Bimodal Pore Lithium Battery Cathode Reducing Internal Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries face challenges in achieving uniform mixing of active materials and conductive agents due to differences in particle sizes, leading to the formation of large pores that increase resistance and decrease output.
Innovation Solution
A positive electrode with a controlled maximum pore diameter of less than 1 µm is achieved by using a positive electrode material mixture layer with bimodal pores and a specific volume ratio of conductive agent to active material, along with a method involving multiple rolling steps to optimize porosity and pore size distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large amount of conductive agent is added to improve electrical conductivity, then electrical conductivity is improved, but large pores are formed due to agglomeration and segregation, increasing resistance and decreasing output
Solution Approach 1:
The patent changes the particle size parameter of the conductive agent to be smaller than or equal to that of the active material. This parameter change prevents agglomeration and segregation, allowing uniform distribution of the conductive agent throughout the electrode material, thereby improving electrical conductivity without forming large harmful pores.
2Ease of manufacture
If particle sizes of active material and conductive agent are different, then mixing is easier, but agglomeration and segregation occur due to particle size difference, forming large pores
Solution Approach 1:
The patent applies homogeneity by making the particle sizes of the conductive agent and active material equal or having the conductive agent particles be smaller. This size uniformity ensures that both materials mix uniformly without agglomeration or segregation, maintaining stable composition throughout the electrode while remaining easy to manufacture.
3Productivity
If pores are present in the electrode, then electrolyte contact is enhanced, but resistance increases and output decreases due to large pore formation
Solution Approach 1:
The patent changes the pore size parameter by controlling the particle size of the conductive agent to be small and uniformly distributed. This results in the formation of only small pores rather than large pores, reducing resistance while maintaining adequate electrolyte contact, thereby improving battery output without the harmful effects of large pore formation.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present invention relates to a positive electrode for a secondary battery, which includes a positive electrode collector, and a positive electrode material mixture layer coated on at least one side of the positive electrode collector, wherein the positive electrode material mixture layer includes a positive electrode active material, a conductive agent, a binder, and bimodal pores composed of first pores and second pores which have different maximum diameters, and, in this case, the conductive agent and the positive electrode active material are included at a volume ratio (K1) of 0.08:1 to 0.32:1, wherein a volume ratio of the conductive agent to the total pores is in a range of 0.1:1 to 0.33:1, a porosity is in a range of 30 vol% to 45 vol%, the maximum diameters of the first pores and the second pores are less than 1 µm, and an average diameter ratio (k) of the first pores to the second pores is in a range of 0.13:1 to 0.27:1, a method of preparing the same, and a secondary battery including the positive electrode.