It's worth nothing that those generic Chinese phones of various brands actually tend to use one of a very few number of (replaceable) battery variations, which tend to be clones of the battery in common models like the Samsung Galaxy S3. The main variables are width/height/depth/pinout, and the former 3 are usually fixed by the battery manufacturers themselves, while the latter is either from cloning another common product or a reference design.

For bigger lithium-ion cells, 18650 is probably the most common size and has gradually made its way into consumer devices too as a replaceable cell, although the safety implications of the much higher energy density mean they have to be treated more carefully than AA/AAA. (E.g. the warnings about not carrying loose cells because they can short and cause burns or fire is far more important with a lion cell, since they have much higher current capacity.) Companies will continue pushing the "safety" excuse to lock-in users with proprietary batteries, but I see the spread of 18650s as starting to counter that trend.

Alkaline batteries are pretty energy-dense, and can beat cheap lithium-ions. That's not the main safety issue.

> I wish more devices used easily replaceable standard size cells of rechargeable and non-rechargeable variety. You can walk to any shop or service station and buy a bunch of AA or AAA batteries if it's urgent. And keep a spare pack at home, in car, etc.

There are already plenty of cell phone chargers in the market that take standard batteries.

I don't want to sound like I'm advertising any product, but I've purchased a cheap chinese cell phone charger that takes AA batteries. It cost me just $1 out of ebay. I actually purchased it on a gamble, expecting it to be awful, but it actually works very well. It's a very simple gadget that uses standard AA batteries connected in series to ramp up the voltage from around 1.5v to a tad above 5V, which is then used to supply energy to a standard 5V USB charger. Depending on the batteries used, a 4-pack of fresh AA batteries provide around 1800mAh of juice.

I've planned on purchasing another just to rig it to take C or D batteries, which provide the same voltage but hold a lot more charge, but honestly the AA pack works very well as it is.

Most people don't want to trade off the size and weight for the flexibility of batteries that they'd rarely, if ever, take advantage of. I have a secondary bike light that takes AA's, it's both much larger and much less bright than my main light, which uses a LiIon battery. I haven't found a comparable AA powered light to my LiIon light. I got the AA light just so I could replace the batteries with easy to find AA's just in case all of my batteries ran low...In the 5 years since I got that light, I've never needed to replace the AA's.

Since most devices are rechargeable via USB these days, most people are probably better off carrying a USB battery pack that uses AA's, then you're only paying for the bulk once (and it's quite light without batteries)

I think most of us moved on from the easily replaceable battery discussion years ago.