Yes, iPhones use lithium-ion batteries, not alkaline or other types
Every iPhone model from the original 2G through the latest versions contains a lithium-ion rechargeable battery. This is the same battery chemistry used in most smartphones, laptops, and portable electronics. Apple does not make alkaline batteries for iPhones, and you cannot swap in a different battery type—the phone is designed specifically for lithium-ion.
Lithium-ion batteries work by moving lithium ions between two terminals (called the anode and cathode) through a chemical electrolyte. This movement creates electrical current that powers your phone. Unlike alkaline batteries you buy at a store, lithium-ion batteries are rechargeable and lose capacity over time with repeated charge cycles.
The specific type Apple uses is a lithium-ion polymer battery, sometimes called Li-Po. This variant is thinner and lighter than older lithium-ion designs, which is why it fits inside the slim iPhone case. The battery is soldered directly to the phone's logic board in most models, meaning you cannot remove it yourself without specialized tools.
Key Takeaways
- All iPhones contain lithium-ion polymer batteries that are rechargeable and built into the phone.
- Lithium-ion batteries lose capacity gradually over time, typically retaining about 80 percent of their original capacity after 500 charge cycles.
- You cannot replace an iPhone battery yourself in most models without damaging the phone, though Apple and authorized repair shops offer battery replacement services.
- Lithium-ion batteries can overheat or swell if damaged, so a cracked screen or water damage may require battery inspection.
How iPhone lithium-ion batteries degrade over time
A lithium-ion battery loses capacity with every charge cycle. One charge cycle means draining the battery from 100 percent to zero and back to 100 percent—not every time you plug in your phone. After about 500 full cycles, most iPhone batteries retain roughly 80 percent of their original capacity. After 1,000 cycles, they typically hold around 60 percent.
This degradation happens because the chemical reactions inside the battery are not perfectly efficient. Each time lithium ions move through the electrolyte, some of the material breaks down slightly. Heat speeds up this process, which is why iPhones that run hot or are left in warm environments lose capacity faster than those kept cool.
Apple's battery health feature (found in Settings > Battery > Battery Health & Charging on iOS 16 and later) shows you the current capacity of your battery as a percentage. If it drops below 80 percent, you may notice your phone shuts down unexpectedly at low battery levels, even though the percentage says 20 or 30 percent remaining. This happens because the degraded battery cannot deliver power as quickly as the phone demands.
What happens when an iPhone lithium-ion battery fails
A failing lithium-ion battery can swell, overheat, or stop holding a charge. Swelling is the most visible sign—the battery expands and can push the screen or back panel away from the frame, creating a visible gap or bulge. This is a safety issue because a swollen battery can rupture and leak electrolyte, which is corrosive.
Overheating happens when the battery's internal resistance increases as it degrades. The phone may feel warm during normal use or even during charging. In rare cases, a damaged lithium-ion battery can catch fire, though this is uncommon in iPhones because Apple includes safety circuits that cut power if the battery overheats.
If your iPhone battery swells, stops charging, or causes the phone to shut down unexpectedly, do not attempt to open the phone yourself. Take it to an Apple Store or an authorized repair shop. They have the tools to safely remove the battery and replace it with a new lithium-ion battery.
iPhone battery replacement options and costs
Apple offers battery replacement through the Apple Store, Apple Authorized Service Providers, and mail-in repair. The cost varies by iPhone model but typically ranges from $50 to $70 for most current models. If your iPhone is still under warranty or covered by AppleCare+, the replacement may be free or discounted.
The process takes one to three hours at an Apple Store if you drop it off, or one to two weeks if you mail it in. During replacement, technicians remove the old lithium-ion battery, test the phone's other components, and install a new battery. The new battery is also lithium-ion polymer, identical to the original.
Third-party repair shops also replace iPhone batteries, often at lower cost than Apple. However, using a non-Apple battery or an unauthorized repair shop may void your warranty and could result in a lower-quality battery that degrades faster or poses safety risks. If you choose a third-party shop, ask whether they use genuine Apple batteries or aftermarket alternatives.
How to extend your iPhone lithium-ion battery life
You can slow down battery degradation by keeping your phone cool, avoiding deep discharges, and using optimized charging settings. Lithium-ion batteries degrade faster when exposed to heat, so avoid leaving your iPhone in direct sunlight, in a hot car, or near heat sources. Even a few degrees of temperature difference can extend battery lifespan by months.
Avoid letting your battery drain completely to zero regularly. While one full discharge cycle is necessary occasionally for battery health, repeatedly draining to zero stresses the battery more than charging from 20 or 30 percent. Most modern phones, including iPhones, are designed to be charged frequently from partial states.
Enable Optimized Battery Charging in Settings > Battery > Battery Health & Charging. This feature learns your charging patterns and slows down charging to 80 percent overnight, then finishes the last 20 percent an hour before you typically wake up. This reduces the time your battery spends at 100 percent, which is when degradation happens fastest.
Use Low Power Mode when your battery drops below 20 percent. This reduces processor speed and background activity, which slows down discharge and reduces heat. Enabling it regularly, even at higher battery levels, can extend the time between replacements.
Lithium-ion vs. other battery types in phones
Lithium-ion is the standard for smartphones because it offers high energy density (lots of power in a small space), rechargeability, and a long lifespan compared to older technologies. Alkaline batteries, which you buy in packs at stores, cannot be recharged and would need to be replaced constantly. Nickel-cadmium and nickel-metal hydride batteries, used in older phones, had memory effects and lower capacity.
Solid-state batteries, which replace the liquid electrolyte with a solid material, are being researched as a future replacement for lithium-ion. They could offer higher capacity and faster charging, but they are not yet in commercial phones. Apple has not announced plans to use solid-state batteries in iPhones, though the company continues to research battery technology.
Some manufacturers experiment with graphene or other materials to improve battery performance, but these are still in development. For now, lithium-ion polymer remains the best balance of safety, cost, and performance for iPhones and nearly all consumer electronics.
Frequently Asked Questions
Can I replace my iPhone battery myself?
Technically yes, but it is not recommended. iPhone batteries are soldered to the logic board and require specialized tools to remove safely. Attempting it yourself risks damaging the screen, logic board, or battery, which can cause the phone to malfunction or the battery to overheat. Apple and authorized repair shops have the proper equipment and training.
Why does my iPhone battery drain faster in cold weather?
Lithium-ion batteries perform poorly in cold temperatures because the chemical reactions inside slow down. Your phone may show a lower battery percentage or shut down unexpectedly, even though the battery is not actually damaged. The battery recovers normal performance once the phone warms up. Extreme cold can cause permanent damage, so avoid leaving your iPhone outside in freezing temperatures for long periods.
Is it bad to leave my iPhone plugged in overnight?
Modern iPhones are designed to handle overnight charging safely. Once the battery reaches 100 percent, the phone stops charging and switches to a trickle charge to maintain the level. Optimized Battery Charging slows this process further by pausing at 80 percent until an hour before you wake up. Leaving your phone plugged in occasionally is fine, but doing it every night may slightly reduce battery lifespan over years.
What does it mean when my iPhone battery health says 79 percent?
It means your battery is retaining 79 percent of its original capacity. This is normal after one to two years of regular use. At this level, you may notice your phone lasts slightly less time per charge than when it was new. Most people do not need to replace the battery until it drops to 70 percent or lower, unless the phone is shutting down unexpectedly.
Can I use a non-Apple charger with my iPhone lithium-ion battery?
Yes, any charger that meets Apple's specifications (USB-C or Lightning connector, appropriate wattage) will charge your iPhone safely. The phone's internal charging circuit controls how much power the battery receives, so a third-party charger cannot overcharge or damage the battery. However, using a very low-wattage charger will charge more slowly, and using a damaged charger could pose a safety risk.