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The electronic energy of secondary batteries is transferred from the chemical reaction too. However, the batteries can be recharged by using an external electric source that reverses the cell reaction and creates a non-equilibrium mixture of reactants. The cycle life varies with material and application. The common products are Lead-Acid、Nickel-Cadmium (Ni-Cd) battery、Nickel-Metal hydride (Ni-MH) battery and Li-ion batteries .Each battery has its suitable applications due to different operational voltage, capacity and safety concern.Although secondary batteries can be used in many times, many metals comprised still serously impact the environment and our health.
Li-ion Batteries
LiCoO2 and LiMnO2 are the two we can find in the market. However, they have safety concerns such as explosion risk at high temperature, or capacity decrease problem. HIBS battery completely avoids these problems, and maintains high performance.
Lithium-Iron Phosphate (HIBS) Batteries
HIBS  is the latest cathode material for Li-ion battery. Although the energy density is lower than Li-Co battery’s, its advantage in high safety makes shorter charge time. The normal cycle life is 2000 times, which is much greater than Li-Co or Li-Mn battery (only 500 times).
Lithium-Cobalt oxide (Li-Co) Batteries
Li-Co battery offers the highest energy density. It’s light and slim, so most cell phones and laptops adapt this type of battery. However, it’s unsafe, so high quality control is required, and the protection circuit design must be high-precision. Otherwise, it may explode while overcharging or over-discharging. In fact, there were 10 million batteries recalled in mid-2006 because of explosion accidents.
Lithium-Manganese oxide (Li-Mn) Batteries
Li-Mn battery is designed to improve safety of Li-Co battery. Although its energy density is lower than Li-Co battery’s, it can be applied to high power applications such as power tools and e-scooters because of improving safety. However, the high temperature performance is bad. The capacity drops 20% at 50℃, and drops 50% at 80℃.
Lead-Acid Batteries
Lead-Acid battery was invented in 1859. The anode is made of lead, and the cathode is made of lead oxide. These electrodes dip in an electrolyte of about 27% to 39% w/w sulfuric acid. The electrolyte of traditional Lead-Acid battery, also known as open Lead-Acid battery, reduces during reaction process, so it requires adding water periodically. However, as the material has improved, the electrolyte doesn’t reduce during reaction process any more, and it’s unnecessary to replenish. It’s called sealed Lead-Acid battery, which is common in the market now. The operation voltage is 2V at 25℃. It’s safe, cheap, but heavy and bulky. It harms the environment severely as well.
Ni-Cd Batteries
Ni-Cd battery was invented in 1899, and was applied widely during 1970s. Although its operation voltage is only 1.2V, which is lower than Lead-Acid’s, it offers advantage of high energy, low resistance and long cycle life. It contains a nickel hydroxide positive electrode plate, a cadmium hydroxide negative electrode plate, a separator, and an alkaline electrolyte. Despite low cost, it suffers from memory effect, the capacity reduces after repeated recharge. Also, Cadmium can cause substantial pollution when landfilled or incinerated. Because of this, many countries now prohibit Ni-Cd batteries.
Ni-MH Batteries
Ni-MH battery is designed to improve the memory effect of Ni-Cd battery. It contains a nickel hydroxide positive electrode plate as Ni-Cd battery, but has a hydrogen-absorbing alloy for the anode instead of cadmium. Compared with Ni-Cd battery, it is capable of higher capacity, but the volumetric energy density is lower and self-discharge is higher. However, because of no pollution concern, it still has a certain market share, including the application of early stage HEV.
Secondary Batteries Comparison

Pollution
Due to safety concerns, lithium-ion batteries cannot be used in high power applications like electric vehicle or power tool although it is capable of high-power and has been widely accepted in 3C products for the past 15 years. Therefore, people have to apply high pollution, bulky, low capacity and low energy efficiency batteries like Lead-Acid, Ni-MH and Ni-Cd batteries to these applications.
Lead and cadmium are the major components of lead-acid and Ni-Cd batteries. Both of these are banned substances listed in RoHS due to high damage to human health, especially to children.
 
After lead is absorbed by the human body, 80% is stored in bones and teeth, and the other exists in bloodstream and soft tissue. When acid concentration of bloodstream increases due to tiredness or fever, the lead in bones and teeth enters the bloodstream, which exacerbates symptoms of lead poisoning.
Symptoms of lead poisoning：
Anemia, lead-gray face
Muscle asthenia, shiver and paralysis. There is more serious impact oninfants, which causes mental retardation, epilepsy, cerebral palsy,optic nerve atrophy, auditory nerve disability etc.
Kidney problem, vibriosis, or miscarriage.
Cadmium is not easily absorbed into the gastrointestinal tract, but it can be gradually stored in liver and kidney. Cadmium can interfere with calcium absorption, which causes osteomalacia. The patients suffer from extremity aches, which is called “itai-itai disease.