energy density of lithium-ion batteries makes them convenient to use for a long time, especially when it comes to portable devices or appliances.

Compatibility

Since NiMH batteries come in standard sizes, they tend to be a lot more compatible with multiple devices as compared to lithium-ion batteries that are more dependent on their manufacturers for their size.

Further, lithium-ion batteries are more commonly used in larger appliances such as electric vehicles, power tools like drills, saws and other equipment as well as in electronic devices like smartphones, laptops, cameras and more.

In fact, these batteries have now also replaced NiMH batteries in electric cars.

NiMH batteries can more commonly be found in smaller devices that require standard-sized batteries, such as torches, clocks, watches and more.

Capacity

NiMH batteries have a smaller voltage per cell, which is only 1.2 volts. This is a bit lesser as compared to other batteries such as lithium-ion batteries that have a cell voltage of 3-3.85 volts each.

This does, however, imply a more steady flow of power from the batteries into the devices but falls short in terms of strength.

However, the current drawn from NiMH batteries is higher at nearly 2,000-2,700 mAh as compared to that of lithium-ion batteries at approximately 1,500 mAh.

The range in NiMH varies according to the self-discharge rate of the batteries, with lower self-discharge rates showing lower capacities.

Safety

NiMH batteries are generally safer than lithium-ion batteries. This is because lithium-ion batteries comprise elements that are highly reactive, including lithium itself.

Depending on the kinds of substances used in lithium-ion batteries, the reactivity of these batteries could differ and can lead to major accidents such as explosions or fires if something goes wrong.

Further, due to the risks of overheating due to high voltages, these batteries can prove to be hazardous. There are also several restrictions on their transportation, such as in airplanes. Several recalls of these batteries have also taken place over the years.

Environmental Impact

While lithium-ion batteries can sometimes pose a safety hazard, they are more environmentally friendly as compared to NiMH batteries. The metals used to make lithium-ion batteries are comparatively safer for landfills and can also be easily recycled.

NiMH batteries present more toxicity in this regard in terms of how they react in the environment. Leakages can further be damaging if not contained.

However, both kinds of batteries still contribute a lot to pollution in terms of their production. Their disposal impacts can be reduced if proper recycling is carried out.

Since these batteries are rechargeable, their environmental impact is still significantly lesser than single-use batteries.

Frequently Asked Questions

Which battery is better?

In terms of the details and specifications discussed through this guide, lithium-ion batteries present a more efficient solution in terms of self-discharge rate, energy density, weight and environmental impact, among others.

However, if you are looking for something more durable, affordable and safer, then NiMH batteries might be a better choice, particularly if you only need to power small appliances and devices.

Apart from that, lithium-ion batteries have been replacing NiMH batteries rapidly.

Do these batteries need special chargers?

You should ideally use special chargers for both lithium-ion and NiMH batteries to ensure compatibility without causing issues like short circuits or reduced efficiency.

Incompatible chargers can also reduce the overall lifespan much quicker as compared to original chargers.

Do these batteries have specific storage requirements?

When it comes to these batteries (or any battery), you should ensure that the external temperature, humidity levels and storage container are all suitable for the batteries.

Extremely cold or hot temperatures and high levels of humidity can reduce the efficiency of these batteries. Further, since lithium-ion has several reactive elements, you should take care of their safety throughout the storage period.

You must also keep them with a partial charge without completely discharging or overcharging either of these batteries.

Can I use these batteries to replace single-use batteries in devices?

In most cases, you should be able to replace your single-use batteries with NiMH batteries since they not only have a low voltage output but also tend to come in standard sizes.

Lithium-ion batteries may not entirely be suitable for replacement due to their higher output and different sizes.

In either case, you should check the device guide to confirm these details.

About the author

Hi, I'm Phil Borges.. thanks for reading.. My wife says I can't shut up about batteries so to save my marriage I've started this blog .. where I'd be ranting about batteries! Please leave a comment if you have any questions, I'm happy to help!

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