Why do mobile phone batteries become less durable as time goes by?

　　(1) I believe you will often notice that if your mobile phone is used for a period of time, you will obviously feel that the charging performance of the mobile phone battery is very different. If your phone is used long enough, your phone may need to be charged several times a day. Have you ever wondered why? First, let's understand how the battery works. Electricity is not magic. In fact, for most of us, this is a rather boring topic. We just hope it can be used when we need it. But to understand why the performance of mobile phone batteries is getting worse, you need to understand the working principle of batteries. Don't worry. I'm talking about basics. Like any energy source, electricity is not something you can create. What we think of as power generation is actually just to convert one form of energy into another form of energy, while batteries use chemical reactions (energy) to generate charges, which can be measured over time. In our mobile phones, we use lithium based batteries because they provide a good output level at a reasonable cost. Inside the cell phone battery, you will find three very important components: the negative electrode (called the anode, usually made of graphite), the positive electrode (called the cathode, made of lithium and other metals), and the electrolyte solution. The chemical reaction of these three materials is very simple, which is why they can be used to store energy. During charging, the lithium ion in the charger is positively charged and attracted to the negative electrode

　　(2) When you remove the charge from the battery, these lithium ions will lose their positive charge and will no longer absorb the negative electrode. The longer the stored energy is removed from the rechargeable battery, the more lithium ions will not be recharged until the remaining lithium ions are insufficient to output and the battery is depleted. Inserting it into the charger will reset the cycle. Loop is an important word here. Because batteries are used to store electric energy, it is difficult to measure the service life of batteries in terms of time. One battery can be used for two years, while others can only use it for six months, because they use it in different ways. Everyone uses different power consumption and charging. Therefore, it is difficult to estimate how long they will last. The battery life is measured by the charging cycle. Mobile phone batteries are usually designed to last 500 to 600 cycles. One cycle means charging a fully depleted battery to 100% and then depleting it again to zero. Charging the battery with 50% of the remaining power and then restoring it to 50% is a partial cycle, which is why you heard it suggests charging the battery before the battery is low. Of course, this does not work because the battery does not actually count the number of charging cycles. 500 is only an estimate

　　(3) However, theoretically, it is feasible to predict the cycle life of the battery, because what will happen when you charge the battery, how it will affect the future charging cycle, the energy that can be stored, and the voltage (voltage) that can store the charge. Oxidation and efficiency Because electric vehicles are a real thing, and the batteries they use are very expensive, people have carried out research on the reasons for the degradation of lithium-ion batteries during their service life. Fortunately, due to chemical changes during charging, this also applies to the cheaper (but still expensive) batteries in our mobile phones. We know that charging the battery can charge lithium ions, and then attract lithium ions magnetically (electricity is magnetic). As more and more charged ions are attracted, the potential difference between the negative electrode and the positive electrode increases. This is a method to measure the voltage and potential energy difference between two electrodes. Once a specific reading is reached, the battery is considered fully charged. When discharging, the situation is just the opposite. Since there are no more positively charged ions on the negative electrode, the potential difference decreases to zero. But that doesn't mean the cathode is clean, just like before you started. Electrode oxidation. Like water and air, iron will rust (which is the source of oxidation), and lithium, graphite and electrolyte salts will cause electrode oxidation. When each positively charged ion is stripped from the anode of the battery, particles in the micro layer still exist and have been chemically bound to the graphite anode. These particles are composed of lithium oxide (lithium combines with oxygen) atoms and lithium carbonate (lithium combines with carbon), neither of which has the same chemical or electrical properties as graphite. This layer interferes with the charging and discharging cycle, the potential difference (voltage) and the number of charged ions that can be attracted change, and finally these changes are enough to attract attention.

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