Liquid Battery VS Solid State Battery
The deep comparison between liquid state battery and solid state battery can be carried out from multiple dimensions such as key technology,performance parameters,and industrialization process,the following is a systematic analysis based on the latest technological progress:
1.Key technology differences
1.1 Electrolyte system
Liquid Battery
Material: Carbonate organic solvents (such as EC/DEC)+LiPF6 lithium salt.
Function: The electrolyte is responsible for ion conduction and needs to be separated from the positive and negative electrodes by a porous membrane (such as PP/PE).
limitations:The narrow electrochemical window (about 4.5V) limits the application of high-voltage positive electrodes,easy to react violently with lithium metal negative electrode,unable to adapt to high-capacity metal lithium negative electrode.
Solid State Battery
Material system:
Oxide (such as LLZO, LATP): high stability but low ionic conductivity (10 ⁻⁴ S/cm).
Sulfides (such as Li ₁₀ GeP ₂ S ₁₂): ion conductivity can reach 10 ⁻ S/cm, but they are prone to oxidation.
Polymer (such as PEO LiTFSI): good flexibility but requires high temperature (>60 ℃) activation.
Function: Integrated electrolyte and diaphragm, combining mechanical support and ion conduction.
1.2 Electrode structure
Liquid Battery
Graphite negative electrode (theoretical capacity 372mAh/g).
Conductive agents (such as Super P) and binders (such as PVDF) need to be added.
Solid State Battery
Metal lithium negative electrode (theoretical capacity 3860mAh/g) can be used, but the dendrite problem needs to be solved.
Electrode materials can be directly combined with solid electrolytes to reduce the proportion of non active substances.
2.Key performance comparison
Liquid Battery Solid State Battery
- Energy Density 200-250Wh/kg (mass production) Laboratory breakthrough 500Wh/kg (such as Toyota)
- Power Density 1500-2000W/kg is limited by interface impedance Approximately 500-1000W/kg
- Cycle Life 2000-8000 times (80% capacity retention) Laboratory over 10000 times (Toyota)
- Working Temp -20℃~60℃ Wide temperature range (-40 ℃~85 ℃, polymer system)
- Self Discharge Rate About 5% per month Monthly<1%
- Thermal Runaway Temp 150-200℃ Up to 500 ℃ or above
3.Challenges and Breakthroughs in Industrialization
3.1 Key bottleneck of solid state battery
Interface impedance: The small contact area of the solid interface leads to severe polarization during the charging process.
Solution:
Nano coating technology (such as ALD deposition of LiNbO3).
Composite electrolytes (such as ceramic polymer blends).
Lithium dendrite inhibition: Metal lithium negative electrode forms dendrites that pierce the electrolyte during charge and discharge processes.
Innovation direction:
3D porous skeleton structure (such as graphene/carbon nanotubes supporting lithium metal).
Artificial SEI film (such as LiF/Al ₂ O3 coating).
Large scale production:
Roll to roll coating technology (UBE in Japan has achieved mass production of sulfide electrolytes).
Solid state battery dedicated laser welding equipment (reduces material oxidation).
3.2 Iteration of liquid battery technology
Semi solid state battery:
Using 50% solid electrolyte and 50% liquid electrolyte (such as CATL Kirin battery).
The energy density can reach 300Wh/kg, and it will be mass-produced in 2023.
High nickel ternary system:
The positive electrode material has been upgraded from NCM811 to NCMA (nickel cobalt manganese aluminum), resulting in a 15% increase in capacity.
4.Economic Analysis
Current cost:
Liquid battery:$ 60-80/kWh (2024 data).
Solid state battery:$ 300-500/kWh (laboratory prototype).
Cost reduction path:
On the material side, the cost of synthesizing sulfide electrolytes has decreased from $500/kg to $50/kg.
Manufacturing end: Roll to roll process can reduce production costs by 30%.
5.Future Trends
Hybrid Solid State Battery will become a transitional solution.
Solid state electrolyte coating technology (such as BYD’s “solid film”) enhances the safety of liquid state batteries.
6.Conclusion
Liquid battery still have advantages in cost and maturity,but breakthroughs in energy density, safety,and wide temperature range performance of solid-state batteries will reshape the battery industry landscape,in the short term, the penetration of semi-solid state batteries will accelerate,and after 2030,all solid state batteries are expected to achieve large-scale commercialization,promoting electric vehicle range into the “thousand kilometer era” and giving birth to emerging application scenarios such as aviation and deep sea.