La batterie de mon téléphone peut encore tenir toute la journée.

French often describes a part of something with the + noun + de + owner/object rather than using a possessive adjective.

So instead of saying my phone’s battery, French naturally says:

la batterie de mon téléphone = the battery of my phone

This is very common with body parts, objects, and components:

• la porte de la voiture = the car door
• l’écran de mon ordinateur = my computer screen
• la batterie de mon téléphone = my phone battery

You could say ma batterie in some contexts, but by itself that usually means my battery in a more general sense, not specifically the battery of my phone.

Here, de shows a relationship like of in English.

• la batterie de mon téléphone = the battery of my phone

English often prefers ’s or noun-noun compounds:

• my phone’s battery
• phone battery

French usually uses de for this kind of link.

A few similar examples:

• le moteur de la voiture = the car’s engine
• la couleur de la maison = the color of the house
• le chargeur de mon téléphone = my phone charger

So de is the normal way to connect battery and phone here.

Peut is the 3rd person singular form of pouvoir in the present tense.

The subject is La batterie, which is it in English, so French uses the il/elle/on form:

• je peux = I can
• tu peux = you can
• il/elle peut = he/she/it can

Since la batterie is singular, the verb must match it:

• La batterie ... peut ...

So:

• La batterie peut = the battery can

Yes—tenir often means to hold, but it has several meanings. In this sentence, it means something like:

• to last
• to keep going
• to hold out

With batteries especially, tenir is very common in everyday French.

So:

• La batterie tient = the battery lasts / holds up
• tenir toute la journée = to last all day

This is a very natural French way to talk about battery life.

Examples:

• Mon téléphone tient encore deux jours. = My phone still lasts two days.
• La batterie ne tient plus longtemps. = The battery doesn’t last long anymore.

Both are possible, but they are slightly different.

• La batterie de mon téléphone tient encore toute la journée.
  = My phone battery still lasts all day.
  This sounds more direct and factual.

• La batterie de mon téléphone peut encore tenir toute la journée.
  = My phone battery can still last all day.
  This adds an idea of possibility/capacity.

Using peut makes the sentence sound a bit more like: the battery is still capable of lasting the whole day.

So peut tenir is not wrong at all—it just emphasizes ability rather than simply stating the result.

Here encore means still.

So:

• peut encore tenir = can still last

It shows that this is true even now, perhaps despite the battery being old or used a lot.

Examples:

• Il fonctionne encore. = It still works.
• J’ai encore faim. = I’m still hungry.
• La batterie peut encore tenir. = The battery can still last / can still hold up.

Be careful: encore can also mean again, depending on context.

• Dis-le encore. = Say it again.
• Il est encore ici. = He is still here.

In your sentence, still is the correct meaning.

Because it modifies the verbal idea peut tenir and is naturally placed after the conjugated verb peut and before the infinitive tenir.

French often places adverbs like this between the conjugated verb and the infinitive:

• Je vais encore essayer. = I’m going to try again/still try.
• Il peut encore venir. = He can still come.
• La batterie peut encore tenir...

This placement is very normal in French.

Because journée is a feminine singular noun, so tout must agree with it:

• masculine singular: tout
• feminine singular: toute
• masculine plural: tous
• feminine plural: toutes

So:

• tout le jour = all the day / the whole day
• toute la journée = all day / the whole day

Since journée is feminine, you need toute.

This is a very common learner question.

Both relate to day, but they are not used in exactly the same way:

• jour often refers to a day as a unit on the calendar
• journée often refers to the duration or the experience of the daytime

In your sentence, the idea is duration: the battery lasts through the whole day. So journée is the natural choice.

Compare:

• Quel jour sommes-nous ? = What day is it?
• Je pars dans trois jours. = I’m leaving in three days.
• J’ai travaillé toute la journée. = I worked all day.
• La batterie tient toute la journée. = The battery lasts all day.

So toute la journée is very idiomatic here.

Yes, you often can, but the nuance is a little different.

• tenir is extremely common for batteries and means to hold up / last
• durer means to last in a more general sense

So these are both possible:

• La batterie tient toute la journée.
• La batterie dure toute la journée.

But for battery life, many native speakers find tenir especially natural in everyday speech.

You may also hear:

• La batterie a une autonomie d’une journée.
• La batterie ne tient pas longtemps.

So durer is understandable and correct, but tenir is very idiomatic here.

In English, we often say last for the whole day or just last all day. French does not need a preposition here.

French simply says:

• tenir toute la journée
• literally: to last the whole day

This is a normal pattern with durations in French:

• J’ai dormi toute la nuit. = I slept all night.
• Il a plu toute la matinée. = It rained all morning.
• La batterie tient toute la journée. = The battery lasts all day.

So the absence of for is completely normal.

Yes, peut can introduce a slight idea of possibility, depending on context.

• La batterie tient toute la journée.
  = It lasts all day.
  More definite.

• La batterie peut encore tenir toute la journée.
  = It can still last all day / it may still be able to last all day.
  Slightly more cautious or capacity-based.

So this version can sound like:

• it is still capable of lasting all day
• it may still make it through the day

The exact nuance depends on the situation and tone.