Sodium-Ion Battery Electrode Design for Accurate SOC Detection
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Solution Overview
Problem
Sodium-ion batteries face challenges in precise state of charge (SOC) determination due to minimal voltage variation at the negative electrode, making it difficult for battery management systems (BMS) to accurately control charging and discharging processes.
Innovation Solution
The sodium-ion battery design includes a negative electrode with a sodium metal layer and a positive electrode active material that exhibits a significant slope change in the SOC-open circuit voltage (OCV) curve, ensuring k≥5 mV/1% SOC over at least a 20% SOC range, facilitating better BMS control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sodium-ion battery uses a negative electrode with sodium metal layer, then the battery achieves high capacity and long lifespan, but the voltage variation at the negative electrode becomes minimal, making SOC determination difficult
Solution Approach 1:
The patent modifies the positive electrode active material composition and structure to change the voltage characteristics of the battery. By selecting specific positive electrode materials with appropriate potentials and capacities, the overall battery voltage curve is optimized to provide sufficient slope for SOC determination despite the flat negative electrode voltage profile.
Solution Approach 2:
The patent introduces the positive electrode active material as an intermediary that translates the sodium ion transfer at the negative electrode into measurable voltage changes. The positive electrode material acts as a mediator that converts the minimal voltage variation at the negative electrode into significant overall battery voltage changes that can be used for SOC determination.
2Measurement precision
If the positive electrode active material is optimized to increase SOC-OCV curve slope, then BMS control precision is improved, but the battery composition becomes more complex
Solution Approach 1:
The patent systematically adjusts parameters of the positive electrode active material, including composition ratios, particle size distribution, and surface area, to optimize the SOC-OCV curve slope. By changing these material parameters rather than adding complex structural components, the patent achieves improved measurement precision while controlling composition complexity.
Solution Approach 2:
The patent employs composite positive electrode active materials that combine different compounds with complementary characteristics. This composite approach allows optimization of the voltage curve slope through material selection and ratio adjustment, achieving improved SOC determination without significantly increasing overall battery system complexity.
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 design enables precise control of the battery management system by providing a clear SOC-OCV curve slope, reducing the risk of overcharging and improving the accuracy of SOC detection and state of health (SOH) monitoring.
Implementation Method 1
A slope of a state of charge SOC-open circuit voltage OCV curve of the sodium-ion battery is denoted as k, and the state of charge SOC-open circuit voltage OCV curve of the sodium-ion battery satisfies: accumulated SOC≥20%, and k≥5 mV/1% SOC
Data Source
AI summary
The present application provides a sodium-ion battery, a battery, and an electric apparatus. The sodium-ion battery includes a negative electrode plate and a positive electrode plate containing a positive electrode active material. The negative electrode plate includes a negative electrode current collector and a sodium metal layer disposed on at least one surface of the negative electrode current collector. A slope of a state of charge SOC-open circuit voltage OCV curve of the sodium-ion battery is denoted as k, and the state of charge SOC-open circuit voltage OCV curve of the sodium-ion battery satisfies: accumulated SOC≥20%, and k≥5 mV/1% SOC.