Lithium Ion Battery Negative Electrode Binder Optimization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lithium ion secondary batteries with graphite structure negative electrodes face challenges in maintaining bonding strength between active material particles, leading to swelling issues due to repeated charge/discharge cycles, as conventional cellulose ether compounds fail to optimize physical properties and distribution states, affecting viscosity and bonding properties.
Innovation Solution
A negative electrode with a cellulose ether compound having a degree of etherification between 0.25 and 0.7 and an average degree of polymerization between 20 and 1200, combined with rubber particles, is used to enhance bonding strength between active material particles, optimizing the balance of viscosity and bonding properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cellulose ether compounds with high average degree of polymerization (100-2000) are used as binders, then capacity retention rate is improved, but bonding strength between active material particles decreases and negative electrode mixture layer thickness increases causing case swelling
Solution Approach 1:
The patent changes the physical and chemical parameters of the cellulose ether compound, specifically reducing the average degree of polymerization to 50-500 and controlling the degree of etherification to 0.1-1.5, which optimizes both bonding strength and capacity retention without causing electrode swelling
Solution Approach 2:
The patent uses a composite binder system combining cellulose ether compound with rubber particles (styrene-butadiene rubber, nitrile-butadiene rubber, or polybutadiene) to achieve synergistic effects that improve bonding strength while maintaining capacity retention rate
2Reliability
If cellulose ether compound with high average degree of polymerization is used, then capacity retention is improved, but viscosity control becomes difficult and workability decreases
Solution Approach 1:
The patent reduces the average degree of polymerization from the conventional 100-2000 range to 50-500, which significantly improves the viscosity characteristics and workability of the negative electrode mixture slurry while still maintaining high capacity retention through the optimized binder composition
3Strength
If binder amount is increased to improve bonding strength, then bonding strength between active material particles is improved, but excessive coverage of active material particles occurs reducing capacity
Solution Approach 1:
The patent optimizes the binder composition parameters (cellulose ether with specific polymerization degree and etherification level combined with rubber particles) to achieve high bonding strength with minimal binder content, preventing excessive coverage of active material particles and maintaining high capacity
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 results in a lithium ion secondary battery with high bonding strength between active material particles, effectively suppressing swelling and maintaining high capacity and coulombic efficiency, while ensuring workability and preventing excessive coverage of active material particles.
Implementation Method 1
a binder for bonding the active material particles. The binder includes a cellulose ether compound and rubber particles
Implementation Method 2
The binder includes a cellulose ether compound and rubber particles
Data Source
AI summary
A negative electrode for a lithium ion secondary battery includes a negative electrode core member and a negative electrode mixture layer adhering to the negative electrode core member. The negative electrode mixture layer includes active material particles, a cellulose ether compound, and rubber particles. The cellulose ether compound has a degree of etherification of 0.25 or more and 0.7 or less and an average degree of polymerization of 20 or more and 1200 or less. The negative electrode mixture layer contains remaining particles including a water-insoluble portion of the cellulose ether compound and having a mean particle size of 1 μm or more and 75 μm or less. The bonding strength between the active material particles is 98 N/cm2 or more.