IN A Doodle: Why Your MacBook Battery is Dying

Batteries & The Future of Lithium-Ion

Elly Peng
8 min readFeb 13, 2022

One thing I love hating about my Mac is the battery life.

A fully-charged MacBook Pro battery is supposed to last you 10 hours with its “impressive all-day battery life,” but mine barely makes it into the “impressive all-morning battery life” group.

But, here are a few things I’ve heard (and done) to improve my battery life.

… with minimal success. Okay, okay, they do work, but they’re not going to improve your battery lifespan by 2x 5x or even 10x.

But what will?

The main problem we’re working with is charge cycles.

Let’s unpack that.

Cycle = discharging 100% of a battery (related to battery capacity)

Cycle count = # of cycles the battery can undergo over its lifetime (related to battery lifespan)

The length of one cycle differs from one battery to another, and so does the count. An average laptop battery has about 500 to 700 charge cycles, but the length of one cycle varies. For any Tesla, the battery will last for at least 262 miles on a single charge and has about 1 500 charge cycles.

To improve batteries, we can a) extend their cycle duration or b) increase the total # of cycles. Or both.

So… what about:

Tip 7 — Wait for the future developments of silicon anode lithium-ion batteries?

Before we go there, let’s take a few steps back and talk about secondary batteries.

I know about secondary batteries, skip to lithium-ion components.

Types of Secondary Batteries

Primary batteries = single-use / disposable

Secondary batteries = rechargeable

Let’s look at the most common secondary batteries to see which ones are potential candidates for our MacBooks or Electric Vehicles.

Lead-Acid Batteries

This is an older type of battery and usually is pretty heavy and big.


Typical uses are energy storage, emergency power, communication systems, emergency lighting systems — basically emergency backup.

The Good & Bad

Pros — It’s cheap, powerful, easily rechargeable, and has high power output capabilities.

Cons — It’s cumbersome. Lead-acid batteries are usually large bricks as their power density is very low. Also, it’s pretty sensitive to temperature — optimum function at 25°C (77°F).

So, not ideal for slim, agile designs.


Nickel-Cadmium Batteries

Along with lead-acid batteries, Ni-Cd batteries are among the oldest battery types available today.


Ni-Cd batteries are used in telephone systems, standby generators, and industrial critical backup applications because of their ability to operate through a high-temperature range (a capability lead-acid batteries don’t have).

The Good & Bad

Pros — It’s cheap, heavy-duty, and easy to recharge.

Cons — Again, had a low power density, requires full discharge and recharge cycles, so it doesn’t lose life span as quickly (search: memory effect), and contains toxic metal.

Would be annoying to wait for your computer to die before you recharge it, so let’s pass on this one.

Nickel-Metal Hydride Batteries

Nickel-metal hydride is a relatively new type of battery.


It’s used in some phones, shavers, computers, and other portable applications. It’s also seen in hybrids (example: Toyota).

The Good & Bad

Pros — It has high power density, comes in standard sizes, and has a good amount of charge cycles.

Cons––It self-discharges quickly (loses charge even when not used) and generates a lot of heat while charging ( inconvenient to use at the same time).

Now, here’s when things get interesting.

Lithium-Ion Batteries

MacBooks use Lithium-ion batteries. So do Teslas!


A lot of day-to-day appliances and utilities use Li-ion batteries.

  1. Portable electronic devices: watches, cameras, phones, laptops
  2. Entertainment: radios, all infrared remote controls, toys, games, keyboards.
  3. Household: clocks, alarms, flashlights, toothbrushes, portable power tools (drills, screwdriver)

And also, it’s used in most EVs (example: Tesla, Jaguar)

The Good & Bad

Pros — it’s ultra-light, high power, high capability, high cell voltage

Cons — It’s more expensive, delicate, can explode if misused!

As you’ve probably realized, Lithium-ion batteries are the real deal, but how do we improve them? Let’s unpack the components of Li-ion batteries.

I generally know about lithium-ion batteries, skip to energy vs power density.

The 4 Parts of Lithium-Ion Batteries

The 4 main components are the anode (made of graphite), cathode (transition metal oxides), separator, and electrolyte.

Here’s a visual breakdown:

The electrolyte carries positively charged lithium ions (and prevents other compounds) from the anode to the cathode.

When a battery is charging, ions flow from the cathode to the anode.

When it’s discharging, the ions flow from the anode to the cathode.

The separator blocks the flow of electrons inside the battery, creating a current.

Energy VS Power Density

Two important concepts when dealing with battery efficiency are energy density and power density.

Energy density is the amount of energy the battery can store in comparison to mass.

Power density is the amount of power generated in comparison to mass. This is how quickly the battery can discharge.

Fun analogy time! Energy density is like the size of a bathtub. Power density is how fast the bathtub can be drained.

History of Li-ion Batteries

In 1994, graphite anodes allowed Li-ions to become commercially viable and are still used in the vast majority of anodes.

It’s low-cost, abundant, and offers solid energy and power density.

Starting from 2010, research and development focus on increasing energy and power density by incorporating silicon (SiOx) or even switching to silicon anodes.

Silicon Anodes in Li-ion Batteries?

Silicon is already used in computer chips and other tech-y products (cue Silicon Valley). It can hold 10x the electrical charge per gram in comparison to graphite.

So, with a theoretical capacity of 10x graphite, it has the potential to at least double the capacity of lithium-ions.

New problem…

Silicon’s ability to absorb lithium and expand during charging actually causes a problem: it breaks down quickly.

Even thorough silicon can take on more lithium than graphite, it expands around 300% when it encounters lithium and is too weak to withstand the pressure of the electrode.

Before we despair, scientists are exploring ways to protect the silicon. One of them is creating a gatekeeper. This means creating a coating over the silicon to allow the lithium ions in and out of the anode without other components of the electrolyte interfering.

What now?

Will graphite remain an essential part of lithium-ion batteries in the near future? Probably yes.

Is the research into silicon promising? Hopefully.

Next time you’re scrambling for a charger to save your Mac, think about what life would be like with silicon anode Li-ion batteries. Or don’t.

Let’s be friends :)

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