Nowadays, new energy vehicles have gradually become the mainstream of the automobile market, and the power battery of new energy vehicles has become a key concern for many consumers. solid state battery has become a new and popular type of battery.
Table of Contents
What is a solid state battery?
1. Definition of solid state battery
According to the classification of electrolyte, lithium batteries can be divided into four categories: liquid, semi-solid, quasi-solid and all-solid, of which semi-solid, quasi-solid and all-solid are collectively called solid state battery. And due to the different states of electrolyte, solid state battery is different from liquid lithium-ion batteries in terms of structure.
2. Development of lithium battery
As the development of lithium battery industry , the core requirements for lithium batteries such as specific capacity, first-time efficiency, safety and cycle times are getting higher and higher in the fields of power batteries and energy storage batteries. The energy density of lithium-ion power batteries is expected to increase to more than 300Wh/kg in the next five years, but it is difficult to achieve the target of battery energy density higher than 350Wh/kg by relying on the existing ternary system.
The solid state battery has obvious improvement in specific capacity and safety due to its structure, cathode materials, anode materials and electrolyte materials.
Comparison of liquid and solid state battery
1. Safety
The safety hazard of liquid batteries is mainly due to the liquid electrolyte. According to the latest news, the accidents caused by batteries in electric vehicles are mainly spontaneous combustion and deflagration. And the main trigger of spontaneous combustion is the thermal runaway of the battery pack. The battery is short-circuited in the over-charged, low-temperature or high-temperature environment, and the battery releases a lot of heat in a short period of time, which ignites the liquid electrolyte inside the battery and eventually causes the battery to catch fire.
Solid state battery, on the other hand, use solid electrolyte, most of which is non-combustible, solving the flammability of electrolyte; at the same time, the solid electrolyte film is dense and non-porous, with high mechanical strength, effectively inhibiting the problem of short circuit caused by negative electrode; it is also better than electrolyte in terms of thermal and electrochemical stability, greatly enhancing the safety performance of lithium batteries.
2. Energy density
The energy density of the battery is directly determined by the theoretical gram capacity and electrochemical potential difference of the cathode and anode materials. According to the latest progress of solid state battery, the energy density of Tesla 4680 large cylindrical battery is 283Wh/kg, while according to the structure of CATL Solid state battery, the energy density of lithium iron phosphate 160wh/kg, ternary high nickel up to 250wh/kg.
And in October 2022 NASA introduced on its official website, NASA’s current research and development of successful solid state battery energy density reached 500Wh/kg, almost twice as high as ternary high nickel.
The cathode and anode materials of solid state battery can be used with greater potential difference, and due to the stability advantage of solid structure, the capacity of cathode and anode materials can be expanded in the manufacturing process to improve the overall energy density of the battery.
All solid state battery can use lithium metal as the negative electrode (the specific capacity of lithium metal is nearly 10 times that of graphite negative electrode), which is expected to increase the energy density by more than 50% under the same positive electrode system, and at the same time improve the PACK energy density of the battery and reduce the cost of the battery.
Solid-state electrolyte material technology route
The core requirements to focus on in the process of building a high-performance solid-state electrolyte include.
① High electrical conductivity.
② Good chemical stability, not reacting with the internal materials of the battery.
③ High lithium ion migration number, ion migration number greater than 1 is the most ideal state.
④ Mechanical properties and toughness, for five levels of solid electrolytes, there is generally a more brittle and fragile phenomenon.
Currently there are three major technical routes with solid-state electrolytes: polymer, oxide, and sulfide. The performance parameters of the three types of solid electrolytes have their own advantages and disadvantages.
According to the public information query, in October 2022 NASA’s sulfide route product, the energy density reached 500 Wh/kg. 2018 Suzhou, China, advertised the development of a product based on the oxide route, the energy density of solid state battery reached 400 Wh/kg; in December 2019 Sakti3 claimed to have developed a solid state battery with an energy density of over 1000 Wh/kg.
Solid state battery interface
The solid state battery interface refers to: ① The interface inside the solid electrolyte
② The interface inside the composite cathode material
③ The interface between the solid electrolyte and the cathode material
④ The interface between the solid electrolyte and the negative electrode material
The interface concept is induced in solid state battery mainly because the solid-phase interfaces of solid materials have no wettability between them, making it difficult to make sufficient contact and forming a higher contact resistance. In addition, phenomena such as elemental interdiffusion and formation of space charge layers occur during cycling, which affect the cell performance. A large number of grain boundaries exist in the crystalline electrolyte, and the high grain boundary resistance is not conducive to the transport of lithium ions between the positive and negative electrodes.
In order to improve the performance of different interfaces (e.g., conductivity, space charge layer, etc.), special R&D and design in the structure, preparation process, and material selection of solid state battery is required.
Market demand
The global demand for solid state battery in 2030 is expected to be close to 500GWH, with a market space of more than 150 billion, of which the demand for solid-state power batteries is more than 350GWH.
According to the Institute’s forecast, China’s solid state battery shipments are expected to grow at a high rate from 2022 to 2030, and may exceed 250 GWH by 2030, while on the cost side, with the continuous progress of solid state battery technology, the cost price of solid state battery will also continue to decline, with the cost price of solid state battery in China expected to drop from 1.9 yuan/Wh in 2022 to 0.8 yuan/Wh in 2030.
The cost price of ternary lithium battery in 2022 is about 1 yuan/Wh, and the cost price of lithium iron phosphate battery is 0.8 yuan/Wh.
For the time being, liquid batteries have a greater advantage in cost compared to solid state battery. However, with the development of solid state battery technology and the implementation of mass production, the cost will be close to that of liquid batteries, while the advantages of its high energy density and high safety will be highlighted.
Ayan Chen
Dear readers, My professional journey began with a master's degree in Electronic Engineering, after which I directed my focus towards in lithium battery swap systems. As a engineer at a renowned battery company, I've not only wholeheartedly contributed to several successful battery swapping station projects, but have also gained a wealth of experience. Through my writing, I aspire to share insights and knowledge about motorcycle battery swapping for you.
Solid state battery industry research
What is a solid state battery?
1. Definition of solid state battery
According to the classification of electrolyte, lithium batteries can be divided into four categories: liquid, semi-solid, quasi-solid and all-solid, of which semi-solid, quasi-solid and all-solid are collectively called solid state battery. And due to the different states of electrolyte, solid state battery is different from liquid lithium-ion batteries in terms of structure.
2. Development of lithium battery
As the development of lithium battery industry , the core requirements for lithium batteries such as specific capacity, first-time efficiency, safety and cycle times are getting higher and higher in the fields of power batteries and energy storage batteries. The energy density of lithium-ion power batteries is expected to increase to more than 300Wh/kg in the next five years, but it is difficult to achieve the target of battery energy density higher than 350Wh/kg by relying on the existing ternary system.
The solid state battery has obvious improvement in specific capacity and safety due to its structure, cathode materials, anode materials and electrolyte materials.
Comparison of liquid and solid state battery
1. Safety
The safety hazard of liquid batteries is mainly due to the liquid electrolyte. According to the latest news, the accidents caused by batteries in electric vehicles are mainly spontaneous combustion and deflagration. And the main trigger of spontaneous combustion is the thermal runaway of the battery pack. The battery is short-circuited in the over-charged, low-temperature or high-temperature environment, and the battery releases a lot of heat in a short period of time, which ignites the liquid electrolyte inside the battery and eventually causes the battery to catch fire.
Solid state battery, on the other hand, use solid electrolyte, most of which is non-combustible, solving the flammability of electrolyte; at the same time, the solid electrolyte film is dense and non-porous, with high mechanical strength, effectively inhibiting the problem of short circuit caused by negative electrode; it is also better than electrolyte in terms of thermal and electrochemical stability, greatly enhancing the safety performance of lithium batteries.
2. Energy density
The energy density of the battery is directly determined by the theoretical gram capacity and electrochemical potential difference of the cathode and anode materials. According to the latest progress of solid state battery, the energy density of Tesla 4680 large cylindrical battery is 283Wh/kg, while according to the structure of CATL Solid state battery, the energy density of lithium iron phosphate 160wh/kg, ternary high nickel up to 250wh/kg.
And in October 2022 NASA introduced on its official website, NASA’s current research and development of successful solid state battery energy density reached 500Wh/kg, almost twice as high as ternary high nickel.
The cathode and anode materials of solid state battery can be used with greater potential difference, and due to the stability advantage of solid structure, the capacity of cathode and anode materials can be expanded in the manufacturing process to improve the overall energy density of the battery.
All solid state battery can use lithium metal as the negative electrode (the specific capacity of lithium metal is nearly 10 times that of graphite negative electrode), which is expected to increase the energy density by more than 50% under the same positive electrode system, and at the same time improve the PACK energy density of the battery and reduce the cost of the battery.
Solid-state electrolyte material technology route
The core requirements to focus on in the process of building a high-performance solid-state electrolyte include.
① High electrical conductivity.
② Good chemical stability, not reacting with the internal materials of the battery.
③ High lithium ion migration number, ion migration number greater than 1 is the most ideal state.
④ Mechanical properties and toughness, for five levels of solid electrolytes, there is generally a more brittle and fragile phenomenon.
Currently there are three major technical routes with solid-state electrolytes: polymer, oxide, and sulfide. The performance parameters of the three types of solid electrolytes have their own advantages and disadvantages.
According to the public information query, in October 2022 NASA’s sulfide route product, the energy density reached 500 Wh/kg. 2018 Suzhou, China, advertised the development of a product based on the oxide route, the energy density of solid state battery reached 400 Wh/kg; in December 2019 Sakti3 claimed to have developed a solid state battery with an energy density of over 1000 Wh/kg.
Solid state battery interface
The solid state battery interface refers to:
① The interface inside the solid electrolyte
② The interface inside the composite cathode material
③ The interface between the solid electrolyte and the cathode material
④ The interface between the solid electrolyte and the negative electrode material
The interface concept is induced in solid state battery mainly because the solid-phase interfaces of solid materials have no wettability between them, making it difficult to make sufficient contact and forming a higher contact resistance. In addition, phenomena such as elemental interdiffusion and formation of space charge layers occur during cycling, which affect the cell performance. A large number of grain boundaries exist in the crystalline electrolyte, and the high grain boundary resistance is not conducive to the transport of lithium ions between the positive and negative electrodes.
In order to improve the performance of different interfaces (e.g., conductivity, space charge layer, etc.), special R&D and design in the structure, preparation process, and material selection of solid state battery is required.
Market demand
The global demand for solid state battery in 2030 is expected to be close to 500GWH, with a market space of more than 150 billion, of which the demand for solid-state power batteries is more than 350GWH.
According to the Institute’s forecast, China’s solid state battery shipments are expected to grow at a high rate from 2022 to 2030, and may exceed 250 GWH by 2030, while on the cost side, with the continuous progress of solid state battery technology, the cost price of solid state battery will also continue to decline, with the cost price of solid state battery in China expected to drop from 1.9 yuan/Wh in 2022 to 0.8 yuan/Wh in 2030.
The cost price of ternary lithium battery in 2022 is about 1 yuan/Wh, and the cost price of lithium iron phosphate battery is 0.8 yuan/Wh.
For the time being, liquid batteries have a greater advantage in cost compared to solid state battery. However, with the development of solid state battery technology and the implementation of mass production, the cost will be close to that of liquid batteries, while the advantages of its high energy density and high safety will be highlighted.