JP4107567B2 - Lithium-ion battery deterioration diagnosis method and apparatus incorporating the deterioration diagnosis method - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、リチウムイオン電池の劣化診断方法及びその装置に関するものであり、特にリチウムイオン電池の電池容量低下の劣化因子である正極及び負極の活物質の劣化及び抵抗成分の増加状態を測定することのできるリチウムイオン電池の劣化診断方法及びその劣化診断方法を内蔵した装置に関するものである。
【０００２】
【従来の技術】
リチウムイオン電池の充放電の繰り返し使用により電池容量の低下が生じるが、この電池容量の低下の主たる要因は、正極及び負極の活物質の劣化及び正極及び負極の表面に成長する抵抗薄膜による内部インピーダンスの増加である。
これらの劣化の程度を検査又は観測する方法としては、例えば、ｘ線回折法、ｘ線マイクロアナライザーなどによる正極，負極の活物質の検査、ｘ線光電子分光法，インピーダンス法などによる抵抗薄膜の検査が知られている。
【０００３】
【発明が解決しようとする課題】
しかしながら、前述した測定方法は、いずれも測定に高価な専用装置や特殊な付属装置が必要であり、また測定には多くの時間と熟練を要する。さらに、得られるデータは定性的であって定量的に把握することは困難であるなどの問題があった。
本発明は、リチウムイオン電池の劣化機構とその劣化因子の劣化に及ぼす割合を電圧と時間の関数から求める解析法であり、この劣化診断方法及びその装置は、電池劣化に関する有益な情報を簡便・短時間に提供可能であって、リチウムイオン電池の研究開発、或いは検査業務等に極めて有益である。
【０００４】
【課題を解決するための手段】
本願の第１の発明であるリチウムイオン電池の劣化診断方法は、リチウムイオン電池の定電流による初期充放電における通常の時間率充放電試験の充電終了直前付近及び放電終了直前付近に生ずるプラトー電圧変化を検出して、該各電圧変化部分の各下限電圧値と各上限電圧値をそれぞれ測定すると共に、前記通常の時間率での容量確認試験における前記下限電圧値から上限電圧値までの充電電圧変化に要した第１の充電時間及び前記上限電圧値から下限電圧値までの放電電圧変化に要した第１の放電時間を測定し、かつ前記初期充放電における長時間の時間率での容量確認試験を行い前記充電電圧変化に要した第２の充電時間及び前記放電電圧変化に要した第２の放電時間を測定し、
該初期充放電試験後に前記通常の時間率充放電のサイクル試験を行い、該サイクル試験後の前記通常の時間率での容量確認試験における前記充電電圧変化に要した第３の充電時間及び前記放電電圧変化に要した第３の放電時間を測定し、かつ前記サイクル試験後における長時間の時間率での容量確認試験を行い前記充電電圧変化に要した第４の充電時間及び前記放電電圧変化に要した第４の放電時間を測定し、
前記第１充電時間と前記第３充電時間との比率により前記リチウムイオン電池の正極全体の劣化率と、前記第１放電時間と前記第３放電時間との比率により前記リチウムイオン電池の負極全体の劣化率と、前記第２充電時間と前記第４充電時間との比率により前記正極の活物質の劣化率と、前記第２放電時間と前記第４放電時間との比率により前記負極の活物質の劣化率とを求めると共に、前記正極全体の劣化率から前記正極の活物質の劣化率を差し引き前記正極のインピーダンス増加率と、前記負極全体の劣化率から前記負極の活物質の劣化率を差し引き前記負極のインピーダンス増加率とを求めるようにしたものである。
【０００５】
本願の第２の発明であるリチウムイオン電池の劣化診断装置は、リチウムイオン電池の定電流による通常の時間率充放電試験の初期充放電における充電終了直前付近及び放電終了直前付近に生ずる各プラトー電圧変化を検出する電圧変化検出手段と、
前記の各プラトー電圧変化部分の各下限電圧値と各上限電圧値をそれぞれ測定し記憶する記憶手段と、
前記通常の時間率での容量確認試験における前記下限電圧値から上限電圧値までの充電電圧変化に要した第１の充電時間，及び前記上限電圧値から下限電圧値までの放電電圧変化に要した第１の放電時間を測定し記憶する第１の充放電時間記憶手段と、
前記初期充放電状態での長時間の時間率での容量確認試験における前記充電電圧変化に要した第２の充電時間、及び前記放電電圧変化に要した第２の放電時間を測定し記憶する第２の充放電時間記憶手段と、
前記初期充放電試験後の前記通常の時間率充放電のサイクル試験後の前記通常の時間率での容量確認試験における前記充電電圧変化に要した第３の充電時間及び前記放電電圧変化に要した第３の放電時間を測定し記憶する第３の充放電時間記憶手段と、
前記サイクル試験後の前記長時間の時間率での容量確認試験における前記充電電圧変化に要した第４の充電時間及び前記放電電圧変化に要した第４の放電時間を測定し記憶する第４の充放電時間記憶手段と、
前記第１充電時間と前記第３充電時間との比率と前記第１放電時間と前記第３放電時間との比率により前記リチウムイオン電池の正極全体と負極全体の各劣化率を求める演算手段と、
前記第２充電時間と前記第４充電時間との比率と前記第２放電時間と前記第４放電時間との比率により前記正極と前記負極の各活物質の劣化率を求める演算手段と、
前記正極全体の劣化率と前記正極の活物質の劣化率との差と前記負極全体の劣化率と前記負極の活物質の劣化率との差から前記正極と前記負極の各インピーダンス増加率を求める演算手段とを備えたものである。
【０００６】
【発明の実施の形態】
本発明のリチウムイオン電池の診断方法の一実施例を図１及び図２に基づいて説明する。図１は円筒型のリチウムイオン電池の定電流試験における充放電電圧特性を示すものであり、この充放電電圧特性の充電及び放電の開始初期と終了間際にそれぞれプラトーと言われる電圧変化のピーク１〜４が現れる。このピーク１〜４は充放電に伴って可逆的に現れるものであり、ピーク１と４は負極（黒鉛炭素）のステージ構造変化に起因し、ピーク２と３は正極（ＬｉＣｏＯ2 ）の構造変化に起因して現れる。
本発明はこの各ピークが出現する電圧範囲に要する時間をサイクルの関数として比較することにより、活物質の劣化程度を求めることが可能となることに着目して成されたものである。
【０００７】
しかし、電池の内部抵抗はサイクル試験と共に増加し、抵抗成分の増加による分極が大きくなる。この結果、ピーク１の充電初期及びピーク３の放電初期は分極の増大に伴って検出できなくなる場合が生じるため、正極に起因する劣化の解析はピーク２、同様に負極に起因する劣化はピーク４を用いて解析するものである。また、電池容量低下の確認試験は、通常８〜１０時間率（通常の時間率）に相当する充放電電流値で行うものである。
【０００８】
図２は、図１に示したピーク２と４の部分を拡大して、解析の詳細を示すものであり、正極の劣化は充電末の下限電圧値の４．０Ｖから上限電圧値の４．１５Ｖ、負極の劣化は放電末の上限電圧値の３．７５Ｖから下限電圧値の３．６Ｖの電圧範囲を基準として、この電圧範囲の変化に要した初期の充放電試験とサイクル試験経過後との時間差から劣化程度を解析するものである。
即ち、初期の充放電試験として例えば３回の充放電試験の前記電圧範囲の平均充電時間及び放電時間をそれぞれΔＴとし、例えば９７０サイクル試験後の同電圧範囲に要する充電時間及び放電時間をそれぞれΔＴｎとして、次式（１）から正極及び負極の容量低下率が求められる。
【０００９】
容量低下率＝〔１−（ΔＴｎ／ΔＴ）〕×１００ ……（１）
【００１０】
しかし、８〜１０時間率に相当する充放電電流値での容量確認試験から得られる容量低下率には電流値が大きいため、活物質だけでなく分極成分（抵抗成分）の影響も含まれた値となる。
【００１１】
このため、分極成分の影響を極力排除して活物質の劣化を見積る（測定する）手段として、３０〜５０時間率（長時間の時間率）に相当する極低率での容量確認試験を並行して行う。この極低率での容量確認試験も、前述の８〜１０時間率による充放電電流値での容量確認試験の際に検出したピーク２と４のそれぞれの下限電圧値と上限電圧値との差である電圧範囲を用いるものであり、充放電試験の初期時の３０〜５０時間率による当該電圧範囲の変化に要した充電時間ΔＴ又は放電時間ΔＴと、サイクル試験経過後の３０〜５０時間率による当該電圧範囲の変化に要した充電時間ΔＴｎ又は放電時間ΔＴｎとの時間差から求めるものである。
【００１２】
この極低率での容量確認試験により、正極及び負極の表面に成長した抵抗薄膜を充電電流又は放電電流は透過するため、その抵抗薄膜の影響を無視し得るようにして正極及び負極の活物質の劣化分の容量低下率として検出するものである。従って、この正極及び負極の活物質の劣化分の容量低下率を、前述の８〜１０時間率による充放電試験において求めた容量低下率から差し引いた容量低下率が、正極及び負極の表面に成長した抵抗薄膜の抵抗成分による容量低下率として見積る（測定する）ことができる。
即ち、通常の８〜１０時間率容量確認試験と共に３０〜５０時間率の極低率容量試験を併用することにより、正極及び負極の活物質の劣化及び抵抗成分の増加を分離し、かつ定量的に測定することを可能にしたものである。
【００１３】
【実施例】
本発明のリチウムイオン電池の劣化診断方法又はその装置を用いて、円筒１８６５０型リウチムイオン電池を充放電サイクルしたものを複数パターン用意し、解析した結果を図３及び図４に示す。図３は電池容量低下率に占める各劣化因子の割合を示すデータ表であり、図４は図３のに示したデータを棒グラフに表したグラフ図である。
【００１４】
この試験データは、温度と充放電率との各試験条件における、▲１▼電池全体の容量低下率，▲２▼負極全体の劣化率，▲３▼負極活物質の劣化率，▲４▼負極抵抗成分（インピーダンス）の増加率（▲２▼負極全体の劣化率−▲３▼負極活物質の劣化率），▲５▼正極全体の劣化率，▲６▼正極活物質の劣化率，▲７▼正極抵抗成分（インピーダンス）の増加率（▲５▼正極全体の劣化率−▲６▼正極活物質の劣化率）を示しているものである。この図３及び図４から明らかなように，電池の容量低下原因の内訳を定量的に示すことができると共に、解析の精度は、電池の容量低下率に対して負極全体の劣化率は９０〜１１０％範囲内に含まれているものであり、相当高い精度での試験が可能である。
【００１５】
次に本発明のリチウムイオン電池の劣化診断装置を説明する。この劣化診断装置は、リチウムイオン電池の通常の定電流充放電による容量試験装置を用い、通常の時間率、例えば８〜１０時間率により行うものである。この容量試験の初期充放電試験の際の充電終了直前付近及び放電終了直前付近のプラトー電圧変化を検出する検出手段と、この各電圧変化の下限電圧値と上限電圧値とを読取り、メモリに記憶させる記憶手段とを有すると共に、初期充放電試験時とサイクル充放電試験後の前述した通常の時間率、例えば８〜１０時間率での容量確認試験と長時間の時間率、例えば３０〜５０時間率での容量確認試験を行う際の、前述した各電圧変化に要する充電時間と放電時間を測定する測定手段とこの測定結果をメモリに記憶させる記憶手段とを有している。
【００１６】
即ち、初期充放電試験時の前記下限電圧値から上限電圧値までの充電電圧変化と、前記上限電圧値から下限電圧値までの放電電圧変化のそれぞれにおける通常の時間率と長時間の時間率での各充電時間（第１充電時間と第２充電時間）及び各放電時間（第１放電時間と第２放電時間）と、サイクル充放電試験後の前記下限電圧値から上限電圧値までの充電電圧変化と、前記上限電圧値から下限電圧値までの放電電圧変化のそれぞれにおける通常の時間率と長時間の時間率での各充電時間（第３充電時間と第４充電時間）及び各放電時間（第３放電時間と第４放電時間）とを測定する測定手段及びこの測定結果を記憶する記憶手段を有しているものである。
【００１７】
また、前述した第１充電時間〜第４充電時間と、第１放電時間〜第４放電時間とから、正極全体の劣化率▲５▼及び負極全体の劣化率▲２▼，正極の活物質の劣化率▲６▼及び負極の活物質の劣化率▲３▼，正極の表面に成長する抵抗薄膜によるインピーダンスの増加率▲７▼及び負極の同インピーダンスの増加率▲４▼を演算する演算回路とを有している。
【００１８】
即ち、前記式（１）に第１充電時間△Ｔと第３充電時間△Ｔｎを代入して、正極全体の劣化率▲５▼を求め、第１放電時間△Ｔと第３放電時間△Ｔｎから同様に負極全体の劣化率▲２▼を求める。また、前記式（１）に第２充電時間△Ｔと第４充電時間△Ｔｎを代入して、正極の活物質の劣化率▲６▼を求め、第２放電時間△Ｔと第４放電時間△Ｔｎから同様に負極の活物質の劣化率▲３▼を求める。
更に、前述した正極全体の劣化率▲５▼から正極の活物質の劣化率▲６▼を差し引き正極のインピーダンスの増加率▲７▼を求め、負極全体の劣化率▲２▼から負極の活物質の劣化率▲３▼を差し引き負極のインピーダンスの増加率▲４▼を求めるそれぞれの演算回路を有しているものである。
【００１９】
図５に前述のリチウムイオン電池の劣化診断装置による試験，測定，演算の処理工程を示す。図５において、Ｆ1 は初期充放電時の８〜１０時間率の要領測定とプラトー部の所用時間測定、Ｆ2 は初期充放電時の３０〜５０時間率のプラトー部の所用時間測定、Ｆ3 は各種サイクル試験、Ｆ4 はサイクル試験後の８〜１０時間率の要領測定とプラトー部の所用時間測定、Ｆ5 は同試験後の３０〜５０時間率のプラトー部の所用時間測定、Ｆ6 はＦ1 ，Ｆ2 ，Ｆ4 及びＦ5 の各測定データの演算部で、リチウムイオン電池の容量低下率と共に、容量低下の要因解析を行う。即ち、正極，負極の各劣化率，正極，負極の各活物質の劣化率，正極，負極の各インピーダンスの増加率を求める。Ｆ7 で当該電池のサイクル試験を終了する。
【００２０】
前述したリチウムイオン電池の劣化診断方法及びその劣化診断装置の説明では、初期充放電試験時と例えば９７０回のサイクル試験終了後に、それぞれ通常の時間率と長時間の時間率の容量確認試験を行い正極及び負極の各劣化率を測定しているが、前述のサイクル試験の途中の、例えば２００サイクル，５００サイクル．８００サイクルなどの中途においても同様な測定，演算により、電池の劣化状態をも診断することが可能である。
この診断解析に必要なデータの収集および診断解析に必要な計算プログラムは、従来の電池充放電試験システムに容易に組み入れることができ、これによって、サイクル試験経過に伴う劣化過程を自動的に解析・出力することを可能としたものである。
【００２１】
本発明のリチウムイオン電池の劣化診断方法及びその装置の対象は、主としてリチウムイオン電池用正極としては遷移金属酸化物（ＬｉＣｏＯ2 ，ＬｉＮｉＯ2 ，ＬｉＭｎ2Ｏ4 等）を用いる電池系であり、またリチウムイオン電池用負極としては黒鉛系炭素材料を用いる電池系である。
【００２２】
【発明の効果】
以上の説明より明らかなように、本発明は、電池の劣化状況をサイクル試験データとしての電圧，時間，電流から求めるものであり、従来のように劣化評価に専用装置や技術の熟練性などを必要とせず、セルサイズにも関係なく安全に、迅速にかつ定量的に評価し得るもので、リチウムイオン電池の開発の加速化や検査の効率化に極めて有効に寄与するものである。
【図面の簡単な説明】
【図１】本発明を適用するリチウムイオン電池の代表的な充放電電圧特性を示す。
【図２】本発明のリチウムイオン電池の劣化診断の主要構成である電圧と時間の関係の一例を説明する特性図である。
【図３】本発明により測定した電圧と時間の関係により求めた電池容量低下率に占める各劣化因子の割合の一例を示すデータ表である。
【図４】図３のデータ表に示したデータを棒グラフに表したグラフ図である。
【図５】本発明のリチウムイオン電池の劣化診断装置における処理工程図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for diagnosing deterioration of a lithium ion battery, and in particular, measuring the deterioration of the active material of the positive electrode and the negative electrode and the increasing state of the resistance component, which are deterioration factors of the battery capacity of the lithium ion battery. The present invention relates to a method for diagnosing deterioration of a lithium ion battery and a device incorporating the method for diagnosing deterioration.
[0002]
[Prior art]
Battery capacity decreases due to repeated use of charge and discharge of lithium ion batteries. The main causes of this decrease in battery capacity are deterioration of the active material of the positive and negative electrodes and internal impedance due to the resistive thin film growing on the surfaces of the positive and negative electrodes. Is an increase.
As a method for inspecting or observing the degree of deterioration, for example, an inspection of positive and negative electrode active materials by an x-ray diffraction method, an x-ray microanalyzer, etc., an inspection of a resistance thin film by an x-ray photoelectron spectroscopy, impedance method, etc. It has been known.
[0003]
[Problems to be solved by the invention]
However, any of the measurement methods described above requires an expensive dedicated device or a special accessory device, and the measurement requires a lot of time and skill. Furthermore, there is a problem that the obtained data is qualitative and difficult to grasp quantitatively.
The present invention is an analysis method for obtaining a deterioration mechanism of a lithium ion battery and a ratio of the deterioration factor to the deterioration from a function of voltage and time. It can be provided in a short time and is extremely useful for research and development of lithium ion batteries or inspection work.
[0004]
[Means for Solving the Problems]
The deterioration diagnosis method for a lithium ion battery according to the first invention of the present application is a plateau voltage change that occurs in the vicinity of immediately before and after the end of the normal time rate charge / discharge test in the initial charge / discharge with a constant current of the lithium ion battery. And measuring each lower limit voltage value and each upper limit voltage value of each voltage change portion, and charging voltage change from the lower limit voltage value to the upper limit voltage value in the capacity check test at the normal time rate The first charge time required for the first charge time and the first discharge time required for the discharge voltage change from the upper limit voltage value to the lower limit voltage value are measured, and the capacity confirmation test at a long time rate in the initial charge / discharge And measuring a second charging time required for the change in the charging voltage and a second discharging time required for the change in the discharge voltage,
A cycle test of the normal time rate charge / discharge is performed after the initial charge / discharge test, and a third charge time and the discharge required for the charge voltage change in the capacity confirmation test at the normal time rate after the cycle test. A third discharge time required for the voltage change is measured, and a capacity confirmation test is performed at a long time rate after the cycle test, and the fourth charge time required for the charge voltage change and the discharge voltage change are determined. Measure the required 4th discharge time,
The deterioration rate of the whole positive electrode of the lithium ion battery according to the ratio between the first charging time and the third charging time, and the whole negative electrode of the lithium ion battery according to the ratio between the first discharging time and the third discharging time. The deterioration rate of the active material of the positive electrode according to the ratio of the deterioration rate and the second charging time and the fourth charging time, and the ratio of the active material of the negative electrode according to the ratio of the second discharge time and the fourth discharge time. And obtaining the deterioration rate, subtracting the deterioration rate of the positive electrode active material from the deterioration rate of the whole positive electrode, subtracting the impedance increase rate of the positive electrode and the deterioration rate of the negative electrode active material from the deterioration rate of the whole negative electrode The increase rate of the impedance of the negative electrode is obtained.
[0005]
The deterioration diagnosis apparatus for a lithium ion battery according to the second invention of the present application provides each plateau voltage generated immediately before the end of charge and immediately before the end of discharge in the initial charge / discharge of a normal time rate charge / discharge test with a constant current of the lithium ion battery. Voltage change detection means for detecting changes;
Storage means for measuring and storing each lower limit voltage value and each upper limit voltage value of each plateau voltage change part,
The first charging time required for the charge voltage change from the lower limit voltage value to the upper limit voltage value in the capacity confirmation test at the normal time rate, and the discharge voltage change required from the upper limit voltage value to the lower limit voltage value First charge / discharge time storage means for measuring and storing the first discharge time;
A second charge time required for the charge voltage change and a second discharge time required for the discharge voltage change in the capacity confirmation test at a long time rate in the initial charge / discharge state are measured and stored. Two charge / discharge time storage means;
It took the third charge time and the discharge voltage change required for the charge voltage change in the capacity check test at the normal time rate after the normal time rate charge / discharge cycle test after the initial charge / discharge test. Third charge / discharge time storage means for measuring and storing a third discharge time;
Measuring and storing a fourth charge time required for the charge voltage change and a fourth discharge time required for the discharge voltage change in the capacity check test at the long time rate after the cycle test; Charge / discharge time storage means;
Calculating means for determining respective deterioration rates of the whole positive electrode and the whole negative electrode of the lithium ion battery according to a ratio of the first charging time and the third charging time and a ratio of the first discharging time and the third discharging time;
Calculating means for determining a deterioration rate of each active material of the positive electrode and the negative electrode according to a ratio of the second charge time and the fourth charge time and a ratio of the second discharge time and the fourth discharge time;
The respective impedance increase rates of the positive electrode and the negative electrode are obtained from the difference between the deterioration rate of the entire positive electrode and the deterioration rate of the active material of the positive electrode and the difference between the deterioration rate of the entire negative electrode and the deterioration rate of the active material of the negative electrode. And an arithmetic means.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a diagnostic method for a lithium ion battery of the present invention will be described with reference to FIGS. FIG. 1 shows a charge / discharge voltage characteristic in a constant current test of a cylindrical lithium ion battery. A
The present invention is made by paying attention to the degree of deterioration of the active material by comparing the time required for the voltage range in which each peak appears as a function of the cycle.
[0007]
However, the internal resistance of the battery increases with the cycle test, and the polarization due to the increase of the resistance component increases. As a result, the initial charge of
[0008]
FIG. 2 shows the details of the analysis by enlarging the
That is, as an initial charge / discharge test, for example, the average charge time and discharge time in the voltage range of three charge / discharge tests are each ΔT, and for example, the charge time and discharge time required for the same voltage range after the 970 cycle test are ΔTn, respectively. As described above, the capacity reduction rate of the positive electrode and the negative electrode is obtained from the following formula (1).
[0009]
Capacity reduction rate = [1- (ΔTn / ΔT)] × 100 (1)
[0010]
However, the capacity reduction rate obtained from the capacity check test at the charge / discharge current value corresponding to the 8-10 hour rate has a large current value, and therefore includes not only the active material but also the influence of the polarization component (resistance component). Value.
[0011]
For this reason, as a means of estimating (measuring) the deterioration of the active material by eliminating the influence of the polarization component as much as possible, a capacity confirmation test at an extremely low rate corresponding to a 30 to 50 hour rate (long time rate) is performed in parallel. And do it. The capacity check test at this extremely low rate is also the difference between the lower limit voltage value and the upper limit voltage value of
[0012]
In this capacity confirmation test at a very low rate, charging current or discharging current passes through the resistive thin film grown on the surface of the positive electrode and the negative electrode, so that the influence of the resistive thin film can be ignored, and the active material of the positive electrode and the negative electrode It is detected as a capacity reduction rate of the deterioration of the above. Therefore, the capacity reduction rate obtained by subtracting the capacity reduction rate of the active material of the positive electrode and the negative electrode from the capacity reduction rate obtained in the above-described charge / discharge test at the 8-10 hour rate grows on the surfaces of the positive electrode and the negative electrode. It can be estimated (measured) as a capacity reduction rate due to the resistance component of the resistance thin film.
That is, by combining a normal low rate capacity test of 30 to 50 hours with a normal 8 to 10 hour rate capacity confirmation test, the deterioration of the active material and the increase of the resistance component of the positive electrode and the negative electrode are separated and quantitative. It makes it possible to measure.
[0013]
【Example】
A plurality of patterns prepared by charging and discharging a cylindrical 18650 type lithium ion battery using the method for diagnosing deterioration of a lithium ion battery or the apparatus of the present invention are prepared, and the analysis results are shown in FIGS. FIG. 3 is a data table showing the ratio of each deterioration factor in the battery capacity reduction rate, and FIG. 4 is a graph showing the data shown in FIG. 3 in a bar graph.
[0014]
This test data includes: (1) overall battery capacity reduction rate, (2) overall negative electrode degradation rate, (3) negative electrode active material degradation rate, and (4) negative electrode under each test condition of temperature and charge / discharge rate. Increase rate of resistance component (impedance) ((2) Degradation rate of the entire negative electrode-(3) Degradation rate of the negative electrode active material), (5) Degradation rate of the entire positive electrode, (6) Degradation rate of the positive electrode active material, (7) The rate of increase of the positive electrode resistance component (impedance) ((5) Deterioration rate of the entire positive electrode-(6) Deterioration rate of the positive electrode active material) is shown. As can be seen from FIGS. 3 and 4, the breakdown of the cause of the battery capacity decrease can be quantitatively shown, and the accuracy of the analysis is that the deterioration rate of the whole negative electrode is 90 to 90% of the battery capacity decrease rate. It is included within the range of 110%, and a test with considerably high accuracy is possible.
[0015]
Next, a deterioration diagnosis apparatus for a lithium ion battery according to the present invention will be described. This deterioration diagnosis apparatus uses a capacity test apparatus based on normal constant current charging / discharging of a lithium ion battery, and is performed at a normal time rate, for example, 8 to 10 hour rate. A detection means for detecting plateau voltage changes near the end of charging and immediately before the end of discharge in the initial charge / discharge test of the capacity test, and the lower limit voltage value and the upper limit voltage value of each voltage change are read and stored in a memory. Storage means, and the aforementioned normal time rate during the initial charge / discharge test and after the cycle charge / discharge test, for example, the capacity check test at a rate of 8 to 10 hours and a long time rate, for example, 30 to 50 hours. When the capacity confirmation test is performed at a rate, the above-mentioned measuring means for measuring the charging time and discharging time required for each voltage change and the storage means for storing the measurement results in the memory are provided.
[0016]
That is, at a normal time rate and a long time rate in the charge voltage change from the lower limit voltage value to the upper limit voltage value and the discharge voltage change from the upper limit voltage value to the lower limit voltage value in the initial charge / discharge test, respectively. Each charging time (first charging time and second charging time) and each discharging time (first discharging time and second discharging time), and the charging voltage from the lower limit voltage value to the upper limit voltage value after the cycle charging / discharging test Each charge time (third charge time and fourth charge time) and each discharge time at a normal time rate and a long time rate in each change of the discharge voltage change from the upper limit voltage value to the lower limit voltage value ( (3rd discharge time and 4th discharge time) and the memory | storage means which memorize | stores this measurement result.
[0017]
Further, from the first charging time to the fourth charging time and the first discharging time to the fourth discharging time, the deterioration rate of the whole positive electrode (5) and the deterioration rate of the whole negative electrode (2), the active material of the positive electrode An arithmetic circuit for calculating a deterioration rate (6), a deterioration rate of the active material of the negative electrode (3), an increase rate of impedance by the resistive thin film growing on the surface of the positive electrode (7), and an increase rate of the same impedance of the negative electrode (4); have.
[0018]
That is, by substituting the first charging time ΔT and the third charging time ΔTn into the equation (1), the deterioration rate (5) of the entire positive electrode is obtained, and the first discharging time ΔT and the third discharging time ΔTn. Similarly, the deterioration rate (2) of the whole negative electrode is obtained. Further, the second charging time ΔT and the fourth charging time ΔTn are substituted into the formula (1) to obtain the deterioration rate (6) of the active material of the positive electrode, and the second discharging time ΔT and the fourth discharging time. Similarly, the deterioration rate (3) of the negative electrode active material is obtained from ΔTn.
Further, by subtracting the deterioration rate (6) of the positive electrode active material from the deterioration rate (5) of the whole positive electrode described above, the increase rate (7) of the impedance of the positive electrode is obtained, and the negative electrode active material is calculated from the deterioration rate (2) of the whole negative electrode. Are provided with respective arithmetic circuits for subtracting the deterioration rate (3) of the above and obtaining the increase rate (4) of the impedance of the negative electrode.
[0019]
FIG. 5 shows test, measurement, and calculation processing steps by the above-described lithium ion battery deterioration diagnosis apparatus. In FIG. 5, F1 is a method for measuring the rate of 8 to 10 hours at the initial charge / discharge and measurement of the time required for the plateau part, F2 is a time measurement for the plateau part at the rate of 30 to 50 hours during the initial charge / discharge, and F3 is various values. Cycle test, F4: 8-10 hour rate after cycle test and plateau time measurement, F5: 30-50 hour plateau time measurement after test, F6: F1, F2, In the calculation unit for each measurement data of F4 and F5, the cause of the capacity decrease is analyzed together with the capacity decrease rate of the lithium ion battery. That is, the positive electrode and negative electrode deterioration rates, the positive electrode and negative electrode active material deterioration rates, and the positive and negative electrode impedance increase rates are obtained. The cycle test of the battery is completed at F7.
[0020]
In the above-described method for diagnosing deterioration of a lithium ion battery and the apparatus for diagnosing the deterioration, a capacity check test for a normal time rate and a long time rate is performed at the initial charge / discharge test and after 970 cycle tests, for example. Although the respective deterioration rates of the positive electrode and the negative electrode are measured, for example, 200 cycles, 500 cycles, etc. during the cycle test described above. It is possible to diagnose the deterioration state of the battery by the same measurement and calculation even in the middle of 800 cycles.
The data collection required for this diagnostic analysis and the calculation program required for the diagnostic analysis can be easily incorporated into a conventional battery charge / discharge test system. It is possible to output.
[0021]
The object of the degradation diagnosis method and apparatus of a lithium ion battery of the present invention is a battery system that mainly uses a transition metal oxide (LiCoO2, LiNiO2, LiMn2O4, etc.) as a positive electrode for a lithium ion battery, and a negative electrode for a lithium ion battery. Is a battery system using a graphite-based carbon material.
[0022]
【The invention's effect】
As is clear from the above description, the present invention obtains the deterioration status of the battery from the voltage, time, and current as cycle test data. It can be safely, quickly and quantitatively evaluated regardless of cell size, and contributes to the acceleration of the development of lithium ion batteries and the efficiency of inspections.
[Brief description of the drawings]
FIG. 1 shows typical charge / discharge voltage characteristics of a lithium ion battery to which the present invention is applied.
FIG. 2 is a characteristic diagram for explaining an example of a relationship between voltage and time, which is a main component of deterioration diagnosis of the lithium ion battery of the present invention.
FIG. 3 is a data table showing an example of the ratio of each deterioration factor in the battery capacity reduction rate obtained from the relationship between voltage and time measured according to the present invention.
4 is a graph showing the data shown in the data table of FIG. 3 in a bar graph. FIG.
FIG. 5 is a process diagram in the deterioration diagnosis apparatus for a lithium ion battery according to the present invention.
Claims (6)
該初期充放電試験後に前記通常の時間率充放電のサイクル試験を行い、該サイクル試験後の前記通常の時間率での容量確認試験における前記充電電圧変化に要した第３の充電時間及び前記放電電圧変化に要した第３の放電時間を測定し、かつ前記サイクル試験後における長時間の時間率での容量確認試験を行い前記充電電圧変化に要した第４の充電時間及び前記放電電圧変化に要した第４の放電時間を測定し、
前記第１充電時間と前記第３充電時間との比率により前記リチウムイオン電池の正極全体の劣化率と、前記第１放電時間と前記第３放電時間との比率により前記リチウムイオン電池の負極全体の劣化率と、前記第２充電時間と前記第４充電時間との比率により前記正極の活物質の劣化率と、前記第２放電時間と前記第４放電時間との比率により前記負極の活物質の劣化率とを求めると共に、前記正極全体の劣化率から前記正極の活物質の劣化率を差し引き前記正極のインピーダンス増加率と、前記負極全体の劣化率から前記負極の活物質の劣化率を差し引き前記負極のインピーダンス増加率とを求めるようにしたリチウムイオン電池の劣化診断方法。Detection of plateau voltage changes that occur near the end of charging and near the end of discharge in the normal time rate charge / discharge test in the initial charge / discharge with a constant current of a lithium ion battery, and the lower limit voltage value of each voltage change portion and each The upper limit voltage value is measured, and the first charging time required for the change of the charging voltage from the lower limit voltage value to the upper limit voltage value in the capacity check test at the normal time rate, and the upper limit voltage value to the lower limit voltage value. And measuring the first discharge time required for the change in the discharge voltage up to and performing a capacity check test at a long time rate in the initial charge / discharge, and the second charge time required for the change in the charge voltage and the discharge Measure the second discharge time required for the voltage change,
A cycle test of the normal time rate charge / discharge is performed after the initial charge / discharge test, and a third charge time and the discharge required for the charge voltage change in the capacity confirmation test at the normal time rate after the cycle test. A third discharge time required for the voltage change is measured, and a capacity confirmation test is performed at a long time rate after the cycle test, and the fourth charge time required for the charge voltage change and the discharge voltage change are determined. Measure the required 4th discharge time,
The deterioration rate of the whole positive electrode of the lithium ion battery according to the ratio between the first charging time and the third charging time, and the whole negative electrode of the lithium ion battery according to the ratio between the first discharging time and the third discharging time. The deterioration rate of the active material of the positive electrode according to the ratio of the deterioration rate and the second charging time and the fourth charging time, and the ratio of the active material of the negative electrode according to the ratio of the second discharge time and the fourth discharge time. And obtaining the deterioration rate, subtracting the deterioration rate of the positive electrode active material from the deterioration rate of the whole positive electrode, subtracting the impedance increase rate of the positive electrode and the deterioration rate of the negative electrode active material from the deterioration rate of the whole negative electrode A method for diagnosing deterioration of a lithium ion battery in which the rate of increase in impedance of the negative electrode is obtained.
前記の各プラトー電圧変化部分の各下限電圧値と各上限電圧値をそれぞれ測定し記憶する記憶手段と、
前記通常の時間率での容量確認試験における前記下限電圧値から上限電圧値までの充電電圧変化に要した第１の充電時間，及び前記上限電圧値から下限電圧値までの放電電圧変化に要した第１の放電時間を測定し記憶する第１の充放電時間記憶手段と、
前記初期充放電状態での長時間の時間率での容量確認試験における前記充電電圧変化に要した第２の充電時間、及び前記放電電圧変化に要した第２の放電時間を測定し記憶する第２の充放電時間記憶手段と、
前記初期充放電試験後の前記通常の時間率充放電のサイクル試験後の前記通常の時間率での容量確認試験における前記充電電圧変化に要した第３の充電時間及び前記放電電圧変化に要した第３の放電時間を測定し記憶する第３の充放電時間記憶手段と、
前記サイクル試験後の前記長時間の時間率での容量確認試験における前記充電電圧変化に要した第４の充電時間及び前記放電電圧変化に要した第４の放電時間を測定し記憶する第４の充放電時間記憶手段と、
前記第１充電時間と前記第３充電時間との比率と前記第１放電時間と前記第３放電時間との比率により前記リチウムイオン電池の正極全体と負極全体の各劣化率を求める演算手段と、
前記第２充電時間と前記第４充電時間との比率と前記第２放電時間と前記第４放電時間との比率により前記正極と前記負極の各活物質の劣化率を求める演算手段と、
前記正極全体の劣化率と前記正極の活物質の劣化率との差と、前記負極全体の劣化率と前記負極の活物質の劣化率との差から前記正極と前記負極の各インピーダンス増加率を求める演算手段とを備えたリチウムイオン電池の劣化診断装置。Voltage change detection means for detecting each plateau voltage change that occurs in the vicinity of immediately before and after the end of charge in the initial charge and discharge of a normal time rate charge and discharge test with a constant current of a lithium ion battery; and
Storage means for measuring and storing each lower limit voltage value and each upper limit voltage value of each plateau voltage change part,
The first charging time required for the charge voltage change from the lower limit voltage value to the upper limit voltage value in the capacity confirmation test at the normal time rate, and the discharge voltage change required from the upper limit voltage value to the lower limit voltage value First charge / discharge time storage means for measuring and storing the first discharge time;
A second charge time required for the charge voltage change and a second discharge time required for the discharge voltage change in the capacity confirmation test at a long time rate in the initial charge / discharge state are measured and stored. Two charge / discharge time storage means;
It took the third charge time and the discharge voltage change required for the charge voltage change in the capacity check test at the normal time rate after the normal time rate charge / discharge cycle test after the initial charge / discharge test. Third charge / discharge time storage means for measuring and storing a third discharge time;
Measuring and storing a fourth charge time required for the charge voltage change and a fourth discharge time required for the discharge voltage change in the capacity check test at the long time rate after the cycle test; Charge / discharge time storage means;
Calculating means for determining respective deterioration rates of the whole positive electrode and the whole negative electrode of the lithium ion battery according to a ratio of the first charging time and the third charging time and a ratio of the first discharging time and the third discharging time;
Calculating means for determining a deterioration rate of each active material of the positive electrode and the negative electrode according to a ratio of the second charge time and the fourth charge time and a ratio of the second discharge time and the fourth discharge time;
From the difference between the deterioration rate of the entire positive electrode and the deterioration rate of the active material of the positive electrode, and the difference between the deterioration rate of the entire negative electrode and the deterioration rate of the active material of the negative electrode, the respective impedance increase rates of the positive electrode and the negative electrode A deterioration diagnosis apparatus for a lithium ion battery, comprising: a calculating means for obtaining.
該初期充放電試験時及びサイクル試験後の測定容量から容量低下率を求める手段とを備えた請求項３に記載のリチウムイオン電池の劣化診断装置。Means for measuring the capacity at the time of the initial charge / discharge test by the constant current of the lithium ion battery and after the cycle test;
The deterioration diagnosis apparatus for a lithium ion battery according to claim 3, further comprising means for obtaining a capacity reduction rate from the measured capacity during the initial charge / discharge test and after the cycle test.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2002116443A JP4107567B2 (en) | 2002-04-18 | 2002-04-18 | Lithium-ion battery deterioration diagnosis method and apparatus incorporating the deterioration diagnosis method |
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| JP4798534B2 (en) * | 2005-01-19 | 2011-10-19 | Ｔｄｋラムダ株式会社 | Lithium-ion battery charging method |
| US7859226B2 (en) | 2007-07-17 | 2010-12-28 | Tdk-Lambda Corporation | Method and device for safety protection of secondary battery |
| JP5656415B2 (en) * | 2009-03-26 | 2015-01-21 | プライムアースＥｖエナジー株式会社 | Secondary battery state determination device and control device |
| JP4952808B2 (en) | 2010-02-22 | 2012-06-13 | トヨタ自動車株式会社 | Lithium deposition discrimination device for lithium ion secondary battery, method thereof, and vehicle equipped with the device |
| JP5537236B2 (en) * | 2010-04-13 | 2014-07-02 | トヨタ自動車株式会社 | Lithium ion secondary battery deterioration determination device and deterioration determination method |
| JP5548784B2 (en) * | 2010-11-30 | 2014-07-16 | 本田技研工業株式会社 | Secondary battery deterioration estimation device |
| CN103329339B (en) * | 2011-01-14 | 2015-12-09 | 丰田自动车株式会社 | The degradation speed presuming method of lithium ion battery and degradation speed estimating device |
| JPWO2012095913A1 (en) | 2011-01-14 | 2014-06-09 | パナソニック株式会社 | Lithium ion secondary battery deterioration evaluation method and battery pack |
| JP5889548B2 (en) * | 2011-05-31 | 2016-03-22 | 株式会社東芝 | Battery deterioration calculation device |
| JP5517997B2 (en) | 2011-06-06 | 2014-06-11 | 株式会社日立製作所 | Lithium ion secondary battery inspection device, inspection method, and secondary battery module |
| WO2013179480A1 (en) * | 2012-06-01 | 2013-12-05 | トヨタ自動車株式会社 | Degradation diagnosis device for cell, degradation diagnosis method, and method for manufacturing cell |
| JP5731717B2 (en) * | 2012-09-20 | 2015-06-10 | 積水化学工業株式会社 | Storage battery operation control device, storage battery operation control method, and program |
| JP2017168361A (en) * | 2016-03-17 | 2017-09-21 | 富士電機株式会社 | Secondary battery device, charge control device, and charge control method |
| CN109061490A (en) * | 2018-07-30 | 2018-12-21 | 中国电力科学研究院有限公司 | A kind of prediction echelon is in the method and system of capacity acceleration decling phase using power battery |
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