SiOx Negative Electrode Composition for Low-Swelling Fast-Charging Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lithium ion secondary batteries using Si-based negative electrode active materials face challenges in suppressing expansion and contraction during charge and discharge, leading to reduced lifespan and rapid charging properties.
Innovation Solution
A negative electrode for nonaqueous electrolyte secondary batteries comprising a specific combination of silicon-based and carbon-based active materials with controlled specific surface areas, a binder, and a conductive additive, optimized to minimize expansion and contraction, and improve electrical contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si-based negative electrode active materials are used to increase capacity, then energy density is improved, but expansion and contraction during charge and discharge increases leading to reduced lifespan
Solution Approach 1:
The patent uses a composite negative electrode active material consisting of SiOx particles (0.5 ≤ x ≤ 1.6) combined with carbon particles. The SiOx provides high capacity while the carbon component suppresses expansion and contraction during charge-discharge cycles, resolving the contradiction between high capacity and lifespan reliability
Solution Approach 2:
The patent optimizes the specific surface area parameters of both SiOx particles (0.3-3.0 m²/g) and carbon particles (0.5-5.0 m²/g), as well as their mass ratio (SiOx:carbon = 95:5 to 50:50). By controlling these parameters, the composite material achieves both high capacity and suppressed volume change, improving lifespan
2Quantity of substance
If Si-based negative electrode active materials are used to increase capacity, then energy density is improved, but rapid charging property deteriorates
Solution Approach 1:
The carbon component in the composite material provides excellent electrical conductivity that compensates for the poor conductivity of SiOx. This enables rapid lithium ion insertion and extraction while maintaining high capacity, thus improving rapid charging property
Solution Approach 2:
By optimizing the specific surface area of carbon particles (0.5-5.0 m²/g) and the mass ratio of SiOx to carbon (95:5 to 50:50), the patent achieves a balance between capacity and electrical conductivity, enabling both high capacity and rapid charging capability
3Reliability
If graphite is used as negative electrode active material, then safety and cycle stability are improved, but energy density cannot be further improved
Solution Approach 1:
The patent creates a composite material where SiOx (providing high capacity) is combined with carbon (providing safety and stability). The carbon component maintains the safety characteristics of conventional graphite electrodes while the SiOx component significantly increases the energy density, resolving the contradiction between safety and energy density
Data Source
AI summary
An objective of the present invention is to suppress the expansion and contraction when charging and discharging a nonaqueous electrolyte secondary battery, including lithium ion secondary batteries, when an Si-based negative electrode active material is used, to improve the lifespan (cycle characteristics) of the nonaqueous electrolyte secondary battery, and to improve rapid charging properties. The negative electrode active material contains: a silicon-based active material (A) containing SiOx (in the formula, x is a number satisfying 0.5≤x≤1.6); a carbon-based active material (B) composed of secondary particles formed by aggregating primary particles; and a carbon-based active material (C) composed of primary particles different from the carbon-based active material (B). If the specific surface area of the silicon-based active material (A), the carbon-based active material (B), and the carbon-based active material (C) are SA[m2/g], SB[m2/g], and SC[m2/g ], respectively, the value of the maximum specific surface area among said specific surface areas is Smax, and the value of the minimum specific surface area among said specific surface areas is Smin, the value of Smax/Smin is 3 or less, and Smax is 3 or less.