Lithium Secondary Battery Composites for Silicon Swelling Stability
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Solution Overview
Problem
Current lithium-ion battery anode materials, such as silicon, face issues with severe volume changes leading to cracking and poor cycling performance, while cathode materials like high-nickel ternary materials suffer from instability and safety concerns, including thermal runaway and capacity decay.
Innovation Solution
A lithium secondary battery design incorporating a high-nickel cathode composite material stabilized by lithium iron manganese phosphate and a silicon anode composite material coated with a high-entropy alloy to stabilize the volume changes and enhance safety and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based anode materials are used to increase capacity, then the theoretical capacity increases significantly (4200mAh/g vs 372mAh/g), but severe volume expansion (300%) occurs during charging causing particle cracking and poor cycling performance
Solution Approach 1:
The patent embeds silicon particles inside a porous carbon matrix structure, creating a nested configuration where silicon is contained within carbon. This nested structure allows silicon to expand and contract during lithium insertion/extraction cycles without cracking, while the porous carbon provides structural support and maintains electrical conductivity, thereby improving cycling performance while utilizing silicon's high capacity
Solution Approach 2:
The patent employs a flexible porous carbon matrix that can accommodate silicon's volume changes. The carbon structure acts as a flexible container that expands and contracts with silicon during charge-discharge cycles, preventing particle cracking and maintaining structural integrity, thus improving cycling performance while preserving silicon's high capacity
2Quantity of substance
If high-nickel ternary cathode materials are used to increase capacity, then the energy density improves, but the material becomes unstable and prone to thermal runaway and capacity decay
Solution Approach 1:
The patent uses composite cathode materials consisting of high-nickel ternary material particles coated with or embedded in a lithium iron phosphate matrix. This composite structure combines the high capacity of nickel-rich materials with the thermal stability and structural robustness of lithium iron phosphate, achieving both high energy density and improved material stability, thereby reducing thermal runaway risk and capacity decay
Solution Approach 2:
The patent creates local quality differences by having lithium iron phosphate-rich regions surrounding nickel-rich regions within the cathode structure. The lithium iron phosphate provides local thermal stability and structural support where needed, while the nickel-rich areas provide high capacity, achieving a balance between energy density and stability through spatially differentiated material properties
3Reliability
If lithium iron manganese phosphate is blended into ternary materials to improve safety, then thermal stability improves, but the volumetric energy density decreases significantly
Solution Approach 1:
The patent applies local quality by concentrating lithium iron manganese phosphate in specific regions (as a coating or matrix surrounding active material particles) rather than uniformly blending it throughout. This localized approach provides thermal stability where needed while minimizing the volume occupied by lower-density material, thereby improving safety with less sacrifice to volumetric energy density
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
The composite materials improve cycling performance, capacity, and safety of lithium-ion batteries by stabilizing the volume changes of silicon anodes and reducing thermal risks in the cathode, while using a water-based solvent system enhances environmental safety and cost-effectiveness.
Implementation Method 1
a silicon anode composite material formed by coating silicon particles with a high-entropy material... to stabilize the volume changes
Implementation Method 2
a high-nickel cathode composite material stabilized by lithium iron manganese phosphate... reducing thermal risks in the cathode
Data Source
Figure 1~2B
Figure 3A~3B
Figure 4~5
AI summary
An embodiment of the present application proposes a lithium secondary battery (10) and a method for preparing the same. The lithium secondary battery (10) comprises a separator (12), a cathode (11), and an anode (13). The cathode (11) is disposed on one side of the separator (12). The cathode (11) comprises a cathode active material, and the cathode active material comprises a first composite material (200) based on a high-nickel material. The anode (13) is disposed on the opposite side of the separator (12). The anode (13) comprises an anode active material (M1), and the anode active material (M1) comprises a second composite material (200) formed from silicon particles (210) and a high-entropy material. The high-entropy material consists of at least five elements, and the percentage of each element in the high-entropy material does not exceed 50%.