BYD iron battery Toyota all solid battery advantages and disadvantages comparison

In Japan, the development of "all-solid batteries", which is a new generation of batteries that are superior to the current mainstream lithium-ion batteries, is constantly emerging. Tohoku University and Toyota Motor have reduced the charging time of all solid-state batteries to one-tenth of that of conventional batteries. Other R&D teams at Northeastern University have developed lightweight all-solid batteries and reduced operating temperatures. In addition, South Korea's Samsung Electronics is also developing technologies to improve the life of all solid batteries. In Japan and abroad, competition for practical development is becoming increasingly fierce.

An electrolyte solution which is a main material of a lithium battery contains an organic solvent which is easily ignited. An all solid battery uses a solid electrolyte instead of a liquid electrolyte. Since lithium ions move in a hard-to-burn solid electrolyte, safety is greatly improved. Although theoretically compared with batteries using electrolytes, all solid-state batteries have more power storage and higher output power. However, the all-solid-state batteries developed in the past have been difficult to exceed the performance of conventional batteries, and it is difficult to put them into practical use.

In the study, Associate Professor Ichiro Taro of Tohoku University of Japan and others focused on the electrolyte and electrode interface problems. The electrolyte and the electrode are perfectly fitted by using a vacuum device and adjusting the manufacturing method of the battery. Lithium ions are easily moved in the battery due to the close fitting of the interface. The problem that the solid electrolyte and the electrode are not closely adhered to by the influence of cracks and impurities is solved.

In an experiment conducted using a prototype all-solid battery, the charging time was shortened from 30 minutes or more required for a conventional battery using an electrolytic solution to 3 minutes. If an all-solid battery is used for a battery of an electric vehicle (EV), fast charging will be achieved. In the future, we will promote development together with Toyota and battery manufacturers.

The same use of lithium and hydrogen compounds as electrolytes for Northeastern University's Prof. Yan Mao and Prof. Yu and the lecturers reduced the weight of all solid batteries by more than half. Previously developed all-solid batteries using sulfides and oxides as electrolytes were heavier than batteries using electrolytes.

After using a compound of lithium and hydrogen, there is a problem that it can be operated only in a high temperature environment, but the composition of the electrolyte is improved from the original 120 degrees Celsius to 90 degrees Celsius. The goal in the future is to make the battery work properly at room temperature. The company plans to cooperate with Mitsubishi Gas Chemicals to achieve a practical level of batteries as pure electric vehicles after five years.

Samsung Electronics has increased the durability of all-solid batteries using sulfides. After repeated charge and discharge for 500 times, the capacity can still be maintained at about 80%, which is close to the practical level. In the past, there has been a problem that the capacity is rapidly reduced after repeated charge and discharge. However, this problem has been solved by carefully improving the structure of the positive electrode and uniformly dispersing a substance that is easily energized in the positive electrode. This achievement was released at the battery seminar held in Kyoto last month.

At present, the mainstream lithium-ion battery has a higher output per unit volume and a larger storage capacity. Mainly used in portable terminals and pure electric vehicles. However, fever may cause damage, and there are opinions that indicate a safety hazard.

A new generation of batteries: Pure electric vehicles equipped with existing lithium-ion batteries have a single electric travel distance of only about 200 kilometers. A gasoline car, on the other hand, can travel about 500 kilometers on a full tank. The goal of the new generation of batteries is to increase performance to levels equal to or higher than gasoline vehicles. Also strive to improve safety and durability, and shorten charging time.

In addition to all-solid-state batteries and sodium-ion batteries, the new-generation batteries that are currently being developed include air batteries that use air in the air to reduce weight, and multi-valent ion batteries that use a large amount of electricity such as magnesium ions.

Similar to the "all solid battery", after the actual operation test of electric vehicles in recent years, the safety of BYD iron battery has been affirmed by the industry giants, but what are the advantages and disadvantages of the "all solid battery" iron battery?

In fact, the lithium battery is only a general term. If it is subdivided according to its cathode material, there will be lithium cobaltate, lithium manganate and lithium iron phosphate. The advantages and disadvantages of the lithium battery are described below.

What is lithium iron phosphate battery?

The interior of a lithium-ion battery is mainly composed of a positive electrode, a negative electrode electrolyte and a separator. The positive, negative and electrolyte of a lithium ion battery may have different performances and different names depending on the materials used. Lithium batteries that are commonly used on the market are classified into lithium cobaltate (LiCoO2) and lithium manganate (LiMn2O4), and the main character in this article, lithium iron phosphate (LiFePO4).

As a kind of lithium battery, lithium iron phosphate is mainly used in the field of power systems, such as electric vehicles, militaryspecial, power tools and UPS. It is more suitable because of its excellent structural stability, safety performance and long service life. Used in the field of power systems. Lithium iron phosphate batteries have at least five advantages over lithium ion batteries that use other positive materials.

Five advantages, safety and longevity

Compared with the more common lithium cobalt oxide and lithium manganate batteries currently on the market, lithium iron phosphate batteries have at least five advantages: higher safety, longer service life, and no heavy metals and rare metals (raw materials), low cost, fast charging and wide operating temperature range.

Higher security

Lithium iron phosphate completely solves the safety hazard problem of lithium cobaltate and lithium manganate. It shows that the bonding strength of phosphate chemical bond is stronger than that of traditional excessive metal oxide structure, so the structure is more stable and it is not easy to release oxygen.

Longer service life

At present, most lithium-ion batteries used in mobile power supplies on the market have a cycle life of about 500-800 times, while lithium iron phosphate batteries have a service life of at least 2,000 times, and their capacity can be maintained at above 80 %. Therefore, if the internal power storage unit of the mobile power supply is a lithium iron phosphate product, it has an absolute normal service life advantage.

Does not contain any heavy metals and rare metals

The lithium iron phosphate battery cathode material does not contain precious metals and rare metals, so it is more environmentally friendly and can effectively reduce environmental pollution. In addition, a wide range of material sources also make it lower in material cost and superior in price.

Support fast charging

In terms of charging speed, lithium iron phosphate also has a greater advantage, supporting the fast charging characteristics to support at least 2C charging speed (C is the charging parameter, such as the capacity of 1000mAh battery, 2C current is 1000mA × 2 =2000mA), which Can significantly reduce the charging time.

Wide operating temperature range

Compared with other lithium batteries, lithium iron phosphate batteries have a larger operating temperature range, and can work normally at -20 ° C to +75 ° C. Some lithium iron phosphate batteries with high temperature resistance can also be used at 350. Normal operation in the range of °C to 500 °C, has more advantages than the 200 ° C limit of lithium manganate and lithium cobalt oxide.

Therefore, compared to lithium cobalt oxide and lithium manganate batteries, the most obvious advantages of lithium iron phosphate are the extremely high safety factor, support for fast charging (high current charging) and a wider operating temperature range. It allows consumers to worry about the safety of lithium batteries and to use them in more harsh environments. However, there are some shortcomings in lithium iron phosphate compared to the widely used lithium cobalt oxide and lithium manganate batteries, see below.

The three major drawbacks are still not perfect

After briefly introducing the advantages of lithium iron phosphate batteries, let us look at some of the shortcomings that exist. It is mainly divided into three aspects: low tap density, consistency problem and high production cost.

Low tap density

For lithium-ion batteries, the tap density can determine the size of the battery at the same capacity, and the lower tap density is a shortcoming that needs to be solved in the current lithium iron phosphate battery. Compared with lithium cobaltate and lithium manganate, lithium iron phosphate batteries of the same capacity are larger, which is one reason why lithium iron phosphate batteries have not risen in the field of mobile phones and the like.

Consistency problem

Although lithium iron phosphate batteries have an absolute lead over life compared to lithium cobalt oxide and lithium manganate batteries. However, in battery mode, its life will be greatly reduced. Because the battery pack is connected by a large number of single cells in series, if one battery in the entire battery pack fails, the replacement is very troublesome, which is why the current battery pack nominal cycle in the electric vehicle. The reason for the same life is 500 times.

Higher production costs

Since the physical properties of the material in the lithium iron phosphate positive electrode are quite different from those of other lithium battery materials, the particle size is small, the tap density is small, and the like, so the process requirements in the manufacturing process are high, and the nominal voltage is 3.2. V, lower than the ordinary 3.7V lithium battery voltage, so the requirements for manufacturing the entire battery composition and related manufacturing equipment and processes are higher than other lithium batteries.

In addition to the above three major drawbacks of lithium iron phosphate batteries, there is still a potential problem that hinders the development of lithium iron phosphate batteries, which is the patent dispute of cathode materials. Let the current overall cost of lithium iron phosphate be higher than the lithium cobalt oxide and lithium manganate batteries that have been popularized. However, it is gratifying that the patent issue has been eased recently.

Bright future

The following table compares several obvious data comparisons between lithium iron phosphate batteries and lithium manganate and lithium cobalt oxide batteries, mainly through several aspects such as nominal voltage, charge and discharge voltage range, and volume specific energy.

Summary: Whether it is lithium iron phosphate, lithium cobalt oxide, lithium manganate or all-solid battery, the next development direction can not only focus on the improvement of energy density, the safety of the battery must also be concerned, in the next few years, the battery will be used in large scale. After that, this problem will be highlighted. R&D institutions need to plan ahead and kill these hidden dangers in the cradle. It is a paralyzed situation to avoid the take-off of the electric vehicle industry.

The page contains the contents of the machine translation.