The most common batteries use alkaline solutions, zinc-carbon, or lithium to store energy. All three options are inorganic materials that are either toxic or flammable. Biological batteries, on the other hand, are energy storage devices that are powered by organic compounds, like glucose, a kind of sugar.
Researchers and engineers are developing bio-batteries because they are non-toxic and non-flammmable options and therefore are clean, renewable alternatives to regular batteries. The bio-batteries have high energy density, meaning that they can hold a much greater charge than a smartphone's lithium-ion battery. They are also instantly rechargeable if you provide a constant supply of sugar or glucose.
However, there are some obstacles to overcome, and until we can show that bio-batteries are at least as good as, if not better than, inorganic batteries, then mass production and wide-usage seems unlikely (at least in the near future). One of the obstacles that bio-batteries must overcome is the fact that they do not have very good energy retention. They tend to lose energy over time much faster than inorganic batteries, even when you leave them alone to sit. We are also not sure how many cycles bio-batteries can last before needing to be replaced.
We are also looking into bacteria-powered batteries to help the current global energy crisis. This also has its own set of problems: the output energy is still quite low and the power increase when you scale up the battery size is also small. If we try to make the batteries tiny, then manufacturing costs increase more than we can justify. Lastly, trying to keep bacteria alive in a cell requires a lot of systems to keep its living environment (the battery) in ideal conditions, assuming no system malfunction.
So where does that leave us? The potential bio-batteries have to help our energy crisis is enormous, but we’re only just scraping the surface of the research needed to make it a practical reality.