Lithium-Ion Battery Electrolyte With Lithium Iodide for Cycle Life
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Solution Overview
Problem
Current lithium-ion secondary batteries have a limited cycle life and high-temperature storage performance, falling short of the requirements for long-life electric buses and large-scale energy storage systems, despite efforts to optimize positive and negative active materials, electrolyte formulations, and solid electrolyte interphase films.
Innovation Solution
Incorporating lithium iodide into the electrolytic solution and precisely controlling its amount, along with the coating weight of the positive electrode film, ensures the total active lithium content in the battery system, enhancing cycle life and high-temperature storage performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte formulations and electrode optimizations are used, then battery performance is improved, but cycle life remains limited to 5000-6000 times
Solution Approach 1:
The patent introduces lithium iodide as a new chemical component in the electrolyte formulation, changing the chemical composition parameters of the battery system. This parameter change enables the formation of a protective film on the electrode surface, which significantly extends cycle life from 5000-6000 times to over 10000 times while maintaining good discharge performance.
2Stability of the object's composition
If active lithium ions are reduced to improve stability, then side reactions are suppressed, but cycle life improvement is limited
Solution Approach 1:
Lithium iodide acts as an intermediary substance that mediates between the electrolyte and electrode surfaces. It forms a protective interface layer that suppresses side reactions and stabilizes the electrode structure, thereby extending cycle life without requiring reduction of active lithium ions. This intermediary mechanism achieves both stability and reliability improvement.
3Reliability
If electrode film formulations are optimized, then storage performance improves, but high-temperature storage performance remains insufficient
Solution Approach 1:
The patent changes the chemical composition parameter of the electrolyte by adding lithium iodide, which forms a thermally stable protective film on the electrode surfaces. This film formulation change significantly improves high-temperature storage performance while maintaining good storage performance at normal temperatures, overcoming the limitation of conventional electrode film optimizations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly improves the cycle life and high-temperature storage performance of lithium-ion secondary batteries, maintaining a cycle retention rate of 91.9% or more and storage capacity retention rate of 94% or more, surpassing the performance of batteries without lithium iodide.
Implementation Method 1
by adding a specific amount of lithium iodide to the electrolytic solution, the coating weight of the specific area (coating weight per unit area) of the positive electrode film is determined, so that the total amount of active lithium in the battery system is ensured from the source
Implementation Method 2
a positive electrode sheet, including a positive electrode current collector and a positive electrode film that is disposed on a surface of the positive electrode current collector and contains a positive active material; and an electrolytic solution, including lithium iodide, a lithium salt, a solvent, and an additive
Data Source
AI summary
A lithium-ion secondary battery includes a negative electrode sheet including a negative electrode current collector and a negative electrode film disposed on a surface of the negative electrode current collector and containing a negative active material, a positive electrode sheet including a positive electrode current collector and a positive electrode film disposed on a surface of the positive electrode current collector and containing a positive active material, and an electrolytic solution including lithium iodide, a lithium salt, a solvent, and an additive. A coating weight per unit area, CW1/S0, of the positive electrode film satisfies CW1/S0=((CW2/S0)×b×C2/CB−m×X×(199 mAh/g)/S)/(C1×a).